ATMEL AT90PWM3-16SQ

Features
• High Performance, Low Power AVR ® 8-bit Microcontroller
• Advanced RISC Architecture
•
•
•
•
•
•
– Powerful Instructions - Most Single Clock Cycle Execution
– 32 x 8 General Purpose Working Registers
– Fully Static Operation
– Up to 1 MIPS throughput per MHz
– On-chip 2-cycle Multiplier
Data and Non-Volatile Program Memory
– 8K Bytes Flash of In-System Programmable Program Memory
• Endurance: 10,000 Write/Erase Cycles
– Optional Boot Code Section with Independent Lock Bits
In-System Programming by On-chip Boot Program
True Read-While-Write Operation
– 512 Bytes of In-System Programmable EEPROM
• Endurance: 100,000 Write/Erase Cycles
– 512 Bytes Internal SRAM
– Programming Lock for Flash Program and EEPROM Data Security
On Chip Debug Interface (debugWIRE)
Peripheral Features
– Two or three 12-bit High Speed PSC (Power Stage Controllers) with 4-bit
Resolution Enhancement
• Non Overlapping Inverted PWM Output Pins With Flexible Dead-Time
• Variable PWM duty Cycle and Frequency
• Synchronous Update of all PWM Registers
• Auto Stop Function for Event Driven PFC Implementation
• Less than 25 Hz Step Width at 150 kHz Output Frequency
• PSC2 with four Output Pins and Output Matrix
– One 8-bit General purpose Timer/Counter with Separate Prescaler and Capture
Mode
– One 16-bit General purpose Timer/Counter with Separate Prescaler, Compare
Mode and Capture Mode
– Programmable Serial USART
• Standard UART mode
• 16/17 bit Biphase Mode for DALI Communications
– Master/Slave SPI Serial Interface
– 10-bit ADC
• Up To 11 Single Ended Channels and 2 Fully Differential ADC Channel Pairs
• Programmable Gain (5x, 10x, 20x, 40x on Differential Channels)
• Internal Reference Voltage
– 10-bit DAC
– Two or three Analog Comparator with Resistor-Array to Adjust Comparison
Voltage
– 4 External Interrupts
– Programmable Watchdog Timer with Separate On-Chip Oscillator
Special Microcontroller Features
– Low Power Idle, Noise Reduction, and Power Down Modes
– Power On Reset and Programmable Brown Out Detection
– Flag Array in Bit-programmable I/O Space (4 bytes)
– In-System Programmable via SPI Port
– Internal Calibrated RC Oscillator ( 8 MHz)
– On-chip PLL for fast PWM ( 32 MHz, 64 MHz) and CPU (16 MHz)
Operating Voltage: 2.7V - 5.5V
Extended Operating Temperature:
– -40°C to +105° (full analog from -40 to 90°C)
8-bit
Microcontroller
with 8K Bytes
In-System
Programmable
Flash
AT90PWM2
AT90PWM3
Preliminary
4317B–AVR–02/05
1
Disclaimer
2
Product
Package
12 bit
PWM
ADC
Input
ADC
Diff
Analog
Compar
Application
AT90PWM2
SO24
2
8
1
2
One fluorescent ballast
AT90PWM3
SO32,
QFN32
3
11
2
3
HID ballast, fluorescent
ballast, Motor control
Typical values contained in this datasheet are based on simulations and characterization of other AVR microcontrollers manufactured on the same process technology. Min
and Max values will be available after the device is characterized.
AT90PWM2/3
4317B–AVR–02/05
AT90PWM2/3
Pin Configurations
Figure 1. SOIC 24-pin Package
AT90PWM2
SOIC24
(PSCOUT00/XCK/SS_A) PD0
(RESET/OCD) PE0
(PSCIN0/CLKO) PD1
(PSCIN2/OC1A/MISO_A) PD2
(TXD/DALI/OC0A/SS/MOSI_A) PD3
VCC
GND
(MISO/PSCOUT20) PB0
(MOSI/PSCOUT21) PB1
(OC0B/XTAL1) PE1
(ADC0/XTAL2) PE2
(ADC1/RXD/DALI/ICP1A/SCK_A) PD4
1
2
3
4
5
6
7
8
9
10
11
12
24
23
22
21
20
19
18
17
16
15
14
13
PB7(ADC4/PSCOUT01/SCK)
PB6 (ADC7/ICP1B)
PB5 (ADC6/INT2)
PB4 (AMP0+)
PB3 (AMP0-)
AREF
AGND
AVCC
PB2 (ADC5/INT1)
PD7 (ACMP0)
PD6 (ADC3/ACMPM/INT0)
PD5 (ADC2/ACMP2)
Figure 2. SOIC 32-pin Package
AT90PWM3
SOIC 32
(PSCOUT00/XCK/SS_A) PD0
(INT3/PSCOUT10) PC0
(RESET/OCD) PE0
(PSCIN0/CLKO) PD1
(PSCIN2/OC1A/MISO_A) PD2
(TXD/DALI/OC0A/SS/MOSI_A) PD3
(PSCIN1/OC1B) PC1
VCC
GND
(T0/PSCOUT22) PC2
(T1/PSCOUT23) PC3
(MISO/PSCOUT20) PB0
(MOSI/PSCOUT21) PB1
(OC0B/XTAL1) PE1
(ADC0/XTAL2) PE2
(ADC1/RXD/DALI/ICP1A/SCK_A) PD4
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
32
31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
PB7(ADC4/PSCOUT01/SCK)
PB6 (ADC7/PSCOUT11/ICP1B)
PB5 (ADC6/INT2)
PC7 (D2A)
PB4 (AMP0+)
PB3 (AMP0-)
PC6 (ADC10/ACMP1)
AREF
AGND
AVCC
PC5 (ADC9/AMP1+)
PC4 (ADC8/AMP1-)
PB2 (ADC5/INT1)
PD7 (ACMP0)
PD6 (ADC3/ACMPM/INT0)
PD5 (ADC2/ACMP2)
3
4317B–AVR–02/05
(MOSI/PSCOUT21) PB1
(OC0B/XTAL1) PE1
(ADC0/XTAL2) PE2
(ADC1/RXD/DALI/ICP1_A/SCK_A) PD4
(ADC2/ACMP2 ) PD5
(ADC3/ACMPM/INT0) PD6
(ACMP0) PD7
(ADC5/INT1) PB2
9
10
11
12
13
14
15
16
32
31
30
29
28
27
26
25
(PSCIN2/OC1A/MISO_A) PD2
(TXD/DALI/OC0A/SS/MOSI_A) PD3
(PSCIN1/OC1B) PC1
VCC
GND
(T0/PSCOUT22) PC2
(T1/PSCOUT23) PC3
(MISO/PSCOUT20) PB0
4
PB7 (ADC4/PSCOUT01/SCK)
PB6 (ADC7/PSCOUT11/ICP1B)
PB5 (ADC6/INT2)
PC7 (D2A)
PD0 (PSCOUT00/XCK/SS_A)
PC0(INT3/PSCOUT10)
PE0 (RESET/OCD)
PD1(PSCIN0/CLKO)
Figure 3. QFN32 (7*7 mm) Package.
AT90PWM3 QFN 32
1
2
3
4
5
6
7
8
24
23
22
21
20
19
18
17
PB4 (AMP0+)
PB3 (AMP0-)
PC6 (ADC10/ACMP1)
AREF
AGND
AVCC
PC5 (ADC9/AMP1+)
PC4 (ADC8/AMP1-)
AT90PWM2/3
4317B–AVR–02/05
AT90PWM2/3
Pin Descriptions
:
Table 1. Pin out description
S024 Pin
Number
SO32 Pin
Number
QFN32 Pin
Number
Mnemonic
Type
7
9
5
GND
Power
Ground: 0V reference
18
24
20
AGND
Power
Analog Ground: 0V reference for analog part
6
8
4
VCC
power
Power Supply:
17
23
19
AVCC
Power
Analog Power Supply: This is the power supply voltage for analog
part
Name, Function & Alternate Function
For a normal use this pin must be connected.
Analog Reference : reference for analog converter . This is the
reference voltage of the A/D converter. As output, can be used by
external analog
19
25
21
AREF
Power
8
12
8
PBO
I/O
9
13
9
PB1
I/O
16
20
16
PB2
I/O
20
27
23
PB3
I/O
AMP0- (Analog Differential Amplifier 0 Input Channel )
21
28
24
PB4
I/O
AMP0+ (Analog Differential Amplifier 0 Input Channel )
22
30
26
PB5
I/O
23
31
27
PB6
I/O
MISO (SPI Master In Slave Out)
PSCOUT20 output
MOSI (SPI Master Out Slave In)
PSCOUT21 output
ADC5 (Analog Input Channel5 )
INT1
ADC6 (Analog Input Channel 6)
INT 2
ADC7 (Analog Input Channel 7)
ICP1B (Timer 1 input capture alternate input)
PSCOUT11 output (see note 1)
PSCOUT01 output
24
32
28
PB7
I/O
ADC4 (Analog Input Channel 4)
SCK (SPI Clock)
5
4317B–AVR–02/05
Table 1. Pin out description (Continued)
S024 Pin
Number
SO32 Pin
Number
QFN32 Pin
Number
Mnemonic
Type
2
30
PC0
I/O
7
3
PC1
I/O
10
6
PC2
I/O
11
7
PC3
I/O
21
17
PC4
22
18
PC5
I/O
26
22
PC6
I/O
29
25
PC7
I/O
1
29
PD0
I/O
NA
I/O
Name, Function & Alternate Function
PSCOUT10 output (see note 1)
INT3
PSCIN1 (PSC 1 Digital Input)
OC1B (Timer 1 Output Compare B)
T0 (Timer 0 clock input)
PSCOUT22 output
T1 (Timer 1 clock input)
PSCOUT23 output
ADC8 (Analog Input Channel 8)
AMP1- (Analog Differential Amplifier 1 Input Channel )
ADC9 (Analog Input Channel 9)
AMP1+ (Analog Differential Amplifier 1 Input Channel )
ADC10 (Analog Input Channel 10)
ACMP1 (Analog Comparator 1 Positive Input )
D2A : DAC output
PSCOUT00 output
1
XCK (UART Transfer Clock)
SS_A (Alternate SPI Slave Select)
3
4
32
PD1
I/O
4
5
1
PD2
I/O
PSCIN0 (PSC 0 Digital Input )
CLKO (System Clock Output)
PSCIN2 (PSC 2 Digital Input)
OC1A (Timer 1 Output Compare A)
MISO_A (Programming & alternate SPI Master In Slave Out)
TXD (Dali/UART Tx data)
5
6
2
PD3
I/O
OC0A (Timer 0 Output Compare A)
SS (SPI Slave Select)
MOSI_A (Programming & alternate Master Out SPI Slave In)
ADC1 (Analog Input Channel 1)
12
16
12
PD4
I/O
RXD (Dali/UART Rx data)
ICP1A (Timer 1 input capture)
SCK_A (Programming & alternate SPI Clock)
13
17
13
PD5
I/O
14
18
14
PD6
I/O
ADC2 (Analog Input Channel 2)
ACMP2 (Analog Comparator 2 Positive Input )
ADC3 (Analog Input Channel 3 )
ACMPM reference for analog comparators
INT0
6
15
19
15
PD7
I/O
2
3
31
PE0
I/O or I
10
14
10
PE1
I/O
ACMP0 (Analog Comparator 0 Positive Input )
RESET (Reset Input)
OCD (On Chip Debug I/O)
XTAL1: XTAL Input
OC0B (Timer 0 Output Compare B)
AT90PWM2/3
4317B–AVR–02/05
AT90PWM2/3
Table 1. Pin out description (Continued)
S024 Pin
Number
SO32 Pin
Number
QFN32 Pin
Number
Mnemonic
Type
11
15
11
PE2
I/O
Name, Function & Alternate Function
XTAL2: XTAL OuTput
ADC0 (Analog Input Channel 0)
1. PSCOUT10 & PSCOUT11 are not present on 24 pins package
7
4317B–AVR–02/05
Overview
The AT90PWM2/3 is a low-power CMOS 8-bit microcontroller based on the AVR
enhanced RISC architecture. By executing powerful instructions in a single clock cycle,
the AT90PWM2/3 achieves throughputs approaching 1 MIPS per MHz allowing the system designer to optimize power consumption versus processing speed.
Block Diagram
Figure 4. Block Diagram
Data Bus 8-bit
8Kx8 Flash
Program
Memory
Program
Counter
Status
and Control
SPI
Unit
32 x 8
General
Purpose
Registrers
Instruction
Register
Watchdog
Timer
Direct Addressing
Indirect Addressing
3 Analog
Comparators
Instruction
Decoder
Control Lines
Interrupt
Unit
ALU
DALI USART
Timer 0
Timer 1
Data
SRAM
512 bytes
EEPROM
512 bytes
I/O Lines
ADC
DAC
PSC 2/1/0
The AVR core combines a rich instruction set with 32 general purpose working registers.
All the 32 registers are directly connected to the Arithmetic Logic Unit (ALU), allowing
two independent registers to be accessed in one single instruction executed in one clock
cycle. The resulting architecture is more code efficient while achieving throughputs up to
ten times faster than conventional CISC microcontrollers.
The AT90PWM2/3 provides the following features: 8K bytes of In-System Programmable Flash with Read-While-Write capabilities, 512 bytes EEPROM, 512 bytes SRAM, 53
general purpose I/O lines, 32 general purpose working registers,three Power Stage
Controllers, two flexible Timer/Counters with compare modes and PWM, one USART
8
AT90PWM2/3
4317B–AVR–02/05
AT90PWM2/3
with DALI mode, an 11-channel 10-bit ADC with two differential input stage with programmable gain, a 10-bit DAC, a programmable Watchdog Timer with Internal
Oscillator, an SPI serial port, an On-chip Debug system and four software selectable
power saving modes.
The Idle mode stops the CPU while allowing the SRAM, Timer/Counters, SPI ports and
interrupt system to continue functioning. The Power-down mode saves the register contents but freezes the Oscillator, disabling all other chip functions until the next interrupt
or Hardware Reset. The ADC Noise Reduction mode stops the CPU and all I/O modules
except ADC, to minimize switching noise during ADC conversions. In Standby mode,
the Crystal/Resonator Oscillator is running while the rest of the device is sleeping. This
allows very fast start-up combined with low power consumption.
The device is manufactured using Atmel’s high-density nonvolatile memory technology.
The On-chip ISP Flash allows the program memory to be reprogrammed in-system
through an SPI serial interface, by a conventional nonvolatile memory programmer, or
by an On-chip Boot program running on the AVR core. The boot program can use any
interface to download the application program in the application Flash memory. Software in the Boot Flash section will continue to run while the Application Flash section is
updated, providing true Read-While-Write operation. By combining an 8-bit RISC CPU
with In-System Self-Programmable Flash on a monolithic chip, the Atmel AT90PWM2/3
is a powerful microcontroller that provides a highly flexible and cost effective solution to
many embedded control applications.
The AT90PWM2/3 AVR is supported with a full suite of program and system development tools including: C compilers, macro assemblers, program debugger/simulators, incircuit emulators, and evaluation kits.
9
4317B–AVR–02/05
Pin Descriptions
VCC
Digital supply voltage.
GND
Ground.
Port B (PB7..PB0)
Port B is an 8-bit bi-directional I/O port with internal pull-up resistors (selected for each
bit). The Port B output buffers have symmetrical drive characteristics with both high sink
and source capability. As inputs, Port B pins that are externally pulled low will source
current if the pull-up resistors are activated. The Port B pins are tri-stated when a reset
condition becomes active, even if the clock is not running.
Port B also serves the functions of various special features of the AT90PWM2/3 as
listed on page 70.
Port C (PC7..PC0)
Port C is an 8-bit bi-directional I/O port with internal pull-up resistors (selected for each
bit). The Port C output buffers have symmetrical drive characteristics with both high sink
and source capability. As inputs, Port C pins that are externally pulled low will source
current if the pull-up resistors are activated. The Port C pins are tri-stated when a reset
condition becomes active, even if the clock is not running.
Port C is not available on 24 pins package.
Port C also serves the functions of special features of the AT90PWM2/3 as listed on
page 73.
Port D (PD7..PD0)
Port D is an 8-bit bi-directional I/O port with internal pull-up resistors (selected for each
bit). The Port D output buffers have symmetrical drive characteristics with both high sink
and source capability. As inputs, Port D pins that are externally pulled low will source
current if the pull-up resistors are activated. The Port D pins are tri-stated when a reset
condition becomes active, even if the clock is not running.
Port D also serves the functions of various special features of the AT90PWM2/3 as
listed on page 75.
Port E (PE2..0) RESET/ XTAL1/ Port E is an 3-bit bi-directional I/O port with internal pull-up resistors (selected for each
XTAL2
bit). The Port E output buffers have symmetrical drive characteristics with both high sink
and source capability. As inputs, Port E pins that are externally pulled low will source
current if the pull-up resistors are activated. The Port E pins are tri-stated when a reset
condition becomes active, even if the clock is not running.
If the RSTDISBL Fuse is programmed, PE0 is used as an I/O pin. Note that the electrical characteristics of PE0 differ from those of the other pins of Port C.
If the RSTDISBL Fuse is unprogrammed, PE0 is used as a Reset input. A low level on
this pin for longer than the minimum pulse length will generate a Reset, even if the clock
is not running. The minimum pulse length is given in Table 14 on page 45. Shorter
pulses are not guaranteed to generate a Reset.
Depending on the clock selection fuse settings, PE1 can be used as input to the inverting Oscillator amplifier and input to the internal clock operating circuit.
Depending on the clock selection fuse settings, PE2 can be used as output from the
inverting Oscillator amplifier.
10
AT90PWM2/3
4317B–AVR–02/05
AT90PWM2/3
The various special features of Port E are elaborated in “Alternate Functions of Port E”
on page 78 and “Clock Systems and their Distribution” on page 30.
AVCC
AVCC is the supply voltage pin for the A/D Converter on Port F. It should be externally
connected to VCC, even if the ADC is not used. If the ADC is used, it should be connected to VCC through a low-pass filter.
AREF
This is the analog reference pin for the A/D Converter.
About Code Examples
This documentation contains simple code examples that briefly show how to use various
parts of the device. These code examples assume that the part specific header file is
included before compilation. Be aware that not all C compiler vendors include bit definitions in the header files and interrupt handling in C is compiler dependent. Please
confirm with the C compiler documentation for more details.
11
4317B–AVR–02/05
AVR CPU Core
Introduction
This section discusses the AVR core architecture in general. The main function of the
CPU core is to ensure correct program execution. The CPU must therefore be able to
access memories, perform calculations, control peripherals, and handle interrupts.
Architectural Overview
Figure 5. Block Diagram of the AVR Architecture
Data Bus 8-bit
Flash
Program
Memory
Program
Counter
Status
and Control
32 x 8
General
Purpose
Registrers
Control Lines
Direct Addressing
Instruction
Decoder
Indirect Addressing
Instruction
Register
Interrupt
Unit
SPI
Unit
Watchdog
Timer
ALU
Analog
Comparator
I/O Module1
Data
SRAM
I/O Module 2
I/O Module n
EEPROM
I/O Lines
In order to maximize performance and parallelism, the AVR uses a Harvard architecture
– with separate memories and buses for program and data. Instructions in the program
memory are executed with a single level pipelining. While one instruction is being executed, the next instruction is pre-fetched from the program memory. This concept
enables instructions to be executed in every clock cycle. The program memory is InSystem Reprogrammable Flash memory.
The fast-access Register File contains 32 x 8-bit general purpose working registers with
a single clock cycle access time. This allows single-cycle Arithmetic Logic Unit (ALU)
operation. In a typical ALU operation, two operands are output from the Register File,
12
AT90PWM2/3
4317B–AVR–02/05
AT90PWM2/3
the operation is executed, and the result is stored back in the Register File – in one
clock cycle.
Six of the 32 registers can be used as three 16-bit indirect address register pointers for
Data Space addressing – enabling efficient address calculations. One of the these
address pointers can also be used as an address pointer for look up tables in Flash program memory. These added function registers are the 16-bit X-, Y-, and Z-register,
described later in this section.
The ALU supports arithmetic and logic operations between registers or between a constant and a register. Single register operations can also be executed in the ALU. After
an arithmetic operation, the Status Register is updated to reflect information about the
result of the operation.
Program flow is provided by conditional and unconditional jump and call instructions,
able to directly address the whole address space. Most AVR instructions have a single
16-bit word format. Every program memory address contains a 16- or 32-bit instruction.
Program Flash memory space is divided in two sections, the Boot Program section and
the Application Program section. Both sections have dedicated Lock bits for write and
read/write protection. The SPM (Store Program Memory) instruction that writes into the
Application Flash memory section must reside in the Boot Program section.
During interrupts and subroutine calls, the return address Program Counter (PC) is
stored on the Stack. The Stack is effectively allocated in the general data SRAM, and
consequently the Stack size is only limited by the total SRAM size and the usage of the
SRAM. All user programs must initialize the SP in the Reset routine (before subroutines
or interrupts are executed). The Stack Pointer (SP) is read/write accessible in the I/O
space. The data SRAM can easily be accessed through the five different addressing
modes supported in the AVR architecture.
The memory spaces in the AVR architecture are all linear and regular memory maps.
A flexible interrupt module has its control registers in the I/O space with an additional
Global Interrupt Enable bit in the Status Register. All interrupts have a separate Interrupt
Vector in the Interrupt Vector table. The interrupts have priority in accordance with their
Interrupt Vector position. The lower the Interrupt Vector address, the higher is the
priority.
The I/O memory space contains 64 addresses for CPU peripheral functions as Control
Registers, SPI, and other I/O functions. The I/O Memory can be accessed directly, or as
the Data Space locations following those of the Register File, 0x20 - 0x5F. In addition,
the AT90PWM2/3 has Extended I/O space from 0x60 - 0xFF in SRAM where only the
ST/STS/STD and LD/LDS/LDD instructions can be used.
ALU – Arithmetic Logic
Unit
The high-performance AVR ALU operates in direct connection with all the 32 general
purpose working registers. Within a single clock cycle, arithmetic operations between
general purpose registers or between a register and an immediate are executed. The
ALU operations are divided into three main categories – arithmetic, logical, and bit-functions. Some implementations of the architecture also provide a powerful multiplier
supporting both signed/unsigned multiplication and fractional format. See the “Instruction Set” section for a detailed description.
13
4317B–AVR–02/05
Status Register
The Status Register contains information about the result of the most recently executed
arithmetic instruction. This information can be used for altering program flow in order to
perform conditional operations. Note that the Status Register is updated after all ALU
operations, as specified in the Instruction Set Reference. This will in many cases
remove the need for using the dedicated compare instructions, resulting in faster and
more compact code.
The Status Register is not automatically stored when entering an interrupt routine and
restored when returning from an interrupt. This must be handled by software.
The AVR Status Register – SREG – is defined as:
Bit
7
6
5
4
3
2
1
0
I
T
H
S
V
N
Z
C
Read/Write
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
Initial Value
0
0
0
0
0
0
0
0
SREG
• Bit 7 – I: Global Interrupt Enable
The Global Interrupt Enable bit must be set to enabled the interrupts. The individual
interrupt enable control is then performed in separate control registers. If the Global
Interrupt Enable Register is cleared, none of the interrupts are enabled independent of
the individual interrupt enable settings. The I-bit is cleared by hardware after an interrupt
has occurred, and is set by the RETI instruction to enable subsequent interrupts. The Ibit can also be set and cleared by the application with the SEI and CLI instructions, as
described in the instruction set reference.
• Bit 6 – T: Bit Copy Storage
The Bit Copy instructions BLD (Bit LoaD) and BST (Bit STore) use the T-bit as source or
destination for the operated bit. A bit from a register in the Register File can be copied
into T by the BST instruction, and a bit in T can be copied into a bit in a register in the
Register File by the BLD instruction.
• Bit 5 – H: Half Carry Flag
The Half Carry Flag H indicates a Half Carry in some arithmetic operations. Half Carry Is
useful in BCD arithmetic. See the “Instruction Set Description” for detailed information.
• Bit 4 – S: Sign Bit, S = N
⊕V
The S-bit is always an exclusive or between the negative flag N and the Two’s Complement Overflow Flag V. See the “Instruction Set Description” for detailed information.
• Bit 3 – V: Two’s Complement Overflow Flag
The Two’s Complement Overflow Flag V supports two’s complement arithmetics. See
the “Instruction Set Description” for detailed information.
• Bit 2 – N: Negative Flag
The Negative Flag N indicates a negative result in an arithmetic or logic operation. See
the “Instruction Set Description” for detailed information.
• Bit 1 – Z: Zero Flag
The Zero Flag Z indicates a zero result in an arithmetic or logic operation. See the
“Instruction Set Description” for detailed information.
• Bit 0 – C: Carry Flag
The Carry Flag C indicates a carry in an arithmetic or logic operation. See the “Instruction Set Description” for detailed information.
14
AT90PWM2/3
4317B–AVR–02/05
AT90PWM2/3
General Purpose
Register File
The Register File is optimized for the AVR Enhanced RISC instruction set. In order to
achieve the required performance and flexibility, the following input/output schemes are
supported by the Register File:
•
One 8-bit output operand and one 8-bit result input
•
Two 8-bit output operands and one 8-bit result input
•
Two 8-bit output operands and one 16-bit result input
•
One 16-bit output operand and one 16-bit result input
Figure 6 shows the structure of the 32 general purpose working registers in the CPU.
Figure 6. AVR CPU General Purpose Working Registers
7
0
Addr.
R0
0x00
R1
0x01
R2
0x02
…
R13
0x0D
General
R14
0x0E
Purpose
R15
0x0F
Working
R16
0x10
Registers
R17
0x11
…
R26
0x1A
X-register Low Byte
R27
0x1B
X-register High Byte
R28
0x1C
Y-register Low Byte
R29
0x1D
Y-register High Byte
R30
0x1E
Z-register Low Byte
R31
0x1F
Z-register High Byte
Most of the instructions operating on the Register File have direct access to all registers,
and most of them are single cycle instructions.
As shown in Figure 6, each register is also assigned a data memory address, mapping
them directly into the first 32 locations of the user Data Space. Although not being physically implemented as SRAM locations, this memory organization provides great
flexibility in access of the registers, as the X-, Y- and Z-pointer registers can be set to
index any register in the file.
15
4317B–AVR–02/05
The X-register, Y-register, and
Z-register
The registers R26..R31 have some added functions to their general purpose usage.
These registers are 16-bit address pointers for indirect addressing of the data space.
The three indirect address registers X, Y, and Z are defined as described in Figure 7.
Figure 7. The X-, Y-, and Z-registers
15
X-register
XH
XL
7
0
R27 (0x1B)
YH
YL
7
0
R29 (0x1D)
Z-register
0
R26 (0x1A)
15
Y-register
0
7
0
7
0
R28 (0x1C)
15
ZH
7
0
ZL
7
R31 (0x1F)
0
0
R30 (0x1E)
In the different addressing modes these address registers have functions as fixed displacement, automatic increment, and automatic decrement (see the instruction set
reference for details).
Stack Pointer
The Stack is mainly used for storing temporary data, for storing local variables and for
storing return addresses after interrupts and subroutine calls. The Stack Pointer Register always points to the top of the Stack. Note that the Stack is implemented as growing
from higher memory locations to lower memory locations. This implies that a Stack
PUSH command decreases the Stack Pointer.
The Stack Pointer points to the data SRAM Stack area where the Subroutine and Interrupt Stacks are located. This Stack space in the data SRAM must be defined by the
program before any subroutine calls are executed or interrupts are enabled. The Stack
Pointer must be set to point above 0x100. The Stack Pointer is decremented by one
when data is pushed onto the Stack with the PUSH instruction, and it is decremented by
two when the return address is pushed onto the Stack with subroutine call or interrupt.
The Stack Pointer is incremented by one when data is popped from the Stack with the
POP instruction, and it is incremented by two when data is popped from the Stack with
return from subroutine RET or return from interrupt RETI.
The AVR Stack Pointer is implemented as two 8-bit registers in the I/O space. The number of bits actually used is implementation dependent. Note that the data space in some
implementations of the AVR architecture is so small that only SPL is needed. In this
case, the SPH Register will not be present.
Bit
Read/Write
Initial Value
Instruction Execution
Timing
16
15
14
13
12
11
10
9
8
SP15
SP14
SP13
SP12
SP11
SP10
SP9
SP8
SPH
SP7
SP6
SP5
SP4
SP3
SP2
SP1
SP0
SPL
7
6
5
4
3
2
1
0
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
This section describes the general access timing concepts for instruction execution. The
AVR CPU is driven by the CPU clock clkCPU, directly generated from the selected clock
source for the chip. No internal clock division is used.
AT90PWM2/3
4317B–AVR–02/05
AT90PWM2/3
Figure 8 shows the parallel instruction fetches and instruction executions enabled by the
Harvard architecture and the fast-access Register File concept. This is the basic pipelining concept to obtain up to 1 MIPS per MHz with the corresponding unique results for
functions per cost, functions per clocks, and functions per power-unit.
Figure 8. The Parallel Instruction Fetches and Instruction Executions
T1
T2
T3
T4
clkCPU
1st Instruction Fetch
1st Instruction Execute
2nd Instruction Fetch
2nd Instruction Execute
3rd Instruction Fetch
3rd Instruction Execute
4th Instruction Fetch
Figure 9 shows the internal timing concept for the Register File. In a single clock cycle
an ALU operation using two register operands is executed, and the result is stored back
to the destination register.
Figure 9. Single Cycle ALU Operation
T1
T2
T3
T4
clkCPU
Total Execution Time
Register Operands Fetch
ALU Operation Execute
Result Write Back
Reset and Interrupt
Handling
The AVR provides several different interrupt sources. These interrupts and the separate
Reset Vector each have a separate program vector in the program memory space. All
interrupts are assigned individual enable bits which must be written logic one together
with the Global Interrupt Enable bit in the Status Register in order to enable the interrupt.
Depending on the Program Counter value, interrupts may be automatically disabled
when Boot Lock bits BLB02 or BLB12 are programmed. This feature improves software
security. See the section “Memory Programming” on page 287 for details.
The lowest addresses in the program memory space are by default defined as the Reset
and Interrupt Vectors. The complete list of vectors is shown in “Interrupts” on page 56.
The list also determines the priority levels of the different interrupts. The lower the
address the higher is the priority level. RESET has the highest priority, and next is PSC2
CAPT – the PSC2 Capture Event. The Interrupt Vectors can be moved to the start of the
Boot Flash section by setting the IVSEL bit in the MCU Control Register (MCUCR).
Refer to “Interrupts” on page 56 for more information. The Reset Vector can also be
moved to the start of the Boot Flash section by programming the BOOTRST Fuse, see
“Boot Loader Support – Read-While-Write Self-Programming” on page 273.
17
4317B–AVR–02/05
Interrupt Behavior
When an interrupt occurs, the Global Interrupt Enable I-bit is cleared and all interrupts
are disabled. The user software can write logic one to the I-bit to enable nested interrupts. All enabled interrupts can then interrupt the current interrupt routine. The I-bit is
automatically set when a Return from Interrupt instruction – RETI – is executed.
There are basically two types of interrupts. The first type is triggered by an event that
sets the interrupt flag. For these interrupts, the Program Counter is vectored to the
actual Interrupt Vector in order to execute the interrupt handling routine, and hardware
clears the corresponding interrupt flag. Interrupt flags can also be cleared by writing a
logic one to the flag bit position(s) to be cleared. If an interrupt condition occurs while the
corresponding interrupt enable bit is cleared, the interrupt flag will be set and remembered until the interrupt is enabled, or the flag is cleared by software. Similarly, if one or
more interrupt conditions occur while the Global Interrupt Enable bit is cleared, the corresponding interrupt flag(s) will be set and remembered until the Global Interrupt Enable
bit is set, and will then be executed by order of priority.
The second type of interrupts will trigger as long as the interrupt condition is present.
These interrupts do not necessarily have interrupt flags. If the interrupt condition disappears before the interrupt is enabled, the interrupt will not be triggered.
When the AVR exits from an interrupt, it will always return to the main program and execute one more instruction before any pending interrupt is served.
Note that the Status Register is not automatically stored when entering an interrupt routine, nor restored when returning from an interrupt routine. This must be handled by
software.
When using the CLI instruction to disable interrupts, the interrupts will be immediately
disabled. No interrupt will be executed after the CLI instruction, even if it occurs simultaneously with the CLI instruction. The following example shows how this can be used to
avoid interrupts during the timed EEPROM write sequence..
Assembly Code Example
in r16, SREG
; store SREG value
cli
; disable interrupts during timed sequence
sbi EECR, EEMWE
; start EEPROM write
sbi EECR, EEWE
out SREG, r16
; restore SREG value (I-bit)
C Code Example
char cSREG;
cSREG = SREG;
/* store SREG value */
/* disable interrupts during timed sequence */
_CLI();
EECR |= (1<<EEMWE); /* start EEPROM write */
EECR |= (1<<EEWE);
SREG = cSREG;
/* restore SREG value (I-bit) */
When using the SEI instruction to enable interrupts, the instruction following SEI will be
executed before any pending interrupts, as shown in this example.
Assembly Code Example
18
AT90PWM2/3
4317B–AVR–02/05
AT90PWM2/3
sei
; set Global Interrupt Enable
sleep; enter sleep, waiting for interrupt
; note: will enter sleep before any pending
; interrupt(s)
C Code Example
_SEI(); /* set Global Interrupt Enable */
_SLEEP(); /* enter sleep, waiting for interrupt */
/* note: will enter sleep before any pending interrupt(s) */
Interrupt Response Time
The interrupt execution response for all the enabled AVR interrupts is four clock cycles
minimum. After four clock cycles the program vector address for the actual interrupt
handling routine is executed. During this four clock cycle period, the Program Counter is
pushed onto the Stack. The vector is normally a jump to the interrupt routine, and this
jump takes three clock cycles. If an interrupt occurs during execution of a multi-cycle
instruction, this instruction is completed before the interrupt is served. If an interrupt
occurs when the MCU is in sleep mode, the interrupt execution response time is
increased by four clock cycles. This increase comes in addition to the start-up time from
the selected sleep mode.
A return from an interrupt handling routine takes four clock cycles. During these four
clock cycles, the Program Counter (two bytes) is popped back from the Stack, the Stack
Pointer is incremented by two, and the I-bit in SREG is set.
19
4317B–AVR–02/05
Memories
This section describes the different memories in the AT90PWM2/3. The AVR architecture has two main memory spaces, the Data Memory and the Program Memory space.
In addition, the AT90PWM2/3 features an EEPROM Memory for data storage. All three
memory spaces are linear and regular.
In-System
Reprogrammable Flash
Program Memory
The AT90PWM2/3 contains 8K bytes On-chip In-System Reprogrammable Flash memory for program storage. Since all AVR instructions are 16 or 32 bits wide, the Flash is
organized as 4K x 16. For software security, the Flash Program memory space is
divided into two sections, Boot Program section and Application Program section.
The Flash memory has an endurance of at least 10,000 write/erase cycles. The
AT90PWM2/3 Program Counter (PC) is 12 bits wide, thus addressing the 4K program
memory locations. The operation of Boot Program section and associated Boot Lock
bits for software protection are described in detail in “Boot Loader Support – ReadWhile-Write Self-Programming” on page 273. “Memory Programming” on page 287 contains a detailed description on Flash programming in SPI or Parallel programming
mode.
Constant tables can be allocated within the entire program memory address space (see
the LPM – Load Program Memory.
Timing diagrams for instruction fetch and execution are presented in “Instruction Execution Timing” on page 16.
Figure 10. Program Memory Map
Program Memory
0x0000
Application Flash Section
Boot Flash Section
0x0FFF
20
AT90PWM2/3
4317B–AVR–02/05
AT90PWM2/3
SRAM Data Memory
Figure 11 shows how the AT90PWM2/3 SRAM Memory is organized.
The AT90PWM2/3 is a complex microcontroller with more peripheral units than can be
supported within the 64 locations reserved in the Opcode for the IN and OUT instructions. For the Extended I/O space from 0x60 - 0xFF in SRAM, only the ST/STS/STD and
LD/LDS/LDD instructions can be used.
The lower 768 data memory locations address both the Register File, the I/O memory,
Extended I/O memory, and the internal data SRAM. The first 32 locations address the
Register File, the next 64 location the standard I/O memory, then 160 locations of
Extended I/O memory, and the next 512 locations address the internal data SRAM.
The five different addressing modes for the data memory cover: Direct, Indirect with Displacement, Indirect, Indirect with Pre-decrement, and Indirect with Post-increment. In
the Register File, registers R26 to R31 feature the indirect addressing pointer registers.
The direct addressing reaches the entire data space.
The Indirect with Displacement mode reaches 63 address locations from the base
address given by the Y- or Z-register.
When using register indirect addressing modes with automatic pre-decrement and postincrement, the address registers X, Y, and Z are decremented or incremented.
The 32 general purpose working registers, 64 I/O Registers, 160 Extended I/O Registers, and the 512 bytes of internal data SRAM in the AT90PWM2/3 are all accessible
through all these addressing modes. The Register File is described in “General Purpose
Register File” on page 15.
Figure 11. Data Memory Map
Data Memory
32 Registers
64 I/O Registers
160 Ext I/O Reg.
0x0000 - 0x001F
0x0020 - 0x005F
0x0060 - 0x00FF
0x0100
Internal SRAM
(512 x 8)
0x02FF
SRAM Data Access Times
This section describes the general access timing concepts for internal memory access.
The internal data SRAM access is performed in two clkCPU cycles as described in Figure
12.
21
4317B–AVR–02/05
Figure 12. On-chip Data SRAM Access Cycles
T1
T2
T3
clkCPU
Address
Compute Address
Address valid
Write
Data
WR
Read
Data
RD
Memory Access Instruction
22
Next Instruction
AT90PWM2/3
4317B–AVR–02/05
AT90PWM2/3
EEPROM Data Memory
The AT90PWM2/3 contains 512 bytes of data EEPROM memory. It is organized as a
separate data space, in which single bytes can be read and written. The EEPROM has
an endurance of at least 100,000 write/erase cycles. The access between the EEPROM
and the CPU is described in the following, specifying the EEPROM Address Registers,
the EEPROM Data Register, and the EEPROM Control Register.
For a detailed description of SPI and Parallel data downloading to the EEPROM, see
“Serial Downloading” on page 304 , and “Parallel Programming Parameters, Pin Mapping, and Commands” on page 292 respectively.
EEPROM Read/Write Access
The EEPROM Access Registers are accessible in the I/O space.
The write access time for the EEPROM is given in Table 2. A self-timing function, however, lets the user software detect when the next byte can be written. If the user code
contains instructions that write the EEPROM, some precautions must be taken. In
heavily filtered power supplies, VCC is likely to rise or fall slowly on power-up/down. This
causes the device for some period of time to run at a voltage lower than specified as
minimum for the clock frequency used. See “Preventing EEPROM Corruption” on page
27.for details on how to avoid problems in these situations.
In order to prevent unintentional EEPROM writes, a specific write procedure must be followed. Refer to the description of the EEPROM Control Register for details on this.
When the EEPROM is read, the CPU is halted for four clock cycles before the next
instruction is executed. When the EEPROM is written, the CPU is halted for two clock
cycles before the next instruction is executed.
The EEPROM Address
Registers – EEARH and
EEARL
Bit
Read/Write
Initial Value
15
14
13
12
11
10
9
8
–
–
–
–
–
–
–
EEAR8
EEARH
EEAR7
EEAR6
EEAR5
EEAR4
EEAR3
EEAR2
EEAR1
EEAR0
EEARL
7
6
5
4
3
2
1
0
R
R
R
R
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
0
0
0
0
X
X
X
X
X
X
X
X
X
X
X
X
• Bits 15..9 – Reserved Bits
These bits are reserved bits in the AT90PWM2/3 and will always read as zero.
• Bits 8..0 – EEAR8..0: EEPROM Address
The EEPROM Address Registers – EEARH and EEARL specify the EEPROM address
in the 512 bytes EEPROM space. The EEPROM data bytes are addressed linearly
between 0 and 511. The initial value of EEAR is undefined. A proper value must be written before the EEPROM may be accessed.
The EEPROM Data Register –
EEDR
Bit
7
6
5
4
3
2
1
0
EEDR7
EEDR6
EEDR5
EEDR4
EEDR3
EEDR2
EEDR1
EEDR0
Read/Write
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
Initial Value
0
0
0
0
0
0
0
0
EEDR
• Bits 7..0 – EEDR7.0: EEPROM Data
For the EEPROM write operation, the EEDR Register contains the data to be written to
the EEPROM in the address given by the EEAR Register. For the EEPROM read oper23
4317B–AVR–02/05
ation, the EEDR contains the data read out from the EEPROM at the address given by
EEAR.
The EEPROM Control
Register – EECR
Bit
7
6
5
4
3
2
1
0
–
–
–
–
EERIE
EEMWE
EEWE
EERE
Read/Write
R
R
R
R
R/W
R/W
R/W
R/W
Initial Value
0
0
0
0
0
0
X
0
EECR
• Bits 7..4 – Reserved Bits
These bits are reserved bits in the AT90PWM2/3 and will always read as zero.
• Bit 3 – EERIE: EEPROM Ready Interrupt Enable
Writing EERIE to one enables the EEPROM Ready Interrupt if the I bit in SREG is set.
Writing EERIE to zero disables the interrupt. The EEPROM Ready interrupt generates a
constant interrupt when EEWE is cleared.
• Bit 2 – EEMWE: EEPROM Master Write Enable
The EEMWE bit determines whether setting EEWE to one causes the EEPROM to be
written. When EEMWE is set, setting EEWE within four clock cycles will write data to the
EEPROM at the selected address If EEMWE is zero, setting EEWE will have no effect.
When EEMWE has been written to one by software, hardware clears the bit to zero after
four clock cycles. See the description of the EEWE bit for an EEPROM write procedure.
• Bit 1 – EEWE: EEPROM Write Enable
The EEPROM Write Enable Signal EEWE is the write strobe to the EEPROM. When
address and data are correctly set up, the EEWE bit must be written to one to write the
value into the EEPROM. The EEMWE bit must be written to one before a logical one is
written to EEWE, otherwise no EEPROM write takes place. The following procedure
should be followed when writing the EEPROM (the order of steps 3 and 4 is not
essential):
1. Wait until EEWE becomes zero.
2. Wait until SPMEN (Store Program Memory Enable) in SPMCSR (Store Program
Memory Control and Status Register) becomes zero.
3. Write new EEPROM address to EEAR (optional).
4. Write new EEPROM data to EEDR (optional).
5. Write a logical one to the EEMWE bit while writing a zero to EEWE in EECR.
6. Within four clock cycles after setting EEMWE, write a logical one to EEWE.
The EEPROM can not be programmed during a CPU write to the Flash memory. The
software must check that the Flash programming is completed before initiating a new
EEPROM write. Step 2 is only relevant if the software contains a Boot Loader allowing
the CPU to program the Flash. If the Flash is never being updated by the CPU, step 2
can be omitted. See “Boot Loader Support – Read-While-Write Self-Programming” on
page 273 for details about Boot programming.
Caution: An interrupt between step 5 and step 6 will make the write cycle fail, since the
EEPROM Master Write Enable will time-out. If an interrupt routine accessing the
EEPROM is interrupting another EEPROM access, the EEAR or EEDR Register will be
modified, causing the interrupted EEPROM access to fail. It is recommended to have
the Global Interrupt Flag cleared during all the steps to avoid these problems.
When the write access time has elapsed, the EEWE bit is cleared by hardware. The
user software can poll this bit and wait for a zero before writing the next byte. When
24
AT90PWM2/3
4317B–AVR–02/05
AT90PWM2/3
EEWE has been set, the CPU is halted for two cycles before the next instruction is
executed.
• Bit 0 – EERE: EEPROM Read Enable
The EEPROM Read Enable Signal EERE is the read strobe to the EEPROM. When the
correct address is set up in the EEAR Register, the EERE bit must be written to a logic
one to trigger the EEPROM read. The EEPROM read access takes one instruction, and
the requested data is available immediately. When the EEPROM is read, the CPU is
halted for four cycles before the next instruction is executed.
The user should poll the EEWE bit before starting the read operation. If a write operation
is in progress, it is neither possible to read the EEPROM, nor to change the EEAR
Register.
The calibrated Oscillator is used to time the EEPROM accesses. Table 2 lists the typical
programming time for EEPROM access from the CPU.
Table 2. EEPROM Programming Time.
Symbol
EEPROM write
(from CPU)
Note:
Number of Calibrated RC Oscillator Cycles
Typ Programming Time
67 584
8.5 ms
1. Uses 1 MHz clock, independent of CKSEL Fuse settings.
25
4317B–AVR–02/05
The following code examples show one assembly and one C function for writing to the
EEPROM. The examples assume that interrupts are controlled (e.g. by disabling interrupts globally) so that no interrupts will occur during execution of these functions. The
examples also assume that no Flash Boot Loader is present in the software. If such
code is present, the EEPROM write function must also wait for any ongoing SPM command to finish.
Assembly Code Example
EEPROM_write:
; Wait for completion of previous write
sbic EECR,EEWE
rjmp EEPROM_write
; Set up address (r18:r17) in address register
out EEARH, r18
out EEARL, r17
; Write data (r16) to data register
out EEDR,r16
; Write logical one to EEMWE
sbi EECR,EEMWE
; Start eeprom write by setting EEWE
sbi EECR,EEWE
ret
C Code Example
void EEPROM_write (unsigned int uiAddress, unsigned char ucData)
{
/* Wait for completion of previous write */
while(EECR & (1<<EEWE))
;
/* Set up address and data registers */
EEAR = uiAddress;
EEDR = ucData;
/* Write logical one to EEMWE */
EECR |= (1<<EEMWE);
/* Start eeprom write by setting EEWE */
EECR |= (1<<EEWE);
}
26
AT90PWM2/3
4317B–AVR–02/05
AT90PWM2/3
The next code examples show assembly and C functions for reading the EEPROM. The
examples assume that interrupts are controlled so that no interrupts will occur during
execution of these functions.
Assembly Code Example
EEPROM_read:
; Wait for completion of previous write
sbic EECR,EEWE
rjmp EEPROM_read
; Set up address (r18:r17) in address register
out EEARH, r18
out EEARL, r17
; Start eeprom read by writing EERE
sbi EECR,EERE
; Read data from data register
in
r16,EEDR
ret
C Code Example
unsigned char EEPROM_read(unsigned int uiAddress)
{
/* Wait for completion of previous write */
while(EECR & (1<<EEWE))
;
/* Set up address register */
EEAR = uiAddress;
/* Start eeprom read by writing EERE */
EECR |= (1<<EERE);
/* Return data from data register */
return EEDR;
}
Preventing EEPROM
Corruption
During periods of low VCC, the EEPROM data can be corrupted because the supply voltage is too low for the CPU and the EEPROM to operate properly. These issues are the
same as for board level systems using EEPROM, and the same design solutions should
be applied.
An EEPROM data corruption can be caused by two situations when the voltage is too
low. First, a regular write sequence to the EEPROM requires a minimum voltage to
operate correctly. Secondly, the CPU itself can execute instructions incorrectly, if the
supply voltage is too low.
E EP R O M da ta c o r r up ti on ca n e as i l y b e av o id ed by fo ll o wi ng t hi s de si g n
recommendation:
Keep the AVR RESET active (low) during periods of insufficient power supply voltage.
This can be done by enabling the internal Brown-out Detector (BOD). If the detection
level of the internal BOD does not match the needed detection level, an external low
VCC reset Protection circuit can be used. If a reset occurs while a write operation is in
progress, the write operation will be completed provided that the power supply voltage is
sufficient.
27
4317B–AVR–02/05
I/O Memory
The I/O space definition of the AT90PWM2/3 is shown in “Register Summary” on page
348.
All AT90PWM2/3 I/Os and peripherals are placed in the I/O space. All I/O locations may
be accessed by the LD/LDS/LDD and ST/STS/STD instructions, transferring data
between the 32 general purpose working registers and the I/O space. I/O registers
within the address range 0x00 - 0x1F are directly bit-accessible using the SBI and CBI
instructions. In these registers, the value of single bits can be checked by using the
SBIS and SBIC instructions. Refer to the instruction set section for more details. When
using the I/O specific commands IN and OUT, the I/O addresses 0x00 - 0x3F must be
used. When addressing I/O registers as data space using LD and ST instructions, 0x20
must be added to these addresses. The AT90PWM2/3 is a complex microcontroller with
more peripheral units than can be supported within the 64 location reserved in Opcode
for the IN and OUT instructions. For the Extended I/O space from 0x60 - 0xFF in SRAM,
only the ST/STS/STD and LD/LDS/LDD instructions can be used.
For compatibility with future devices, reserved bits should be written to zero if accessed.
Reserved I/O memory addresses should never be written.
Some of the status flags are cleared by writing a logical one to them. Note that, unlike
most other AVR’s, the CBI and SBI instructions will only operate on the specified bit, and
can therefore be used on registers containing such status flags. The CBI and SBI
instructions work with registers 0x00 to 0x1F only.
The I/O and peripherals control registers are explained in later sections.
28
AT90PWM2/3
4317B–AVR–02/05
AT90PWM2/3
General Purpose I/O
Registers
The AT90PWM2/3 contains four General Purpose I/O Registers. These registers can be
used for storing any information, and they are particularly useful for storing global variables and status flags.
The General Purpose I/O Registers, within the address range 0x00 - 0x1F, are directly
bit-accessible using the SBI, CBI, SBIS, and SBIC instructions.
General Purpose I/O Register
0 – GPIOR0
Bit
7
6
5
4
3
2
1
0
GPIOR07 GPIOR06 GPIOR05 GPIOR04 GPIOR03 GPIOR02 GPIOR01 GPIOR00
General Purpose I/O Register
1 – GPIOR1
Read/Write
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
Initial Value
0
0
0
0
0
0
0
0
7
6
5
4
3
2
1
0
Bit
GPIOR17 GPIOR16 GPIOR15 GPIOR14 GPIOR13 GPIOR12 GPIOR11 GPIOR10
General Purpose I/O Register
2 – GPIOR2
Read/Write
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
Initial Value
0
0
0
0
0
0
0
0
7
6
5
4
3
2
1
0
Bit
GPIOR27 GPIOR26 GPIOR25 GPIOR24 GPIOR23 GPIOR22 GPIOR21 GPIOR20
General Purpose I/O Register
3– GPIOR3
Read/Write
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
Initial Value
0
0
0
0
0
0
0
0
7
6
5
4
3
2
1
0
Bit
GPIOR37 GPIOR36 GPIOR35 GPIOR34 GPIOR33 GPIOR32 GPIOR31 GPIOR30
Read/Write
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
Initial Value
0
0
0
0
0
0
0
0
GPIOR0
GPIOR1
GPIOR2
GPIOR3
29
4317B–AVR–02/05
System Clock
Clock Systems and their
Distribution
Figure 13 presents the principal clock systems in the AVR and their distribution. All of
the clocks need not be active at a given time. In order to reduce power consumption, the
clocks to unused modules can be halted by using different sleep modes, as described in
“Power Management and Sleep Modes” on page 39. The clock systems are detailed
below.
Figure 13. Clock Distribution
PSC0/1/2
General I/O
Modules
CLK PLL
ADC
CPU Core
RAM
Flash and
EEPROM
clkADC
PLL
clkI/O
clkCPU
AVR Clock
Control Unit
clkFLASH
Reset Logic
Source Clock
Clock
Multiplexer
External Clock
Watchdog Timer
Watchdog Clock
Watchdog
Oscillator
(Crystal
Oscillator)
Calibrated RC
Oscillator
CPU Clock – clkCPU
The CPU clock is routed to parts of the system concerned with operation of the AVR
core. Examples of such modules are the General Purpose Register File, the Status Register and the data memory holding the Stack Pointer. Halting the CPU clock inhibits the
core from performing general operations and calculations.
I/O Clock – clkI/O
The I/O clock is used by the majority of the I/O modules, like Timer/Counters, SPI,
USART. The I/O clock is also used by the External Interrupt module, but note that some
external interrupts are detected by asynchronous logic, allowing such interrupts to be
detected even if the I/O clock is halted.
Flash Clock – clkFLASH
The Flash clock controls operation of the Flash interface. The Flash clock is usually
active simultaneously with the CPU clock.
PLL Clock – clkPLL
The PLL clock allows the PSC modules to be clocked directly from a 64/32 MHz clock. A
16 MHz clock is also derived for the CPU.
30
AT90PWM2/3
4317B–AVR–02/05
AT90PWM2/3
ADC Clock – clkADC
The ADC is provided with a dedicated clock domain. This allows halting the CPU and
I/O clocks in order to reduce noise generated by digital circuitry. This gives more accurate ADC conversion results.
Clock Sources
The device has the following clock source options, selectable by Flash Fuse bits as illustrated Table 3. The clock from the selected source is input to the AVR clock generator,
and routed to the appropriate modules.
Table 3. Device Clocking Options Select(1)
Device Clocking Option
CKSEL3..0
External Crystal/Ceramic Resonator
1111 - 1000
PLL output divided by 4 : 16 MHz
0001
Calibrated Internal RC Oscillator
0010
External Clock
0000
Reserved
Note:
0111- 0100, 0011
1. For all fuses “1” means unprogrammed while “0” means programmed.
The various choices for each clocking option is given in the following sections. When the
CPU wakes up from Power-down or Power-save, the selected clock source is used to
time the start-up, ensuring stable Oscillator operation before instruction execution starts.
When the CPU starts from reset, there is an additional delay allowing the power to reach
a stable level before starting normal operation. The Watchdog Oscillator is used for timing this real-time part of the start-up time. The number of WDT Oscillator cycles used for
each time-out is shown in Table 4. The frequency of the Watchdog Oscillator is voltage
dependent as shown in “Watchdog Oscillator Frequency vs. VCC” on page 342.
Table 4. Number of Watchdog Oscillator Cycles
Default Clock Source
Typ Time-out (VCC = 5.0V)
Typ Time-out (VCC = 3.0V)
Number of Cycles
4.1 ms
4.3 ms
4K (4,096)
65 ms
69 ms
64K (65,536)
The device is shipped with CKSEL = “0010”, SUT = “10”, and CKDIV8 programmed.
The default clock source setting is the Internal RC Oscillator with longest start-up time
and an initial system clock prescaling of 8. This default setting ensures that all users can
make their desired clock source setting using an In-System or Parallel programmer.
31
4317B–AVR–02/05
Low Power Crystal
Oscillator
XTAL1 and XTAL2 are input and output, respectively, of an inverting amplifier which can
be configured for use as an On-chip Oscillator, as shown in Figure 14. Either a quartz
crystal or a ceramic resonator may be used.
This Crystal Oscillator is a low power oscillator, with reduced voltage swing on the
XTAL2 output. It gives the lowest power consumption, but is not capable of driving other
clock inputs.
C1 and C2 should always be equal for both crystals and resonators. The optimal value
of the capacitors depends on the crystal or resonator in use, the amount of stray capacitance, and the electromagnetic noise of the environment. Some initial guidelines for
choosing capacitors for use with crystals are given in Table 5. For ceramic resonators,
the capacitor values given by the manufacturer should be used. For more information on
how to choose capacitors and other details on Oscillator operation, refer to the Multipurpose Oscillator Application Note.
Figure 14. Crystal Oscillator Connections
C2
C1
XTAL2
XTAL1
GND
The Oscillator can operate in three different modes, each optimized for a specific frequency range. The operating mode is selected by the fuses CKSEL3..1 as shown in
Table 5.
Table 5. Crystal Oscillator Operating Modes
CKSEL3..1
Frequency Range(1) (MHz)
Recommended Range for Capacitors C1
and C2 for Use with Crystals (pF)
100(2)
0.4 - 0.9
–
101
0.9 - 3.0
12 - 22
110
3.0 - 8.0
12 - 22
111
8.0 -16.0
12 - 22
Notes:
1. The frequency ranges are preliminary values. Actual values are TBD.
2. This option should not be used with crystals, only with ceramic resonators.
The CKSEL0 Fuse together with the SUT1..0 Fuses select the start-up times as shown
in Table 6.
32
AT90PWM2/3
4317B–AVR–02/05
AT90PWM2/3
Table 6. Start-up Times for the Oscillator Clock Selection
CKSEL0
Additional Delay
from Reset
(VCC = 5.0V)
Recommended Usage
(1)
14CK + 4.1 ms
Ceramic resonator, fast
rising power
0
00
258 CK
0
01
258 CK(1)
14CK + 65 ms
Ceramic resonator,
slowly rising power
0
10
1K CK(2)
14CK
Ceramic resonator,
BOD enabled
0
11
1K CK(2)
14CK + 4.1 ms
Ceramic resonator, fast
rising power
1
00
1K CK(2)
14CK + 65 ms
Ceramic resonator,
slowly rising power
01
16K CK
14CK
Crystal Oscillator, BOD
enabled
10
16K CK
14CK + 4.1 ms
Crystal Oscillator, fast
rising power
11
16K CK
14CK + 65 ms
Crystal Oscillator,
slowly rising power
1
1
1
Notes:
Calibrated Internal RC
Oscillator
SUT1..0
Start-up Time from
Power-down and
Power-save
1. These options should only be used when not operating close to the maximum frequency of the device, and only if frequency stability at start-up is not important for the
application. These options are not suitable for crystals.
2. These options are intended for use with ceramic resonators and will ensure frequency stability at start-up. They can also be used with crystals when not operating
close to the maximum frequency of the device, and if frequency stability at start-up is
not important for the application.
The calibrated internal RC Oscillator by default provides a 8.0 MHz clock. The frequency
is nominal value at 3V and 25°C. The device is shipped with the CKDIV8 Fuse programmed. See “System Clock Prescaler” on page 37 for more details. This clock may
be selected as the system clock by programming the CKSEL Fuses as shown in Table
3. If selected, it will operate with no external components. During reset, hardware loads
the calibration byte into the OSCCAL Register and thereby automatically calibrates the
RC Oscillator. At 3V and 25°C, this calibration gives a frequency of 8 MHz ± 1%. The
oscillator can be calibrated to any frequency in the range 7.3 - 8.1 MHz within ±1%
accuracy, by changing the OSCCAL register. When this Oscillator is used as the chip
clock, the Watchdog Oscillator will still be used for the Watchdog Timer and for the
Reset Time-out. For more information on the pre-programmed calibration value, see the
section “Calibration Byte” on page 291.
Table 7. Internal Calibrated RC Oscillator Operating Modes(1)(3)
Notes:
Frequency Range(2) (MHz)
CKSEL3..0
7.3 - 8.1
0010
1. The device is shipped with this option selected.
2. The frequency ranges are preliminary values. Actual values are TBD.
3. If 8 MHz frequency exceeds the specification of the device (depends on VCC), the
CKDIV8 Fuse can be programmed in order to divide the internal frequency by 8.
33
4317B–AVR–02/05
When this Oscillator is selected, start-up times are determined by the SUT Fuses as
shown in Table 8 on page 34.
Table 8. Start-up times for the internal calibrated RC Oscillator clock selection
Start-up Time from Powerdown and Power-save
Power Conditions
BOD enabled
6 CK
Fast rising power
6 CK
Slowly rising power
Additional Delay from
Reset (VCC = 5.0V)
14CK
SUT1..0
(1)
00
14CK + 4.1 ms
01
(2)
6 CK
14CK + 65 ms
10
Reserved
Note:
11
1. If the RSTDISBL fuse is programmed, this start-up time will be increased to
14CK + 4.1 ms to ensure programming mode can be entered.
2. The device is shipped with this option selected.
Oscillator Calibration Register
– OSCCAL
Bit
Read/Write
Initial Value
7
6
5
4
3
2
1
0
CAL7
CAL6
CAL5
CAL4
CAL3
CAL2
CAL1
CAL0
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
OSCCAL
Device Specific Calibration Value
• Bits 7..0 – CAL7..0: Oscillator Calibration Value
The Oscillator Calibration Register is used to trim the Calibrated Internal RC Oscillator
to remove process variations from the oscillator frequency. The factory-calibrated value
is automatically written to this register during chip reset, giving an oscillator frequency of
8.0 MHz at 25°C. The application software can write this register to change the oscillator
frequency. The oscillator can be calibrated to any frequency in the range 7.3 - 8.1 MHz
within ±1% accuracy. Calibration outside that range is not guaranteed.
Note that this oscillator is used to time EEPROM and Flash write accesses, and these
write times will be affected accordingly. If the EEPROM or Flash are written, do not calibrate to more than 8.8 MHz. Otherwise, the EEPROM or Flash write may fail.
The CAL7 bit determines the range of operation for the oscillator. Setting this bit to 0
gives the lowest frequency range, setting this bit to 1 gives the highest frequency range.
The two frequency ranges are overlapping, in other words a setting of OSCCAL = 0x7F
gives a higher frequency than OSCCAL = 0x80.
The CAL6..0 bits are used to tune the frequency within the selected range. A setting of
0x00 gives the lowest frequency in that range, and a setting of 0x7F gives the highest
frequency in the range. Incrementing CAL6..0 by 1 will give a frequency increment of
less than 2% in the frequency range 7.3 - 8.1 MHz.
PLL
To generate high frequency and accurate PWM waveforms, the ‘PSC’s need high frequency clock input. This clock is generated by a PLL. To keep all PWM accuracy, the
frequency factor of PLL must be configurable by software. With a system clock of 8
MHz, the PLL output is 32Mhz or 64Mhz.
Internal PLL for PSC
The internal PLL in AT90PWM2/3 generates a clock frequency that is 64x multiplied
from nominally 1 MHz input. The source of the 1 MHz PLL input clock is the output of the
internal RC Oscillator which is divided down to 1 MHz. See the Figure 15 on page 35.
34
AT90PWM2/3
4317B–AVR–02/05
AT90PWM2/3
The PLL is locked on the RC Oscillator and adjusting the RC Oscillator via OSCCAL
Register will adjust the fast peripheral clock at the same time. However, even if the possibly divided RC Oscillator is taken to a higher frequency than 1 MHz, the fast peripheral
clock frequency saturates at 70 MHz (worst case) and remains oscillating at the maximum frequency. It should be noted that the PLL in this case is not locked any more with
the RC Oscillator clock.
Therefore it is recommended not to take the OSCCAL adjustments to a higher frequency than 1 MHz in order to keep the PLL in the correct operating range. The internal
PLL is enabled only when the PLLE bit in the register PLLCSR is set. The bit PLOCK
from the register PLLCSR is set when PLL is locked.
Both internal 1 MHz RC Oscillator and PLL are switched off in Power-down and Standby
sleep modes.
Figure 15. PCK Clocking System
OSCCAL
PLLF
PLLE
PLOCK
Lock
Detector
DIVIDE
BY 8
RC OSCILLATOR 8 MHz
PLL
64x
CLK PLL
DIVIDE
BY 2
DIVIDE
BY 4
CK SOURCE
XTAL1
XTAL2
PLL Control and Status
Register – PLLCSR
OSCILLATORS
Bit
7
6
5
4
3
2
1
0
$29 ($29)
–
–
–
–
–
PLLF
PLLE
PLOCK
Read/Write
R
R
R
R
R
R/W
R/W
R
Initial Value
0
0
0
0
0
0
0/1
0
PLLCSR
• Bit 7..3 – Res: Reserved Bits
These bits are reserved bits in the AT90PWM2/3 and always read as zero.
• Bit 2 – PLLF: PLL Factor
The PLLF bit is used to select the division factor of the PLL.
If PLLF is set, the PLL output is 64Mhz.
If PLLF is clear, the PLL output is 32Mhz.
• Bit 1 – PLLE: PLL Enable
When the PLLE is set, the PLL is started and if not yet started the internal RC Oscillator
is started as PLL reference clock. If PLL is selected as a system clock source the value
for this bit is always 1.
• Bit 0 – PLOCK: PLL Lock Detector
When the PLOCK bit is set, the PLL is locked to the reference clock, and it is safe to
enable CLKPLL for PSC. After the PLL is enabled, it takes about 100 ms for the PLL to
lock.
35
4317B–AVR–02/05
128 kHz Internal
Oscillator
The 128 kHz internal Oscillator is a low power Oscillator providing a clock of 128 kHz.
The frequency is nominal at 3V and 25°C. This clock is used by the Watchdog
Oscillator.
External Clock
To drive the device from an external clock source, XTAL1 should be driven as shown in
Figure 16. To run the device on an external clock, the CKSEL Fuses must be programmed to “0000”.
Figure 16. External Clock Drive Configuration
NC
XTAL2
External
Clock
Signal
XTAL1
GND
Table 9. External Clock Frequency
CKSEL3..0
Frequency Range
0000
0 - 16 MHz
When this clock source is selected, start-up times are determined by the SUT Fuses as
shown in Table 10.
Table 10. Start-up Times for the External Clock Selection
SUT1..0
Start-up Time from Powerdown and Power-save
Additional Delay from
Reset (VCC = 5.0V)
00
6 CK
14CK
01
6 CK
14CK + 4.1 ms
Fast rising power
10
6 CK
14CK + 65 ms
Slowly rising power
11
Recommended Usage
BOD enabled
Reserved
When applying an external clock, it is required to avoid sudden changes in the applied
clock frequency to ensure stable operation of the MCU. A variation in frequency of more
than 2% from one clock cycle to the next can lead to unpredictable behavior. It is
required to ensure that the MCU is kept in Reset during such changes in the clock
frequency.
Note that the System Clock Prescaler can be used to implement run-time changes of
the internal clock frequency while still ensuring stable operation. Refer to “System Clock
Prescaler” on page 37 for details.
Clock Output Buffer
36
When the CKOUT Fuse is programmed, the system Clock will be output on CLKO. This
mode is suitable when chip clock is used to drive other circuits on the system. The clock
will be output also during reset and the normal operation of I/O pin will be overridden
when the fuse is programmed. Any clock source, including internal RC Oscillator, can be
selected when CLKO serves as clock output. If the System Clock Prescaler is used, it is
the divided system clock that is output (CKOUT Fuse programmed).
AT90PWM2/3
4317B–AVR–02/05
AT90PWM2/3
System Clock Prescaler
The AT90PWM2/3 system clock can be divided by setting the Clock Prescale Register –
CLKPR. This feature can be used to decrease power consumption when the requirement for processing power is low. This can be used with all clock source options, and it
will affect the clock frequency of the CPU and all synchronous peripherals. clkI/O, clkADC,
clkCPU, and clkFLASH are divided by a factor as shown in Table 11.
When switching between prescaler settings, the System Clock Prescaler ensures that
no glitches occurs in the clock system. It also ensures that no intermediate frequency is
higher than neither the clock frequency corresponding to the previous setting, nor the
clock frequency corresponding to the new setting. The ripple counter that implements
the prescaler runs at the frequency of the undivided clock, which may be faster than the
CPU's clock frequency. Hence, it is not possible to determine the state of the prescaler even if it were readable, and the exact time it takes to switch from one clock division to
the other cannot be exactly predicted. From the time the CLKPS values are written, it
takes between T1 + T2 and T1 + 2 * T2 before the new clock frequency is active. In this
interval, 2 active clock edges are produced. Here, T1 is the previous clock period, and
T2 is the period corresponding to the new prescaler setting.
To avoid unintentional changes of clock frequency, a special write procedure must be
followed to change the CLKPS bits:
1. Write the Clock Prescaler Change Enable (CLKPCE) bit to one and all other bits
in CLKPR to zero.
2. Within four cycles, write the desired value to CLKPS while writing a zero to
CLKPCE.
Interrupts must be disabled when changing prescaler setting to make sure the write procedure is not interrupted.
Clock Prescaler Register –
CLKPR
Bit
7
6
5
4
3
2
1
0
CLKPCE
–
–
–
CLKPS3
CLKPS2
CLKPS1
CLKPS0
Read/Write
R/W
R
R
R
R/W
R/W
R/W
R/W
Initial Value
0
0
0
0
CLKPR
See Bit Description
• Bit 7 – CLKPCE: Clock Prescaler Change Enable
The CLKPCE bit must be written to logic one to enable change of the CLKPS bits. The
CLKPCE bit is only updated when the other bits in CLKPR are simultaniosly written to
zero. CLKPCE is cleared by hardware four cycles after it is written or when CLKPS bits
are written. Rewriting the CLKPCE bit within this time-out period does neither extend the
time-out period, nor clear the CLKPCE bit.
• Bits 3..0 – CLKPS3..0: Clock Prescaler Select Bits 3 - 0
These bits define the division factor between the selected clock source and the internal
system clock. These bits can be written run-time to vary the clock frequency to suit the
application requirements. As the divider divides the master clock input to the MCU, the
speed of all synchronous peripherals is reduced when a division factor is used. The division factors are given in Table 11.
The CKDIV8 Fuse determines the initial value of the CLKPS bits. If CKDIV8 is unprogrammed, the CLKPS bits will be reset to “0000”. If CKDIV8 is programmed, CLKPS bits
are reset to “0011”, giving a division factor of 8 at start up. This feature should be used if
the selected clock source has a higher frequency than the maximum frequency of the
device at the present operating conditions. Note that any value can be written to the
CLKPS bits regardless of the CKDIV8 Fuse setting. The Application software must
37
4317B–AVR–02/05
ensure that a sufficient division factor is chosen if the selcted clock source has a higher
frequency than the maximum frequency of the device at the present operating conditions. The device is shipped with the CKDIV8 Fuse programmed.
Table 11. Clock Prescaler Select
38
CLKPS3
CLKPS2
CLKPS1
CLKPS0
Clock Division Factor
0
0
0
0
1
0
0
0
1
2
0
0
1
0
4
0
0
1
1
8
0
1
0
0
16
0
1
0
1
32
0
1
1
0
64
0
1
1
1
128
1
0
0
0
256
1
0
0
1
Reserved
1
0
1
0
Reserved
1
0
1
1
Reserved
1
1
0
0
Reserved
1
1
0
1
Reserved
1
1
1
0
Reserved
1
1
1
1
Reserved
AT90PWM2/3
4317B–AVR–02/05
AT90PWM2/3
Power Management and Sleep Modes
Sleep modes enable the application to shut down unused modules in the MCU, thereby
saving power. The AVR provides various sleep modes allowing the user to tailor the
power consumption to the application’s requirements.
To enter any of the five sleep modes, the SE bit in SMCR must be written to logic one
and a SLEEP instruction must be executed. The SM2, SM1, and SM0 bits in the SMCR
Register select which sleep mode (Idle, ADC Noise Reduction, Power-down, Powersave, or Standby) will be activated by the SLEEP instruction. See Table 12 for a summary. If an enabled interrupt occurs while the MCU is in a sleep mode, the MCU wakes
up. The MCU is then halted for four cycles in addition to the start-up time, executes the
interrupt routine, and resumes execution from the instruction following SLEEP. The contents of the register file and SRAM are unaltered when the device wakes up from sleep.
If a reset occurs during sleep mode, the MCU wakes up and executes from the Reset
Vector.
Figure 13 on page 30 presents the different clock systems in the AT90PWM2/3, and
their distribution. The figure is helpful in selecting an appropriate sleep mode.
Sleep Mode Control Register –
SMCR
The Sleep Mode Control Register contains control bits for power management.
Bit
7
6
5
4
3
2
1
0
–
–
–
–
SM2
SM1
SM0
SE
Read/Write
R
R
R
R
R/W
R/W
R/W
R/W
Initial Value
0
0
0
0
0
0
0
0
SMCR
• Bits 3..1 – SM2..0: Sleep Mode Select Bits 2, 1, and 0
These bits select between the five available sleep modes as shown in Table 12.
Table 12. Sleep Mode Select
Note:
SM2
SM1
SM0
Sleep Mode
0
0
0
Idle
0
0
1
ADC Noise Reduction
0
1
0
Power-down
0
1
1
Reserved
1
0
0
Reserved
1
0
1
Reserved
1
1
0
Standby(1)
1
1
1
Reserved
1. Standby mode is only recommended for use with external crystals or resonators.
• Bit 1 – SE: Sleep Enable
The SE bit must be written to logic one to make the MCU enter the sleep mode when the
SLEEP instruction is executed. To avoid the MCU entering the sleep mode unless it is
the programmer’s purpose, it is recommended to write the Sleep Enable (SE) bit to one
just before the execution of the SLEEP instruction and to clear it immediately after waking up.
39
4317B–AVR–02/05
Idle Mode
When the SM2..0 bits are written to 000, the SLEEP instruction makes the MCU enter
Idle mode, stopping the CPU but allowing SPI, USART, Analog Comparator, ADC,
Timer/Counters, Watchdog, and the interrupt system to continue operating. This sleep
mode basically halt clkCPU and clkFLASH, while allowing the other clocks to run.
Idle mode enables the MCU to wake up from external triggered interrupts as well as
internal ones like the Timer Overflow and USART Transmit Complete interrupts. If
wake-up from the Analog Comparator interrupt is not required, the Analog Comparator
can be powered down by setting the ACD bit in the Analog Comparator Control and Status Register – ACSR. This will reduce power consumption in Idle mode. If the ADC is
enabled, a conversion starts automatically when this mode is entered.
ADC Noise Reduction
Mode
When the SM2..0 bits are written to 001, the SLEEP instruction makes the MCU enter
ADC Noise Reduction mode, stopping the CPU but allowing the ADC, the External
Interrupts, Timer/Counter (if their clock source is external - T0 or T1) and the Watchdog
to continue operating (if enabled). This sleep mode basically halts clkI/O, clkCPU, and
clkFLASH, while allowing the other clocks to run.
This improves the noise environment for the ADC, enabling higher resolution measurements. If the ADC is enabled, a conversion starts automatically when this mode is
entered. Apart from the ADC Conversion Complete interrupt, only an External Reset, a
Watchdog Reset, a Brown-out Reset, a Timer/Counter interrupt, an SPM/EEPROM
ready interrupt, an External Level Interrupt on INT3:0 can wake up the MCU from ADC
Noise Reduction mode.
Power-down Mode
When the SM2..0 bits are written to 010, the SLEEP instruction makes the MCU enter
Power-down mode. In this mode, the External Oscillator is stopped, while the External
Interrupts and the Watchdog continue operating (if enabled). Only an External Reset, a
Watchdog Reset, a Brown-out Reset, a PSC Interrupt, an External Level Interrupt on
INT3:0 can wake up the MCU. This sleep mode basically halts all generated clocks,
allowing operation of asynchronous modules only.
Note that if a level triggered interrupt is used for wake-up from Power-down mode, the
changed level must be held for some time to wake up the MCU. Refer to “External Interrupts” on page 82 for details.
When waking up from Power-down mode, there is a delay from the wake-up condition
occurs until the wake-up becomes effective. This allows the clock to restart and become
stable after having been stopped. The wake-up period is defined by the same CKSEL
fuses that define the Reset Time-out period, as described in “Clock Sources” on page
31.
Standby Mode
40
When the SM2..0 bits are 110 and an external crystal/resonator clock option is selected,
the SLEEP instruction makes the MCU enter Standby mode. This mode is identical to
AT90PWM2/3
4317B–AVR–02/05
AT90PWM2/3
Power-down with the exception that the Oscillator is kept running. From Standby mode,
the device wakes up in six clock cycles.
Table 13. Active Clock Domains and Wake-up Sources in the Different Sleep Modes.
clkPLL
Main Clock
Source Enabled
INT3..0
PSC
SPM/EEPROM
Ready
ADC
WDT
OtherI/O
X
X
X
X
X
X
X
X
X
X
X
X
X
X(2)
X
X
X
X
Sleep Mode
Idle
ADC Noise
Reduction
(2)
Power-down
X
Standby(1)
Notes:
Power Reduction
Register
Wake-up Sources
clkADC
Oscillators
clkIO
clkFLASH
clkCPU
Active Clock Domains
X
X
X(2)
X
1. Only recommended with external crystal or resonator selected as clock source.
2. Only level interrupt.
The Power Reduction Register, PRR, provides a method to stop the clock to individual
peripherals to reduce power consumption. The current state of the peripheral is frozen
and the I/O registers can not be read or written. Resources used by the peripheral when
stopping the clock will remain occupied, hence the peripheral should in most cases be
disabled before stopping the clock. Waking up a module, which is done by clearing the
bit in PRR, puts the module in the same state as before shutdown.
A full predictible behaviour of a peripheral is not guaranteed during and after a cycle of
stopping and starting of its clock. So its recommended to stop a peripheral before
stopping its clock with PRR register.
Module shutdown can be used in Idle mode and Active mode to significantly reduce the
overall power consumption. In all other sleep modes, the clock is already stopped.
Power Reduction Register PRR
Bit
7
6
5
4
3
2
1
0
PRPSC2
PRPSC1
PRPSC0
PRTIM1
PRTIM0
PRSPI
PRUSART
PRADC
Read/Write
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
Initial Value
0
0
0
0
0
0
0
0
PRR
• Bit 7 - PRPSC2: Power Reduction PSC2
Writing a logic one to this bit reduces the consumption of the PSC2 by stopping the
clock to this module. When waking up the PSC2 again, the PSC2 should be re initialized
to ensure proper operation.
• Bit 6 - PRPSC1: Power Reduction PSC1
Writing a logic one to this bit reduces the consumption of the PSC1 by stopping the
clock to this module. When waking up the PSC1 again, the PSC1 should be re initialized
to ensure proper operation.
• Bit 5 - PRPSC0: Power Reduction PSC0
Writing a logic one to this bit reduces the consumption of the PSC0 by stopping the
clock to this module. When waking up the PSC0 again, the PSC0 should be re initialized
to ensure proper operation.
41
4317B–AVR–02/05
• Bit 4 - PRTIM1: Power Reduction Timer/Counter1
Writing a logic one to this bit reduces the consumption of the Timer/Counter1 module.
When the Timer/Counter1 is enabled, operation will continue like before the setting of
this bit.
• Bit 3 - PRTIM0: Power Reduction Timer/Counter0
Writing a logic one to this bit reduces the consumption of the Timer/Counter0 module.
When the Timer/Counter0 is enabled, operation will continue like before the setting of
this bit.
• Bit 2 - PRSPI: Power Reduction Serial Peripheral Interface
Writing a logic one to this bit reduces the consumption of the Serial Peripheral Interface
by stopping the clock to this module. When waking up the SPI again, the SPI should be
re initialized to ensure proper operation.
• Bit 1 - PRUSART0: Power Reduction USART0
Writing a logic one to this bit reduces the consumption of the USART by stopping the
clock to this module. When waking up the USART again, the USART should be re initialized to ensure proper operation.
• Bit 0 - PRADC: Power Reduction ADC
Writing a logic one to this bit reduces the consumption of the ADC by stopping the clock
to this module. The ADC must be disabled before using this function. The analog comparator cannot use the ADC input MUX when the clock of ADC is stopped.
Minimizing Power
Consumption
There are several issues to consider when trying to minimize the power consumption in
an AVR controlled system. In general, sleep modes should be used as much as possible, and the sleep mode should be selected so that as few as possible of the device’s
functions are operating. All functions not needed should be disabled. In particular, the
following modules may need special consideration when trying to achieve the lowest
possible power consumption.
Analog to Digital Converter
If enabled, the ADC will be enabled in all sleep modes. To save power, the ADC should
be disabled before entering any sleep mode. When the ADC is turned off and on again,
the next conversion will be an extended conversion. Refer to “CROSS REFERENCE
REMOVED” for details on ADC operation.
Analog Comparator
When entering Idle mode, the Analog Comparator should be disabled if not used. When
entering ADC Noise Reduction mode, the Analog Comparator should be disabled. In
other sleep modes, the Analog Comparator is automatically disabled. However, if the
Analog Comparator is set up to use the Internal Voltage Reference as input, the Analog
Comparator should be disabled in all sleep modes. Otherwise, the Internal Voltage Reference will be enabled, independent of sleep mode. Refer to “Analog Comparator” on
page 236 for details on how to configure the Analog Comparator.
42
AT90PWM2/3
4317B–AVR–02/05
AT90PWM2/3
Brown-out Detector
If the Brown-out Detector is not needed by the application, this module should be turned
off. If the Brown-out Detector is enabled by the BODLEVEL Fuses, it will be enabled in
all sleep modes, and hence, always consume power. In the deeper sleep modes, this
will contribute significantly to the total current consumption. Refer to “Brown-out Detection” on page 47 for details on how to configure the Brown-out Detector.
Internal Voltage Reference
The Internal Voltage Reference will be enabled when needed by the Brown-out Detection, the Analog Comparator or the ADC. If these modules are disabled as described in
the sections above, the internal voltage reference will be disabled and it will not be consuming power. When turned on again, the user must allow the reference to start up
before the output is used. If the reference is kept on in sleep mode, the output can be
used immediately. Refer to “Internal Voltage Reference” on page 49 for details on the
start-up time.
Watchdog Timer
If the Watchdog Timer is not needed in the application, the module should be turned off.
If the Watchdog Timer is enabled, it will be enabled in all sleep modes, and hence,
always consume power. In the deeper sleep modes, this will contribute significantly to
the total current consumption. Refer to “Watchdog Timer” on page 50 for details on how
to configure the Watchdog Timer.
Port Pins
When entering a sleep mode, all port pins should be configured to use minimum power.
The most important is then to ensure that no pins drive resistive loads. In sleep modes
where both the I/O clock (clkI/O) and the ADC clock (clkADC) are stopped, the input buffers of the device will be disabled. This ensures that no power is consumed by the input
logic when not needed. In some cases, the input logic is needed for detecting wake-up
conditions, and it will then be enabled. Refer to the section “I/O-Ports” on page 62 for
details on which pins are enabled. If the input buffer is enabled and the input signal is
left floating or have an analog signal level close to VCC/2, the input buffer will use excessive power.
For analog input pins, the digital input buffer should be disabled at all times. An analog
signal level close to VCC/2 on an input pin can cause significant current even in active
mode. Digital input buffers can be disabled by writing to the Digital Input Disable Registers (DIDR1 and DIDR0). Refer to “Digital Input Disable Register 1– DIDR1” and “Digital
Input Disable Register 0 – DIDR0” on page 241 and page 260 for details.
On-chip Debug System
If the On-chip debug system is enabled by OCDEN Fuse and the chip enter sleep mode,
the main clock source is enabled, and hence, always consumes power. In the deeper
sleep modes, this will contribute significantly to the total current consumption.
43
4317B–AVR–02/05
System Control and Reset
Resetting the AVR
During reset, all I/O Registers are set to their initial values, and the program starts execution from the Reset Vector. The instruction placed at the Reset Vector must be a JMP
– Absolute Jump – instruction to the reset handling routine. If the program never
enables an interrupt source, the Interrupt Vectors are not used, and regular program
code can be placed at these locations. This is also the case if the Reset Vector is in the
Application section while the Interrupt Vectors are in the Boot section or vice versa. The
circuit diagram in Figure 17 shows the reset logic. Table 14 defines the electrical parameters of the reset circuitry.
The I/O ports of the AVR are immediately reset to their initial state when a reset source
goes active. This does not require any clock source to be running.
After all reset sources have gone inactive, a delay counter is invoked, stretching the
internal reset. This allows the power to reach a stable level before normal operation
starts. The time-out period of the delay counter is defined by the user through the SUT
and CKSEL Fuses. The different selections for the delay period are presented in “Clock
Sources” on page 31.
Reset Sources
44
The AT90PWM2/3 has five sources of reset:
•
Power-on Reset. The MCU is reset when the supply voltage is below the Power-on
Reset threshold (VPOT).
•
External Reset. The MCU is reset when a low level is present on the RESET pin for
longer than the minimum pulse length.
•
Watchdog Reset. The MCU is reset when the Watchdog Timer period expires and
the Watchdog is enabled.
•
Brown-out Reset. The MCU is reset when the supply voltage VCC is below the
Brown-out Reset threshold (VBOT) and the Brown-out Detector is enabled.
AT90PWM2/3
4317B–AVR–02/05
AT90PWM2/3
Figure 17. Reset Logic
DATA BUS
PORF
BORF
EXTRF
WDRF
MCU Status
Register (MCUSR)
Power-on Reset
Circuit
Brown-out
Reset Circuit
BODLEVEL [2..0]
Pull-up Resistor
Spike
Filter
Watchdog
Oscillator
Clock
Generator
CK
Delay Counters
TIMEOUT
CKSEL[3:0]
SUT[1:0]
Table 14. Reset Characteristics(1)
Symbol Parameter
Condition
Min.
(TBD)
Power-on Reset Threshold Voltage (rising)
VPOT
Power-on Reset Threshold Voltage (falling)
VRST
RESET Pin Threshold Voltage
tRST
Minimum pulse width on RESET Pin
Notes:
(2)
Typ.
(TBD)
Max.
(TBD)
Units
TBD
TBD
V
TBD
TBD
V
TBD
V
TBD
TBD
ns
1. Values are guidelines only..
2. The Power-on Reset will not work unless the supply voltage has been below VPOT
(falling)
45
4317B–AVR–02/05
Power-on Reset
A Power-on Reset (POR) pulse is generated by an On-chip detection circuit. The detection level is defined in Table 14. The POR is activated whenever VCC is below the
detection level. The POR circuit can be used to trigger the start-up Reset, as well as to
detect a failure in supply voltage.
A Power-on Reset (POR) circuit ensures that the device is reset from Power-on. Reaching the Power-on Reset threshold voltage invokes the delay counter, which determines
how long the device is kept in RESET after V CC rise. The RESET signal is activated
again, without any delay, when VCC decreases below the detection level.
Figure 18. MCU Start-up, RESET Tied to VCC
VCC
RESET
VPOT
VRST
tTOUT
TIME-OUT
INTERNAL
RESET
Figure 19. MCU Start-up, RESET Extended Externally
VCC
RESET
TIME-OUT
VPOT
VRST
tTOUT
INTERNAL
RESET
External Reset
46
An External Reset is generated by a low level on the RESET pin. Reset pulses longer
than the minimum pulse width (see Table 14) will generate a reset, even if the clock is
not running. Shorter pulses are not guaranteed to generate a reset. When the applied
signal reaches the Reset Threshold Voltage – VRST – on its positive edge, the delay
counter starts the MCU after the Time-out period – tTOUT – has expired.
AT90PWM2/3
4317B–AVR–02/05
AT90PWM2/3
Figure 20. External Reset During Operation
CC
Brown-out Detection
AT90PWM2/3 has an On-chip Brown-out Detection (BOD) circuit for monitoring the VCC
level during operation by comparing it to a fixed trigger level. The trigger level for the
BOD can be selected by the BODLEVEL Fuses. The trigger level has a hysteresis to
ensure spike free Brown-out Detection. The hysteresis on the detection level should be
interpreted as VBOT+ = VBOT + VHYST/2 and VBOT- = VBOT - VHYST/2.
Table 15. BODLEVEL Fuse Coding(1)(2)
BODLEVEL 2..0 Fuses
Notes:
Min VBOT
Typ VBOT
Max VBOT
Units
111
BOD Disabled
110
4.5
V
101
2.7
V
100
4.3
V
011
4.4
V
010
4.2
V
001
2.8
V
000
2.6
V
1. VBOT may be below nominal minimum operating voltage for some devices. For
devices where this is the case, the device is tested down to VCC = VBOT during the
production test. This guarantees that a Brown-Out Reset will occur before VCC drops
to a voltage where correct operation of the microcontroller is no longer guaranteed.
The test is performed using BODLEVEL = 010 for Low Operating Voltage and
BODLEVEL = 101 for High Operating Voltage .
2. Values are guidelines only.
Table 16. Brown-out Characteristics(1)
Min.
(TBD)
Typ.
(TBD)
Max.
(TBD)
Symbol
Parameter
VHYST
Brown-out Detector Hysteresis
TBD
mV
tBOD
Min Pulse Width on Brown-out Reset
TBD
µs
Notes:
Units
1. Values are guidelines only.
47
4317B–AVR–02/05
When the BOD is enabled, and VCC decreases to a value below the trigger level (VBOTin Figure 21), the Brown-out Reset is immediately activated. When VCC increases above
the trigger level (VBOT+ in Figure 21), the delay counter starts the MCU after the Timeout period tTOUT has expired.
The BOD circuit will only detect a drop in VCC if the voltage stays below the trigger level
for longer than tBOD given in Table 16.
Figure 21. Brown-out Reset During Operation
VCC
VBOT+
VBOT-
RESET
tTOUT
TIME-OUT
INTERNAL
RESET
Watchdog Reset
When the Watchdog times out, it will generate a short reset pulse of one CK cycle duration. On the falling edge of this pulse, the delay timer starts counting the Time-out period
tTOUT. Refer to page 50 for details on operation of the Watchdog Timer.
Figure 22. Watchdog Reset During Operation
CC
CK
MCU Status Register –
MCUSR
The MCU Status Register provides information on which reset source caused an MCU
reset.
Bit
7
6
5
4
3
2
1
0
–
–
–
–
WDRF
BORF
EXTRF
PORF
Read/Write
R
R
R
R
R/W
R/W
R/W
R/W
Initial Value
0
0
0
0
MCUSR
See Bit Description
• Bit 3 – WDRF: Watchdog Reset Flag
This bit is set if a Watchdog Reset occurs. The bit is reset by a Power-on Reset, or by
writing a logic zero to the flag.
48
AT90PWM2/3
4317B–AVR–02/05
AT90PWM2/3
• Bit 2 – BORF: Brown-out Reset Flag
This bit is set if a Brown-out Reset occurs. The bit is reset by a Power-on Reset, or by
writing a logic zero to the flag.
• Bit 1 – EXTRF: External Reset Flag
This bit is set if an External Reset occurs. The bit is reset by a Power-on Reset, or by
writing a logic zero to the flag.
• Bit 0 – PORF: Power-on Reset Flag
This bit is set if a Power-on Reset occurs. The bit is reset only by writing a logic zero to
the flag.
To make use of the Reset flags to identify a reset condition, the user should read and
then reset the MCUSR as early as possible in the program. If the register is cleared
before another reset occurs, the source of the reset can be found by examining the reset
flags.
Internal Voltage
Reference
AT90PWM2/3 features an internal bandgap reference. This reference is used for Brownout Detection. It can also be used as a voltage reference for the DAC and/or the ADC,
and can be used as analog input for the analog comparators. In order to use the internal
Vref, it is necessary to configure it thanks to the REFS1 and REFS0 bits in the ADMUX
register and to set an analog feature which requires it.
Voltage Reference Enable
Signals and Start-up Time
The voltage reference has a start-up time that may influence the way it should be used.
The start-up time is given in Table 17. To save power, the reference is not always turned
on. The reference is on during the following situations:
1. When the BOD is enabled (by programming the BODLEVEL [2..0] Fuse).
2. When the bandgap reference is connected to the Analog Comparator (by setting
the ACBG bit in ACSR).
3. When the ADC is enabled.
4. When the DAC is enabled.
Thus, when the BOD is not enabled, after setting the ACBG bit or enabling the ADC or
the DAC, the user must always allow the reference to start up before the output from the
Analog Comparator or ADC or DAC is used. To reduce power consumption in Powerdown mode, the user can avoid the three conditions above to ensure that the reference
is turned off before entering Power-down mode.
Voltage Reference
Characteristics
Table 17. Internal Voltage Reference Characteristics(1)
Symbol
Parameter
Condition
Min.
(TBD)
Typ.
(TBD)
Max.
(TBD)
Units
TBD
TBD
TBD
V
TBD
µs
VBG
Bandgap reference voltage
tBG
Bandgap reference start-up time
TBD
IBG
Bandgap reference current
consumption
TBD
Note:
µA
1. Values are guidelines only.
49
4317B–AVR–02/05
Watchdog Timer
AT90PWM2/3 has an Enhanced Watchdog Timer (WDT). The main features are:
• Clocked from separate On-chip Oscillator
• 3 Operating modes
– Interrupt
– System Reset
– Interrupt and System Reset
• Selectable Time-out period from 16ms to 8s
• Possible Hardware fuse Watchdog always on (WDTON) for fail-safe mode
Figure 23. Watchdog Timer
OSC/8K
OSC/2K
OSC/4K
128 KHz
OSCILLATOR
WDP3
MCU RESET
WDIF
INTERRUPT
WDIE
The Watchdog Timer (WDT) is a timer counting cycles of a separate on-chip 128 kHz
oscillator. The WDT gives an interrupt or a system reset when the counter reaches a
given time-out value. In normal operation mode, it is required that the system uses the
WDR - Watchdog Timer Reset - instruction to restart the counter before the time-out
value is reached. If the system doesn't restart the counter, an interrupt or system reset
will be issued.
In Interrupt mode, the WDT gives an interrupt when the timer expires. This interrupt can
be used to wake the device from sleep-modes, and also as a general system timer. One
example is to limit the maximum time allowed for certain operations, giving an interrupt
when the operation has run longer than expected. In System Reset mode, the WDT
gives a reset when the timer expires. This is typically used to prevent system hang-up in
case of runaway code. The third mode, Interrupt and System Reset mode, combines the
other two modes by first giving an interrupt and then switch to System Reset mode. This
mode will for instance allow a safe shutdown by saving critical parameters before a system reset.
The “Watchdog Timer Always On” (WDTON) fuse, if programmed, will force the Watchdog Timer to System Reset mode. With the fuse programmed the System Reset mode
bit (WDE) and Interrupt mode bit (WDIE) are locked to 1 and 0 respectively. To further
ensure program security, alterations to the Watchdog set-up must follow timed
sequences. The sequence for clearing WDE and changing time-out configuration is as
follows:
50
AT90PWM2/3
4317B–AVR–02/05
AT90PWM2/3
1. In the same operation, write a logic one to the Watchdog change enable bit
(WDCE) and WDE. A logic one must be written to WDE regardless of the previous value of the WDE bit.
2. Within the next four clock cycles, write the WDE and Watchdog prescaler bits
(WDP) as desired, but with the WDCE bit cleared. This must be done in one
operation.
The following code example shows one assembly and one C function for turning off the
Watchdog Timer. The example assumes that interrupts are controlled (e.g. by disabling
interrupts globally) so that no interrupts will occur during the execution of these
functions.
Assembly Code Example(1)
51
4317B–AVR–02/05
WDT_off:
; Turn off global interrupt
cli
; Reset Watchdog Timer
wdr
; Clear WDRF in MCUSR
in
r16, MCUSR
andi
r16, (0xff & (0<<WDRF))
out
MCUSR, r16
; Write logical one to WDCE and WDE
; Keep old prescaler setting to prevent unintentional time-out
lds r16, WDTCSR
ori
r16, (1<<WDCE) | (1<<WDE)
sts WDTCSR, r16
; Turn off WDT
ldi
r16, (0<<WDE)
sts WDTCSR, r16
; Turn on global interrupt
sei
ret
C Code Example(1)
void WDT_off(void)
{
__disable_interrupt();
__watchdog_reset();
/* Clear WDRF in MCUSR */
MCUSR &= ~(1<<WDRF);
/* Write logical one to WDCE and WDE */
/* Keep old prescaler setting to prevent unintentional time-out
*/
WDTCSR |= (1<<WDCE) | (1<<WDE);
/* Turn off WDT */
WDTCSR = 0x00;
__enable_interrupt();
}
Note:
1. The example code assumes that the part specific header file is included.
Note: If the Watchdog is accidentally enabled, for example by a runaway pointer or
brown-out condition, the device will be reset and the Watchdog Timer will stay enabled.
If the code is not set up to handle the Watchdog, this might lead to an eternal loop of
time-out resets. To avoid this situation, the application software should always clear the
Watchdog System Reset Flag (WDRF) and the WDE control bit in the initialisation routine, even if the Watchdog is not in use.
The following code example shows one assembly and one C function for changing the
time-out value of the Watchdog Timer.
52
AT90PWM2/3
4317B–AVR–02/05
AT90PWM2/3
Assembly Code Example(1)
WDT_Prescaler_Change:
; Turn off global interrupt
cli
; Reset Watchdog Timer
wdr
; Start timed sequence
lds r16, WDTCSR
ori
r16, (1<<WDCE) | (1<<WDE)
sts WDTCSR, r16
; --
Got four cycles to set the new values from here -
; Set new prescaler(time-out) value = 64K cycles (~0.5 s)
ldi
r16, (1<<WDE) | (1<<WDP2) | (1<<WDP0)
sts WDTCSR, r16
; --
Finished setting new values, used 2 cycles -
; Turn on global interrupt
sei
ret
C Code Example(1)
void WDT_Prescaler_Change(void)
{
__disable_interrupt();
__watchdog_reset();
/* Start timed
equence */
WDTCSR |= (1<<WDCE) | (1<<WDE);
/* Set new prescaler(time-out) value = 64K cycles (~0.5 s) */
WDTCSR
= (1<<WDE) | (1<<WDP2) | (1<<WDP0);
__enable_interrupt();
}
Note:
1. The example code assumes that the part specific header file is included.
Note: The Watchdog Timer should be reset before any change of the WDP bits, since a
change in the WDP bits can result in a time-out when switching to a shorter time-out
period;
53
4317B–AVR–02/05
Watchdog Timer Control
Register - WDTCSR
Bit
7
6
5
4
3
2
1
0
WDIF
WDIE
WDP3
WDCE
WDE
WDP2
WDP1
WDP0
Read/Write
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
Initial Value
0
0
0
0
X
0
0
0
WDTCSR
• Bit 7 - WDIF: Watchdog Interrupt Flag
This bit is set when a time-out occurs in the Watchdog Timer and the Watchdog Timer is
configured for interrupt. WDIF is cleared by hardware when executing the corresponding
interrupt handling vector. Alternatively, WDIF is cleared by writing a logic one to the flag.
When the I-bit in SREG and WDIE are set, the Watchdog Time-out Interrupt is
executed.
• Bit 6 - WDIE: Watchdog Interrupt Enable
When this bit is written to one and the I-bit in the Status Register is set, the Watchdog
Interrupt is enabled. If WDE is cleared in combination with this setting, the Watchdog
Timer is in Interrupt Mode, and the corresponding interrupt is executed if time-out in the
Watchdog Timer occurs.
If WDE is set, the Watchdog Timer is in Interrupt and System Reset Mode. The first
time-out in the Watchdog Timer will set WDIF. Executing the corresponding interrupt
vector will clear WDIE and WDIF automatically by hardware (the Watchdog goes to System Reset Mode). This is useful for keeping the Watchdog Timer security while using
the interrupt. To stay in Interrupt and System Reset Mode, WDIE must be set after each
interrupt. This should however not be done within the interrupt service routine itself, as
this might compromise the safety-function of the Watchdog System Reset mode. If the
interrupt is not executed before the next time-out, a System Reset will be applied.
Table 18. Watchdog Timer Configuration
WDTON(1)
WDE
WDIE
0
0
0
Note:
Mode
Action on Time-out
0
Stopped
None
0
1
Interrupt Mode
Interrupt
0
1
0
System Reset Mode
Reset
0
1
1
Interrupt and System
Reset Mode
Interrupt, then go to
System Reset Mode
1
x
x
System Reset Mode
Reset
1. For the WDTON Fuse “1” means unprogrammed while “0” means programmed.
• Bit 4 - WDCE: Watchdog Change Enable
This bit is used in timed sequences for changing WDE and prescaler bits. To clear the
WDE bit, and/or change the prescaler bits, WDCE must be set.
Once written to one, hardware will clear WDCE after four clock cycles.
• Bit 3 - WDE: Watchdog System Reset Enable
WDE is overridden by WDRF in MCUSR. This means that WDE is always set when
WDRF is set. To clear WDE, WDRF must be cleared first. This feature ensures multiple
resets during conditions causing failure, and a safe start-up after the failure.
• Bit 5, 2..0 - WDP3..0: Watchdog Timer Prescaler 3, 2, 1 and 0
The WDP3..0 bits determine the Watchdog Timer prescaling when the Watchdog Timer
is running. The different prescaling values and their corresponding time-out periods are
shown in Table 19 on page 55.
54
AT90PWM2/3
4317B–AVR–02/05
AT90PWM2/3
.
Table 19. Watchdog Timer Prescale Select
WDP3
WDP2
WDP1
WDP0
Number of WDT Oscillator
Cycles
Typical Time-out at
VCC = 5.0V
0
0
0
0
2K (2048) cycles
16 ms
0
0
0
1
4K (4096) cycles
32 ms
0
0
1
0
8K (8192) cycles
64 ms
0
0
1
1
16K (16384) cycles
0.125 s
0
1
0
0
32K (32768) cycles
0.25 s
0
1
0
1
64K (65536) cycles
0.5 s
0
1
1
0
128K (131072) cycles
1.0 s
0
1
1
1
256K (262144) cycles
2.0 s
1
0
0
0
512K (524288) cycles
4.0 s
1
0
0
1
1024K (1048576) cycles
8.0 s
1
0
1
0
1
0
1
1
1
1
0
0
1
1
0
1
1
1
1
0
1
1
1
1
Reserved
55
4317B–AVR–02/05
Interrupts
This section describes the specifics of the interrupt handling as performed in
AT90PWM2/3. For a general explanation of the AVR interrupt handling, refer to “Reset
and Interrupt Handling” on page 17.
Interrupt Vectors in
AT90PWM2/3
56
Table 20. Reset and Interrupt Vectors
Vector
No.
Program
Address
Source
Interrupt Definition
1
0x0000
RESET
External Pin, Power-on Reset, Brown-out Reset,
Watchdog Reset, and Emulation AVR Reset
2
0x0001
PSC2 CAPT
PSC2 Capture Event
3
0x0002
PSC2 EC
PSC2 End Cycle
4
0x0003
PSC1 CAPT
PSC1 Capture Event
5
0x0004
PSC1 EC
PSC1 End Cycle
6
0x0005
PSC0 CAPT
PSC0 Capture Event
7
0x0006
PSC0 EC
PSC0 End Cycle
8
0x0007
ANACOMP 0
Analog Comparator 0
9
0x0008
ANACOMP 1
Analog Comparator 1
10
0x0009
ANACOMP 2
Analog Comparator 2
11
0x000A
INT0
External Interrupt Request 0
12
0x000B
TIMER1 CAPT
Timer/Counter1 Capture Event
13
0x000C
TIMER1 COMPA
Timer/Counter1 Compare Match A
14
0x000D
TIMER1 COMPB
Timer/Counter1 Compare Match B
15
0x000E
16
0x000F
TIMER1 OVF
Timer/Counter1 Overflow
17
0x0010
TIMER0 COMPA
Timer/Counter0 Compare Match A
18
0x0011
TIMER0 OVF
Timer/Counter0 Overflow
19
0x0012
ADC
ADC Conversion Complete
20
0x0013
INT1
External Interrupt Request 1
21
0x0014
SPI, STC
SPI Serial Transfer Complete
22
0x0015
USART0, RX
USART0, Rx Complete
23
0x0016
USART0, UDRE
USART0 Data Register Empty
24
0x0017
USART0, TX
USART0, Tx Complete
25
0x0018
INT2
External Interrupt Request 2
26
0x0019
WDT
Watchdog Time-Out Interrupt
27
0x001A
EE READY
EEPROM Ready
28
0x001B
TIMER0 COMPB
Timer/Counter0 Compare Match B
29
0x001C
INT3
External Interrupt Request 3
AT90PWM2/3
4317B–AVR–02/05
AT90PWM2/3
Table 20. Reset and Interrupt Vectors
Vector
No.
Program
Address
30
0x001D
31
0x001E
32
0x001F
Notes:
Source
Interrupt Definition
SPM READY
Store Program Memory Ready
1. When the BOOTRST Fuse is programmed, the device will jump to the Boot Loader
address at reset, see “Boot Loader Support – Read-While-Write Self-Programming”
on page 273.
2. When the IVSEL bit in MCUCR is set, Interrupt Vectors will be moved to the start of
the Boot Flash Section. The address of each Interrupt Vector will then be the address
in this table added to the start address of the Boot Flash Section.
Table 21 shows reset and Interrupt Vectors placement for the various combinations of
BOOTRST and IVSEL settings. If the program never enables an interrupt source, the
Interrupt Vectors are not used, and regular program code can be placed at these locations. This is also the case if the Reset Vector is in the Application section while the
Interrupt Vectors are in the Boot section or vice versa.
Table 21. Reset and Interrupt Vectors Placement in AT90PWM2/3(1)
BOOTRST
IVSEL
1
Note:
Reset Address
Interrupt Vectors Start Address
0
0x000
0x001
1
1
0x000
Boot Reset Address + 0x001
0
0
Boot Reset Address
0x001
0
1
Boot Reset Address
Boot Reset Address + 0x001
1. The Boot Reset Address is shown in Table 114 on page 286. For the BOOTRST
Fuse “1” means unprogrammed while “0” means programmed.
The most typical and general program setup for the Reset and Interrupt Vector
Addresses in AT90PWM2/3 is:
Address Labels Code
Comments
0x000
rjmp
RESET
; Reset Handler
0x001
rjmp
PSC2_CAPT
; PSC2 Capture event Handler
0x002
rjmp
PSC2_EC
; PSC2 End Cycle Handler
0x003
rjmp
PSC1_CAPT
; PSC1 Capture event Handler
0x004
rjmp
PSC1_EC
; PSC1 End Cycle Handler
0x005
rjmp
PSC0_CAPT
; PSC0 Capture event Handler
0x006
rjmp
PSC0_EC
; PSC0 End Cycle Handler
0x007
rjmp
ANA_COMP_0
; Analog Comparator 0 Handler
0x008
rjmp
ANA_COMP_1
; Analog Comparator 1 Handler
0x009
rjmp
ANA_COMP_2
; Analog Comparator 2 Handler
0x00A
rjmp
EXT_INT0
; IRQ0 Handler
0x00B
rjmp
TIM1_CAPT
; Timer1 Capture Handler
0x00C
rjmp
TIM1_COMPA
; Timer1 Compare A Handler
0x00D
rjmp
TIM1_COMPB
; Timer1 Compare B Handler
57
4317B–AVR–02/05
0x00F
rjmp
TIM1_OVF
; Timer1 Overflow Handler
0x010
rjmp
TIM0_COMPA
; Timer0 Compare A Handler
0x011
rjmp
TIM0_OVF
; Timer0 Overflow Handler
0x012
Handler
rjmp
ADC
; ADC Conversion Complete
0x013
rjmp
EXT_INT1
; IRQ1 Handler
0x014
rjmp
SPI_STC
; SPI Transfer Complete Handler
0x015
rjmp
USART_RXC
; USART, RX Complete Handler
0x016
rjmp
USART_UDRE
; USART, UDR Empty Handler
0x017
rjmp
USART_TXC
; USART, TX Complete Handler
0x018
rjmp
EXT_INT2
; IRQ2 Handler
0x019
rjmp
WDT
; Watchdog Timer Handler
0x01A
rjmp
EE_RDY
; EEPROM Ready Handler
0x01B
rjmp
TIM0_COMPB
; Timer0 Compare B Handler
0x01C
rjmp
EXT_INT3
; IRQ3 Handler
0x01F
Handler
rjmp
SPM_RDY
; Store Program Memory Ready
0x020RESET:
ldi
r16, high(RAMEND); Main program start
0x021
RAM
out
SPH,r16
0x022
ldi
r16, low(RAMEND)
0x023
0x024
out
sei
;
0x025
...
SPL,r16
; Enable interrupts
<instr>
...
...
; Set Stack Pointer to top of
xxx
...
When the BOOTRST Fuse is unprogrammed, the Boot section size set to 2K bytes and
the IVSEL bit in the MCUCR Register is set before any interrupts are enabled, the most
typical and general program setup for the Reset and Interrupt Vector Addresses in
AT90PWM2/3 is:
Address Labels Code
Comments
0x000
RESET: ldi
r16,high(RAMEND); Main program start
0x001
RAM
out
SPH,r16
0x002
ldi
r16,low(RAMEND)
0x003
0x004
out
sei
SPL,r16
0x005
<instr>
; Set Stack Pointer to top of
; Enable interrupts
xxx
;
.org 0xC01
0xC01
58
rjmp
PSC2_CAPT
; PSC2 Capture event Handler
0xC02
rjmp
PSC2_EC
; PSC2 End Cycle Handler
...
...
...
;
0xC1F
Handler
rjmp
SPM_RDY
; Store Program Memory Ready
AT90PWM2/3
4317B–AVR–02/05
AT90PWM2/3
When the BOOTRST Fuse is programmed and the Boot section size set to 2K bytes, the
most typical and general program setup for the Reset and Interrupt Vector Addresses in
AT90PWM2/3 is:
Address Labels Code
Comments
.org 0x001
0x001
rjmp
PSC2_CAPT
; PSC2 Capture event Handler
0x002
rjmp
PSC2_EC
; PSC2 End Cycle Handler
...
...
...
;
0x01F
Handler
rjmp
SPM_RDY
; Store Program Memory Ready
;
.org 0xC00
0xC00
RESET: ldi
r16,high(RAMEND); Main program start
0xC01
RAM
out
SPH,r16
0xC02
ldi
r16,low(RAMEND)
0xC03
0xC04
out
sei
SPL,r16
0xC05
<instr>
; Set Stack Pointer to top of
; Enable interrupts
xxx
When the BOOTRST Fuse is programmed, the Boot section size set to 2K bytes and the
IVSEL bit in the MCUCR Register is set before any interrupts are enabled, the most typical and general program setup for the Reset and Interrupt Vector Addresses in
AT90PWM2/3 is:
Address Labels Code
Comments
;
.org 0xC00
0xC00
rjmp
RESET
; Reset handler
0xC01
rjmp
PSC2_CAPT
; PSC2 Capture event Handler
0xC02
rjmp
PSC2_EC
; PSC2 End Cycle Handler
...
...
...
;
0xC1F
Handler
rjmp
SPM_RDY
; Store Program Memory Ready
;
0xC20
RESET: ldi
0xC21
RAM
out
r16,high(RAMEND); Main program start
SPH,r16
0xC22
ldi
r16,low(RAMEND)
0xC23
0xC24
out
sei
SPL,r16
0xC25
<instr>
; Set Stack Pointer to top of
; Enable interrupts
xxx
59
4317B–AVR–02/05
Moving Interrupts Between
Application and Boot Space
The MCU Control Register controls the placement of the Interrupt Vector table.
MCU Control Register –
MCUCR
Bit
7
6
5
4
3
2
1
0
SPIPS
–
–
PUD
–
–
IVSEL
IVCE
Read/Write
R/W
R
R
R/W
R
R
R/W
R/W
Initial Value
0
0
0
0
0
0
0
0
MCUCR
•
• Bit 1 – IVSEL: Interrupt Vector Select
When the IVSEL bit is cleared (zero), the Interrupt Vectors are placed at the start of the
Flash memory. When this bit is set (one), the Interrupt Vectors are moved to the beginning of the Boot Loader section of the Flash. The actual address of the start of the Boot
Flash Section is determined by the BOOTSZ Fuses. Refer to the section “Boot Loader
Support – Read-While-Write Self-Programming” on page 273 for details. To avoid unintentional changes of Interrupt Vector tables, a special write procedure must be followed
to change the IVSEL bit:
1. Write the Interrupt Vector Change Enable (IVCE) bit to one.
2. Within four cycles, write the desired value to IVSEL while writing a zero to
IVCE.
Interrupts will automatically be disabled while this sequence is executed. Interrupts are
disabled in the cycle IVCE is set, and they remain disabled until after the instruction following the write to IVSEL. If IVSEL is not written, interrupts remain disabled for four
cycles. The I-bit in the Status Register is unaffected by the automatic disabling.
Note:
If Interrupt Vectors are placed in the Boot Loader section and Boot Lock bit BLB02 is programmed, interrupts are disabled while executing from the Application section. If
Interrupt Vectors are placed in the Application section and Boot Lock bit BLB12 is programed, interrupts are disabled while executing from the Boot Loader section. Refer to
the section “Boot Loader Support – Read-While-Write Self-Programming” on page 273
for details on Boot Lock bits.
• Bit 0 – IVCE: Interrupt Vector Change Enable
The IVCE bit must be written to logic one to enable change of the IVSEL bit. IVCE is
cleared by hardware four cycles after it is written or when IVSEL is written. Setting the
IVCE bit will disable interrupts, as explained in the IVSEL description above. See Code
Example below.
60
AT90PWM2/3
4317B–AVR–02/05
AT90PWM2/3
Assembly Code Example
Move_interrupts:
; Enable change of Interrupt Vectors
ldi r16, (1<<IVCE)
out MCUCR, r16
; Move interrupts to Boot Flash section
ldi r16, (1<<IVSEL)
out MCUCR, r16
ret
C Code Example
void Move_interrupts(void)
{
/* Enable change of Interrupt Vectors */
MCUCR = (1<<IVCE);
/* Move interrupts to Boot Flash section */
MCUCR = (1<<IVSEL);
}
61
4317B–AVR–02/05
I/O-Ports
Introduction
All AVR ports have true Read-Modify-Write functionality when used as general digital
I/O ports. This means that the direction of one port pin can be changed without unintentionally changing the direction of any other pin with the SBI and CBI instructions. The
same applies when changing drive value (if configured as output) or enabling/disabling
of pull-up resistors (if configured as input). Each output buffer has symmetrical drive
characteristics with both high sink and source capability. All port pins have individually
selectable pull-up resistors with a supply-voltage invariant resistance. All I/O pins have
protection diodes to both VCC and Ground as indicated in Figure 24. Refer to “Electrical
Characteristics(1)” on page 308 for a complete list of parameters.
Figure 24. I/O Pin Equivalent Schematic
Rpu
Pxn
Logic
Cpin
See Figure
"General Digital I/O" for
Details
All registers and bit references in this section are written in general form. A lower case
“x” represents the numbering letter for the port, and a lower case “n” represents the bit
number. However, when using the register or bit defines in a program, the precise form
must be used. For example, PORTB3 for bit no. 3 in Port B, here documented generally
as PORTxn. The physical I/O Registers and bit locations are listed in “Register Description for I/O-Ports”.
Three I/O memory address locations are allocated for each port, one each for the Data
Register – PORTx, Data Direction Register – DDRx, and the Port Input Pins – PINx. The
Port Input Pins I/O location is read only, while the Data Register and the Data Direction
Register are read/write. However, writing a logic one to a bit in the PINx Register, will
result in a toggle in the corresponding bit in the Data Register. In addition, the Pull-up
Disable – PUD bit in MCUCR disables the pull-up function for all pins in all ports when
set.
Using the I/O port as General Digital I/O is described in “Ports as General Digital I/O”.
Most port pins are multiplexed with alternate functions for the peripheral features on the
device. How each alternate function interferes with the port pin is described in “Alternate
Port Functions” on page 68. Refer to the individual module sections for a full description
of the alternate functions.
Note that enabling the alternate function of some of the port pins does not affect the use
of the other pins in the port as general digital I/O.
62
AT90PWM2/3
4317B–AVR–02/05
AT90PWM2/3
Ports as General Digital
I/O
The ports are bi-directional I/O ports with optional internal pull-ups. Figure 25 shows a
functional description of one I/O-port pin, here generically called Pxn.
Figure 25. General Digital I/O(1)
PUD
Q
D
DDxn
Q CLR
WDx
RESET
1
Q
Pxn
D
0
PORTxn
Q CLR
WPx
DATA BUS
RDx
RESET
WRx
RRx
SLEEP
SYNCHRONIZER
D
Q
L
Q
D
RPx
Q
PINxn
Q
clk I/O
PUD: PULLUP DISABLE
SLEEP: SLEEP CONTROL
clkI/O : I/O CLOCK
Note:
Configuring the Pin
WDx:
RDx:
WRx:
RRx:
RPx:
WPx:
WRITE DDRx
READ DDRx
WRITE PORTx
READ PORTx REGISTER
READ PORTx PIN
WRITE PINx REGISTER
1. WRx, WPx, WDx, RRx, RPx, and RDx are common to all pins within the same port.
clkI/O, SLEEP, and PUD are common to all ports.
Each port pin consists of three register bits: DDxn, PORTxn, and PINxn. As shown in
“Register Description for I/O-Ports” on page 80, the DDxn bits are accessed at the
DDRx I/O address, the PORTxn bits at the PORTx I/O address, and the PINxn bits at
the PINx I/O address.
The DDxn bit in the DDRx Register selects the direction of this pin. If DDxn is written
logic one, Pxn is configured as an output pin. If DDxn is written logic zero, Pxn is configured as an input pin.
If PORTxn is written logic one when the pin is configured as an input pin, the pull-up
resistor is activated. To switch the pull-up resistor off, PORTxn has to be written logic
zero or the pin has to be configured as an output pin
The port pins are tri-stated when reset condition becomes active, even if no clocks are
running.
63
4317B–AVR–02/05
If PORTxn is written logic one when the pin is configured as an output pin, the port pin is
driven high (one). If PORTxn is written logic zero when the pin is configured as an output pin, the port pin is driven low (zero).
Toggling the Pin
Writing a logic one to PINxn toggles the value of PORTxn, independent on the value of
DDRxn. Note that the SBI instruction can be used to toggle one single bit in a port.
Switching Between Input and
Output
When switching between tri-state ({DDxn, PORTxn} = 0b00) and output high ({DDxn,
PORTxn} = 0b11), an intermediate state with either pull-up enabled {DDxn, PORTxn} =
0b01) or output low ({DDxn, PORTxn} = 0b10) must occur. Normally, the pull-up
enabled state is fully acceptable, as a high-impedant environment will not notice the difference between a strong high driver and a pull-up. If this is not the case, the PUD bit in
the MCUCR Register can be set to disable all pull-ups in all ports.
Switching between input with pull-up and output low generates the same problem. The
user must use either the tri-state ({DDxn, PORTxn} = 0b00) or the output high state
({DDxn, PORTxn} = 0b11) as an intermediate step.
Table 22 summarizes the control signals for the pin value.
Table 22. Port Pin Configurations
Reading the Pin Value
64
DDxn
PORTxn
PUD
(in MCUCR)
I/O
Pull-up
0
0
X
Input
No
Default configuration after Reset.
Tri-state (Hi-Z)
0
1
0
Input
Yes
Pxn will source current if ext. pulled
low.
0
1
1
Input
No
Tri-state (Hi-Z)
1
0
X
Output
No
Output Low (Sink)
1
1
X
Output
No
Output High (Source)
Comment
Independent of the setting of Data Direction bit DDxn, the port pin can be read through
the PINxn Register bit. As shown in Figure 25, the PINxn Register bit and the preceding
latch constitute a synchronizer. This is needed to avoid metastability if the physical pin
changes value near the edge of the internal clock, but it also introduces a delay. Figure
26 shows a timing diagram of the synchronization when reading an externally applied
pin value. The maximum and minimum propagation delays are denoted tpd,max and tpd,min
respectively.
AT90PWM2/3
4317B–AVR–02/05
AT90PWM2/3
Figure 26. Synchronization when Reading an Externally Applied Pin value
SYSTEM CLK
INSTRUCTIONS
XXX
XXX
in r17, PINx
SYNC LATCH
PINxn
r17
0x00
0xFF
t pd, max
t pd, min
65
4317B–AVR–02/05
Consider the clock period starting shortly after the first falling edge of the system clock.
The latch is closed when the clock is low, and goes transparent when the clock is high,
as indicated by the shaded region of the “SYNC LATCH” signal. The signal value is
latched when the system clock goes low. It is clocked into the PINxn Register at the succeeding positive clock edge. As indicated by the two arrows tpd,max and tpd,min, a single
signal transition on the pin will be delayed between ½ and 1½ system clock period
depending upon the time of assertion.
When reading back a software assigned pin value, a nop instruction must be inserted as
indicated in Figure 27. The out instruction sets the “SYNC LATCH” signal at the positive
edge of the clock. In this case, the delay tpd through the synchronizer is 1 system clock
period.
Figure 27. Synchronization when Reading a Software Assigned Pin Value
SYSTEM CLK
r16
INSTRUCTIONS
0xFF
out PORTx, r16
nop
in r17, PINx
SYNC LATCH
PINxn
r17
0x00
0xFF
t pd
66
AT90PWM2/3
4317B–AVR–02/05
AT90PWM2/3
The following code example shows how to set port B pins 0 and 1 high, 2 and 3 low, and
define the port pins from 4 to 7 as input with pull-ups assigned to port pins 6 and 7. The
resulting pin values are read back again, but as previously discussed, a nop instruction
is included to be able to read back the value recently assigned to some of the pins.
Assembly Code Example(1)
...
; Define pull-ups and set outputs high
; Define directions for port pins
ldi
r16, (1<<PB7)|(1<<PB6)|(1<<PB1)|(1<<PB0)
ldi
r17, (1<<DDB3)|(1<<DDB2)|(1<<DDB1)|(1<<DDB0)
out
PORTB, r16
out
DDRB, r17
; Insert nop for synchronization
nop
; Read port pins
in
r16, PINB
...
C Code Example
unsigned char i;
...
/* Define pull-ups and set outputs high */
/* Define directions for port pins */
PORTB = (1<<PB7)|(1<<PB6)|(1<<PB1)|(1<<PB0);
DDRB = (1<<DDB3)|(1<<DDB2)|(1<<DDB1)|(1<<DDB0);
/* Insert nop for synchronization*/
_NOP();
/* Read port pins */
i = PINB;
...
Note:
Digital Input Enable and Sleep
Modes
1. For the assembly program, two temporary registers are used to minimize the time
from pull-ups are set on pins 0, 1, 6, and 7, until the direction bits are correctly set,
defining bit 2 and 3 as low and redefining bits 0 and 1 as strong high drivers.
As shown in Figure 25, the digital input signal can be clamped to ground at the input of
the schmitt-trigger. The signal denoted SLEEP in the figure, is set by the MCU Sleep
Controller in Power-down mode, Power-save mode, and Standby mode to avoid high
power consumption if some input signals are left floating, or have an analog signal level
close to VCC/2.
SLEEP is overridden for port pins enabled as external interrupt pins. If the external interrupt request is not enabled, SLEEP is active also for these pins. SLEEP is also
overridden by various other alternate functions as described in “Alternate Port Functions” on page 68.
If a logic high level (“one”) is present on an Asynchronous External Interrupt pin configured as “Interrupt on Rising Edge, Falling Edge, or Any Logic Change on Pin” while the
external interrupt is not enabled, the corresponding External Interrupt Flag will be set
when resuming from the above mentioned sleep modes, as the clamping in these sleep
modes produces the requested logic change.
67
4317B–AVR–02/05
Alternate Port Functions
Most port pins have alternate functions in addition to being general digital I/Os. Figure
28 shows how the port pin control signals from the simplified Figure 25 can be overridden by alternate functions. The overriding signals may not be present in all port pins, but
the figure serves as a generic description applicable to all port pins in the AVR microcontroller family.
Figure 28. Alternate Port Functions(1)
PUOExn
PUOVxn
1
PUD
0
DDOExn
DDOVxn
1
Q D
DDxn
0
Q CLR
WDx
PVOExn
RESET
RDx
1
1
Pxn
Q
0
D
0
PORTxn
PTOExn
Q CLR
DIEOExn
DATA BUS
PVOVxn
WPx
DIEOVxn
RESET
WRx
1
0
RRx
SLEEP
SYNCHRONIZER
D
SET
Q
RPx
Q
D
PINxn
L
CLR
Q
CLR
Q
clk I/O
DIxn
AIOxn
PUOExn: Pxn PULL-UP OVERRIDE ENABLE
PUOVxn:
DDOExn:
DDOVxn:
PVOExn:
PVOVxn:
DIEOExn:
Pxn PULL-UP OVERRIDE VALUE
Pxn DATA DIRECTION OVERRIDE ENABLE
Pxn DATA DIRECTION OVERRIDE VALUE
Pxn PORT VALUE OVERRIDE ENABLE
Pxn PORT VALUE OVERRIDE VALUE
Pxn DIGITAL INPUT-ENABLE OVERRIDE ENABLE
DIEOVxn: Pxn DIGITAL INPUT-ENABLE OVERRIDE VALUE
SLEEP: SLEEP CONTROL
PTOExn: Pxn, PORT TOGGLE OVERRIDE ENABLE
Note:
PUD: PULLUP DISABLE
WDx:
RDx:
RRx:
WRx:
RPx:
WPx:
clkI/O:
DIxn:
AIOxn:
WRITE DDRx
READ DDRx
READ PORTx REGISTER
WRITE PORTx
READ PORTx PIN
WRITE PINx
I/O CLOCK
DIGITAL INPUT PIN n ON PORTx
ANALOG INPUT/OUTPUT PIN n ON PORTx
1. WRx, WPx, WDx, RRx, RPx, and RDx are common to all pins within the same port.
clkI/O, SLEEP, and PUD are common to all ports. All other signals are unique for each
pin.
Table 23 summarizes the function of the overriding signals. The pin and port indexes
from Figure 28 are not shown in the succeeding tables. The overriding signals are generated internally in the modules having the alternate function.
68
AT90PWM2/3
4317B–AVR–02/05
AT90PWM2/3
Table 23. Generic Description of Overriding Signals for Alternate Functions
Signal Name
Full Name
Description
PUOE
Pull-up Override
Enable
If this signal is set, the pull-up enable is controlled by the
PUOV signal. If this signal is cleared, the pull-up is
enabled when {DDxn, PORTxn, PUD} = 0b010.
PUOV
Pull-up Override
Value
If PUOE is set, the pull-up is enabled/disabled when
PUOV is set/cleared, regardless of the setting of the
DDxn, PORTxn, and PUD Register bits.
DDOE
Data Direction
Override Enable
If this signal is set, the Output Driver Enable is controlled
by the DDOV signal. If this signal is cleared, the Output
driver is enabled by the DDxn Register bit.
DDOV
Data Direction
Override Value
If DDOE is set, the Output Driver is enabled/disabled
when DDOV is set/cleared, regardless of the setting of
the DDxn Register bit.
PVOE
Port Value
Override Enable
If this signal is set and the Output Driver is enabled, the
port value is controlled by the PVOV signal. If PVOE is
cleared, and the Output Driver is enabled, the port Value
is controlled by the PORTxn Register bit.
PVOV
Port Value
Override Value
If PVOE is set, the port value is set to PVOV, regardless
of the setting of the PORTxn Register bit.
PTOE
Port Toggle
Override Enable
If PTOE is set, the PORTxn Register bit is inverted.
DIEOE
Digital Input
Enable Override
Enable
If this bit is set, the Digital Input Enable is controlled by
the DIEOV signal. If this signal is cleared, the Digital Input
Enable is determined by MCU state (Normal mode, sleep
mode).
DIEOV
Digital Input
Enable Override
Value
If DIEOE is set, the Digital Input is enabled/disabled when
DIEOV is set/cleared, regardless of the MCU state
(Normal mode, sleep mode).
DI
Digital Input
This is the Digital Input to alternate functions. In the
figure, the signal is connected to the output of the schmitt
trigger but before the synchronizer. Unless the Digital
Input is used as a clock source, the module with the
alternate function will use its own synchronizer.
AIO
Analog
Input/Output
This is the Analog Input/output to/from alternate
functions. The signal is connected directly to the pad, and
can be used bi-directionally.
The following subsections shortly describe the alternate functions for each port, and
relate the overriding signals to the alternate function. Refer to the alternate function
description for further details.
69
4317B–AVR–02/05
MCU Control Register –
MCUCR
Bit
7
6
5
4
3
2
1
0
SPIPS
–
–
PUD
–
–
IVSEL
IVCE
Read/Write
R/W
R
R
R/W
R
R
R/W
R/W
Initial Value
0
0
0
0
0
0
0
0
MCUCR
• Bit 4 – PUD: Pull-up Disable
When this bit is written to one, the pull-ups in the I/O ports are disabled even if the DDxn
and PORTxn Registers are configured to enable the pull-ups ({DDxn, PORTxn} = 0b01).
Se
Alternate Functions of Port B
The Port B pins with alternate functions are shown in Table 24.
Table 24. Port B Pins Alternate Functions
Port Pin
Alternate Functions
PB7
PSCOUT01 output
ADC4 (Analog Input Channel 4)
SCK (SPI Bus Serial Clock)
PB6
ADC7 (Analog Input Channel 7)
ICP1B (Timer 1 input capture alternate input)
PSCOUT11 output (see note 4)
PB5
ADC6 (Analog Input Channel 6)
INT2
PB4
AMP0+ (Analog Differential Amplifier 0 Input Channel )
PB3
AMP0- (Analog Differential Amplifier 0 Input Channel )
PB2
ADC5 (Analog Input Channel5 )
INT1
PB1
MOSI (SPI Master Out Slave In)
PSCOUT21 output
PB0
MISO (SPI Master In Slave Out)
PSCOUT20 output
The alternate pin configuration is as follows:
• PSCOUT01/ADC4/SCK – Bit 7
PSCOUT01: Output 1 of PSC 0.
ADC4, Analog to Digital Converter, input channel 4.
SCK: Master Clock output, Slave Clock input pin for SPI channel. When the SPI is
enabled as a slave, this pin is configured as an input regardless of the setting of DDB7.
When the SPI is enabled as a master, the data direction of this pin is controlled by
DDB7. When the pin is forced to be an input, the pull-up can still be controlled by the
PORTB7 bit.
• ADC7/ICP1B/PSCOUT11 – Bit 6
ADC7, Analog to Digital Converter, input channel 7.
ICP1B, Input Capture Pin: The PB6 pin can act as an Input Capture Pin for
Timer/Counter1.
70
AT90PWM2/3
4317B–AVR–02/05
AT90PWM2/3
PSCOUT11: Output 1 of PSC 1.
• ADC6/INT2 – Bit 5
ADC6, Analog to Digital Converter, input channel 6.
INT2, External Interrupt source 2. This pin can serve as an External Interrupt source to
the MCU.
• APM0+ – Bit 4
AMP0+, Analog Differential Amplifier 0 Positive Input Channel.
• AMP0- – Bit 3
AMP0-, Analog Differential Amplifier 0 Negative Input Channel.
• ADC5/INT1 – Bit 2
ADC5, Analog to Digital Converter, input channel 5.
INT1, External Interrupt source 1. This pin can serve as an external interrupt source to
the MCU.
• MOSI/PSCOUT21 – Bit 1
MOSI: SPI Master Data output, Slave Data input for SPI channel. When the SPI is
enabled as a slave, this pin is configured as an input regardless of the setting of DDB1
When the SPI is enabled as a master, the data direction of this pin is controlled by
DDB1. When the pin is forced to be an input, the pull-up can still be controlled by the
PORTB1 and PUD bits.
PSCOUT21: Output 1 of PSC 2.
• MISO/PSC20 – Bit 0
MISO: Master Data input, Slave Data output pin for SPI channel. When the SPI is
enabled as a master, this pin is configured as an input regardless of the setting of
DDB0. When the SPI is enabled as a slave, the data direction of this pin is controlled by
DDB0. When the pin is forced to be an input, the pull-up can still be controlled by the
PORTB0 and PUD bits.
PSCOUT20: Output 0 of PSC 2.
71
4317B–AVR–02/05
Table 25 and Table 26 relates the alternate functions of Port B to the overriding signals
shown in Figure 28 on page 68.
Table 25. Overriding Signals for Alternate Functions in PB7..PB4
Signal Name
PB7
PB6/
PB5/
PB4/
PUOE
–
–
–
–
PUOV
–
–
–
–
DDOE
–
–
–
–
DDOV
–
–
–
–
PVOE
–
–
–
–
PVOV
–
–
–
–
PTOE
–
–
–
–
DIEOE
–
–
–
–
DIEOV
–
–
–
–
DI
–
–
–
–
AIO
–
–
–
–
Table 26. Overriding Signals for Alternate Functions in PB3..PB0
72
Signal Name
PB3/
PB2/
PB1/
PB0/
PUOE
–
–
–
–
PUOV
–
–
–
–
DDOE
–
–
–
–
DDOV
–
–
–
–
PVOE
–
–
–
–
PVOV
–
–
–
–
PTOE
–
–
–
–
DIEOE
–
–
–
–
DIEOV
–
–
–
–
DI
–
–
–
–
AIO
–
–
–
–
AT90PWM2/3
4317B–AVR–02/05
AT90PWM2/3
Alternate Functions of Port C
The Port C pins with alternate functions are shown in Table 27.
Table 27. Port C Pins Alternate Functions
Port Pin
Alternate Function
PC7
D2A : DAC output
PC6
ADC10 (Analog Input Channel 10)
ACMP1 (Analog Comparator 1 Positive Input )
PC5
ADC9 (Analog Input Channel 9)
AMP1+ (Analog Differential Amplifier 1 Input Channel )
PC4
ADC8 (Analog Input Channel 8)
AMP1- (Analog Differential Amplifier 1 Input Channel )
PC3
T1 (Timer 1 clock input)
PSCOUT23 output
PC2
T0 (Timer 0 clock input)
PSCOUT22 output
PC1
PSCIN1 (PSC 1 Digital Input)
OC1B (Timer 1 Output Compare B)
PC0
PSCOUT10 output (see note 4)
INT3
The alternate pin configuration is as follows:
• D2A – Bit 7
D2A, Digital to Analog output
• ADC10/ACMP1 – Bit 6
ADC10, Analog to Digital Converter, input channel 10.
ACMP1, Analog Comparator 1 Positive Input. Configure the port pin as input with the
internal pull-up switched off to avoid the digital port function from interfering with the
function of the Analog Comparator.
• ADC9/AMP1+ – Bit 5
ADC9, Analog to Digital Converter, input channel 9.
AMP1+, Analog Differential Amplifier 1 Positive Input Channel.
• ADC8/AMP1- – Bit 4
ADC8, Analog to Digital Converter, input channel 8.
AMP1-, Analog Differential Amplifier 1 Negative Input Channel.
• T1/PSCOUT23 – Bit 3
T1, Timer/Counter1 counter source.
PSCOUT23: Output 3 of PSC 2.
• T0/PSCOUT22 – Bit 2
T0, Timer/Counter0 counter source.
PSCOUT22: Output 2 of PSC 2.
• PSCIN1/OC1B, Bit 1
PCSIN1, PSC 1 Digital Input.
73
4317B–AVR–02/05
OC1B, Output Compare Match B output: This pin can serve as an external output for the
Timer/Counter1 Output Compare B. The pin has to be configured as an output (DDC1
set “one”) to serve this function. This pin is also the output pin for the PWM mode timer
function.
• PSCOUT10/INT3 – Bit 0
PSCOUT10: Output 0 of PSC 1.
INT3, External Interrupt source 3: This pin can serve as an external interrupt source to
the MCU.
Table 28 and Table 29 relate the alternate functions of Port C to the overriding signals
shown in Figure 28 on page 68.
Table 28. Overriding Signals for Alternate Functions in PC7..PC4
Signal Name
PC7
PC6
PC5
PC4
PUOE
–
–
–
–
PUOV
–
–
–
–
DDOE
–
–
–
–
DDOV
–
–
–
–
PVOE
–
–
–
–
PVOV
–
–
–
–
PTOE
–
–
–
–
DIEOE
–
–
–
–
DIEOV
–
–
–
–
DI
–
–
–
–
AIO
–
–
–
–
Table 29. Overriding Signals for Alternate Functions in PC3..PC0
74
Signal Name
PC3
PC2
PC1
PC0
PUOE
–
–
–
–
PUOV
–
–
–
–
DDOE
–
–
–
–
DDOV
–
–
–
–
PVOE
–
–
–
–
PVOV
–
–
–
–
PTOE
–
–
–
–
DIEOE
–
–
–
–
DIEOV
–
–
–
–
DI
–
–
–
–
AIO
–
–
–
–
AT90PWM2/3
4317B–AVR–02/05
AT90PWM2/3
Alternate Functions of Port D
The Port D pins with alternate functions are shown in Table 30.
Table 30. Port D Pins Alternate Functions
Port Pin
Alternate Function
PD7
ACMP0 (Analog Comparator 0 Positive Input )
PD6
ADC3 (Analog Input Channel 3 )
ACMPM reference for analog comparators
INT0
PD5
ADC2 (Analog Input Channel 2)
ACMP2 (Analog Comparator 2 Positive Input )
PD4
ADC1 (Analog Input Channel 1)
RXD (Dali/UART Rx data)
ICP1 (Timer 1 input capture)
SCK_A (Programming & alternate SPI Clock)
PD3
TXD (Dali/UART Tx data)
OC0A (Timer 0 Output Compare A)
SS (SPI Slave Select)
MOSI_A (Programming & alternate SPI Master Out Slave In)
PD2
PSCIN2 (PSC 2 Digital Input)
OC1A (Timer 1 Output Compare A)
MISO_A (Programming & alternate Master In SPI Slave Out)
PD1
PSCIN0 (PSC 0 Digital Input )
CLKO (System Clock Output)
PD0
PSCOUT00 output
XCK (UART Transfer Clock)
SS_A (Alternate SPI Slave Select)
The alternate pin configuration is as follows:
• ACMP0 – Bit 7
ACMP0, Analog Comparator 0 Positive Input. Configure the port pin as input with the
internal pull-up switched off to avoid the digital port function from interfering with the
function of the Analog Comparator.
• ADC3/ACMPM/INT0 – Bit 6
ADC3, Analog to Digital Converter, input channel 3.
ACMPM, Analog Comparators Negative Input. Configure the port pin as input with the
internal pull-up switched off to avoid the digital port function from interfering with the
function of the Analog Comparator.
INT0, External Interrupt source 0. This pin can serve as an external interrupt source to
the MCU.
• ADC2/ACMP2 – Bit 5
ADC2, Analog to Digital Converter, input channel 2.
75
4317B–AVR–02/05
ACMP2, Analog Comparator 1 Positive Input. Configure the port pin as input with the
internal pull-up switched off to avoid the digital port function from interfering with the
function of the Analog Comparator.
• ADC1/RXD/ICP1/SCK_A – Bit 4
ADC1, Analog to Digital Converter, input channel 1.
RXD, USART Receive Pin. Receive Data (Data input pin for the USART). When the
USART receiver is enabled this pin is configured as an input regardless of the value of
DDRD4. When the USART forces this pin to be an input, a logical one in PORTD4 will
turn on the internal pull-up.
ICP1 – Input Capture Pin1: This pin can act as an input capture pin for Timer/Counter1.
SCK_A: Master Clock output, Slave Clock input pin for SPI channel. When the SPI is
enabled as a slave, this pin is configured as an input regardless of the setting of DDD4.
When the SPI is enabled as a master, the data direction of this pin is controlled by
DDD4. When the pin is forced to be an input, the pull-up can still be controlled by the
PORTD4 bit.
• TXD/OC0A/SS/MOSI_A, Bit 3
TXD, UART Transmit pin. Data output pin for the USART. When the USART Transmitter
is enabled, this pin is configured as an output regardless of the value of DDD3.
OC0A, Output Compare Match A output: This pin can serve as an external output for the
Timer/Counter0 Output Compare A. The pin has to be configured as an output (DDD3
set “one”) to serve this function. The OC0A pin is also the output pin for the PWM mode
SS: Slave Port Select input. When the SPI is enabled as a slave, this pin is configured
as an input regardless of the setting of DDD3. As a slave, the SPI is activated when this
pin is driven low. When the SPI is enabled as a master, the data direction of this pin is
controlled by DDD3. When the pin is forced to be an input, the pull-up can still be controlled by the PORTD3 bit.
MOSI_A: SPI Master Data output, Slave Data input for SPI channel. When the SPI is
enabled as a slave, this pin is configured as an input regardless of the setting of DDD3
When the SPI is enabled as a master, the data direction of this pin is controlled by
DDD3. When the pin is forced to be an input, the pull-up can still be controlled by the
PORTD3 bit.
• PSCIN2/OC1A/MISO_A, Bit 2
PCSIN2, PSC 2 Digital Input.
OC1A, Output Compare Match A output: This pin can serve as an external output for the
Timer/Counter1 Output Compare A. The pin has to be configured as an output (DDD2
set “one”) to serve this function. The OC1A pin is also the output pin for the PWM mode
timer function.
MISO_A: Master Data input, Slave Data output pin for SPI channel. When the SPI is
enabled as a master, this pin is configured as an input regardless of the setting of
DDD2. When the SPI is enabled as a slave, the data direction of this pin is controlled by
DDD2. When the pin is forced to be an input, the pull-up can still be controlled by the
PORTD2 bit.
• PSCIN0/CLKO – Bit 1
PCSIN0, PSC 0 Digital Input.
76
AT90PWM2/3
4317B–AVR–02/05
AT90PWM2/3
CLKO, Divided System Clock: The divided system clock can be output on this pin. The
divided system clock will be output if the CKOUT Fuse is programmed, regardless of the
PORTD1 and DDD1 settings. It will also be output during reset.
• PSCOUT00/XCK/SS_A – Bit 0
PSCOUT00: Output 0 of PSC 0.
XCK, USART External clock. The Data Direction Register (DDD0) controls whether the
clock is output (DDD0 set) or input (DDD0 cleared). The XCK0 pin is active only when
the USART operates in Synchronous mode.
SS_A: Slave Port Select input. When the SPI is enabled as a slave, this pin is configured as an input regardless of the setting of DDD0. As a slave, the SPI is activated when
this pin is driven low. When the SPI is enabled as a master, the data direction of this pin
is controlled by DDD0. When the pin is forced to be an input, the pull-up can still be controlled by the PORTD0 bit.
Table 31 and Table 32 relates the alternate functions of Port D to the overriding signals
shown in Figure 28 on page 68.
Table 31. Overriding Signals for Alternate Functions PD7..PD4
Signal Name
PD7
PD6
PD5/
PD4/
PUOE
–
–
–
–
PUOV
–
–
–
–
DDOE
–
–
–
–
DDOV
–
–
–
–
PVOE
–
–
–
–
PVOV
–
–
–
–
PTOE
–
–
–
–
DIEOE
–
–
–
–
DIEOV
–
–
–
–
DI
–
–
–
–
AIO
–
–
–
–
77
4317B–AVR–02/05
Table 32. Overriding Signals for Alternate Functions in PD3..PD0
Alternate Functions of Port E
Signal Name
PD3/I
PD2/
PD1/I
PD0/
PUOE
–
–
–
–
PUOV
–
–
–
–
DDOE
–
–
–
–
DDOV
–
–
–
–
PVOE
–
–
–
–
PVOV
–
–
–
–
PTOE
–
–
–
–
DIEOE
–
–
–
–
DIEOV
–
–
–
–
DI
–
–
–
–
AIO
–
–
–
–
The Port E pins with alternate functions are shown in Table 33.
Table 33. Port E Pins Alternate Functions
Port Pin
Alternate Function
PE2
XTAL2: XTAL Output
ADC0 (Analog Input Channel 0)
PE1
XTAL1: XTAL Input
OC0B (Timer 0 Output Compare B)
PE0
RESET# (Reset Input)
OCD (On Chip Debug I/O)
The alternate pin configuration is as follows:
• XTAL2/ADC0 – Bit 2
XTAL2: Chip clock Oscillator pin 2. Used as clock pin for crystal Oscillator or Low-frequency crystal Oscillator. When used as a clock pin, the pin can not be used as an I/O
pin.
ADC0, Analog to Digital Converter, input channel 0.
• XTAL1/OC0B – Bit 1
XTAL1: Chip clock Oscillator pin 1. Used for all chip clock sources except internal calibrated RC Oscillator. When used as a clock pin, the pin can not be used as an I/O pin.
OC0B, Output Compare Match B output: This pin can serve as an external output for the
Timer/Counter0 Output Compare B. The pin has to be configured as an output (DDE1
set “one”) to serve this function. This pin is also the output pin for the PWM mode timer
function.
• RESET/OCD – Bit 0
78
AT90PWM2/3
4317B–AVR–02/05
AT90PWM2/3
RESET, Reset pin: When the RSTDISBL Fuse is programmed, this pin functions as a
normal I/O pin, and the part will have to rely on Power-on Reset and Brown-out Reset as
its reset sources. When the RSTDISBL Fuse is unprogrammed, the reset circuitry is
connected to the pin, and the pin can not be used as an I/O pin.
If PE0 is used as a reset pin, DDE0, PORTE0 and PINE0 will all read 0.
Table 34 relates the alternate functions of Port E to the overriding signals shown in Figure 28 on page 68.
Table 34. Overriding Signals for Alternate Functions in PE2..PE0
Signal Name
PE2
PE1
PE0
PUOE
–
–
–
PUOV
–
–
–
DDOE
–
–
–
DDOV
–
–
–
PVOE
–
–
–
PVOV
–
–
–
PTOE
–
–
–
DIEOE
–
–
–
DIEOV
–
–
–
DI
–
–
–
AIO
–
–
–
79
4317B–AVR–02/05
Register Description for
I/O-Ports
Port B Data Register – PORTB
Bit
Port B Data Direction Register
– DDRB
Port B Input Pins Address –
PINB
7
6
5
4
3
2
1
0
PORTB7
PORTB6
PORTB5
PORTB4
PORTB3
PORTB2
PORTB1
PORTB0
Read/Write
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
Initial Value
0
0
0
0
0
0
0
0
Bit
7
6
5
4
3
2
1
0
DDB7
DDB6
DDB5
DDB4
DDB3
DDB2
DDB1
DDB0
Read/Write
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
Initial Value
0
0
0
0
0
0
0
0
Bit
7
6
5
4
3
2
1
0
PINB7
PINB6
PINB5
PINB4
PINB3
PINB2
PINB1
PINB0
Read/Write
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
Initial Value
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
PORTB
DDRB
PINB
Port C Data Register – PORTC
Bit
Port C Data Direction Register
– DDRC
Port C Input Pins Address –
PINC
7
6
5
4
3
2
1
0
PORTC7
PORTC6
PORTC5
PORTC4
PORTC3
PORTC2
PORTC1
PORTC0
Read/Write
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
Initial Value
0
0
0
0
0
0
0
0
Bit
7
6
5
4
3
2
1
0
DDC7
DDC6
DDC5
DDC4
DDC3
DDC2
DDC1
DDC0
Read/Write
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
Initial Value
0
0
0
0
0
0
0
0
Bit
7
6
5
4
3
2
1
0
PINC7
PINC6
PINC5
PINC4
PINC3
PINC2
PINC1
PINC0
Read/Write
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
Initial Value
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
PORTC
DDRC
PINC
Port D Data Register – PORTD
Bit
Port D Data Direction Register
– DDRD
Port D Input Pins Address –
PIND
7
6
5
4
3
2
1
0
PORTD7
PORTD6
PORTD5
PORTD4
PORTD3
PORTD2
PORTD1
PORTD0
Read/Write
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
Initial Value
0
0
0
0
0
0
0
0
Bit
7
6
5
4
3
2
1
0
DDD7
DDD6
DDD5
DDD4
DDD3
DDD2
DDD1
DDD0
Read/Write
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
Initial Value
0
0
0
0
0
0
0
0
Bit
Read/Write
80
7
6
5
4
3
2
1
0
PIND7
PIND6
PIND5
PIND4
PIND3
PIND2
PIND1
PIND0
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
PORTD
DDRD
PIND
AT90PWM2/3
4317B–AVR–02/05
AT90PWM2/3
Initial Value
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
7
6
5
4
3
2
1
0
–
–
–
–
–
PORTE2
PORTE1
PORTE0
Read/Write
R
R
R
R
R
R/W
R/W
R/W
Initial Value
0
0
0
0
0
0
0
0
Bit
7
6
5
4
3
2
1
0
–
–
–
–
–
DDE2
DDE1
DDE0
Read/Write
R
R
R
R
R
R/W
R/W
R/W
Initial Value
0
0
0
0
0
0
0
0
Bit
7
6
5
4
3
2
1
0
–
–
–
–
–
PINE2
PINE1
PINE0
Read/Write
R
R
R
R
R
R/W
R/W
R/W
Initial Value
0
0
0
0
0
N/A
N/A
N/A
Port E Data Register – PORTE
Bit
Port E Data Direction Register
– DDRE
Port E Input Pins Address –
PINE
PORTE
DDRE
PINE
81
4317B–AVR–02/05
External Interrupts
The External Interrupts are triggered by the INT3:0 pins. Observe that, if enabled, the
interrupts will trigger even if the INT3:0 pins are configured as outputs. This feature provides a way of generating a software interrupt. The External Interrupts can be triggered
by a falling or rising edge or a low level. This is set up as indicated in the specification for
the External Interrupt Control Registers – EICRA (INT3:0). When the external interrupt
is enabled and is configured as level triggered, the interrupt will trigger as long as the pin
is held low. Note that recognition of falling or rising edge interrupts on INT3:0 requires
the presence of an I/O clock, described in “Clock Systems and their Distribution” on
page 30. The I/O clock is halted in all sleep modes except Idle mode.
Note that if a level triggered interrupt is used for wake-up from Power-down mode, the
changed level must be held for some time to wake up the MCU. This makes the MCU
less sensitive to noise. The changed level is sampled twice by the Watchdog Oscillator
clock. The period of the Watchdog Oscillator is 1 µs (nominal) at 5.0V and 25°C. The
frequency of the Watchdog Oscillator is voltage dependent as shown in the “Electrical
Characteristics(1)” on page 308. The MCU will wake up if the input has the required
level during this sampling or if it is held until the end of the start-up time. The start-up
time is defined by the SUT fuses as described in “System Clock” on page 30. If the level
is sampled twice by the Watchdog Oscillator clock but disappears before the end of the
start-up time, the MCU will still wake up, but no interrupt will be generated. The required
level must be held long enough for the MCU to complete the wake up to trigger the level
interrupt.
External Interrupt Control
Register A – EICRA
Bit
7
6
5
4
3
2
1
0
ISC31
ISC30
ISC21
ISC20
ISC11
ISC10
ISC01
ISC00
Read/Write
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
Initial Value
0
0
0
0
0
0
0
0
EICRA
• Bits 7..0 – ISC31, ISC30 – ISC01, ISC00: External Interrupt 3 - 0 Sense Control
Bits
The External Interrupts 3 - 0 are activated by the external pins INT3:0 if the SREG I-flag
and the corresponding interrupt mask in the EIMSK is set. The level and edges on the
external pins that activate the interrupts are defined in Table 35. Edges on INT3..INT0
are registered asynchronously.The value on the INT3:0 pins are sampled before detecting edges. If edge or toggle interrupt is selected, pulses that last longer than one clock
period will generate an interrupt. Shorter pulses are not guaranteed to generate an interrupt. Observe that CPU clock frequency can be lower than the XTAL frequency if the
XTAL divider is enabled. If low level interrupt is selected, the low level must be held until
the completion of the currently executing instruction to generate an interrupt. If enabled,
a level triggered interrupt will generate an interrupt request as long as the pin is held
low.
82
AT90PWM2/3
4317B–AVR–02/05
AT90PWM2/3
Table 35. Interrupt Sense Control(1)
ISCn1
ISCn0
0
0
The low level of INTn generates an interrupt request.
0
1
Any logical change on INTn generates an interrupt request
1
0
The falling edge between two samples of INTn generates an interrupt
request.
1
Note:
External Interrupt Mask
Register – EIMSK
Description
The rising edge between two samples of INTn generates an interrupt
request.
1. n = 3, 2, 1 or 0.
When changing the ISCn1/ISCn0 bits, the interrupt must be disabled by clearing its
Interrupt Enable bit in the EIMSK Register. Otherwise an interrupt can occur when
the bits are changed.
Bit
1
7
6
5
4
3
2
1
0
-
-
-
-
INT3
INT2
INT1
IINT0
Read/Write
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
Initial Value
0
0
0
0
0
0
0
0
EIMSK
• Bits 3..0 – INT3 – INT0: External Interrupt Request 3 - 0 Enable
When an INT3 – INT0 bit is written to one and the I-bit in the Status Register (SREG) is
set (one), the corresponding external pin interrupt is enabled. The Interrupt Sense Control bits in the External Interrupt Control Register – EICRA – defines whether the
external interrupt is activated on rising or falling edge or level sensed. Activity on any of
these pins will trigger an interrupt request even if the pin is enabled as an output. This
provides a way of generating a software interrupt.
External Interrupt Flag
Register – EIFR
Bit
7
6
5
4
3
2
1
0
-
-
-
-
INTF3
INTF2
INTF1
IINTF0
Read/Write
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
Initial Value
0
0
0
0
0
0
0
0
EIFR
• Bits 3..0 – INTF3 - INTF0: External Interrupt Flags 3 - 0
When an edge or logic change on the INT3:0 pin triggers an interrupt request, INTF3:0
becomes set (one). If the I-bit in SREG and the corresponding interrupt enable bit,
INT3:0 in EIMSK, are set (one), the MCU will jump to the interrupt vector. The flag is
cleared when the interrupt routine is executed. Alternatively, the flag can be cleared by
writing a logical one to it. These flags are always cleared when INT3:0 are configured as
level interrupt.
83
4317B–AVR–02/05
Timer/Counter0 and
Timer/Counter1
Prescalers
Timer/Counter1 and Timer/Counter0 share the same prescaler module, but the
Timer/Counters can have different prescaler settings. The description below applies to
both Timer/Counter1 and Timer/Counter0.
Internal Clock Source
The Timer/Counter can be clocked directly by the system clock (by setting the CSn2:0 =
1). This provides the fastest operation, with a maximum Timer/Counter clock frequency
equal to system clock frequency (fCLK_I/O). Alternatively, one of four taps from the prescaler can be used as a clock source. The prescaled clock has a frequency of either
fCLK_I/O/8, fCLK_I/O/64, fCLK_I/O/256, or fCLK_I/O/1024.
Prescaler Reset
The prescaler is free running, i.e., operates independently of the Clock Select logic of
the Timer/Counter, and it is shared by Timer/Counter1 and Timer/Counter0. Since the
prescaler is not affected by the Timer/Counter’s clock select, the state of the prescaler
will have implications for situations where a prescaled clock is used. One example of
prescaling artifacts occurs when the timer is enabled and clocked by the prescaler (6 >
CSn2:0 > 1). The number of system clock cycles from when the timer is enabled to the
first count occurs can be from 1 to N+1 system clock cycles, where N equals the prescaler divisor (8, 64, 256, or 1024).
It is possible to use the prescaler reset for synchronizing the Timer/Counter to program
execution. However, care must be taken if the other Timer/Counter that shares the
same prescaler also uses prescaling. A prescaler reset will affect the prescaler period
for all Timer/Counters it is connected to.
External Clock Source
An external clock source applied to the Tn/T0 pin can be used as Timer/Counter clock
(clkT1/clkT0). The Tn/T0 pin is sampled once every system clock cycle by the pin synchronization logic. The synchronized (sampled) signal is then passed through the edge
detector. Figure 29 shows a functional equivalent block diagram of the Tn/T0 synchronization and edge detector logic. The registers are clocked at the positive edge of the
internal system clock (clkI/O). The latch is transparent in the high period of the internal
system clock.
The edge detector generates one clkT1/clkT0 pulse for each positive (CSn2:0 = 7) or negative (CSn2:0 = 6) edge it detects.
Figure 29. Tn/T0 Pin Sampling
Tn
D
Q
D
Q
D
Tn_sync
(To Clock
Select Logic)
Q
LE
clk I/O
Synchronization
Edge Detector
The synchronization and edge detector logic introduces a delay of 2.5 to 3.5 system
clock cycles from an edge has been applied to the Tn/T0 pin to the counter is updated.
Enabling and disabling of the clock input must be done when Tn/T0 has been stable for
at least one system clock cycle, otherwise it is a risk that a false Timer/Counter clock
pulse is generated.
Each half period of the external clock applied must be longer than one system clock
cycle to ensure correct sampling. The external clock must be guaranteed to have less
than half the system clock frequency (fExtClk < fclk_I/O/2) given a 50/50% duty cycle. Since
84
AT90PWM2/3
4317B–AVR–02/05
AT90PWM2/3
the edge detector uses sampling, the maximum frequency of an external clock it can
detect is half the sampling frequency (Nyquist sampling theorem). However, due to variation of the system clock frequency and duty cycle caused by Oscillator source (crystal,
resonator, and capacitors) tolerances, it is recommended that maximum frequency of an
external clock source is less than fclk_I/O/2.5.
An external clock source can not be prescaled.
Figure 30. Prescaler for Timer/Counter0 and Timer/Counter1(1)
clk I/O
Clear
PSRSYNC
T0
Synchronization
T1
Synchronization
clkT1
Note:
General Timer/Counter
Control Register – GTCCR
clkT0
1. The synchronization logic on the input pins (Tn/T0) is shown in Figure 29.
Bit
7
6
5
4
3
2
1
0
TSM
ICPSEL1
–
–
–
–
–
PSRSYNC
Read/Write
R/W
R/W
R
R
R
R
R
R/W
Initial Value
0
0
0
0
0
0
0
0
GTCCR
• Bit 7 – TSM: Timer/Counter Synchronization Mode
Writing the TSM bit to one activates the Timer/Counter Synchronization mode. In this
mode, the value that is written to the PSRSYNC bit is kept, hence keeping the corresponding prescaler reset signals asserted. This ensures that the corresponding
Timer/Counters are halted and can be configured to the same value without the risk of
one of them advancing during configuration. When the TSM bit is written to zero, the
PSRSYNC bit is cleared by hardware, and the Timer/Counters start counting
simultaneously.
85
4317B–AVR–02/05
• Bit6 – ICPSEL1: Timer 1 Input Capture selection
Timer 1 capture function has two possible inputs ICP1A (PD4) and ICP1B (PB7). The
selection is made thanks to ICPSEL1 bit as described in Table .
Table 36. ICPSEL1
ICPSEL1
Description
0
Select ICP1A as trigger for timer 1 input capture
1
Select ICP1B as trigger for timer 1 input capture
• Bit 0 – PSRSYNC: Prescaler Reset
When this bit is one, Timer/Counter1 and Timer/Counter0 prescaler will be Reset. This
bit is normally cleared immediately by hardware, except if the TSM bit is set. Note that
Timer/Counter1 and Timer/Counter0 share the same prescaler and a reset of this prescaler will affect both timers.
86
AT90PWM2/3
4317B–AVR–02/05
AT90PWM2/3
8-bit Timer/Counter0 with PWM
Timer/Counter0 is a general purpose 8-bit Timer/Counter module, with two independent
Output Compare Units, and with PWM support. It allows accurate program execution
timing (event management) and wave generation. The main features are:
• Two Independent Output Compare Units
• Double Buffered Output Compare Registers
• Clear Timer on Compare Match (Auto Reload)
• Glitch Free, Phase Correct Pulse Width Modulator (PWM)
• Variable PWM Period
• Frequency Generator
• Three Independent Interrupt Sources (TOV0, OCF0A, and OCF0B)
Overview
A simplified block diagram of the 8-bit Timer/Counter is shown in Figure 31. For the
actual placement of I/O pins, refer to “Pin Descriptions” on page 10. CPU accessible I/O
Registers, including I/O bits and I/O pins, are shown in bold. The device-specific I/O
Register and bit locations are listed in the “8-bit Timer/Counter Register Description” on
page 97.
The PRTIM0 bit in “Power Reduction Register” on page 41 must be written to zero to
enable Timer/Counter0 module.
Figure 31. 8-bit Timer/Counter Block Diagram
count
TOVn
(Int.Req.)
clear
Control Logic
direction
clk Tn
Clock Select
Edge
Detector
DATA BUS
TOP
Tn
BOTTOM
( From Prescaler )
Timer/Counter
TCNTn
=
=0
OCnA
(Int.Req.)
Waveform
Generation
=
OCRnx
OCnB
(Int.Req.)
Fixed
TOP
Values
=
OCnA
Waveform
Generation
OCnB
OCRnx
TCCRnA
Definitions
TCCRnB
Many register and bit references in this section are written in general form. A lower case
“n” replaces the Timer/Counter number, in this case 0. A lower case “x” replaces the
Output Compare Unit, in this case Compare Unit A or Compare Unit B. However, when
using the register or bit defines in a program, the precise form must be used, i.e.,
TCNT0 for accessing Timer/Counter0 counter value and so on.
The definitions in Table 37 are also used extensively throughout the document.
87
4317B–AVR–02/05
Table 37. Definitions
Registers
BOTTOM
The counter reaches the BOTTOM when it becomes 0x00.
MAX
The counter reaches its MAXimum when it becomes 0xFF (decimal 255).
TOP
The counter reaches the TOP when it becomes equal to the highest
value in the count sequence. The TOP value can be assigned to be the
fixed value 0xFF (MAX) or the value stored in the OCR0A Register. The
assignment is dependent on the mode of operation.
The Timer/Counter (TCNT0) and Output Compare Registers (OCR0A and OCR0B) are
8-bit registers. Interrupt request (abbreviated to Int.Req. in the figure) signals are all visible in the Timer Interrupt Flag Register (TIFR0). All interrupts are individually masked
with the Timer Interrupt Mask Register (TIMSK0). TIFR0 and TIMSK0 are not shown in
the figure.
The Timer/Counter can be clocked internally, via the prescaler, or by an external clock
source on the T0 pin. The Clock Select logic block controls which clock source and edge
the Timer/Counter uses to increment (or decrement) its value. The Timer/Counter is
inactive when no clock source is selected. The output from the Clock Select logic is
referred to as the timer clock (clkT0).
The double buffered Output Compare Registers (OCR0A and OCR0B) are compared
with the Timer/Counter value at all times. The result of the compare can be used by the
Waveform Generator to generate a PWM or variable frequency output on the Output
Compare pins (OC0A and OC0B). See “Using the Output Compare Unit” on page 114.
for details. The compare match event will also set the Compare Flag (OCF0A or
OCF0B) which can be used to generate an Output Compare interrupt request.
Timer/Counter Clock
Sources
The Timer/Counter can be clocked by an internal or an external clock source. The clock
source is selected by the Clock Select logic which is controlled by the Clock Select
(CS02:0) bits located in the Timer/Counter Control Register (TCCR0B). For details on
clock sources and prescaler, see “Timer/Counter0 and Timer/Counter1 Prescalers” on
page 84.
Counter Unit
The main part of the 8-bit Timer/Counter is the programmable bi-directional counter unit.
Figure 32 shows a block diagram of the counter and its surroundings.
Figure 32. Counter Unit Block Diagram
TOVn
(Int.Req.)
DATA BUS
Clock Select
count
TCNTn
clear
Control Logic
clkTn
Edge
Detector
Tn
direction
( From Prescaler )
bottom
top
Signal description (internal signals):
88
count
Increment or decrement TCNT0 by 1.
direction
Select between increment and decrement.
AT90PWM2/3
4317B–AVR–02/05
AT90PWM2/3
clear
Clear TCNT0 (set all bits to zero).
clkTn
Timer/Counter clock, referred to as clkT0 in the following.
top
Signalize that TCNT0 has reached maximum value.
bottom
Signalize that TCNT0 has reached minimum value (zero).
Depending of the mode of operation used, the counter is cleared, incremented, or decremented at each timer clock (clkT0). clkT0 can be generated from an external or internal
clock source, selected by the Clock Select bits (CS02:0). When no clock source is
selected (CS02:0 = 0) the timer is stopped. However, the TCNT0 value can be accessed
by the CPU, regardless of whether clkT0 is present or not. A CPU write overrides (has
priority over) all counter clear or count operations.
The counting sequence is determined by the setting of the WGM01 and WGM00 bits
located in the Timer/Counter Control Register (TCCR0A) and the WGM02 bit located in
the Timer/Counter Control Register B (TCCR0B). There are close connections between
how the counter behaves (counts) and how waveforms are generated on the Output
Compare outputs OC0A and OC0B. For more details about advanced counting
sequences and waveform generation, see “Modes of Operation” on page 92.
The Timer/Counter Overflow Flag (TOV0) is set according to the mode of operation
selected by the WGM02:0 bits. TOV0 can be used for generating a CPU interrupt.
Output Compare Unit
The 8-bit comparator continuously compares TCNT0 with the Output Compare Registers (OCR0A and OCR0B). Whenever TCNT0 equals OCR0A or OCR0B, the
comparator signals a match. A match will set the Output Compare Flag (OCF0A or
OCF0B) at the next timer clock cycle. If the corresponding interrupt is enabled, the Output Compare Flag generates an Output Compare interrupt. The Output Compare Flag is
automatically cleared when the interrupt is executed. Alternatively, the flag can be
cleared by software by writing a logical one to its I/O bit location. The Waveform Generator uses the match signal to generate an output according to operating mode set by the
WGM02:0 bits and Compare Output mode (COM0x1:0) bits. The max and bottom signals are used by the Waveform Generator for handling the special cases of the extreme
values in some modes of operation (“Modes of Operation” on page 92).
Figure 33 shows a block diagram of the Output Compare unit.
89
4317B–AVR–02/05
Figure 33. Output Compare Unit, Block Diagram
DATA BUS
OCRnx
TCNTn
= (8-bit Comparator )
OCFnx (Int.Req.)
top
bottom
Waveform Generator
OCnx
FOCn
WGMn1:0
COMnx1:0
The OCR0x Registers are double buffered when using any of the Pulse Width Modulation (PWM) modes. For the normal and Clear Timer on Compare (CTC) modes of
operation, the double buffering is disabled. The double buffering synchronizes the
update of the OCR0x Compare Registers to either top or bottom of the counting
sequence. The synchronization prevents the occurrence of odd-length, non-symmetrical
PWM pulses, thereby making the output glitch-free.
The OCR0x Register access may seem complex, but this is not case. When the double
buffering is enabled, the CPU has access to the OCR0x Buffer Register, and if double
buffering is disabled the CPU will access the OCR0x directly.
Force Output Compare
In non-PWM waveform generation modes, the match output of the comparator can be
forced by writing a one to the Force Output Compare (FOC0x) bit. Forcing compare
match will not set the OCF0x Flag or reload/clear the timer, but the OC0x pin will be
updated as if a real compare match had occurred (the COM0x1:0 bits settings define
whether the OC0x pin is set, cleared or toggled).
Compare Match Blocking by
TCNT0 Write
All CPU write operations to the TCNT0 Register will block any compare match that
occur in the next timer clock cycle, even when the timer is stopped. This feature allows
OCR0x to be initialized to the same value as TCNT0 without triggering an interrupt when
the Timer/Counter clock is enabled.
Using the Output Compare
Unit
Since writing TCNT0 in any mode of operation will block all compare matches for one
timer clock cycle, there are risks involved when changing TCNT0 when using the Output
Compare Unit, independently of whether the Timer/Counter is running or not. If the
value written to TCNT0 equals the OCR0x value, the compare match will be missed,
resulting in incorrect waveform generation. Similarly, do not write the TCNT0 value
equal to BOTTOM when the counter is downcounting.
The setup of the OC0x should be performed before setting the Data Direction Register
for the port pin to output. The easiest way of setting the OC0x value is to use the Force
Output Compare (FOC0x) strobe bits in Normal mode. The OC0x Registers keep their
values even when changing between Waveform Generation modes.
90
AT90PWM2/3
4317B–AVR–02/05
AT90PWM2/3
Be aware that the COM0x1:0 bits are not double buffered together with the compare
value. Changing the COM0x1:0 bits will take effect immediately.
Compare Match Output
Unit
The Compare Output mode (COM0x1:0) bits have two functions. The Waveform Generator uses the COM0x1:0 bits for defining the Output Compare (OC0x) state at the next
compare match. Also, the COM0x1:0 bits control the OC0x pin output source. Figure 34
shows a simplified schematic of the logic affected by the COM0x1:0 bit setting. The I/O
Registers, I/O bits, and I/O pins in the figure are shown in bold. Only the parts of the
general I/O port control registers (DDR and PORT) that are affected by the COM0x1:0
bits are shown. When referring to the OC0x state, the reference is for the internal OC0x
Register, not the OC0x pin. If a system reset occur, the OC0x Register is reset to “0”.
Figure 34. Compare Match Output Unit, Schematic
COMnx1
COMnx0
FOCn
Waveform
Generator
D
Q
1
OCnx
DATA BUS
D
0
OCnx
Pin
Q
PORT
D
Q
DDR
clk I/O
The general I/O port function is overridden by the Output Compare (OC0x) from the
Waveform Generator if either of the COM0x1:0 bits are set. However, the OC0x pin
direction (input or output) is still controlled by the Data Direction Register (DDR) for the
port pin. The Data Direction Register bit for the OC0x pin (DDR_OC0x) must be set as
output before the OC0x value is visible on the pin. The port override function is independent of the Waveform Generation mode.
The design of the Output Compare pin logic allows initialization of the OC0x state before
the output is enabled. Note that some COM0x1:0 bit settings are reserved for certain
modes of operation. See “8-bit Timer/Counter Register Description” on page 97.
Compare Output Mode and
Waveform Generation
The Waveform Generator uses the COM0x1:0 bits differently in Normal, CTC, and PWM
modes. For all modes, setting the COM0x1:0 = 0 tells the Waveform Generator that no
action on the OC0x Register is to be performed on the next compare match. For compare output actions in the non-PWM modes refer to Table 38 on page 97. For fast PWM
mode, refer to Table 39 on page 98, and for phase correct PWM refer to Table 40 on
page 98.
A change of the COM0x1:0 bits state will have effect at the first compare match after the
bits are written. For non-PWM modes, the action can be forced to have immediate effect
by using the FOC0x strobe bits.
91
4317B–AVR–02/05
Modes of Operation
The mode of operation, i.e., the behavior of the Timer/Counter and the Output Compare
pins, is defined by the combination of the Waveform Generation mode (WGM02:0) and
Compare Output mode (COM0x1:0) bits. The Compare Output mode bits do not affect
the counting sequence, while the Waveform Generation mode bits do. The COM0x1:0
bits control whether the PWM output generated should be inverted or not (inverted or
non-inverted PWM). For non-PWM modes the COM0x1:0 bits control whether the output should be set, cleared, or toggled at a compare match (See “Compare Match Output
Unit” on page 91.).
For detailed timing information refer to “Timer/Counter Timing Diagrams” on page 96.
Normal Mode
The simplest mode of operation is the Normal mode (WGM02:0 = 0). In this mode the
counting direction is always up (incrementing), and no counter clear is performed. The
counter simply overruns when it passes its maximum 8-bit value (TOP = 0xFF) and then
restarts from the bottom (0x00). In normal operation the Timer/Counter Overflow Flag
(TOV0) will be set in the same timer clock cycle as the TCNT0 becomes zero. The
TOV0 Flag in this case behaves like a ninth bit, except that it is only set, not cleared.
However, combined with the timer overflow interrupt that automatically clears the TOV0
Flag, the timer resolution can be increased by software. There are no special cases to
consider in the Normal mode, a new counter value can be written anytime.
The Output Compare unit can be used to generate interrupts at some given time. Using
the Output Compare to generate waveforms in Normal mode is not recommended,
since this will occupy too much of the CPU time.
Clear Timer on Compare
Match (CTC) Mode
In Clear Timer on Compare or CTC mode (WGM02:0 = 2), the OCR0A Register is used
to manipulate the counter resolution. In CTC mode the counter is cleared to zero when
the counter value (TCNT0) matches the OCR0A. The OCR0A defines the top value for
the counter, hence also its resolution. This mode allows greater control of the compare
match output frequency. It also simplifies the operation of counting external events.
The timing diagram for the CTC mode is shown in Figure 35. The counter value
(TCNT0) increases until a compare match occurs between TCNT0 and OCR0A, and
then counter (TCNT0) is cleared.
Figure 35. CTC Mode, Timing Diagram
OCnx Interrupt Flag Set
TCNTn
OCn
(Toggle)
Period
(COMnx1:0 = 1)
1
2
3
4
An interrupt can be generated each time the counter value reaches the TOP value by
using the OCF0A Flag. If the interrupt is enabled, the interrupt handler routine can be
used for updating the TOP value. However, changing TOP to a value close to BOTTOM
when the counter is running with none or a low prescaler value must be done with care
since the CTC mode does not have the double buffering feature. If the new value written
to OCR0A is lower than the current value of TCNT0, the counter will miss the compare
92
AT90PWM2/3
4317B–AVR–02/05
AT90PWM2/3
match. The counter will then have to count to its maximum value (0xFF) and wrap
around starting at 0x00 before the compare match can occur.
For generating a waveform output in CTC mode, the OC0A output can be set to toggle
its logical level on each compare match by setting the Compare Output mode bits to toggle mode (COM0A1:0 = 1). The OC0A value will not be visible on the port pin unless the
data direction for the pin is set to output. The waveform generated will have a maximum
frequency of fOC0 = fclk_I/O/2 when OCR0A is set to zero (0x00). The waveform frequency
is defined by the following equation:
f clk_I/O
f OCnx = -------------------------------------------------2 ⋅ N ⋅ ( 1 + OCRnx )
The N variable represents the prescale factor (1, 8, 64, 256, or 1024).
As for the Normal mode of operation, the TOV0 Flag is set in the same timer clock cycle
that the counter counts from MAX to 0x00.
Fast PWM Mode
The fast Pulse Width Modulation or fast PWM mode (WGM02:0 = 3 or 7) provides a high
frequency PWM waveform generation option. The fast PWM differs from the other PWM
option by its single-slope operation. The counter counts from BOTTOM to TOP then
restarts from BOTTOM. TOP is defined as 0xFF when WGM2:0 = 3, and OCR0A when
WGM2:0 = 7. In non-inverting Compare Output mode, the Output Compare (OC0x) is
cleared on the compare match between TCNT0 and OCR0x, and set at BOTTOM. In
inverting Compare Output mode, the output is set on compare match and cleared at
BOTTOM. Due to the single-slope operation, the operating frequency of the fast PWM
mode can be twice as high as the phase correct PWM mode that use dual-slope operation. This high frequency makes the fast PWM mode well suited for power regulation,
rectification, and DAC applications. High frequency allows physically small sized external components (coils, capacitors), and therefore reduces total system cost.
In fast PWM mode, the counter is incremented until the counter value matches the TOP
value. The counter is then cleared at the following timer clock cycle. The timing diagram
for the fast PWM mode is shown in Figure 36. The TCNT0 value is in the timing diagram
shown as a histogram for illustrating the single-slope operation. The diagram includes
non-inverted and inverted PWM outputs. The small horizontal line marks on the TCNT0
slopes represent compare matches between OCR0x and TCNT0.
Figure 36. Fast PWM Mode, Timing Diagram
OCRnx Interrupt Flag Set
OCRnx Update and
TOVn Interrupt Flag Set
TCNTn
OCn
(COMnx1:0 = 2)
OCn
(COMnx1:0 = 3)
Period
1
2
3
4
5
6
7
93
4317B–AVR–02/05
The Timer/Counter Overflow Flag (TOV0) is set each time the counter reaches TOP. If
the interrupt is enabled, the interrupt handler routine can be used for updating the compare value.
In fast PWM mode, the compare unit allows generation of PWM waveforms on the
OC0x pins. Setting the COM0x1:0 bits to two will produce a non-inverted PWM and an
inverted PWM output can be generated by setting the COM0x1:0 to three: Setting the
COM0A1:0 bits to one allows the OC0A pin to toggle on Compare Matches if the
WGM02 bit is set. This option is not available for the OC0B pin (see Table 42 on page
99). The actual OC0x value will only be visible on the port pin if the data direction for the
port pin is set as output. The PWM waveform is generated by setting (or clearing) the
OC0x Register at the compare match between OCR0x and TCNT0, and clearing (or setting) the OC0x Register at the timer clock cycle the counter is cleared (changes from
TOP to BOTTOM).
The PWM frequency for the output can be calculated by the following equation:
f clk_I/O
f OCnxPWM = -----------------N ⋅ 256
The N variable represents the prescale factor (1, 8, 64, 256, or 1024).
The extreme values for the OCR0A Register represents special cases when generating
a PWM waveform output in the fast PWM mode. If the OCR0A is set equal to BOTTOM,
the output will be a narrow spike for each MAX+1 timer clock cycle. Setting the OCR0A
equal to MAX will result in a constantly high or low output (depending on the polarity of
the output set by the COM0A1:0 bits.)
A frequency (with 50% duty cycle) waveform output in fast PWM mode can be achieved
by setting OC0x to toggle its logical level on each compare match (COM0x1:0 = 1). The
waveform generated will have a maximum frequency of fOC0 = fclk_I/O/2 when OCR0A is
set to zero. This feature is similar to the OC0A toggle in CTC mode, except the double
buffer feature of the Output Compare unit is enabled in the fast PWM mode.
Phase Correct PWM Mode
The phase correct PWM mode (WGM02:0 = 1 or 5) provides a high resolution phase
correct PWM waveform generation option. The phase correct PWM mode is based on a
dual-slope operation. The counter counts repeatedly from BOTTOM to TOP and then
from TOP to BOTTOM. TOP is defined as 0xFF when WGM2:0 = 1, and OCR0A when
WGM2:0 = 5. In non-inverting Compare Output mode, the Output Compare (OC0x) is
cleared on the compare match between TCNT0 and OCR0x while upcounting, and set
on the compare match while downcounting. In inverting Output Compare mode, the
operation is inverted. The dual-slope operation has lower maximum operation frequency
than single slope operation. However, due to the symmetric feature of the dual-slope
PWM modes, these modes are preferred for motor control applications.
In phase correct PWM mode the counter is incremented until the counter value matches
TOP. When the counter reaches TOP, it changes the count direction. The TCNT0 value
will be equal to TOP for one timer clock cycle. The timing diagram for the phase correct
PWM mode is shown on Figure 37. The TCNT0 value is in the timing diagram shown as
a histogram for illustrating the dual-slope operation. The diagram includes non-inverted
and inverted PWM outputs. The small horizontal line marks on the TCNT0 slopes represent compare matches between OCR0x and TCNT0.
94
AT90PWM2/3
4317B–AVR–02/05
AT90PWM2/3
Figure 37. Phase Correct PWM Mode, Timing Diagram
OCnx Interrupt Flag Set
OCRnx Update
TOVn Interrupt Flag Set
TCNTn
OCnx
(COMnx1:0 = 2)
OCnx
(COMnx1:0 = 3)
Period
1
2
3
The Timer/Counter Overflow Flag (TOV0) is set each time the counter reaches BOTTOM. The Interrupt Flag can be used to generate an interrupt each time the counter
reaches the BOTTOM value.
In phase correct PWM mode, the compare unit allows generation of PWM waveforms on
the OC0x pins. Setting the COM0x1:0 bits to two will produce a non-inverted PWM. An
inverted PWM output can be generated by setting the COM0x1:0 to three: Setting the
COM0A0 bits to one allows the OC0A pin to toggle on Compare Matches if the WGM02
bit is set. This option is not available for the OC0B pin (see Table 43 on page 99). The
actual OC0x value will only be visible on the port pin if the data direction for the port pin
is set as output. The PWM waveform is generated by clearing (or setting) the OC0x
Register at the compare match between OCR0x and TCNT0 when the counter increments, and setting (or clearing) the OC0x Register at compare match between OCR0x
and TCNT0 when the counter decrements. The PWM frequency for the output when
using phase correct PWM can be calculated by the following equation:
f clk_I/O
f OCnxPCPWM = -----------------N ⋅ 510
The N variable represents the prescale factor (1, 8, 64, 256, or 1024).
The extreme values for the OCR0A Register represent special cases when generating a
PWM waveform output in the phase correct PWM mode. If the OCR0A is set equal to
BOTTOM, the output will be continuously low and if set equal to MAX the output will be
continuously high for non-inverted PWM mode. For inverted PWM the output will have
the opposite logic values.
At the very start of period 2 in Figure 37 OCnx has a transition from high to low even
though there is no Compare Match. The point of this transition is to guarantee symmetry
around BOTTOM. There are two cases that give a transition without Compare Match.
•
OCRnx changes its value from MAX, like in Figure 37. When the OCR0A value is
MAX the OCn pin value is the same as the result of a down-counting Compare
95
4317B–AVR–02/05
Match. To ensure symmetry around BOTTOM the OCnx value at MAX must
correspond to the result of an up-counting Compare Match.
•
Timer/Counter Timing
Diagrams
The timer starts counting from a value higher than the one in OCRnx, and for that
reason misses the Compare Match and hence the OCnx change that would have
happened on the way up.
The Timer/Counter is a synchronous design and the timer clock (clk T0) is therefore
shown as a clock enable signal in the following figures. The figures include information
on when interrupt flags are set. Figure 38 contains timing data for basic Timer/Counter
operation. The figure shows the count sequence close to the MAX value in all modes
other than phase correct PWM mode.
Figure 38. Timer/Counter Timing Diagram, no Prescaling
clkI/O
clkTn
(clkI/O /1)
TCNTn
MAX - 1
MAX
BOTTOM
BOTTOM + 1
TOVn
Figure 39 shows the same timing data, but with the prescaler enabled.
Figure 39. Timer/Counter Timing Diagram, with Prescaler (fclk_I/O/8)
clkI/O
clkTn
(clkI/O /8)
TCNTn
MAX - 1
MAX
BOTTOM
BOTTOM + 1
TOVn
Figure 40 shows the setting of OCF0B in all modes and OCF0A in all modes except
CTC mode and PWM mode, where OCR0A is TOP.
Figure 40. Timer/Counter Timing Diagram, Setting of OCF0x, with Prescaler (fclk_I/O/8)
clkI/O
clkTn
(clkI/O /8)
TCNTn
OCRnx
OCRnx - 1
OCRnx
OCRnx + 1
OCRnx + 2
OCRnx Value
OCFnx
96
AT90PWM2/3
4317B–AVR–02/05
AT90PWM2/3
Figure 41 shows the setting of OCF0A and the clearing of TCNT0 in CTC mode and fast
PWM mode where OCR0A is TOP.
Figure 41. Timer/Counter Timing Diagram, Clear Timer on Compare Match mode, with
Prescaler (fclk_I/O/8)
clkI/O
clkTn
(clkI/O /8)
TCNTn
(CTC)
TOP - 1
TOP
OCRnx
BOTTOM
BOTTOM + 1
TOP
OCFnx
8-bit Timer/Counter
Register Description
Timer/Counter Control
Register A – TCCR0A
Bit
7
6
5
4
3
2
1
0
COM0A1
COM0A0
COM0B1
COM0B0
–
–
WGM01
WGM00
Read/Write
R/W
R/W
R/W
R/W
R
R
R/W
R/W
Initial Value
0
0
0
0
0
0
0
0
TCCR0A
• Bits 7:6 – COM0A1:0: Compare Match Output A Mode
These bits control the Output Compare pin (OC0A) behavior. If one or both of the
COM0A1:0 bits are set, the OC0A output overrides the normal port functionality of the
I/O pin it is connected to. However, note that the Data Direction Register (DDR) bit corresponding to the OC0A pin must be set in order to enable the output driver.
When OC0A is connected to the pin, the function of the COM0A1:0 bits depends on the
WGM02:0 bit setting. Table 38 shows the COM0A1:0 bit functionality when the
WGM02:0 bits are set to a normal or CTC mode (non-PWM).
Table 38. Compare Output Mode, non-PWM Mode
COM0A1
COM0A0
Description
0
0
Normal port operation, OC0A disconnected.
0
1
Toggle OC0A on Compare Match
1
0
Clear OC0A on Compare Match
1
1
Set OC0A on Compare Match
97
4317B–AVR–02/05
Table 39 shows the COM0A1:0 bit functionality when the WGM01:0 bits are set to fast
PWM mode.
Table 39. Compare Output Mode, Fast PWM Mode(1)
COM0A1
COM0A0
0
0
Normal port operation, OC0A disconnected.
0
1
WGM02 = 0: Normal Port Operation, OC0A Disconnected.
WGM02 = 1: Toggle OC0A on Compare Match.
1
0
Clear OC0A on Compare Match, set OC0A at TOP
1
1
Set OC0A on Compare Match, clear OC0A at TOP
Note:
Description
1. A special case occurs when OCR0A equals TOP and COM0A1 is set. In this case,
the Compare Match is ignored, but the set or clear is done at TOP. See “Fast PWM
Mode” on page 93 for more details.
Table 40 shows the COM0A1:0 bit functionality when the WGM02:0 bits are set to
phase correct PWM mode.
Table 40. Compare Output Mode, Phase Correct PWM Mode(1)
COM0A1
COM0A0
0
0
Normal port operation, OC0A disconnected.
0
1
WGM02 = 0: Normal Port Operation, OC0A Disconnected.
WGM02 = 1: Toggle OC0A on Compare Match.
1
0
Clear OC0A on Compare Match when up-counting. Set OC0A on
Compare Match when down-counting.
1
1
Set OC0A on Compare Match when up-counting. Clear OC0A on
Compare Match when down-counting.
Note:
Description
1. A special case occurs when OCR0A equals TOP and COM0A1 is set. In this case,
the Compare Match is ignored, but the set or clear is done at TOP. See “Phase Correct PWM Mode” on page 119 for more details.
• Bits 5:4 – COM0B1:0: Compare Match Output B Mode
These bits control the Output Compare pin (OC0B) behavior. If one or both of the
COM0B1:0 bits are set, the OC0B output overrides the normal port functionality of the
I/O pin it is connected to. However, note that the Data Direction Register (DDR) bit corresponding to the OC0B pin must be set in order to enable the output driver.
When OC0B is connected to the pin, the function of the COM0B1:0 bits depends on the
WGM02:0 bit setting. Table 41 shows the COM0B1:0 bit functionality when the
WGM02:0 bits are set to a normal or CTC mode (non-PWM).
Table 41. Compare Output Mode, non-PWM Mode
98
COM0B1
COM0B0
Description
0
0
Normal port operation, OC0B disconnected.
0
1
Toggle OC0B on Compare Match
1
0
Clear OC0B on Compare Match
1
1
Set OC0B on Compare Match
AT90PWM2/3
4317B–AVR–02/05
AT90PWM2/3
Table 42 shows the COM0B1:0 bit functionality when the WGM02:0 bits are set to fast
PWM mode.
Table 42. Compare Output Mode, Fast PWM Mode(1)
COM0B1
COM0B0
0
0
Normal port operation, OC0B disconnected.
0
1
Reserved
1
0
Clear OC0B on Compare Match, set OC0B at TOP
1
1
Set OC0B on Compare Match, clear OC0B at TOP
Note:
Description
1. A special case occurs when OCR0B equals TOP and COM0B1 is set. In this case,
the Compare Match is ignored, but the set or clear is done at TOP. See “Fast PWM
Mode” on page 93 for more details.
Table 43 shows the COM0B1:0 bit functionality when the WGM02:0 bits are set to
phase correct PWM mode.
Table 43. Compare Output Mode, Phase Correct PWM Mode(1)
COM0B1
COM0B0
0
0
Normal port operation, OC0B disconnected.
0
1
Reserved
1
0
Clear OC0B on Compare Match when up-counting. Set OC0B on
Compare Match when down-counting.
1
1
Set OC0B on Compare Match when up-counting. Clear OC0B on
Compare Match when down-counting.
Note:
Description
1. A special case occurs when OCR0B equals TOP and COM0B1 is set. In this case,
the Compare Match is ignored, but the set or clear is done at TOP. See “Phase Correct PWM Mode” on page 94 for more details.
• Bits 3, 2 – Res: Reserved Bits
These bits are reserved bits in the AT90PWM2/3 and will always read as zero.
• Bits 1:0 – WGM01:0: Waveform Generation Mode
Combined with the WGM02 bit found in the TCCR0B Register, these bits control the
counting sequence of the counter, the source for maximum (TOP) counter value, and
what type of waveform generation to be used, see Table 44. Modes of operation supported by the Timer/Counter unit are: Normal mode (counter), Clear Timer on Compare
Match (CTC) mode, and two types of Pulse Width Modulation (PWM) modes (see
“Modes of Operation” on page 92).
Table 44. Waveform Generation Mode Bit Description
Timer/Count
er Mode of
Operation
TOP
Update of
OCRx at
TOV Flag
Set on(1)(2)
Mode
WGM02
WGM01
WGM00
0
0
0
0
Normal
0xFF
Immediate
MAX
1
0
0
1
PWM, Phase
Correct
0xFF
TOP
BOTTOM
2
0
1
0
CTC
OCRA
Immediate
MAX
3
0
1
1
Fast PWM
0xFF
TOP
MAX
99
4317B–AVR–02/05
Table 44. Waveform Generation Mode Bit Description (Continued)
TOP
Update of
OCRx at
TOV Flag
Set on(1)(2)
–
–
–
OCRA
TOP
BOTTOM
Reserved
–
–
–
Fast PWM
OCRA
TOP
TOP
Mode
WGM02
WGM01
WGM00
4
1
0
0
Reserved
5
1
0
1
PWM, Phase
Correct
6
1
1
0
7
1
1
1
Notes:
Timer/Counter Control
Register B – TCCR0B
Timer/Count
er Mode of
Operation
1. MAX
= 0xFF
2. BOTTOM = 0x00
Bit
7
6
5
4
3
2
1
0
FOC0A
FOC0B
–
–
WGM02
CS02
CS01
CS00
Read/Write
W
W
R
R
R
R
R/W
R/W
Initial Value
0
0
0
0
0
0
0
0
TCCR0B
• Bit 7 – FOC0A: Force Output Compare A
The FOC0A bit is only active when the WGM bits specify a non-PWM mode.
However, for ensuring compatibility with future devices, this bit must be set to zero when
TCCR0B is written when operating in PWM mode. When writing a logical one to the
FOC0A bit, an immediate Compare Match is forced on the Waveform Generation unit.
The OC0A output is changed according to its COM0A1:0 bits setting. Note that the
FOC0A bit is implemented as a strobe. Therefore it is the value present in the
COM0A1:0 bits that determines the effect of the forced compare.
A FOC0A strobe will not generate any interrupt, nor will it clear the timer in CTC mode
using OCR0A as TOP.
The FOC0A bit is always read as zero.
• Bit 6 – FOC0B: Force Output Compare B
The FOC0B bit is only active when the WGM bits specify a non-PWM mode.
However, for ensuring compatibility with future devices, this bit must be set to zero when
TCCR0B is written when operating in PWM mode. When writing a logical one to the
FOC0B bit, an immediate Compare Match is forced on the Waveform Generation unit.
The OC0B output is changed according to its COM0B1:0 bits setting. Note that the
FOC0B bit is implemented as a strobe. Therefore it is the value present in the
COM0B1:0 bits that determines the effect of the forced compare.
A FOC0B strobe will not generate any interrupt, nor will it clear the timer in CTC mode
using OCR0B as TOP.
The FOC0B bit is always read as zero.
• Bits 5:4 – Res: Reserved Bits
These bits are reserved bits in the AT90PWM2/3 and will always read as zero.
• Bit 3 – WGM02: Waveform Generation Mode
See the description in the “Timer/Counter Control Register A – TCCR0A” on page 97.
• Bits 2:0 – CS02:0: Clock Select
100
AT90PWM2/3
4317B–AVR–02/05
AT90PWM2/3
The three Clock Select bits select the clock source to be used by the Timer/Counter.
Table 45. Clock Select Bit Description
CS02
CS01
CS00
Description
0
0
0
No clock source (Timer/Counter stopped)
0
0
1
clkI/O/(No prescaling)
0
1
0
clkI/O/8 (From prescaler)
0
1
1
clkI/O/64 (From prescaler)
1
0
0
clkI/O/256 (From prescaler)
1
0
1
clkI/O/1024 (From prescaler)
1
1
0
External clock source on T0 pin. Clock on falling edge.
1
1
1
External clock source on T0 pin. Clock on rising edge.
If external pin modes are used for the Timer/Counter0, transitions on the T0 pin will
clock the counter even if the pin is configured as an output. This feature allows software
control of the counting.
Timer/Counter Register –
TCNT0
Bit
7
6
5
4
3
2
1
0
TCNT0[7:0]
TCNT0
Read/Write
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
Initial Value
0
0
0
0
0
0
0
0
The Timer/Counter Register gives direct access, both for read and write operations, to
the Timer/Counter unit 8-bit counter. Writing to the TCNT0 Register blocks (removes)
the Compare Match on the following timer clock. Modifying the counter (TCNT0) while
the counter is running, introduces a risk of missing a Compare Match between TCNT0
and the OCR0x Registers.
Output Compare Register A –
OCR0A
Bit
7
6
5
4
3
2
1
0
OCR0A[7:0]
OCR0A
Read/Write
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
Initial Value
0
0
0
0
0
0
0
0
The Output Compare Register A contains an 8-bit value that is continuously compared
with the counter value (TCNT0). A match can be used to generate an Output Compare
interrupt, or to generate a waveform output on the OC0A pin.
Output Compare Register B –
OCR0B
Bit
7
6
5
4
3
2
1
0
OCR0B[7:0]
OCR0B
Read/Write
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
Initial Value
0
0
0
0
0
0
0
0
The Output Compare Register B contains an 8-bit value that is continuously compared
with the counter value (TCNT0). A match can be used to generate an Output Compare
interrupt, or to generate a waveform output on the OC0B pin.
101
4317B–AVR–02/05
Timer/Counter Interrupt Mask
Register – TIMSK0
Bit
7
6
5
4
3
2
1
0
–
–
–
–
–
OCIE0B
OCIE0A
TOIE0
Read/Write
R
R
R
R
R
R/W
R/W
R/W
Initial Value
0
0
0
0
0
0
0
0
TIMSK0
• Bits 7..3 – Res: Reserved Bits
These bits are reserved bits in the AT90PWM2/3 and will always read as zero.
• Bit 2 – OCIE0B: Timer/Counter Output Compare Match B Interrupt Enable
When the OCIE0B bit is written to one, and the I-bit in the Status Register is set, the
Timer/Counter Compare Match B interrupt is enabled. The corresponding interrupt is
executed if a Compare Match in Timer/Counter occurs, i.e., when the OCF0B bit is set in
the Timer/Counter Interrupt Flag Register – TIFR0.
• Bit 1 – OCIE0A: Timer/Counter0 Output Compare Match A Interrupt Enable
When the OCIE0A bit is written to one, and the I-bit in the Status Register is set, the
Timer/Counter0 Compare Match A interrupt is enabled. The corresponding interrupt is
executed if a Compare Match in Timer/Counter0 occurs, i.e., when the OCF0A bit is set
in the Timer/Counter 0 Interrupt Flag Register – TIFR0.
• Bit 0 – TOIE0: Timer/Counter0 Overflow Interrupt Enable
When the TOIE0 bit is written to one, and the I-bit in the Status Register is set, the
Timer/Counter0 Overflow interrupt is enabled. The corresponding interrupt is executed if
an overflow in Timer/Counter0 occurs, i.e., when the TOV0 bit is set in the
Timer/Counter 0 Interrupt Flag Register – TIFR0.
Timer/Counter 0 Interrupt Flag
Register – TIFR0
Bit
7
6
5
4
3
2
1
0
–
–
–
–
–
OCF0B
OCF0A
TOV0
Read/Write
R
R
R
R
R
R/W
R/W
R/W
Initial Value
0
0
0
0
0
0
0
0
TIFR0
• Bits 7..3 – Res: Reserved Bits
These bits are reserved bits in the AT90PWM2/3 and will always read as zero.
• Bit 2 – OCF0B: Timer/Counter 0 Output Compare B Match Flag
The OCF0B bit is set when a Compare Match occurs between the Timer/Counter and
the data in OCR0B – Output Compare Register0 B. OCF0B is cleared by hardware
when executing the corresponding interrupt handling vector. Alternatively, OCF0B is
cleared by writing a logic one to the flag. When the I-bit in SREG, OCIE0B
(Timer/Counter Compare B Match Interrupt Enable), and OCF0B are set, the
Timer/Counter Compare Match Interrupt is executed.
• Bit 1 – OCF0A: Timer/Counter 0 Output Compare A Match Flag
The OCF0A bit is set when a Compare Match occurs between the Timer/Counter0 and
the data in OCR0A – Output Compare Register0. OCF0A is cleared by hardware when
executing the corresponding interrupt handling vector. Alternatively, OCF0A is cleared
by writing a logic one to the flag. When the I-bit in SREG, OCIE0A (Timer/Counter0
Compare Match Interrupt Enable), and OCF0A are set, the Timer/Counter0 Compare
Match Interrupt is executed.
• Bit 0 – TOV0: Timer/Counter0 Overflow Flag
The bit TOV0 is set when an overflow occurs in Timer/Counter0. TOV0 is cleared by
hardware when executing the corresponding interrupt handling vector. Alternatively,
TOV0 is cleared by writing a logic one to the flag. When the SREG I-bit, TOIE0
102
AT90PWM2/3
4317B–AVR–02/05
AT90PWM2/3
(Timer/Counter0 Overflow Interrupt Enable), and TOV0 are set, the Timer/Counter0
Overflow interrupt is executed.
The setting of this flag is dependent of the WGM02:0 bit setting. Refer to Table 44,
“Waveform Generation Mode Bit Description” on page 99.
103
4317B–AVR–02/05
16-bit Timer/Counter1 with PWM
The 16-bit Timer/Counter unit allows accurate program execution timing (event management), wave generation, and signal timing measurement. The main features are:
• True 16-bit Design (i.e., Allows 16-bit PWM)
• Two independent Output Compare Units
• Double Buffered Output Compare Registers
• One Input Capture Unit
• Input Capture Noise Canceler
• Clear Timer on Compare Match (Auto Reload)
• Glitch-free, Phase Correct Pulse Width Modulator (PWM)
• Variable PWM Period
• Frequency Generator
• External Event Counter
• Four independent interrupt Sources (TOV1, OCF1A, OCF1B, and ICF1)
Overview
Most register and bit references in this section are written in general form. A lower case
“n” replaces the Timer/Counter number, and a lower case “x” replaces the Output Compare unit channel. However, when using the register or bit defines in a program, the
precise form must be used, i.e., TCNT1 for accessing Timer/Counter1 counter value
and so on.
A simplified block diagram of the 16-bit Timer/Counter is shown in Figure 42. For the
actual placement of I/O pins, refer to “Pin Descriptions” on page 4. CPU accessible I/O
Registers, including I/O bits and I/O pins, are shown in bold. The device-specific I/O
Register and bit locations are listed in the “16-bit Timer/Counter Register Description”
on page 125.
The PRTIM1 bit in “Power Reduction Register” on page 41 must be written to zero to
enable Timer/Counter1 module.
104
AT90PWM2/3
4317B–AVR–02/05
AT90PWM2/3
Figure 42. 16-bit Timer/Counter Block Diagram(1)
Count
Clear
Direction
TOVn
(Int.Req.)
Control Logic
clkTn
Clock Select
Edge
Detector
TOP
Tn
BOTTOM
( From Prescaler )
Timer/Counter
TCNTn
=
=0
OCnA
(Int.Req.)
Waveform
Generation
=
OCnA
DATA BUS
OCRnA
OCnB
(Int.Req.)
Fixed
TOP
Values
Waveform
Generation
=
OCRnB
ICPSEL1
ICFn (Int.Req.)
Edge
Detector
ICRn
TCCRnA
Note:
Registers
OCnB
Noise
Canceler
0
1
ICPnA
ICPnB
TCCRnB
1. Refer toTable on page 5 for Timer/Counter1 pin placement and description.
The Timer/Counter (TCNTn), Output Compare Registers (OCRnx), and Input Capture
Register (ICRn) are all 16-bit registers. Special procedures must be followed when
accessing the 16-bit registers. These procedures are described in the section “Accessing 16-bit Registers” on page 106. The Timer/Counter Control Registers (TCCRnx) are
8-bit registers and have no CPU access restrictions. Interrupt requests (abbreviated to
Int.Req. in the figure) signals are all visible in the Timer Interrupt Flag Register (TIFRn).
All interrupts are individually masked with the Timer Interrupt Mask Register (TIMSKn).
TIFRn and TIMSKn are not shown in the figure.
The Timer/Counter can be clocked internally, via the prescaler, or by an external clock
source on the Tn pin. The Clock Select logic block controls which clock source and edge
the Timer/Counter uses to increment (or decrement) its value. The Timer/Counter is
inactive when no clock source is selected. The output from the Clock Select logic is
referred to as the timer clock (clkTn).
The double buffered Output Compare Registers (OCRnx) are compared with the
Timer/Counter value at all time. The result of the compare can be used by the Waveform
Generator to generate a PWM or variable frequency output on the Output Compare pin
(OCnx). See “Output Compare Units” on page 112.. The compare match event will also
set the Compare Match Flag (OCFnx) which can be used to generate an Output Compare interrupt request.
105
4317B–AVR–02/05
The Input Capture Register can capture the Timer/Counter value at a given external
(edge triggered) event on either the Input Capture pin (ICPn). The Input Capture unit
includes a digital filtering unit (Noise Canceler) for reducing the chance of capturing
noise spikes.
The TOP value, or maximum Timer/Counter value, can in some modes of operation be
defined by either the OCRnA Register, the ICRn Register, or by a set of fixed values.
When using OCRnA as TOP value in a PWM mode, the OCRnA Register can not be
used for generating a PWM output. However, the TOP value will in this case be double
buffered allowing the TOP value to be changed in run time. If a fixed TOP value is
required, the ICRn Register can be used as an alternative, freeing the OCRnA to be
used as PWM output.
Definitions
The following definitions are used extensively throughout the section:
Table 46. Definitions
Accessing 16-bit
Registers
BOTTOM
The counter reaches the BOTTOM when it becomes 0x0000.
MAX
The counter reaches its MAXimum when it becomes 0xFFFF (decimal 65535).
TOP
The counter reaches the TOP when it becomes equal to the highest value in the
count sequence. The TOP value can be assigned to be one of the fixed values:
0x00FF, 0x01FF, or 0x03FF, or to the value stored in the OCRnA or ICRn Register. The assignment is dependent of the mode of operation.
The TCNTn, OCRnx, and ICRn are 16-bit registers that can be accessed by the AVR
CPU via the 8-bit data bus. The 16-bit register must be byte accessed using two read or
write operations. Each 16-bit timer has a single 8-bit register for temporary storing of the
high byte of the 16-bit access. The same temporary register is shared between all 16-bit
registers within each 16-bit timer. Accessing the low byte triggers the 16-bit read or write
operation. When the low byte of a 16-bit register is written by the CPU, the high byte
stored in the temporary register, and the low byte written are both copied into the 16-bit
register in the same clock cycle. When the low byte of a 16-bit register is read by the
CPU, the high byte of the 16-bit register is copied into the temporary register in the
same clock cycle as the low byte is read.
Not all 16-bit accesses uses the temporary register for the high byte. Reading the
OCRnx 16-bit registers does not involve using the temporary register.
To do a 16-bit write, the high byte must be written before the low byte. For a 16-bit read,
the low byte must be read before the high byte.
The following code examples show how to access the 16-bit Timer Registers assuming
that no interrupts updates the temporary register. The same principle can be used
directly for accessing the OCRnx and ICRn Registers. Note that when using “C”, the
compiler handles the 16-bit access.
106
AT90PWM2/3
4317B–AVR–02/05
AT90PWM2/3
Assembly Code Examples(1)
...
; Set TCNTn to 0x01FF
ldi r17,0x01
ldi r16,0xFF
out TCNTnH,r17
out TCNTnL,r16
; Read TCNTn into r17:r16
in r16,TCNTnL
in r17,TCNTnH
...
C Code Examples(1)
unsigned int i;
...
/* Set TCNTn to 0x01FF */
TCNTn = 0x1FF;
/* Read TCNTn into i */
i = TCNTn;
...
Note:
1. The example code assumes that the part specific header file is included.
For I/O Registers located in extended I/O map, “IN”, “OUT”, “SBIS”, “SBIC”, “CBI”,
and “SBI” instructions must be replaced with instructions that allow access to
extended I/O. Typically “LDS” and “STS” combined with “SBRS”, “SBRC”, “SBR”, and
“CBR”.
The assembly code example returns the TCNTn value in the r17:r16 register pair.
It is important to notice that accessing 16-bit registers are atomic operations. If an interrupt occurs between the two instructions accessing the 16-bit register, and the interrupt
code updates the temporary register by accessing the same or any other of the 16-bit
Timer Registers, then the result of the access outside the interrupt will be corrupted.
Therefore, when both the main code and the interrupt code update the temporary register, the main code must disable the interrupts during the 16-bit access.
107
4317B–AVR–02/05
The following code examples show how to do an atomic read of the TCNTn Register
contents. Reading any of the OCRnx or ICRn Registers can be done by using the same
principle.
Assembly Code Example(1)
TIM16_ReadTCNTn:
; Save global interrupt flag
in r18,SREG
; Disable interrupts
cli
; Read TCNTn into r17:r16
in r16,TCNTnL
in r17,TCNTnH
; Restore global interrupt flag
out SREG,r18
ret
C Code Example(1)
unsigned int TIM16_ReadTCNTn( void )
{
unsigned char sreg;
unsigned int i;
/* Save global interrupt flag */
sreg = SREG;
/* Disable interrupts */
_CLI();
/* Read TCNTn into i */
i = TCNTn;
/* Restore global interrupt flag */
SREG = sreg;
return i;
}
Note:
1. The example code assumes that the part specific header file is included.
For I/O Registers located in extended I/O map, “IN”, “OUT”, “SBIS”, “SBIC”, “CBI”,
and “SBI” instructions must be replaced with instructions that allow access to
extended I/O. Typically “LDS” and “STS” combined with “SBRS”, “SBRC”, “SBR”, and
“CBR”.
The assembly code example returns the TCNTn value in the r17:r16 register pair.
108
AT90PWM2/3
4317B–AVR–02/05
AT90PWM2/3
The following code examples show how to do an atomic write of the TCNTn Register
contents. Writing any of the OCRnx or ICRn Registers can be done by using the same
principle.
Assembly Code Example(1)
TIM16_WriteTCNTn:
; Save global interrupt flag
in r18,SREG
; Disable interrupts
cli
; Set TCNTn to r17:r16
out TCNTnH,r17
out TCNTnL,r16
; Restore global interrupt flag
out SREG,r18
ret
C Code Example(1)
void TIM16_WriteTCNTn( unsigned int i )
{
unsigned char sreg;
unsigned int i;
/* Save global interrupt flag */
sreg = SREG;
/* Disable interrupts */
_CLI();
/* Set TCNTn to i */
TCNTn = i;
/* Restore global interrupt flag */
SREG = sreg;
}
Note:
1. The example code assumes that the part specific header file is included.
For I/O Registers located in extended I/O map, “IN”, “OUT”, “SBIS”, “SBIC”, “CBI”,
and “SBI” instructions must be replaced with instructions that allow access to
extended I/O. Typically “LDS” and “STS” combined with “SBRS”, “SBRC”, “SBR”, and
“CBR”.
The assembly code example requires that the r17:r16 register pair contains the value to
be written to TCNTn.
Reusing the Temporary High
Byte Register
If writing to more than one 16-bit register where the high byte is the same for all registers
written, then the high byte only needs to be written once. However, note that the same
rule of atomic operation described previously also applies in this case.
109
4317B–AVR–02/05
Timer/Counter Clock
Sources
The Timer/Counter can be clocked by an internal or an external clock source. The clock
source is selected by the Clock Select logic which is controlled by the Clock Select
(CSn2:0) bits located in the Timer/Counter control Register B (TCCRnB). For details on
clock sources and prescaler, see “Timer/Counter0 and Timer/Counter1 Prescalers” on
page 84.
Counter Unit
The main part of the 16-bit Timer/Counter is the programmable 16-bit bi-directional
counter unit. Figure 43 shows a block diagram of the counter and its surroundings.
Figure 43. Counter Unit Block Diagram
DATA BUS (8-bit)
TOVn
(Int.Req.)
TEMP (8-bit)
Clock Select
Count
TCNTnH (8-bit)
TCNTnL (8-bit)
TCNTn (16-bit Counter)
Clear
Direction
Control Logic
clkTn
Edge
Detector
Tn
( From Prescaler )
TOP
BOTTOM
Signal description (internal signals):
Count
Increment or decrement TCNTn by 1.
Direction
Select between increment and decrement.
Clear
Clear TCNTn (set all bits to zero).
clkTn
Timer/Counter clock.
TOP
Signalize that TCNTn has reached maximum value.
BOTTOM
Signalize that TCNTn has reached minimum value (zero).
The 16-bit counter is mapped into two 8-bit I/O memory locations: Counter High
(TCNTnH) containing the upper eight bits of the counter, and Counter Low (TCNTnL)
containing the lower eight bits. The TCNTnH Register can only be indirectly accessed
by the CPU. When the CPU does an access to the TCNTnH I/O location, the CPU
accesses the high byte temporary register (TEMP). The temporary register is updated
with the TCNTnH value when the TCNTnL is read, and TCNTnH is updated with the
temporary register value when TCNTnL is written. This allows the CPU to read or write
the entire 16-bit counter value within one clock cycle via the 8-bit data bus. It is important to notice that there are special cases of writing to the TCNTn Register when the
counter is counting that will give unpredictable results. The special cases are described
in the sections where they are of importance.
Depending on the mode of operation used, the counter is cleared, incremented, or decremented at each timer clock (clkTn). The clkTn can be generated from an external or
internal clock source, selected by the Clock Select bits (CSn2:0). When no clock source
is selected (CSn2:0 = 0) the timer is stopped. However, the TCNTn value can be
accessed by the CPU, independent of whether clkTn is present or not. A CPU write overrides (has priority over) all counter clear or count operations.
The counting sequence is determined by the setting of the Waveform Generation mode
bits (WGMn3:0) located in the Timer/Counter Control Registers A and B (TCCRnA and
TCCRnB). There are close connections between how the counter behaves (counts) and
110
AT90PWM2/3
4317B–AVR–02/05
AT90PWM2/3
how waveforms are generated on the Output Compare outputs OCnx. For more details
about advanced counting sequences and waveform generation, see “16-bit
Timer/Counter1 with PWM” on page 104.
The Timer/Counter Overflow Flag (TOVn) is set according to the mode of operation
selected by the WGMn3:0 bits. TOVn can be used for generating a CPU interrupt.
Input Capture Unit
The Timer/Counter incorporates an Input Capture unit that can capture external events
and give them a time-stamp indicating time of occurrence. The external signal indicating
an event, or multiple events, can be applied via the ICPn pin or alternatively, via the
analog-comparator unit. The time-stamps can then be used to calculate frequency, dutycycle, and other features of the signal applied. Alternatively the time-stamps can be
used for creating a log of the events.
The Input Capture unit is illustrated by the block diagram shown in Figure 44. The elements of the block diagram that are not directly a part of the Input Capture unit are gray
shaded. The small “n” in register and bit names indicates the Timer/Counter number.
Figure 44. Input Capture Unit Block Diagram
DATA BUS
(8-bit)
TEMP (8-bit)
ICRnH (8-bit)
WRITE
ICRnL (8-bit)
TCNTnH (8-bit)
ICRn (16-bit Register)
ICPSEL1
TCNTnL (8-bit)
TCNTn (16-bit Counter)
ICNC
ICES
Noise
Canceler
Edge
Detector
ICPnA
ICFn (Int.Req.)
ICPnB
When a change of the logic level (an event) occurs on the Input Capture pin (ICPn),
alternatively on the Analog Comparator output (ACO), and this change confirms to the
setting of the edge detector, a capture will be triggered. When a capture is triggered, the
16-bit value of the counter (TCNTn) is written to the Input Capture Register (ICRn). The
Input Capture Flag (ICFn) is set at the same system clock as the TCNTn value is copied
into ICRn Register. If enabled (ICIEn = 1), the Input Capture Flag generates an Input
Capture interrupt. The ICFn Flag is automatically cleared when the interrupt is executed.
Alternatively the ICFn Flag can be cleared by software by writing a logical one to its I/O
bit location.
Reading the 16-bit value in the Input Capture Register (ICRn) is done by first reading the
low byte (ICRnL) and then the high byte (ICRnH). When the low byte is read the high
byte is copied into the high byte temporary register (TEMP). When the CPU reads the
ICRnH I/O location it will access the TEMP Register.
111
4317B–AVR–02/05
The ICRn Register can only be written when using a Waveform Generation mode that
utilizes the ICRn Register for defining the counter’s TOP value. In these cases the
Waveform Generation mode (WGMn3:0) bits must be set before the TOP value can be
written to the ICRn Register. When writing the ICRn Register the high byte must be written to the ICRnH I/O location before the low byte is written to ICRnL.
For more information on how to access the 16-bit registers refer to “Accessing 16-bit
Registers” on page 106.
Input Capture Trigger Source
The trigger sources for the Input Capture unit arethe Input Capture pin (ICP1A &
ICP1B).
Be aware that changing trigger source can trigger a capture. The Input Capture Flag
must therefore be cleared after the change.
The Input Capture pin (ICPn) IS sampled using the same technique as for the Tn pin
(Figure 29 on page 84). The edge detector is also identical. However, when the noise
canceler is enabled, additional logic is inserted before the edge detector, which
increases the delay by four system clock cycles. Note that the input of the noise canceler and edge detector is always enabled unless the Timer/Counter is set in a
Waveform Generation mode that uses ICRn to define TOP.
An Input Capture can be triggered by software by controlling the port of the ICPn pin.
Noise Canceler
The noise canceler improves noise immunity by using a simple digital filtering scheme.
The noise canceler input is monitored over four samples, and all four must be equal for
changing the output that in turn is used by the edge detector.
The noise canceler is enabled by setting the Input Capture Noise Canceler (ICNCn) bit
in Timer/Counter Control Register B (TCCRnB). When enabled the noise canceler introduces additional four system clock cycles of delay from a change applied to the input, to
the update of the ICRn Register. The noise canceler uses the system clock and is therefore not affected by the prescaler.
Using the Input Capture Unit
The main challenge when using the Input Capture unit is to assign enough processor
capacity for handling the incoming events. The time between two events is critical. If the
processor has not read the captured value in the ICRn Register before the next event
occurs, the ICRn will be overwritten with a new value. In this case the result of the capture will be incorrect.
When using the Input Capture interrupt, the ICRn Register should be read as early in the
interrupt handler routine as possible. Even though the Input Capture interrupt has relatively high priority, the maximum interrupt response time is dependent on the maximum
number of clock cycles it takes to handle any of the other interrupt requests.
Using the Input Capture unit in any mode of operation when the TOP value (resolution)
is actively changed during operation, is not recommended.
Measurement of an external signal’s duty cycle requires that the trigger edge is changed
after each capture. Changing the edge sensing must be done as early as possible after
the ICRn Register has been read. After a change of the edge, the Input Capture Flag
(ICFn) must be cleared by software (writing a logical one to the I/O bit location). For
measuring frequency only, the clearing of the ICFn Flag is not required (if an interrupt
handler is used).
Output Compare Units
112
The 16-bit comparator continuously compares TCNTn with the Output Compare Register (OCRnx). If TCNT equals OCRnx the comparator signals a match. A match will set
AT90PWM2/3
4317B–AVR–02/05
AT90PWM2/3
the Output Compare Flag (OCFnx) at the next timer clock cycle. If enabled (OCIEnx =
1), the Output Compare Flag generates an Output Compare interrupt. The OCFnx Flag
is automatically cleared when the interrupt is executed. Alternatively the OCFnx Flag
can be cleared by software by writing a logical one to its I/O bit location. The Waveform
Generator uses the match signal to generate an output according to operating mode set
by the Waveform Generation mode (WGMn3:0) bits and Compare Output mode
(COMnx1:0) bits. The TOP and BOTTOM signals are used by the Waveform Generator
for handling the special cases of the extreme values in some modes of operation (See
“16-bit Timer/Counter1 with PWM” on page 104.)
A special feature of Output Compare unit A allows it to define the Timer/Counter TOP
value (i.e., counter resolution). In addition to the counter resolution, the TOP value
defines the period time for waveforms generated by the Waveform Generator.
Figure 45 shows a block diagram of the Output Compare unit. The small “n” in the register and bit names indicates the device number (n = n for Timer/Counter n), and the “x”
indicates Output Compare unit (x). The elements of the block diagram that are not
directly a part of the Output Compare unit are gray shaded.
Figure 45. Output Compare Unit, Block Diagram
DATA BUS
(8-bit)
TEMP (8-bit)
OCRnxH Buf. (8-bit)
OCRnxL Buf. (8-bit)
TCNTnH (8-bit)
OCRnx Buffer (16-bit Register)
OCRnxH (8-bit)
TCNTnL (8-bit)
TCNTn (16-bit Counter)
OCRnxL (8-bit)
OCRnx (16-bit Register)
= (16-bit Comparator )
OCFnx (Int.Req.)
TOP
BOTTOM
Waveform Generator
WGMn3:0
OCnx
COMnx1:0
The OCRnx Register is double buffered when using any of the twelve Pulse Width Modulation (PWM) modes. For the Normal and Clear Timer on Compare (CTC) modes of
operation, the double buffering is disabled. The double buffering synchronizes the
update of the OCRnx Compare Register to either TOP or BOTTOM of the counting
sequence. The synchronization prevents the occurrence of odd-length, non-symmetrical
PWM pulses, thereby making the output glitch-free.
The OCRnx Register access may seem complex, but this is not case. When the double
buffering is enabled, the CPU has access to the OCRnx Buffer Register, and if double
buffering is disabled the CPU will access the OCRnx directly. The content of the OCR1x
(Buffer or Compare) Register is only changed by a write operation (the Timer/Counter
does not update this register automatically as the TCNT1 and ICR1 Register). Therefore
113
4317B–AVR–02/05
OCR1x is not read via the high byte temporary register (TEMP). However, it is a good
practice to read the low byte first as when accessing other 16-bit registers. Writing the
OCRnx Registers must be done via the TEMP Register since the compare of all 16 bits
is done continuously. The high byte (OCRnxH) has to be written first. When the high
byte I/O location is written by the CPU, the TEMP Register will be updated by the value
written. Then when the low byte (OCRnxL) is written to the lower eight bits, the high byte
will be copied into the upper 8-bits of either the OCRnx buffer or OCRnx Compare Register in the same system clock cycle.
For more information of how to access the 16-bit registers refer to “Accessing 16-bit
Registers” on page 106.
Force Output Compare
In non-PWM Waveform Generation modes, the match output of the comparator can be
forced by writing a one to the Force Output Compare (FOCnx) bit. Forcing compare
match will not set the OCFnx Flag or reload/clear the timer, but the OCnx pin will be
updated as if a real compare match had occurred (the COMn1:0 bits settings define
whether the OCnx pin is set, cleared or toggled).
Compare Match Blocking by
TCNTn Write
All CPU writes to the TCNTn Register will block any compare match that occurs in the
next timer clock cycle, even when the timer is stopped. This feature allows OCRnx to be
initialized to the same value as TCNTn without triggering an interrupt when the
Timer/Counter clock is enabled.
Using the Output Compare
Unit
Since writing TCNTn in any mode of operation will block all compare matches for one
timer clock cycle, there are risks involved when changing TCNTn when using any of the
Output Compare channels, independent of whether the Timer/Counter is running or not.
If the value written to TCNTn equals the OCRnx value, the compare match will be
missed, resulting in incorrect waveform generation. Do not write the TCNTn equal to
TOP in PWM modes with variable TOP values. The compare match for the TOP will be
ignored and the counter will continue to 0xFFFF. Similarly, do not write the TCNTn value
equal to BOTTOM when the counter is downcounting.
The setup of the OCnx should be performed before setting the Data Direction Register
for the port pin to output. The easiest way of setting the OCnx value is to use the Force
Output Compare (FOCnx) strobe bits in Normal mode. The OCnx Register keeps its
value even when changing between Waveform Generation modes.
Be aware that the COMnx1:0 bits are not double buffered together with the compare
value. Changing the COMnx1:0 bits will take effect immediately.
Compare Match Output
Unit
114
The Compare Output mode (COMnx1:0) bits have two functions. The Waveform Generator uses the COMnx1:0 bits for defining the Output Compare (OCnx) state at the next
compare match. Secondly the COMnx1:0 bits control the OCnx pin output source. Figure 46 shows a simplified schematic of the logic affected by the COMnx1:0 bit setting.
The I/O Registers, I/O bits, and I/O pins in the figure are shown in bold. Only the parts of
the general I/O Port Control Registers (DDR and PORT) that are affected by the
COMnx1:0 bits are shown. When referring to the OCnx state, the reference is for the
internal OCnx Register, not the OCnx pin. If a system reset occur, the OCnx Register is
reset to “0”.
AT90PWM2/3
4317B–AVR–02/05
AT90PWM2/3
Figure 46. Compare Match Output Unit, Schematic
COMnx1
COMnx0
FOCnx
Waveform
Generator
D
Q
1
OCnx
DATA BUS
D
0
OCnx
Pin
Q
PORT
D
Q
DDR
clk I/O
The general I/O port function is overridden by the Output Compare (OCnx) from the
Waveform Generator if either of the COMnx1:0 bits are set. However, the OCnx pin
direction (input or output) is still controlled by the Data Direction Register (DDR) for the
port pin. The Data Direction Register bit for the OCnx pin (DDR_OCnx) must be set as
output before the OCnx value is visible on the pin. The port override function is generally
independent of the Waveform Generation mode, but there are some exceptions. Refer
to Table 47, Table 48 and Table 49 for details.
The design of the Output Compare pin logic allows initialization of the OCnx state before
the output is enabled. Note that some COMnx1:0 bit settings are reserved for certain
modes of operation. See “16-bit Timer/Counter Register Description” on page 125.
The COMnx1:0 bits have no effect on the Input Capture unit.
Compare Output Mode and
Waveform Generation
The Waveform Generator uses the COMnx1:0 bits differently in normal, CTC, and PWM
modes. For all modes, setting the COMnx1:0 = 0 tells the Waveform Generator that no
action on the OCnx Register is to be performed on the next compare match. For compare output actions in the non-PWM modes refer to Table 47 on page 125. For fast
PWM mode refer to Table 48 on page 125, and for phase correct and phase and frequency correct PWM refer to Table 49 on page 126.
A change of the COMnx1:0 bits state will have effect at the first compare match after the
bits are written. For non-PWM modes, the action can be forced to have immediate effect
by using the FOCnx strobe bits.
Modes of Operation
The mode of operation, i.e., the behavior of the Timer/Counter and the Output Compare
pins, is defined by the combination of the Waveform Generation mode (WGMn3:0) and
Compare Output mode (COMnx1:0) bits. The Compare Output mode bits do not affect
the counting sequence, while the Waveform Generation mode bits do. The COMnx1:0
bits control whether the PWM output generated should be inverted or not (inverted or
non-inverted PWM). For non-PWM modes the COMnx1:0 bits control whether the out-
115
4317B–AVR–02/05
put should be set, cleared or toggle at a compare match (See “Compare Match Output
Unit” on page 114.)
For detailed timing information refer to “Timer/Counter Timing Diagrams” on page 123.
Normal Mode
The simplest mode of operation is the Normal mode (WGMn3:0 = 0). In this mode the
counting direction is always up (incrementing), and no counter clear is performed. The
counter simply overruns when it passes its maximum 16-bit value (MAX = 0xFFFF) and
then restarts from the BOTTOM (0x0000). In normal operation the Timer/Counter Overflow Flag (TOVn) will be set in the same timer clock cycle as the TCNTn becomes zero.
The TOVn Flag in this case behaves like a 17th bit, except that it is only set, not cleared.
However, combined with the timer overflow interrupt that automatically clears the TOVn
Flag, the timer resolution can be increased by software. There are no special cases to
consider in the Normal mode, a new counter value can be written anytime.
The Input Capture unit is easy to use in Normal mode. However, observe that the maximum interval between the external events must not exceed the resolution of the counter.
If the interval between events are too long, the timer overflow interrupt or the prescaler
must be used to extend the resolution for the capture unit.
The Output Compare units can be used to generate interrupts at some given time. Using
the Output Compare to generate waveforms in Normal mode is not recommended,
since this will occupy too much of the CPU time.
Clear Timer on Compare
Match (CTC) Mode
In Clear Timer on Compare or CTC mode (WGMn3:0 = 4 or 12), the OCRnA or ICRn
Register are used to manipulate the counter resolution. In CTC mode the counter is
cleared to zero when the counter value (TCNTn) matches either the OCRnA (WGMn3:0
= 4) or the ICRn (WGMn3:0 = 12). The OCRnA or ICRn define the top value for the
counter, hence also its resolution. This mode allows greater control of the compare
match output frequency. It also simplifies the operation of counting external events.
The timing diagram for the CTC mode is shown in Figure 47. The counter value
(TCNTn) increases until a compare match occurs with either OCRnA or ICRn, and then
counter (TCNTn) is cleared.
Figure 47. CTC Mode, Timing Diagram
OCnA Interrupt Flag Set
or ICFn Interrupt Flag Set
(Interrupt on TOP)
TCNTn
OCnA
(Toggle)
Period
(COMnA1:0 = 1)
1
2
3
4
An interrupt can be generated at each time the counter value reaches the TOP value by
either using the OCFnA or ICFn Flag according to the register used to define the TOP
value. If the interrupt is enabled, the interrupt handler routine can be used for updating
the TOP value. However, changing the TOP to a value close to BOTTOM when the
counter is running with none or a low prescaler value must be done with care since the
CTC mode does not have the double buffering feature. If the new value written to
116
AT90PWM2/3
4317B–AVR–02/05
AT90PWM2/3
OCRnA or ICRn is lower than the current value of TCNTn, the counter will miss the compare match. The counter will then have to count to its maximum value (0xFFFF) and
wrap around starting at 0x0000 before the compare match can occur. In many cases
this feature is not desirable. An alternative will then be to use the fast PWM mode using
OCRnA for defining TOP (WGMn3:0 = 15) since the OCRnA then will be double
buffered.
For generating a waveform output in CTC mode, the OCnA output can be set to toggle
its logical level on each compare match by setting the Compare Output mode bits to toggle mode (COMnA1:0 = 1). The OCnA value will not be visible on the port pin unless the
data direction for the pin is set to output (DDR_OCnA = 1). The waveform generated will
have a maximum frequency of fOCnA = fclk_I/O/2 when OCRnA is set to zero (0x0000). The
waveform frequency is defined by the following equation:
f clk_I/O
f OCnA = --------------------------------------------------2 ⋅ N ⋅ ( 1 + OCRnA )
The N variable represents the prescaler factor (1, 8, 64, 256, or 1024).
As for the Normal mode of operation, the TOVn Flag is set in the same timer clock cycle
that the counter counts from MAX to 0x0000.
Fast PWM Mode
The fast Pulse Width Modulation or fast PWM mode (WGMn3:0 = 5, 6, 7, 14, or 15) provides a high frequency PWM waveform generation option. The fast PWM differs from
the other PWM options by its single-slope operation. The counter counts from BOTTOM
to TOP then restarts from BOTTOM. In non-inverting Compare Output mode, the Output
Compare (OCnx) is set on the compare match between TCNTn and OCRnx, and
cleared at TOP. In inverting Compare Output mode output is cleared on compare match
and set at TOP. Due to the single-slope operation, the operating frequency of the fast
PWM mode can be twice as high as the phase correct and phase and frequency correct
PWM modes that use dual-slope operation. This high frequency makes the fast PWM
mode well suited for power regulation, rectification, and DAC applications. High frequency allows physically small sized external components (coils, capacitors), hence
reduces total system cost.
The PWM resolution for fast PWM can be fixed to 8-, 9-, or 10-bit, or defined by either
ICRn or OCRnA. The minimum resolution allowed is 2-bit (ICRn or OCRnA set to
0x0003), and the maximum resolution is 16-bit (ICRn or OCRnA set to MAX). The PWM
resolution in bits can be calculated by using the following equation:
log ( TOP + 1 )
R FPWM = ----------------------------------log ( 2 )
In fast PWM mode the counter is incremented until the counter value matches either
one of the fixed values 0x00FF, 0x01FF, or 0x03FF (WGMn3:0 = 5, 6, or 7), the value in
ICRn (WGMn3:0 = 14), or the value in OCRnA (WGMn3:0 = 15). The counter is then
cleared at the following timer clock cycle. The timing diagram for the fast PWM mode is
shown in Figure 48. The figure shows fast PWM mode when OCRnA or ICRn is used to
define TOP. The TCNTn value is in the timing diagram shown as a histogram for illustrating the single-slope operation. The diagram includes non-inverted and inverted PWM
outputs. The small horizontal line marks on the TCNTn slopes represent compare
matches between OCRnx and TCNTn. The OCnx Interrupt Flag will be set when a compare match occurs.
117
4317B–AVR–02/05
Figure 48. Fast PWM Mode, Timing Diagram
OCRnx/TOP Update and
TOVn Interrupt Flag Set and
OCnA Interrupt Flag Set
or ICFn Interrupt Flag Set
(Interrupt on TOP)
TCNTn
OCnx
(COMnx1:0 = 2)
OCnx
(COMnx1:0 = 3)
Period
1
2
3
4
5
6
7
8
The Timer/Counter Overflow Flag (TOVn) is set each time the counter reaches TOP. In
addition the OCnA or ICFn Flag is set at the same timer clock cycle as TOVn is set
when either OCRnA or ICRn is used for defining the TOP value. If one of the interrupts
are enabled, the interrupt handler routine can be used for updating the TOP and compare values.
When changing the TOP value the program must ensure that the new TOP value is
higher or equal to the value of all of the Compare Registers. If the TOP value is lower
than any of the Compare Registers, a compare match will never occur between the
TCNTn and the OCRnx. Note that when using fixed TOP values the unused bits are
masked to zero when any of the OCRnx Registers are written.
The procedure for updating ICRn differs from updating OCRnA when used for defining
the TOP value. The ICRn Register is not double buffered. This means that if ICRn is
changed to a low value when the counter is running with none or a low prescaler value,
there is a risk that the new ICRn value written is lower than the current value of TCNTn.
The result will then be that the counter will miss the compare match at the TOP value.
The counter will then have to count to the MAX value (0xFFFF) and wrap around starting at 0x0000 before the compare match can occur. The OCRnA Register however, is
double buffered. This feature allows the OCRnA I/O location to be written anytime.
When the OCRnA I/O location is written the value written will be put into the OCRnA
Buffer Register. The OCRnA Compare Register will then be updated with the value in
the Buffer Register at the next timer clock cycle the TCNTn matches TOP. The update is
done at the same timer clock cycle as the TCNTn is cleared and the TOVn Flag is set.
Using the ICRn Register for defining TOP works well when using fixed TOP values. By
using ICRn, the OCRnA Register is free to be used for generating a PWM output on
OCnA. However, if the base PWM frequency is actively changed (by changing the TOP
value), using the OCRnA as TOP is clearly a better choice due to its double buffer
feature.
In fast PWM mode, the compare units allow generation of PWM waveforms on the
OCnx pins. Setting the COMnx1:0 bits to two will produce a non-inverted PWM and an
inverted PWM output can be generated by setting the COMnx1:0 to three (see Table on
page 125). The actual OCnx value will only be visible on the port pin if the data direction
for the port pin is set as output (DDR_OCnx). The PWM waveform is generated by setting (or clearing) the OCnx Register at the compare match between OCRnx and TCNTn,
118
AT90PWM2/3
4317B–AVR–02/05
AT90PWM2/3
and clearing (or setting) the OCnx Register at the timer clock cycle the counter is
cleared (changes from TOP to BOTTOM).
The PWM frequency for the output can be calculated by the following equation:
f clk_I/O
f OCnxPWM = ----------------------------------N ⋅ ( 1 + TOP )
The N variable represents the prescaler divider (1, 8, 64, 256, or 1024).
The extreme values for the OCRnx Register represents special cases when generating
a PWM waveform output in the fast PWM mode. If the OCRnx is set equal to BOTTOM
(0x0000) the output will be a narrow spike for each TOP+1 timer clock cycle. Setting the
OCRnx equal to TOP will result in a constant high or low output (depending on the polarity of the output set by the COMnx1:0 bits.)
A frequency (with 50% duty cycle) waveform output in fast PWM mode can be achieved
by setting OCnA to toggle its logical level on each compare match (COMnA1:0 = 1).
This applies only if OCR1A is used to define the TOP value (WGM13:0 = 15). The waveform generated will have a maximum frequency of fOCnA = fclk_I/O/2 when OCRnA is set to
zero (0x0000). This feature is similar to the OCnA toggle in CTC mode, except the double buffer feature of the Output Compare unit is enabled in the fast PWM mode.
Phase Correct PWM Mode
The phase correct Pulse Width Modulation or phase correct PWM mode (WGMn3:0 = 1,
2, 3, 10, or 11) provides a high resolution phase correct PWM waveform generation
option. The phase correct PWM mode is, like the phase and frequency correct PWM
mode, based on a dual-slope operation. The counter counts repeatedly from BOTTOM
(0x0000) to TOP and then from TOP to BOTTOM. In non-inverting Compare Output
mode, the Output Compare (OCnx) is cleared on the compare match between TCNTn
and OCRnx while upcounting, and set on the compare match while downcounting. In
inverting Output Compare mode, the operation is inverted. The dual-slope operation has
lower maximum operation frequency than single slope operation. However, due to the
symmetric feature of the dual-slope PWM modes, these modes are preferred for motor
control applications.
The PWM resolution for the phase correct PWM mode can be fixed to 8-, 9-, or 10-bit, or
defined by either ICRn or OCRnA. The minimum resolution allowed is 2-bit (ICRn or
OCRnA set to 0x0003), and the maximum resolution is 16-bit (ICRn or OCRnA set to
MAX). The PWM resolution in bits can be calculated by using the following equation:
log ( TOP + 1 )
R PCPWM = ----------------------------------log ( 2 )
In phase correct PWM mode the counter is incremented until the counter value matches
either one of the fixed values 0x00FF, 0x01FF, or 0x03FF (WGMn3:0 = 1, 2, or 3), the
value in ICRn (WGMn3:0 = 10), or the value in OCRnA (WGMn3:0 = 11). The counter
has then reached the TOP and changes the count direction. The TCNTn value will be
equal to TOP for one timer clock cycle. The timing diagram for the phase correct PWM
mode is shown on Figure 49. The figure shows phase correct PWM mode when OCRnA
or ICRn is used to define TOP. The TCNTn value is in the timing diagram shown as a
histogram for illustrating the dual-slope operation. The diagram includes non-inverted
and inverted PWM outputs. The small horizontal line marks on the TCNTn slopes represent compare matches between OCRnx and TCNTn. The OCnx Interrupt Flag will be
set when a compare match occurs.
119
4317B–AVR–02/05
Figure 49. Phase Correct PWM Mode, Timing Diagram
OCRnx/TOP Update and
OCnA Interrupt Flag Set
or ICFn Interrupt Flag Set
(Interrupt on TOP)
TOVn Interrupt Flag Set
(Interrupt on Bottom)
TCNTn
OCnx
(COMnx1:0 = 2)
OCnx
(COMnx1:0 = 3)
Period
1
2
3
4
The Timer/Counter Overflow Flag (TOVn) is set each time the counter reaches BOTTOM. When either OCRnA or ICRn is used for defining the TOP value, the OCnA or
ICFn Flag is set accordingly at the same timer clock cycle as the OCRnx Registers are
updated with the double buffer value (at TOP). The Interrupt Flags can be used to generate an interrupt each time the counter reaches the TOP or BOTTOM value.
When changing the TOP value the program must ensure that the new TOP value is
higher or equal to the value of all of the Compare Registers. If the TOP value is lower
than any of the Compare Registers, a compare match will never occur between the
TCNTn and the OCRnx. Note that when using fixed TOP values, the unused bits are
masked to zero when any of the OCRnx Registers are written. As the third period shown
in Figure 49 illustrates, changing the TOP actively while the Timer/Counter is running in
the phase correct mode can result in an unsymmetrical output. The reason for this can
be found in the time of update of the OCRnx Register. Since the OCRnx update occurs
at TOP, the PWM period starts and ends at TOP. This implies that the length of the falling slope is determined by the previous TOP value, while the length of the rising slope is
determined by the new TOP value. When these two values differ the two slopes of the
period will differ in length. The difference in length gives the unsymmetrical result on the
output.
It is recommended to use the phase and frequency correct mode instead of the phase
correct mode when changing the TOP value while the Timer/Counter is running. When
using a static TOP value there are practically no differences between the two modes of
operation.
In phase correct PWM mode, the compare units allow generation of PWM waveforms on
the OCnx pins. Setting the COMnx1:0 bits to two will produce a non-inverted PWM and
an inverted PWM output can be generated by setting the COMnx1:0 to three (See Table
on page 126). The actual OCnx value will only be visible on the port pin if the data direction for the port pin is set as output (DDR_OCnx). The PWM waveform is generated by
setting (or clearing) the OCnx Register at the compare match between OCRnx and
TCNTn when the counter increments, and clearing (or setting) the OCnx Register at
compare match between OCRnx and TCNTn when the counter decrements. The PWM
120
AT90PWM2/3
4317B–AVR–02/05
AT90PWM2/3
frequency for the output when using phase correct PWM can be calculated by the following equation:
f clk_I/O
f OCnxPCPWM = ---------------------------2 ⋅ N ⋅ TOP
The N variable represents the prescaler divider (1, 8, 64, 256, or 1024).
The extreme values for the OCRnx Register represent special cases when generating a
PWM waveform output in the phase correct PWM mode. If the OCRnx is set equal to
BOTTOM the output will be continuously low and if set equal to TOP the output will be
continuously high for non-inverted PWM mode. For inverted PWM the output will have
the opposite logic values. If OCR1A is used to define the TOP value (WGM13:0 = 11)
and COM1A1:0 = 1, the OC1A output will toggle with a 50% duty cycle.
Phase and Frequency Correct
PWM Mode
The phase and frequency correct Pulse Width Modulation, or phase and frequency correct PWM mode (WGMn3:0 = 8 or 9) provides a high resolution phase and frequency
correct PWM waveform generation option. The phase and frequency correct PWM
mode is, like the phase correct PWM mode, based on a dual-slope operation. The
counter counts repeatedly from BOTTOM (0x0000) to TOP and then from TOP to BOTTOM. In non-inverting Compare Output mode, the Output Compare (OCnx) is cleared
on the compare match between TCNTn and OCRnx while upcounting, and set on the
compare match while downcounting. In inverting Compare Output mode, the operation
is inverted. The dual-slope operation gives a lower maximum operation frequency compared to the single-slope operation. However, due to the symmetric feature of the dualslope PWM modes, these modes are preferred for motor control applications.
The main difference between the phase correct, and the phase and frequency correct
PWM mode is the time the OCRnx Register is updated by the OCRnx Buffer Register,
(see Figure 49 and Figure 50).
The PWM resolution for the phase and frequency correct PWM mode can be defined by
either ICRn or OCRnA. The minimum resolution allowed is 2-bit (ICRn or OCRnA set to
0x0003), and the maximum resolution is 16-bit (ICRn or OCRnA set to MAX). The PWM
resolution in bits can be calculated using the following equation:
log ( TOP + 1 )
R PFCPWM = ----------------------------------log ( 2 )
In phase and frequency correct PWM mode the counter is incremented until the counter
value matches either the value in ICRn (WGMn3:0 = 8), or the value in OCRnA
(WGMn3:0 = 9). The counter has then reached the TOP and changes the count direction. The TCNTn value will be equal to TOP for one timer clock cycle. The timing
diagram for the phase correct and frequency correct PWM mode is shown on Figure 50.
The figure shows phase and frequency correct PWM mode when OCRnA or ICRn is
used to define TOP. The TCNTn value is in the timing diagram shown as a histogram for
illustrating the dual-slope operation. The diagram includes non-inverted and inverted
PWM outputs. The small horizontal line marks on the TCNTn slopes represent compare
matches between OCRnx and TCNTn. The OCnx Interrupt Flag will be set when a compare match occurs.
121
4317B–AVR–02/05
Figure 50. Phase and Frequency Correct PWM Mode, Timing Diagram
OCnA Interrupt Flag Set
or ICFn Interrupt Flag Set
(Interrupt on TOP)
OCRnx/TOP Updateand
TOVn Interrupt Flag Set
(Interrupt on Bottom)
TCNTn
OCnx
(COMnx1:0 = 2)
OCnx
(COMnx1:0 = 3)
Period
1
2
3
4
The Timer/Counter Overflow Flag (TOVn) is set at the same timer clock cycle as the
OCRnx Registers are updated with the double buffer value (at BOTTOM). When either
OCRnA or ICRn is used for defining the TOP value, the OCnA or ICFn Flag set when
TCNTn has reached TOP. The Interrupt Flags can then be used to generate an interrupt
each time the counter reaches the TOP or BOTTOM value.
When changing the TOP value the program must ensure that the new TOP value is
higher or equal to the value of all of the Compare Registers. If the TOP value is lower
than any of the Compare Registers, a compare match will never occur between the
TCNTn and the OCRnx.
As Figure 50 shows the output generated is, in contrast to the phase correct mode, symmetrical in all periods. Since the OCRnx Registers are updated at BOTTOM, the length
of the rising and the falling slopes will always be equal. This gives symmetrical output
pulses and is therefore frequency correct.
Using the ICRn Register for defining TOP works well when using fixed TOP values. By
using ICRn, the OCRnA Register is free to be used for generating a PWM output on
OCnA. However, if the base PWM frequency is actively changed by changing the TOP
value, using the OCRnA as TOP is clearly a better choice due to its double buffer
feature.
In phase and frequency correct PWM mode, the compare units allow generation of
PWM waveforms on the OCnx pins. Setting the COMnx1:0 bits to two will produce a
non-inverted PWM and an inverted PWM output can be generated by setting the
COMnx1:0 to three (See Table on page 126). The actual OCnx value will only be visible
on the port pin if the data direction for the port pin is set as output (DDR_OCnx). The
PWM waveform is generated by setting (or clearing) the OCnx Register at the compare
match between OCRnx and TCNTn when the counter increments, and clearing (or setting) the OCnx Register at compare match between OCRnx and TCNTn when the
counter decrements. The PWM frequency for the output when using phase and frequency correct PWM can be calculated by the following equation:
f clk_I/O
f OCnxPFCPWM = ---------------------------2 ⋅ N ⋅ TOP
122
AT90PWM2/3
4317B–AVR–02/05
AT90PWM2/3
The N variable represents the prescaler divider (1, 8, 64, 256, or 1024).
The extreme values for the OCRnx Register represents special cases when generating
a PWM waveform output in the phase correct PWM mode. If the OCRnx is set equal to
BOTTOM the output will be continuously low and if set equal to TOP the output will be
set to high for non-inverted PWM mode. For inverted PWM the output will have the
opposite logic values. If OCR1A is used to define the TOP value (WGM13:0 = 9) and
COM1A1:0 = 1, the OC1A output will toggle with a 50% duty cycle.
Timer/Counter Timing
Diagrams
The Timer/Counter is a synchronous design and the timer clock (clk Tn) is therefore
shown as a clock enable signal in the following figures. The figures include information
on when Interrupt Flags are set, and when the OCRnx Register is updated with the
OCRnx buffer value (only for modes utilizing double buffering). Figure 51 shows a timing
diagram for the setting of OCFnx.
Figure 51. Timer/Counter Timing Diagram, Setting of OCFnx, no Prescaling
clkI/O
clkTn
(clkI/O /1)
TCNTn
OCRnx - 1
OCRnx
OCRnx
OCRnx + 1
OCRnx + 2
OCRnx Value
OCFnx
Figure 52 shows the same timing data, but with the prescaler enabled.
Figure 52. Timer/Counter Timing Diagram, Setting of OCFnx, with Prescaler (fclk_I/O/8)
clkI/O
clkTn
(clkI/O /8)
TCNTn
OCRnx
OCRnx - 1
OCRnx
OCRnx + 1
OCRnx + 2
OCRnx Value
OCFnx
Figure 53 shows the count sequence close to TOP in various modes. When using phase
and frequency correct PWM mode the OCRnx Register is updated at BOTTOM. The
timing diagrams will be the same, but TOP should be replaced by BOTTOM, TOP-1 by
123
4317B–AVR–02/05
BOTTOM+1 and so on. The same renaming applies for modes that set the TOVn Flag
at BOTTOM.
Figure 53. Timer/Counter Timing Diagram, no Prescaling
clkI/O
clkTn
(clkI/O /1)
TCNTn
(CTC and FPWM)
TCNTn
(PC and PFC PWM)
TOP - 1
TOP
BOTTOM
BOTTOM + 1
TOP - 1
TOP
TOP - 1
TOP - 2
TOVn (FPWM)
and ICFn (if used
as TOP)
OCRnx
(Update at TOP)
Old OCRnx Value
New OCRnx Value
Figure 54 shows the same timing data, but with the prescaler enabled.
Figure 54. Timer/Counter Timing Diagram, with Prescaler (fclk_I/O/8)
clkI/O
clkTn
(clkI/O/8)
TCNTn
(CTC and FPWM)
TCNTn
(PC and PFC PWM)
TOP - 1
TOP
BOTTOM
BOTTOM + 1
TOP - 1
TOP
TOP - 1
TOP - 2
TOVn (FPWM)
and ICF n (if used
as TOP)
OCRnx
(Update at TOP)
124
Old OCRnx Value
New OCRnx Value
AT90PWM2/3
4317B–AVR–02/05
AT90PWM2/3
16-bit Timer/Counter
Register Description
Timer/Counter1 Control
Register A – TCCR1A
Bit
7
6
5
4
3
2
1
0
COM1A1
COM1A0
COM1B1
COM1B0
–
–
WGM11
WGM10
Read/Write
R/W
R/W
R/W
R/W
R
R
R/W
R/W
Initial Value
0
0
0
0
0
0
0
0
TCCR1A
• Bit 7:6 – COMnA1:0: Compare Output Mode for Channel A
• Bit 5:4 – COMnB1:0: Compare Output Mode for Channel B
The COMnA1:0 and COMnB1:0 control the Output Compare pins (OCnA and OCnB
respectively) behavior. If one or both of the COMnA1:0 bits are written to one, the OCnA
output overrides the normal port functionality of the I/O pin it is connected to. If one or
both of the COMnB1:0 bit are written to one, the OCnB output overrides the normal port
functionality of the I/O pin it is connected to. However, note that the Data Direction Register (DDR) bit corresponding to the OCnA or OCnB pin must be set in order to enable
the output driver.
When the OCnA or OCnB is connected to the pin, the function of the COMnx1:0 bits is
dependent of the WGMn3:0 bits setting. Table 47 shows the COMnx1:0 bit functionality
when the WGMn3:0 bits are set to a Normal or a CTC mode (non-PWM).
Table 47. Compare Output Mode, non-PWM
COMnA1/COMnB
1
COMnA0/COMnB
0
0
0
Normal port operation, OCnA/OCnB
disconnected.
0
1
Toggle OCnA/OCnB on Compare Match.
1
0
Clear OCnA/OCnB on Compare Match (Set
output to low level).
1
1
Set OCnA/OCnB on Compare Match (Set output
to high level).
Description
Table 48 shows the COMnx1:0 bit functionality when the WGMn3:0 bits are set to the
fast PWM mode.
Table 48. Compare Output Mode, Fast PWM(1)
COMnA1/COMnB
1
COMnA0/COMnB
0
0
0
Normal port operation, OCnA/OCnB
disconnected.
0
1
WGMn3:0 = 14 or 15: Toggle OC1A on Compare
Match, OC1B disconnected (normal port
operation). For all other WGM1 settings, normal
port operation, OC1A/OC1B disconnected.
1
0
Clear OCnA/OCnB on Compare Match, set
OCnA/OCnB at TOP
1
1
Set OCnA/OCnB on Compare Match, clear
OCnA/OCnB at TOP
Description
125
4317B–AVR–02/05
Note:
1. A special case occurs when OCRnA/OCRnB equals TOP and COMnA1/COMnB1 is
set. In this case the compare match is ignored, but the set or clear is done at TOP.
See “Fast PWM Mode” on page 117. for more details.
Table 49 shows the COMnx1:0 bit functionality when the WGMn3:0 bits are set to the
phase correct or the phase and frequency correct, PWM mode.
Table 49. Compare Output Mode, Phase Correct and Phase and Frequency Correct
PWM(1)
COMnA1/COMnB
1
COMnA0/COMnB
0
0
0
Normal port operation, OCnA/OCnB
disconnected.
0
1
WGMn3:0 = 8, 9 10 or 11: Toggle OCnA on
Compare Match, OCnB disconnected (normal
port operation). For all other WGM1 settings,
normal port operation, OC1A/OC1B
disconnected.
1
0
Clear OCnA/OCnB on Compare Match when upcounting. Set OCnA/OCnB on Compare Match
when downcounting.
1
1
Set OCnA/OCnB on Compare Match when upcounting. Clear OCnA/OCnB on Compare Match
when downcounting.
Note:
Description
1. A special case occurs when OCRnA/OCRnB equals TOP and COMnA1/COMnB1 is
set. See “Phase Correct PWM Mode” on page 119. for more details.
• Bit 1:0 – WGMn1:0: Waveform Generation Mode
Combined with the WGMn3:2 bits found in the TCCRnB Register, these bits control the
counting sequence of the counter, the source for maximum (TOP) counter value, and
what type of waveform generation to be used, see Table 50. Modes of operation supported by the Timer/Counter unit are: Normal mode (counter), Clear Timer on Compare
match (CTC) mode, and three types of Pulse Width Modulation (PWM) modes. (See
“16-bit Timer/Counter1 with PWM” on page 104.).
126
AT90PWM2/3
4317B–AVR–02/05
AT90PWM2/3
Table 50. Waveform Generation Mode Bit Description(1)
Mode
WGMn3
WGMn2
(CTCn)
WGMn1
(PWMn1)
WGMn0
(PWMn0)
Timer/Counter Mode of
Operation
TOP
Update of
OCRnx at
TOVn Flag
Set on
0
0
0
0
0
Normal
0xFFFF
Immediate
MAX
1
0
0
0
1
PWM, Phase Correct, 8-bit
0x00FF
TOP
BOTTOM
2
0
0
1
0
PWM, Phase Correct, 9-bit
0x01FF
TOP
BOTTOM
3
0
0
1
1
PWM, Phase Correct, 10-bit
0x03FF
TOP
BOTTOM
4
0
1
0
0
CTC
OCRnA
Immediate
MAX
5
0
1
0
1
Fast PWM, 8-bit
0x00FF
TOP
TOP
6
0
1
1
0
Fast PWM, 9-bit
0x01FF
TOP
TOP
7
0
1
1
1
Fast PWM, 10-bit
0x03FF
TOP
TOP
8
1
0
0
0
PWM, Phase and Frequency
Correct
ICRn
BOTTOM
BOTTOM
9
1
0
0
1
PWM, Phase and Frequency
Correct
OCRnA
BOTTOM
BOTTOM
10
1
0
1
0
PWM, Phase Correct
ICRn
TOP
BOTTOM
11
1
0
1
1
PWM, Phase Correct
OCRnA
TOP
BOTTOM
12
1
1
0
0
CTC
ICRn
Immediate
MAX
13
1
1
0
1
(Reserved)
–
–
–
14
1
1
1
0
Fast PWM
ICRn
TOP
TOP
15
1
1
1
1
Fast PWM
OCRnA
TOP
TOP
Note:
1. The CTCn and PWMn1:0 bit definition names are obsolete. Use the WGMn2:0 definitions. However, the functionality and
location of these bits are compatible with previous versions of the timer.
Timer/Counter1 Control
Register B – TCCR1B
Bit
7
6
5
4
3
2
1
0
ICNC1
ICES1
–
WGM13
WGM12
CS12
CS11
CS10
Read/Write
R/W
R/W
R
R/W
R/W
R/W
R/W
R/W
Initial Value
0
0
0
0
0
0
0
0
TCCR1B
• Bit 7 – ICNCn: Input Capture Noise Canceler
Setting this bit (to one) activates the Input Capture Noise Canceler. When the noise canceler is activated, the input from the Input Capture pin (ICPn) is filtered. The filter
function requires four successive equal valued samples of the ICPn pin for changing its
output. The Input Capture is therefore delayed by four Oscillator cycles when the noise
canceler is enabled.
• Bit 6 – ICESn: Input Capture Edge Select
This bit selects which edge on the Input Capture pin (ICPn) that is used to trigger a capture event. When the ICESn bit is written to zero, a falling (negative) edge is used as
trigger, and when the ICESn bit is written to one, a rising (positive) edge will trigger the
capture.
When a capture is triggered according to the ICESn setting, the counter value is copied
into the Input Capture Register (ICRn). The event will also set the Input Capture Flag
(ICFn), and this can be used to cause an Input Capture Interrupt, if this interrupt is
enabled.
127
4317B–AVR–02/05
When the ICRn is used as TOP value (see description of the WGMn3:0 bits located in
the TCCRnA and the TCCRnB Register), the ICPn is disconnected and consequently
the Input Capture function is disabled.
• Bit 5 – Reserved Bit
This bit is reserved for future use. For ensuring compatibility with future devices, this bit
must be written to zero when TCCRnB is written.
• Bit 4:3 – WGMn3:2: Waveform Generation Mode
See TCCRnA Register description.
• Bit 2:0 – CSn2:0: Clock Select
The three Clock Select bits select the clock source to be used by the Timer/Counter, see
Figure 51 and Figure 52.
Table 51. Clock Select Bit Description
CSn2
CSn1
CSn0
Description
0
0
0
No clock source (Timer/Counter stopped).
0
0
1
clkI/O/1 (No prescaling)
0
1
0
clkI/O/8 (From prescaler)
0
1
1
clkI/O/64 (From prescaler)
1
0
0
clkI/O/256 (From prescaler)
1
0
1
clkI/O/1024 (From prescaler)
1
1
0
External clock source on Tn pin. Clock on falling edge.
1
1
1
External clock source on Tn pin. Clock on rising edge.
If external pin modes are used for the Timer/Countern, transitions on the Tn pin will
clock the counter even if the pin is configured as an output. This feature allows software
control of the counting.
Timer/Counter1 Control
Register C – TCCR1C
Bit
7
6
5
4
3
2
1
FOC1A
FOC1B
–
–
–
–
–
0
–
Read/Write
R/W
R/W
R
R
R
R
R
R
Initial Value
0
0
0
0
0
0
0
0
TCCR1C
• Bit 7 – FOCnA: Force Output Compare for Channel A
• Bit 6 – FOCnB: Force Output Compare for Channel B
The FOCnA/FOCnB bits are only active when the WGMn3:0 bits specifies a non-PWM
mode. However, for ensuring compatibility with future devices, these bits must be set to
zero when TCCRnA is written when operating in a PWM mode. When writing a logical
one to the FOCnA/FOCnB bit, an immediate compare match is forced on the Waveform
Generation unit. The OCnA/OCnB output is changed according to its COMnx1:0 bits
setting. Note that the FOCnA/FOCnB bits are implemented as strobes. Therefore it is
the value present in the COMnx1:0 bits that determine the effect of the forced compare.
A FOCnA/FOCnB strobe will not generate any interrupt nor will it clear the timer in Clear
Timer on Compare match (CTC) mode using OCRnA as TOP.
The FOCnA/FOCnB bits are always read as zero.
128
AT90PWM2/3
4317B–AVR–02/05
AT90PWM2/3
Timer/Counter1 – TCNT1H and
TCNT1L
Bit
7
6
5
4
3
2
1
0
TCNT1[15:8]
TCNT1H
TCNT1[7:0]
TCNT1L
Read/Write
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
Initial Value
0
0
0
0
0
0
0
0
The two Timer/Counter I/O locations (TCNTnH and TCNTnL, combined TCNTn) give
direct access, both for read and for write operations, to the Timer/Counter unit 16-bit
counter. To ensure that both the high and low bytes are read and written simultaneously
when the CPU accesses these registers, the access is performed using an 8-bit temporary High Byte Register (TEMP). This temporary register is shared by all the other 16-bit
registers. See “Accessing 16-bit Registers” on page 106.
Modifying the counter (TCNTn) while the counter is running introduces a risk of missing
a compare match between TCNTn and one of the OCRnx Registers.
Writing to the TCNTn Register blocks (removes) the compare match on the following
timer clock for all compare units.
Output Compare Register 1 A
– OCR1AH and OCR1AL
Bit
7
6
5
4
3
2
1
0
OCR1A[15:8]
OCR1AH
OCR1A[7:0]
Output Compare Register 1 B
– OCR1BH and OCR1BL
OCR1AL
Read/Write
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
Initial Value
0
0
0
0
0
0
0
0
Bit
7
6
5
4
3
2
1
0
OCR1B[15:8]
OCR1BH
OCR1B[7:0]
OCR1BL
Read/Write
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
Initial Value
0
0
0
0
0
0
0
0
The Output Compare Registers contain a 16-bit value that is continuously compared
with the counter value (TCNTn). A match can be used to generate an Output Compare
interrupt, or to generate a waveform output on the OCnx pin.
The Output Compare Registers are 16-bit in size. To ensure that both the high and low
bytes are written simultaneously when the CPU writes to these registers, the access is
performed using an 8-bit temporary High Byte Register (TEMP). This temporary register
is shared by all the other 16-bit registers. See “Accessing 16-bit Registers” on page 106.
Input Capture Register 1 –
ICR1H and ICR1L
Bit
7
6
5
4
3
2
1
0
ICR1[15:8]
ICR1H
ICR1[7:0]
ICR1L
Read/Write
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
Initial Value
0
0
0
0
0
0
0
0
The Input Capture is updated with the counter (TCNTn) value each time an event occurs
on the ICPn pin (or optionally on the Analog Comparator output for Timer/Counter1).
The Input Capture can be used for defining the counter TOP value.
The Input Capture Register is 16-bit in size. To ensure that both the high and low bytes
are read simultaneously when the CPU accesses these registers, the access is performed using an 8-bit temporary High Byte Register (TEMP). This temporary register is
shared by all the other 16-bit registers. See “Accessing 16-bit Registers” on page 106.
129
4317B–AVR–02/05
Timer/Counter1 Interrupt
Mask Register – TIMSK1
Bit
7
6
5
4
3
2
1
0
–
–
ICIE1
–
–
OCIE1B
OCIE1A
TOIE1
Read/Write
R
R
R/W
R
R
R/W
R/W
R/W
Initial Value
0
0
0
0
0
0
0
0
TIMSK1
• Bit 7, 6 – Res: Reserved Bits
These bits are unused bits in the AT90PWM2/3, and will always read as zero.
• Bit 5 – ICIE1: Timer/Counter1, Input Capture Interrupt Enable
When this bit is written to one, and the I-flag in the Status Register is set (interrupts globally enabled), the Timer/Counter1 Input Capture interrupt is enabled. The
corresponding Interrupt Vector (see “Reset and Interrupt Vectors Placement in
AT90PWM2/3(1)” on page 57) is executed when the ICF1 Flag, located in TIFR1, is set.
• Bit 4, 3 – Res: Reserved Bits
These bits are unused bits in the AT90PWM2/3, and will always read as zero.
• Bit 2 – OCIE1B: Timer/Counter1, Output Compare B Match Interrupt Enable
When this bit is written to one, and the I-flag in the Status Register is set (interrupts globally enabled), the Timer/Counter1 Output Compare B Match interrupt is enabled. The
corresponding Interrupt Vector (see “Reset and Interrupt Vectors Placement in
AT90PWM2/3(1)” on page 57) is executed when the OCF1B Flag, located in TIFR1, is
set.
• Bit 1 – OCIE1A: Timer/Counter1, Output Compare A Match Interrupt Enable
When this bit is written to one, and the I-flag in the Status Register is set (interrupts globally enabled), the Timer/Counter1 Output Compare A Match interrupt is enabled. The
corresponding Interrupt Vector (see “Reset and Interrupt Vectors Placement in
AT90PWM2/3(1)” on page 57) is executed when the OCF1A Flag, located in TIFR1, is
set.
• Bit 0 – TOIE1: Timer/Counter1, Overflow Interrupt Enable
When this bit is written to one, and the I-flag in the Status Register is set (interrupts globally enabled), the Timer/Counter1 Overflow interrupt is enabled. The corresponding
Interrupt Vector (see “Reset and Interrupt Vectors Placement in AT90PWM2/3(1)” on
page 57) is executed when the TOV1 Flag, located in TIFR1, is set.
Timer/Counter1 Interrupt Flag
Register – TIFR1
Bit
7
6
5
4
3
2
1
0
–
–
ICF1
–
–
OCF1B
OCF1A
TOV1
Read/Write
R
R
R/W
R
R
R/W
R/W
R/W
Initial Value
0
0
0
0
0
0
0
0
TIFR1
• Bit 7, 6 – Res: Reserved Bits
These bits are unused bits in the AT90PWM2/3, and will always read as zero.
• Bit 5 – ICF1: Timer/Counter1, Input Capture Flag
This flag is set when a capture event occurs on the ICP1 pin. When the Input Capture
Register (ICR1) is set by the WGMn3:0 to be used as the TOP value, the ICF1 Flag is
set when the counter reaches the TOP value.
ICF1 is automatically cleared when the Input Capture Interrupt Vector is executed. Alternatively, ICF1 can be cleared by writing a logic one to its bit location.
• Bit 4, 3 – Res: Reserved Bits
130
AT90PWM2/3
4317B–AVR–02/05
AT90PWM2/3
These bits are unused bits in the AT90PWM2/3, and will always read as zero.
• Bit 2 – OCF1B: Timer/Counter1, Output Compare B Match Flag
This flag is set in the timer clock cycle after the counter (TCNT1) value matches the Output Compare Register B (OCR1B).
Note that a Forced Output Compare (FOC1B) strobe will not set the OCF1B Flag.
OCF1B is automatically cleared when the Output Compare Match B Interrupt Vector is
executed. Alternatively, OCF1B can be cleared by writing a logic one to its bit location.
• Bit 1 – OCF1A: Timer/Counter1, Output Compare A Match Flag
This flag is set in the timer clock cycle after the counter (TCNT1) value matches the Output Compare Register A (OCR1A).
Note that a Forced Output Compare (FOC1A) strobe will not set the OCF1A Flag.
OCF1A is automatically cleared when the Output Compare Match A Interrupt Vector is
executed. Alternatively, OCF1A can be cleared by writing a logic one to its bit location.
• Bit 0 – TOV1: Timer/Counter1, Overflow Flag
The setting of this flag is dependent of the WGMn3:0 bits setting. In Normal and CTC
modes, the TOV1 Flag is set when the timer overflows. Refer to Table 50 on page 127
for the TOV1 Flag behavior when using another WGMn3:0 bit setting.
TOV1 is automatically cleared when the Timer/Counter1 Overflow Interrupt Vector is
executed. Alternatively, TOV1 can be cleared by writing a logic one to its bit location.
131
4317B–AVR–02/05
Power Stage Controller – (PSC0, PSC1 & PSC2)
The Power Stage Controller is a high performance waveform controller.
Features
•
•
•
•
•
•
•
•
•
•
Overview
Many register and bit references in this section are written in general form.
PWM waveform generation function (2 complementary programmable outputs)
Dead time control
Standard mode up to 12 bit resolution
Frequency Resolution Enhancement Mode (12 + 4 bits)
Frequency up to 64 Mhz
Conditional Waveform on External Events (Zero Crossing, Current Sensing ...)
All on chip PSC synchronization
ADC synchronization
Overload protection function
Abnormality protection function, emergency input to force all outputs to high impedance
or in inactive state (fuse configurable)
• Center aligned and edge aligned modes synchronization
• Fast emergency stop by hardware
•
A lower case “n” replaces the PSC number, in this case 0, 1 or 2. However, when
using the register or bit defines in a program, the precise form must be used, i.e.,
PSOC1 for accessing PSC 0 Synchro and Output Configuration register and so on.
•
A lower case “x” replaces the PSC part , in this case A or B. However, when using
the register or bit defines in a program, the precise form must be used, i.e., PFRCnA
for accessing PSC n Fault/Retrigger n A Control register and so on.
The purpose of a Power Stage Controller (PSC) is to control power modules on a board.
It has two outputs on PSC0 and PSC1 and four outputs on PSC2.
These outputs can be used in various ways:
•
“Two Ouputs” to drive a half bridge (lighting, DC motor ...)
•
“One Output” to drive single power transistor (DC/DC converter, PFC, DC motor ...)
•
“Four Outputs” in the case of PSC2 to drive a full bridge (lighting, DC motor ...)
Each PSC has two inputs the purpose of which is to provide means to act directly on the
generated waveforms:
•
Current sensing regulation
•
Zero crossing retriggering
•
Demagnetization retriggering
•
Fault input
The PSC can be chained and synchronized to provide a configuration to drive three half
bridges. Thanks to this feature it is possible to generate a three phase waveforms for
applications such as Asynchronous or BLDC motor drive.
132
AT90PWM2/3
4317A-3–AVR–02/05
AT90PWM2/3
PSC Description
Figure 55. Power Stage Controller 0 or 1 Block Diagram
PSC Counter
Waveform
Generator B
=
PSCOUTn1
( From Analog
Comparator n Ouput )
OCRnRB
PSC Input
Module B
DATABUS
=
PSCn Input B
OCRnSB
PISELnB
Part A
PSC Input
Module A
=
PSCn Input A
PSCINn
OCRnRA
PISELnA
PSCOUTn0
Waveform
Generator A
=
OCRnSA
Part B
PICRn
PCNFn
PCTLn
Note:
PFRCnB
PFRCnA
POM2(PSC2 only)
PSOCn
n = 0, 1
The principle of the PSC is based on the use of a counter (PSC counter). This counter is
able to count up and count down from and to values stored in registers according to the
selected running mode.
The PSC is seen as two symetrical entities. One part named part A which generates the
output PSCOUTn0 and the second one named part B which generates the PSCOUTn1
output.
Each part A or B has its own PSC Input Module to manage selected input.
133
4317A-3–AVR–02/05
PSC2 distinctive feature
Figure 56. PSC2 versus PSC1&PSC0 Block Diagram
PSC Counter
PSCOUTn3
=
POS23
Waveform
Generator B
PSCOUTn1
( From Analog
Comparator n Ouput )
OCRnRB
DATABUS
=
PSC Input
Module B
OCRnSB
Part A
=
PSC Input
Module A
PSCn Input B
Output
Matrix
PISELnB
PSCn Input A
PSCINn
OCRnRA
=
PISELnA
POS22
Waveform
Generator A
PSCOUTn2
PSCOUTn0
OCRnSA
Part B
PICRn
PCNFn
PCTLn
Note:
PFRCnB
PFRCnA
POM2(PSC2 only)
PSOCn
n=2
PSC2 has two supplementary outputs PSCOUT22 and PSCOUT23. Thanks to a first
selector PSCOUT22 can duplicate PSCOUT20 or PSCOUT21. Thanks to a second
selector PSCOUT23 can duplicate PSCOUT20 or PSCOUT21.
The Output Matrix is a kind of 2*2 look up table which gives the possibility to program
the output values according to a PSC sequence (See “Output Matrix” on page 163 )
Output Polarity
134
The polarity “active high” or “active low” of the PSC outputs is programmable. All the timing diagrams in the following examples are given in the “active high” polarity.
AT90PWM2/3
4317A-3–AVR–02/05
AT90PWM2/3
Signal Description
Figure 57. PSC External Block View
CLK PLL
CLK I/O
SYnIn
StopOut
OCRnRB[11:0]
OCRnSB[11:0]
OCRnRA[11:0]
OCRnSA[11:0]
OCRnRB[15:12]
(Flank Width
Modulation)
12
PSCOUTn0
12
PSCOUTn1
12
(1)
PSCOUTn2
12
(1)
PSCOUTn3
4
PICRn[11:0]
12
PSCINn
IRQ PSCn
Analog
Comparator
n Output
StopIn SYnOut PSCnASY
Note:
1. available only for PSC2
2. n = 0, 1 or 2
Input Description
Table 52. Internal Inputs
Name
Description
Type/
Width
OCRnRB
[11:0]
Compare Value which Reset Signal on Part B
(PSCOUTn1)
Register
12 bits
OCRnSB
[11:0]
Compare Value which Set Signal on Part B (PSCOUTn1)
Register
12 bits
OCRnRA
[11:0]
Compare Value which Reset Signal on Part A
(PSCOUTn0)
Register
12 bits
OCRnSA
[11:0]
Compare Value which Set Signal on Part A (PSCOUTn0)
Register
12 bits
OCRnRB
[15:12]
Frequency Resolution Enhancement value
(Flank Width Modulation)
Register
4 bits
CLK I/O
Clock Input from I/O clock
Signal
135
4317A-3–AVR–02/05
Type/
Width
Name
Description
CLK PLL
Clock Input from PLL
Signal
SYnIn
Synchronization In (from adjacent PSC)(1)
Signal
StopIn
Stop Input (for synchronized mode)
Signal
Note:
1. See Figure 92 on page 165
Table 53. Block Inputs
Name
Description
Type/
Width
PSCINn
Input 0 used for Retrigger or Fault functions
Signal
from A C
Input 1 used for Retrigger or Fault functions
Signal
Output Description
Table 54. Block Outputs
Name
Description
Type/
Width
PSCOUTn0
PSC n Output 0 (from part A of PSC)
Signal
PSCOUTn1
PSC n Output 1 (from part B of PSC)
Signal
PSCOUTn2
(PSC2 only)
PSC n Output 2 (from part A or part B of PSC)
Signal
PSCOUTn3
(PSC2 only)
PSC n Output 3 (from part A or part B of PSC)
Signal
Table 55. Internal Outputs
Name
Description
Type/
Width
SYnOut
Synchronization Output(1)
Signal
PICRn
[11:0]
PSC n Input Capture Register
Counter value at retriggering event
Register
12 bits
IRQPSCn
PSC Interrupt Request : three souces, overflow, fault,
and input capture
Signal
PSCnASY
ADC Synchronization (+ Amplifier Syncho. )(2)
Signal
StopOut
Stop Output (for synchronized mode)
Note:
1. See Figure 92 on page 165
2. See “Analog Synchronization” on page 164
136
AT90PWM2/3
4317A-3–AVR–02/05
AT90PWM2/3
Functional Description
Waveform Cycles
The waveform generated by PSC can be described as a sequence of two waveforms.
The first waveform is relative to PSCOUTn0 output and part A of PSC. The part of this
waveform is sub-cycle A in the following figure.
The second waveform is relative to PSCOUTn1 output and part B of PSC. The part of
this waveform is sub-cycle B in the following figure.
The complete waveform is ended with the end of sub-cycle B. It means at the end of
waveform B.
Figure 58. Cycle Presentation in 1, 2 & 4 Ramp Mode
PSC Cycle
Sub-Cycle A
Sub-Cycle B
4 Ramp Mode
Ramp A0
Ramp A1
Ramp B0
Ramp B1
2 Ramp Mode
Ramp A
Ramp B
1 Ramp Mode
UPDATE
Figure 59. Cycle Presentation in Centered Mode
PSC Cycle
Centered Mode
UPDATE
Ramps illustrate the output of the PSC counter included in the waveform generators.
Centered Mode is like a one ramp mode which count down up and down.
Notice that the update of a new set of values is done regardless of ramp Mode at the top
of the last ramp.
137
4317A-3–AVR–02/05
Running Mode Description
Waveforms and length of output signals are determined by Time Parameters (DT0,
OT0, DT1, OT1) and by the running mode. Four modes are possible :
–
Four Ramp mode
–
Two Ramp mode
–
One Ramp mode
–
Center Aligned mode
Four Ramp Mode
In Four Ramp mode, each time in a cycle has its own definition
Figure 60. PSCn0 & PSCn1 Basic Waveforms in Four Ramp mode
PSC Counter
OCRnSA
OCRnRA
OCRnRB
OCRnSB
0
0
On-Time 0
On-Time 1
PSCOUTn0
PSCOUTn1
Dead-Time 1
Dead-Time 0
PSC Cycle
The input clock of PSC is given by CLKPSC.
PSCOUTn0 and PSCOUTn1 signals are defined by On-Time 0, Dead-Time 0, On-Time
1 and Dead-Time 1 values with :
On-Time 0 = OCRnRAH/L * 1/Fclkpsc
On-Time 1 = OCRnRBH/L * 1/Fclkpsc
Dead-Time 0 = (OCRnSAH/L + 2) * 1/Fclkpsc
Dead-Time 1 = (OCRnSBH/L + 2) * 1/Fclkpsc
Note:
138
Minimal value for Dead-Time 0 and Dead-Time 1 = 2 * 1/Fclkpsc
AT90PWM2/3
4317A-3–AVR–02/05
AT90PWM2/3
Two Ramp Mode
In Two Ramp mode, the whole cycle is divided in two moments
One moment for PSCn0 description with OT0 which gives the time of the whole moment
One moment for PSCn1 description with OT1 which gives the time of the whole moment
Figure 61. PSCn0 & PSCn1 Basic Waveforms in Two Ramp mode
OCRnRA
PSC Counter
OCRnSA
OCRnRB
OCRnSB
0
0
On-Time 0
On-Time 1
PSCOUTn0
PSCOUTn1
Dead-Time 1
Dead-Time 0
PSC Cycle
PSCOUTn0 and PSCOUTn1 signals are defined by On-Time 0, Dead-Time 0, On-Time
1 and Dead-Time 1 values with :
On-Time 0 = (OCRnRAH/L - OCRnSAH/L) * 1/Fclkpsc
On-Time 1 = (OCRnRBH/L - OCRnSBH/L) * 1/Fclkpsc
Dead-Time 0 = (OCRnSAH/L + 1) * 1/Fclkpsc
Dead-Time 1 = (OCRnSBH/L + 1) * 1/Fclkpsc
Note:
Minimal value for Dead-Time 0 and Dead-Time 1 = 1/Fclkpsc
139
4317A-3–AVR–02/05
One Ramp Mode
In One Ramp mode, PSCOUTn0 and PSCOUTn1 outputs can overlap each other.
Figure 62. PSCn0 & PSCn1 Basic Waveforms in One Ramp mode
OCRnRB
OCRnSB
OCRnRA
PSC Counter
OCRnSA
0
On-Time 0
On-Time 1
PSCOUTn0
PSCOUTn1
Dead-Time 1
Dead-Time 0
PSC Cycle
On-Time 0 = (OCRnRAH/L - OCRnSAH/L) * 1/Fclkpsc
On-Time 1 = (OCRnRBH/L - OCRnSBH/L) * 1/Fclkpsc
Dead-Time 0 = (OCRnSAH/L + 1) * 1/Fclkpsc
Dead-Time 1 = (OCRnSBH/L - OCRnRAH/L) * 1/Fclkpsc
Note:
140
Minimal value for Dead-Time 0 = 1/Fclkpsc
AT90PWM2/3
4317A-3–AVR–02/05
AT90PWM2/3
Center Aligned Mode
In center aligned mode, the center of PSCn00 and PSCn01 signals are centered.
Figure 63. PSCn0 & PSCn1 Basic Waveforms in Center Aligned Mode
OCRnRB
PSC Counter
OCRnSB
OCRnSA
0
On-Time 0
On-Time 1
On-Time 1
PSCOUTn0
PSCOUTn1
Dead-Time
Dead-Time
PSC Cycle
On-Time 0 = 2 * OCRnSAH/L * 1/Fclkpsc
On-Time 1 = 2 * (OCRnRBH/L - OCRnSBH/L + 1) * 1/Fclkpsc
Dead-Time = (OCRnSBH/L - OCRnSAH/L) * 1/Fclkpsc
PSC Cycle = 2 * (OCRnRBH/L + 1) * 1/Fclkpsc
Note:
Minimal value for PSC Cycle = 2 * 1/Fclkpsc
OCRnRAH/L is not used to control PSC Output waveform timing. Nevertheless, it can
be useful to adjust ADC synchronization (See “Analog Synchronization” on page 164 ).
Figure 64. Run and Stop Mechanism in Centered Mode
OCRnRB
OCRnSB
OCRnSA
PSC Counter
0
Run
PSCOUTn0
PSCOUTn1
Note:
See “PSC 0 Control Register – PCTL0” on page 173 (or PCTL1 or PCTL2)
141
4317A-3–AVR–02/05
Fifty Percent Waveform
Configuration
When PSCOUTn0 and PSCOUTn1 have the same characteristics, it’s possible to configure the PSC in a Fifty Percent mode. When the PSC is in this configuration, it
duplicates the OCRnSBH/L and OCRnRBH/L registers in OCRnSAH/L and OCRnRAH/L registers. So it is not necessary to program OCRnSAH/L and OCRnRAH/L
registers.
Update of Values
To avoid unasynchronous and incoherent values in a cycle, if an update of one of several values is necessary, all values are updated at the same time at the end of the cycle
by the PSC. The new set of values is calculated by sofware and the update is initiated
by software.
Figure 65. Update at the end of complete PSC cycle.
Regulation Loop
Calculation
Writting in
PSC Registers
Software
Cycle
With Set i
Cycle
With Set i
Cycle
With Set i
Request for
an Update
Cycle
With Set i
PSC
Cycle
With Set j
End of Cycle
The software can stop the cycle before the end to update the values and restart a new
PSC cycle.
Value Update Synchronization
New timing values can be written during the PSC cycle. Thanks to LOCK and
AUTOLOCK configuration bits, the new whole set of values can be taken into account
after the end of the PSC cycle.
When AUTOLOCK configuration bit is set, the update of the PSC internal registers will
be done at the end of the PSC cycle if the Output Compare Register RB has been the
last written.
When LOCK configuration bit is set, there is no update. The update of the PSC internal
registers will be done at the end of the PSC cycle if the LOCK bit is released to zero.
When set, AUTOLOCK configuration bit prevails over LOCK configuration bit.
See “PSC 0 Configuration Register – PCNF0” on page 171
142
AT90PWM2/3
4317A-3–AVR–02/05
AT90PWM2/3
Enhanced Resolution
Lamp Ballast applications need an enhanced resolution down to 50Hz. The method to
improve the normal resolution is based on Flank Width Modulation (also called Fractional Divider). Cycles are grouped into frames of 16 cycles. Cycles are modulated by a
sequence given by the fractional divider number. The resulting output frequency is the
average of the frequencies in the frame. The fractional divider (d) is given by
OCRnRB[15:12].
The PSC output period is directly equal to the PSCOUTn0 On Time + Dead Time
(OT0+DT0) and PSCOUTn1 On Time + DeadTime (OT1+DT1) values. These values
are 12 bits numbers. The frequency adjustment can only be done in steps like the dedicated counters. The step width is defined as the frequency difference between two
neighboring PSC frequencies:
f PLL f PLL
1
∆f = f1 – f2 = ---------- – ------------ = fPSC × -------------------k
k+1
k(k + 1 )
with k is the number of CLK PSC period in a PSC cycle and is given by the following
formula:
fPSC
n = ---------fOP
with fOP is the output operating frequency.
Exemple, in normal mode, with maximum operating frequency 160 kHz and fPLL = 64
Mhz, k equals 400. The resulting resolution is Delta F equals 64MHz / 400 / 401 = 400
Hz.
In enhanced mode, the output frequency is the average of the frame formed by the 16
consecutive cycles.
16 – d
d
f AVERAGE = --------------- × fb1 + ------ × f b2
16
16
fb1 and fb2 are two neightboring base frequencies.
143
4317A-3–AVR–02/05
f PLL
16 – d f PLL d
f AVERAGE = --------------- × ---------- + ------ × -----------n
16
16 n + 1
Then the frequency resolution is divided by 16. In the example above, the resolution
equals 25 Hz.
Frequency distribution
The frequency modulation is done by switching two frequencies in a 16 consecutive
cycle frame. These two frequencies are fb1 and fb2 where fb1 is the nearest base frequency above the wanted frequency and fb2 is the nearest base frequency below the
wanted frequency. The number of fb1 in the frame is (d-16) and the number of fb2 is d.
The fb1 and fb2 frequencies are evenly distributed in the frame according to a predefined
pattern. This pattern can be as given in the following table or by any other implementation which give an equivallent evenly distribution.
Table 56. Distribution of fb2 in the modulated frame
Distribution of fb2 in the modulated frame
PWM - cycle
Fractional
Divider (d)
0
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
0
1
X
2
X
3
X
X
X
4
X
X
X
X
5
X
X
X
X
X
6
X
X
X
X
X
X
7
X
X
X
X
X
X
X
8
X
X
X
X
X
X
X
X
9
X
X
X
X
X
X
X
X
X
10
X
X
X
X
X
X
X
X
X
X
11
X
X
X
X
X
X
X
X
X
X
X
12
X
X
X
X
X
X
X
X
X
X
X
X
13
X
X
X
X
X
X
X
X
X
X
X
X
X
14
X
X
X
X
X
X
X
X
X
X
X
X
X
X
15
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
While ‘X’ in the table, fb2 prime to fb1 in cycle corresponding cycle.
So for each row, a number of fb2 take place of fb1.
144
AT90PWM2/3
4317A-3–AVR–02/05
AT90PWM2/3
Figure 66. Resulting Frequency versus d.
fb1
fb2
fOP
d:
0
1
2
3
4
5
6
7
8
9 10 11 12 13 14 15
Modes of Operation
Normal Mode
The simplest mode of operation is the normal mode. See Figure 60.
The active time of PSCOUTn0 is given by the OT0 value. The active time of PSCOUTn1
is given by the OT1 value. Both of them are 12 bit values. Thanks to DT0 & DT1 to ajust
the dead time between PSCOUTn0 and PSCOUTn1 active signals.
The waveform frequency is defined by the following equation:
f CLK_PSCn
1
f PSCn = ------------------------------ = ---------------------------------------------------------------------- =
PSCnCycle
( OT0 + OT1 + DT0 + DT1 )
Enhanced Mode
= 1
The Enhanced Mode uses the previously described method to generate a high resolution frequency.
Figure 67. Enhanced Mode, Timing Diagram
DT0
OT0
DT1
OT1
DT0
DT1
OT0+1
OT1
DT0
PSCOUTn0
PSCOUTn1
Period
T1
T2
The supplementary step in counting to generate fb2 is added on the PSCn0 signal while
needed in the frame according to the fractional divider. SeeTable 56, “Distribution of fb2
in the modulated frame,” on page 144.
The waveform frequency is defined by the following equations:
f CLK_PSCn
1
f1 PSCn = ------ = ---------------------------------------------------------------------T1
( OT0 + OT1 + DT0 + DT1 )
f CLK_PSCn
1
f2 PSCn = ------ = -------------------------------------------------------------------------------T2
( OT0 + OT1 + DT0 + DT1 + 1 )
145
4317A-3–AVR–02/05
d
16 – d
fAVERAGE = ------ × f1 PSCn + --------------- × f2 PSCn
16
16
d is the fractionel divider factor.
146
AT90PWM2/3
4317A-3–AVR–02/05
AT90PWM2/3
PSC Inputs
Each part A or B of PSC has its own system to take into account one PSC input. According to PSC n Input A/B Control Register (see description page 176), PSCnIN0/1 input
can act has a Retrigger or Fault input.
This system A or B is also configured by this PSC n Input A/B Control Register
(PFRCnA/B).
Figure 68. PSC Input Module
PAOCnA
(PAOCnB)
0
PSCINn
Analog
Comparator
n Output
0
Digital
Filter
1
1
CLK PSC
PFLTEnA
(PFLTEnB)
PISELnA
(PISELnB)
PELEVnA / PCAEnA
(PELEVnB) (PCAEnB)
PRFMnA3:0
(PRFMnB3:0)
2
4
Input
Processing
(retriggering ...)
CLK PSC
PSC Core
(Counter,
Waveform
Generator, ...)
CLK PSC
PSC Retrigger Behaviour
versus PSC running modes
Output
Control
PSCOUTn0
(PSCOUTn1)
(PSCOUT22)
(PSCOUT23)
In centered mode, Retrigger Inputs have no effect.
In two ramp or four ramp mode, Retrigger Inputs A or B cause the end of the corresponding cycle A or B and the beginning of the following cycle B or A.
In one ramp mode, Retrigger Inputs A or B reset the current PSC counting to zero.
Retrigger PSCOUTn0 On
External Event
PSCOUTn0 ouput can be resetted before end of On-Time 0 on the change on PSCn
Input A. PSCn Input A can be configured to do not act or to act on level or edge modes.
The polarity of PSCn Input A is configurable thanks to a sense control block. PSCn Input
A can be the Output of the analog comparator or the PSCINn input.
As the period of the cycle decreases, the instantaneous frequency of the two outputs
increases.
147
4317A-3–AVR–02/05
Figure 69. PSCOUTn0 retriggered by PSCn Input A (Edge Retriggering)
On-Time 0
On-Time 1
PSCOUTn0
PSCOUTn1
PSCn Input A
(falling edge)
PSCn Input A
(rising edge)
Dead-Time 0
Note:
Dead-Time 1
This exemple is given in “Input Mode 8” in “2 or 4 ramp mode” See Figure 85. for details.
Figure 70. PSCOUTn0 retriggered by PSCn Input A (Level Acting)
On-Time 0
On-Time 1
PSCOUTn0
PSCOUTn1
PSCn Input A
(high level)
PSCn Input A
(low level)
Dead-Time 0
Note:
Retrigger PSCOUTn1 On
External Event
Dead-Time 1
This exemple is given in “Input Mode 1” in “2 or 4 ramp mode” See Figure 74. for details.
PSCOUTn1 ouput can be resetted before end of On-Time 1 on the change on PSCn
Input B. The polarity of PSCn Input B is configurable thanks to a sense control block.
PSCn Input B can be configured to do not act or to act on level or edge modes. PSCn
Input B can be the Output of the analog comparator or the PSCINn input.
As the period of the cycle decreases, the instantaneous frequency of the two outputs
increases.
148
AT90PWM2/3
4317A-3–AVR–02/05
AT90PWM2/3
Figure 71. PSCOUTn1 retriggered by PSCn Input B (Edge Retriggering)
On-Time 0
On-Time 1
PSCOUTn0
PSCOUTn1
PSCn Input B
(falling edge)
PSCn Input B
(rising edge)
Dead-Time 0
Note:
Dead-Time 1
Dead-Time 0
This exemple is given in “Input Mode 8” in “2 or 4 ramp mode” See Figure 85. for details.
Figure 72. PSCOUTn1 retriggered by PSCn Input B (Level Acting)
On-Time 0
On-Time 1
PSCOUTn0
PSCOUTn1
PSCn Input B
(high level)
PSCn Input B
(low level)
Dead-Time 0
Burst Generation
Dead-Time 1
Dead-Time 0
Note:
This exemple is given in “Input Mode 1” in “2 or 4 ramp mode” See Figure 74. for details.
Note:
On level mode, it’s possible to use PSC to generate burst by using Input Mode 3
or Mode 4 (See Figure 78. and Figure 79. for details.)
149
4317A-3–AVR–02/05
Figure 73. Burst Generation
OFF
BURST
PSCOUTn0
PSCOUTn1
PSCn Input A
(high level)
PSCn Input A
(low level)
PSC Input Configuration
The PSC Input Configuration is done by programming bits in configuration registers.
Filter Enable
If the “Filter Enable” bit is set, a digital filter of 4 cycles is inserted before evaluation of
the signal. The disable of this function is mainly needed for prescaled PSC clock
sources, where the noise cancellation gives too high latency.
Important: If the digital filter is active, the level sensitivity is true also with a disturbed
PSC clock to deactivate the outputs (emergency protection of external component).
Likewise when used as fault input, PSCn Input A or Input B have to go through PSC to
act on PSCOUTn0/1/2/3 output. This way needs that CLKPSC is running. So thanks to
PSC Asynchronous Output Control bit (PAOCnA/B), PSCnIN0/1 input can desactivate
directly the PSC output. Notice that in this case, input is still taken into account as usually by Input Module System as soon as CLKPSC is running.
PSC Input Filterring
CLKPSC
Digital
Filter
4 x CLK PSC
PSC Input
Module X
Signal Polarity
PSCn Input A or B
Ouput
Stage
PSCOUTnX
PIN
One can select the active edge (edge modes) or the active level (level modes) See
PELEVnx bit description in Section “PSC n Input A Control Register – PFRCnA”,
page 176.
If PELEVnx bit set, the significant edge of PSCn Input A or B is rising (edge modes) or
the active level is high (level modes) and vice versa for unset/falling/low
150
AT90PWM2/3
4317A-3–AVR–02/05
AT90PWM2/3
- In 2- or 4-ramp mode, PSCn Input A is taken into account only during Dead-Time0 and
On-Time0 period (respectively Dead-Time1 and On-Time1 for PSCn Input B).
- In 1-ramp-mode PSC Input A or PSC Input B act on the whole ramp.
Input Mode Operation
Thanks to 4 configuration bits (PRFM3:0), it’s possible to define the mode of the PSC
input. All
Table 57. PSC Input Mode Operation
PRFM3:0
Description
0
0000b
PSCn Input has no action on PSC output
1
0001b
2
0010b
3
0011b
4
0100b
5
0101b
6
0110b
7
0111b
8
1000b
See “PSC Input Mode 1: Stop signal, Jump to Opposite DeadTime and Wait” on page 152
See “PSC Input Mode 2: Stop signal, Execute Opposite DeadTime and Wait” on page 153
See “PSC Input Mode 3: Stop signal, Execute Opposite while
Fault active” on page 154
See “PSC Input Mode 4: Deactivate outputs without changing timing.” on page 155
See “PSC Input Mode 5: Stop signal and Insert Dead-Time” on
page 156
See “PSC Input Mode 6: Stop signal, Jump to Opposite DeadTime and Wait.” on page 157
See “PSC Input Mode 7: Halt PSC and Wait for Software Action”
on page 158
See “PSC Input Mode 8” on page 159
9
1001b
10
1010b
11
1011b
12
1100b
13
1101b
14
1110b
15
1111b
See “PSC Input Mode 9: Fixed Frequency Edge Retrigger PSC”
on page 160
Reserved : Do not use
See “PSC Input Mode 14: Fixed Frequency Edge Retrigger PSC
and Disactivate Output” on page 161
Reserved : Do not use
Notice: All following examples are given with rising edge or high level active inputs.
151
4317A-3–AVR–02/05
PSC Input Mode 1: Stop signal, Jump to Opposite Dead-Time and Wait
Figure 74. PSCn behaviour versus PSCn Input A in Fault Mode 1
DT0
OT0
DT1
OT1
DT0
OT0
DT1
OT1
DT0
OT0
DT1
OT1
PSCOUTn0
PSCOUTn1
PSC Input A
PSC Input B
PSC Input A is taken into account during DT0 and OT0 only. It has no effect during DT1
and OT1.
When PSC Input A event occurs, PSC releases PSCOUTn0, waits for PSC Input A inactive state and then jumps and executes DT1 plus OT1.
Figure 75. PSCn behaviour versus PSCn Input B in Fault Mode 1
DT0
OT0
DT1
OT1
DT0
OT0
DT1
OT1
DT0
OT0
DT1
OT1
PSCOUTn0
PSCOUTn1
PSC Input A
PSC Input B
PSC Input B is take into account during DT1 and OT1 only. It has no effect during DT0
and OT0.
When PSC Input B event occurs, PSC releases PSCOUTn1, waits for PSC Input B inactive state and then jumps and executes DT0 plus OT0.
152
AT90PWM2/3
4317A-3–AVR–02/05
AT90PWM2/3
PSC Input Mode 2: Stop signal, Execute Opposite Dead-Time and Wait
Figure 76. PSCn behaviour versus PSCn Input A in Fault Mode 2
DT0
OT0
DT1
OT1
DT0 OT0 DT1 OT1
DT0
OT0
DT1
OT1
PSCOUTn0
PSCOUTn1
PSC Input A
PSC Input B
PSC Input A is take into account during DT0 and OT0 only. It has no effect during DT1
and OT1.
When PSCn Input A event occurs, PSC releases PSCOUTn0, jumps and executes DT1
plus OT1 and then waits for PSC Input A inactive state.
Even if PSC Input A is released during DT1 or OT1, DT1 plus OT1 sub-cycle is always
completely executed.
Figure 77. PSCn behaviour versus PSCn Input B in Fault Mode 2
DT0
OT0
DT1
OT1
DT0
OT0
DT1
OT1 DT0
OT0
DT1
OT1
PSCOUTn0
PSCOUTn1
PSC Input A
PSC Input B
PSC Input B is take into account during DT1 and OT1 only. It has no effect during DT0
and OT0.
When PSC Input B event occurs, PSC releases PSCOUTn1, jumps and executes DT0
plus OT0 and then waits for PSC Input B inactive state.
Even if PSC Input B is released during DT0 or OT0, DT0 plus OT0 sub-cycle is always
completely executed.
153
4317A-3–AVR–02/05
PSC Input Mode 3: Stop signal, Execute Opposite while Fault active
Figure 78. PSCn behaviour versus PSCn Input A in Mode 3
DT0
OT0
DT1
OT1
DT0 OT0 DT1 OT1
DT1 OT1
DT1 OT1
DT0
OT0
DT1
OT1
PSCOUTn0
PSCOUTn1
PSC Input A
PSC Input B
PSC Input A is taken into account during DT0 and OT0 only. It has no effect during DT1
and OT1.
When PSC Input A event occurs, PSC releases PSCOUTn0, jumps and executes DT1
plus OT1 plus DT0 while PSC Input A is in active state.
Even if PSC Input A is released during DT1 or OT1, DT1 plus OT1 sub-cycle is always
completely executed.
Figure 79. PSCn behaviour versus PSCn Input B in Mode 3
DT0
OT0
DT1
OT1
DT0
OT0
DT1
OT1 DT0
OT0
DT0
OT0
DT0
OT0
DT1
OT1
PSCOUTn0
PSCOUTn1
PSC Input A
PSC Input B
PSC Input B is taken into account during DT1 and OT1 only. It has no effect during DT0
and OT0.
When PSC Input B event occurs, PSC releases PSCnOUT1, jumps and executes DT0
plus OT0 plus DT1 while PSC Input B is in active state.
Even if PSC Input B is released during DT0 or OT0, DT0 plus OT0 sub-cycle is always
completely executed.
154
AT90PWM2/3
4317A-3–AVR–02/05
AT90PWM2/3
PSC Input Mode 4: Deactivate outputs without changing timing.
Figure 80. PSC behaviour versus PSCn Input A or Input B in Mode 4
DT0
OT0
DT1
OT1
DT0
OT0
DT1
OT1
DT0
OT0
DT1
OT1
PSCOUTn0
PSCOUTn1
PSCn Input A
or
PSCn Input B
Figure 81. PSC behaviour versus PSCn Input A or Input B in Fault Mode 4
DT0
OT0
DT1
OT1
DT0
OT0
DT1
OT1
DT0
OT0
DT1
OT1
PSCOUTn0
PSCOUTn1
PSCn Input A
or
PSCn Input B
155
4317A-3–AVR–02/05
PSC Input Mode 5: Stop signal and Insert Dead-Time
PSCOUTn0
DT0 OT0
DT0
DT1
OT1
DT1
DT0
DT1
OT0
DT1
DT0
DT0
Figure 82. PSC behaviour versus PSCn Input A in Fault Mode 5
DT1
OT1
DT0
OT0
DT1
OT1
PSCOUTn1
PSCn Input A
or
PSCn Input B
Used in Fault mode 5, PSCn Input A or PSCn Input B act indifferently on OnTime0/Dead-Time0 or on On-Time1/Dead-Time1.
156
AT90PWM2/3
4317A-3–AVR–02/05
AT90PWM2/3
PSC Input Mode 6: Stop signal, Jump to Opposite Dead-Time and Wait.
Figure 83. PSC behaviour versus PSCn Input A in Fault Mode 6
DT0
OT0
DT1 OT1
DT0 OT0
DT1
OT1
DT0
OT0
DT1
OT1
PSCOUTn0
PSCOUTn1
PSCn Input A
or
PSCn Input B
Used in Fault mode 6, PSCn Input A or PSCn Input B act indifferently on OnTime0/Dead-Time0 or on On-Time1/Dead-Time1.
157
4317A-3–AVR–02/05
PSC Input Mode 7: Halt PSC and Wait for Software Action
Figure 84. PSC behaviour versus PSCn Input A in Fault Mode 8
DT0
OT0
DT1
OT1
DT0 OT0
DT0
OT0
DT1
OT1
PSCOUTn0
PSCOUTn1
PSCn Input A
or
PSCn Input B
Software Action
Used in Fault mode 7, PSCn Input A or PSCn Input B act indifferently on OnTime0/Dead-Time0 or on On-Time1/Dead-Time1.
158
AT90PWM2/3
4317A-3–AVR–02/05
AT90PWM2/3
Edge Retrigger PSC
PSC Input Mode 8
Figure 85. PSC behaviour versus PSCn Input A in Mode 8
DT0
OT0
DT1
DT0 OT0
OT1
DT1
OT1
DT0
OT0
DT1
OT1
PSCOUTn0
PSCOUTn1
PSCn Input A
The output frequency is modulated by the occurence of significative edge of retriggering
input.
Figure 86. PSC behaviour versus PSCn Input Bin Mode 8
DT0
OT0
DT1
OT1
DT0
OT0
DT1
OT1
DT0
OT0
DT1
OT1
PSCOUTn0
PSCOUTn1
PSCn Input B
or
PSCn Input B
The output frequency is modulated by the occurence of significative edge of retriggering
input.
159
4317A-3–AVR–02/05
PSC Input Mode 9: Fixed Frequency Edge Retrigger PSC
Figure 87. PSC behaviour versus PSCn Input A in Mode 9
DT0
OT0
DT1
OT1
DT0
OT0
DT1
OT1
DT0
OT0
DT1
OT1
PSCOUTn0
PSCOUTn1
PSCn Input A
The output frequency is not modified by the occurence of significative edge of retriggering input.
Only the output is disactivated when significative edge on retriggering input occurs.
Note: In this mode the output of the PSC becomes active during the next ramp even if
the Retrigger/Fault input is actve. Only the significative edge of Retrigger/Fault input is
taken into account.
Figure 88. PSC behaviour versus PSCn Input B in Mode 9
DT0
OT0
DT1
OT1
DT0
OT0
DT1
OT1
DT0
OT0
DT1
OT1
PSCOUTn0
PSCOUTn1
PSCn Input B
160
AT90PWM2/3
4317A-3–AVR–02/05
AT90PWM2/3
PSC Input Mode 14: Fixed Frequency Edge Retrigger PSC and Disactivate Output
Figure 89. PSC behaviour versus PSCn Input A in Mode 14
DT0
OT0
DT1
OT1
DT0
OT0
DT1
OT1
DT0
OT0
DT1
OT1
DT0
OT0
DT1
OT1
PSCOUTn0
PSCOUTn1
PSCn Input A
The output frequency is not modified by the occurence of significative edge of retriggering input.
Figure 90. PSC behaviour versus PSCn Input B in Mode 14
DT0
OT0
DT1
OT1
DT0
OT0
DT1
OT1
DT0
OT0
DT1
OT1
DT0
OT0
DT1
OT1
PSCOUTn0
PSCOUTn1
PSCn Input B
The output is disactivated while retriggering input is active.
The output of the PSC is set to an inactive state and the corresponding ramp is not
aborted. The output stays in an inactive state while the Retrigger/Fault input is actve.
The PSC runs at constant frequency.
161
4317A-3–AVR–02/05
Available Input Mode
according to Running Mode
Some Input Modes are not consistent with some Running Modes. So the table below
gives the input modes which are valid according to running modes..
Table 58. Available Input Modes according to Running Modes
Input Mode
Number :
1 Ramp
Mode
2 Ramp
Mode
4 Ramp
Mode
Centered
Mode
1
Valid
Valid
Valid
Do not use
2
Do not use
Valid
Valid
Do not use
3
Do not use
Valid
Valid
Do not use
4
Valid
Valid
Valid
Valid
5
Do not use
Valid
Valid
Do not use
6
Do not use
Valid
Valid
Do not use
7
Valid
Valid
Valid
Valid
8
Valid
Valid
Valid
Do not use
9
Valid
Valid
Valid
Do not use
10
Do not use
11
12
13
14
15
Do not use
Valid
Valid
Do not use
Do not use
Event Capture
The PSC can capture the value of time (PSC counter) when a retrigger event or fault
event occurs on PSC inputs. This value can be read by sofware in PICRnH/L register.
Using the Input Capture Unit
The main challenge when using the Input Capture unit is to assign enough processor
capacity for handling the incoming events. The time between two events is critical. If the
processor has not read the captured value in the PICRn Register before the next event
occurs, the PICRn will be overwritten with a new value. In this case the result of the capture will be incorrect.
When using the Input Capture interrupt, the PICRn Register should be read as early in
the interrupt handler routine as possible. Even though the Input Capture interrupt has
relatively high priority, the maximum interrupt response time is dependent on the maximum number of clock cycles it takes to handle any of the other interrupt requests.
162
AT90PWM2/3
4317A-3–AVR–02/05
AT90PWM2/3
PSC2 Outputs
Output Matrix
PSC2 has an output matrix which allow in 4 ramp mode to program a value of
PSCOUT20 and PSCOUT21 binary value for each ramp.
Table 59. Output Matrix versus ramp number
Ramp 0
Ramp 1
Ramp 2
Ramp 3
PSCOUT20
POMV2A0
POMV2A1
POMV2A2
POMV2A3
PSCOUT21
POMV2B0
POMV2B1
POMV2B2
POMV2B3
PSCOUT2m takes the value given in Table 59. during all corresponding ramp. Thanks
to the Output Matrix it is possible to generate all kind of PSCOUT20/PSCOUT21
combination.
When Output Matrix is used, the PSC n Output Polarity POPn has no action on the
outputs.
PSCOUT22 & PSCOUT23
Selectors
PSC 2 has two supplementary outputs PSCOUT22 and PSCOUT23.
According to POS22 and POS23 bits in PSOC2 register, PSCOUT22 and PSCOUT23
duplicate PSCOUT20 and PSCOU21.
If POS22 bit in PSOC2 register is clear, PSCOUT22 duplicates PSCOUT20.
If POS22 bit in PSOC2 register is set, PSCOUT22 duplicates PSCOUT21.
If POS23 bit in PSOC2 register is clear, PSCOUT23 duplicates PSCOUT21.
If POS23 bit in PSOC2 register is set, PSCOUT23 duplicates PSCOUT20.
Figure 91. PSCOUT22 and PSCOUT23 Outptuts
PSCOUT20
Waveform
Generator A
0
PSCOUT22
1
POS22
POS23
Output
Matrix
1
PSCOUT23
0
Waveform
Generator B
PSC Synchronization
PSCOUT21
2 or 3 PSC can be synchronized together. In this case, two waveform alignments are
possible:
•
The waveforms are center aligned in the Center Aligned mode if master and slaves
are all with the same PSC period (which is the natural use).
•
The waveforms are edge aligned in the 1, 2 or 4 ramp mode
163
4317A-3–AVR–02/05
Analog Synchronization
PSC generates a signal to synchronize the sample and hold; synchronisation is mandatory for measurements.
This signal can be selected between all falling or rising edge of PSCn0 or PSCn1
outputs.
In center aligned mode, all the input values (OT1,OT2,DT1,DT2) are not used. One of
the remainding values can be used to specified the synchronization of the ADC.
Interrupt Handling
As each PSC can be dedicated for one function, each PSC has its own interrupt system
(vector ...)
List of interrupt sources:
164
•
Counter reload (end of On Time 1)
•
PSC Input event (active edge or at the beginning of level configured event)
•
PSC Mutual Synchronization Error
AT90PWM2/3
4317A-3–AVR–02/05
AT90PWM2/3
PSC Synchronization
2 or 3 PSC can be started at the same time by a chained mechanism.
Figure 92. PSC Run Synchronization
SY0In
PRUN0
Run PSC0
PARUN0
SY0Out
PSC0
SY1In
PRUN1
Run PSC1
PARUN1
SY1Out
PSC1
SY2In
PRUN2
Run PSC2
PARUN2
SY2Out
PSC2
If the PSCm has its PARUNn bit set, then it can start at the same time than PSCn-1.
PRUNn and PARUNn bits are located PCTLn register. See page 174.
Note : Do not set the PARUNn bits on the three PSC at the same time.
Thanks to this feature, we can for example configure two PSC in slave mode (PARUNn
= 1 / PRUNn = 0) and one PSC in master mode (PARUNm = 0 / PRUNm = 0). This PSC
master can start all PSC at the same moment ( PRUNm = 1).
Fault events in Autorun mode
To complete this master/slave mechanism, fault events are propagated from PSCn-1 to
PSCn and from PSCn to PSCn-1.
A PSC which propagate a Run signal to the following PSC stops this PSC when the Run
signal is deactivate.
A PSC which receive its Run signal from the previous PSC transmits its fault signal (if
enabled) to this previous PSC. So a slave PSC propagates its fault events when they
are configured and enabled.
PSC Clock Sources
PSC must be able to generate high frequency with enhanced resolution.
Each PSC has two clock inputs:
•
CLK PLL from the PLL
•
CLK I/O
165
4317A-3–AVR–02/05
Figure 93. Clock selection
CLK
PLL
1
CK
CK
CK/4
CK/16
CK/64
01
10
11
0
I/O
00
CLK
PRESCALER
PCLKSELn
PPREn1/0
CLK PSCn
PCLKSELn bit in PSC n Configuration register (PCNFn) is used to select the clock
source.
PPREn1/0 bits in PSC n Control Register (PCTLn) are used to select the divide factor of
the clock.
Table 60. Output Clock versus Selection and Prescaler
PCLKSELn
166
PPREn1
PPREn0
CLKPSCn output
0
0
0
CLK I/O
0
0
1
CLK I/O / 4
0
1
0
CLK I/O / 16
0
1
1
CLK I/O / 64
1
0
0
CLK PLL
1
0
1
CLK PLL / 4
1
1
0
CLK PLL / 16
1
1
1
CLK PLL / 64
AT90PWM2/3
4317A-3–AVR–02/05
AT90PWM2/3
Interrupts
This section describes the specifics of the interrupt handling as performed in
AT90PWM2/3.
List of Interrupt Vector
Each PSC provides 2 interrupt vectors
•
PSCn EC (End of Cycle): When enabled and when a match with OCRnRB occurs
•
PSCn CAPT (Capture Event): When enabled and one of the two following events
occurs : retrigger, capture of the PSC counter or Synchro Error.
See PSCn Interrupt Mask Register page 179 and PSCn Interrupt Flag Register page
180.
PSC Interrupt Vectors in
AT90PWM2/3
Table 61. PSC Interrupt Vectors
Vector
No.
Program
Address
-
-
2
Source
Interrupt Definition
-
-
0x0001
PSC2 CAPT
PSC2 Capture Event or Synchronization Error
3
0x0002
PSC2 EC
PSC2 End Cycle
4
0x0003
PSC1 CAPT
PSC1 Capture Event or Synchronization Error
5
0x0004
PSC1 EC
PSC1 End Cycle
6
0x0005
PSC0 CAPT
PSC0 Capture Event or Synchronization Error
7
0x0006
PSC0 EC
PSC0 End Cycle
-
-
-
-
167
4317A-3–AVR–02/05
PSC Register Definition
PSC 0 Synchro and Output
Configuration – PSOC0
PSC 1 Synchro and Output
Configuration – PSOC1
PSC 2 Synchro and Output
Configuration – PSOC2
Registers are explained for PSC0. They are identical for PSC1. For PSC2 only different
registers are described.
Bit
7
6
5
4
3
2
1
0
-
-
PSYNC01
PSYNC00
-
POEN0B
-
POEN0A
Read/Write
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
Initial Value
0
0
0
0
0
0
0
0
Bit
7
6
5
4
3
2
1
0
-
-
PSYNC11
PSYNC10
-
POEN1B
-
POEN1A
Read/Write
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
Initial Value
0
0
0
0
0
0
0
0
Bit
7
6
5
4
3
2
1
0
POS23
POS22
PSYNC21
PSYNC20
POEN2D
POEN2B
POEN2C
POEN2A
Read/Write
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
Initial Value
0
0
0
0
0
0
0
0
PSOC0
PSOC1
PSOC2
• Bit 7 – POS23 : PSCOUT23 Selection (PSC2 only)
When this bit is clear, PSCOUT23 outputs the waveform generated by Waveform Generator B.
When this bit is set, PSCOUT23 outputs the waveform generated by Waveform Generator A.
• Bit 6 – POS22 : PSCOUT22 Selection (PSC2 only)
When this bit is clear, PSCOUT22 outputs the waveform generated by Waveform Generator A.
When this bit is set, PSCOUT22 outputs the waveform generated by Waveform Generator B.
• Bit 5:4 – PSYNCn1:0: Synchronization Out for ADC Selection
Select the polarity and signal source for generating a signal which will be sent to the
ADC for synchronization.
Table 62. Synchronization Source Description in One/Two/Four Ramp Modes
168
PSYNCn1
PSYNCn0
Description
0
0
Send signal on leading edge of PSCOUTn0 (match with OCRnSA)
0
1
Send signal on trailing edge of PSCOUTn0 (match with OCRnRA
or fault/retrigger on part A)
1
0
Send signal on leading edge of PSCOUTn1 (match with OCRnSB)
1
1
Send signal on trailing edge of PSCOUTn1 (match with OCRnRB
or fault/retrigger on part B)
AT90PWM2/3
4317A-3–AVR–02/05
AT90PWM2/3
Table 63. Synchronization Source Description in Centered Mode
PSYNCn1
PSYNCn0
Description
0
0
Send signal on match with OCRnSA (during counting down of
PSC)
0
1
Send signal on match with OCRnSA (during counting up of PSC)
1
0
no synchronization signal
1
1
no synchronization signal
• Bit 3 – POEN2D : PSCOUT23 Output Enable (PSC2 only)
When this bit is clear, second I/O pin affected to PSCOUT23 acts as a standard port.
When this bit is set, second I/O pin affected to PSCOUT23 is connected to the PSC
waveform generator B output and is set and clear according to the PSC operation.
• Bit 2 – POENnB: PSC n OUT Part B Output Enable
When this bit is clear, I/O pin affected to PSCOUTn1 acts as a standard port.
When this bit is set, I/O pin affected to PSCOUTn1 is connected to the PSC waveform
generator B output and is set and clear according to the PSC operation.
• Bit 1 – POEN2C : PSCOUT22 Output Enable (PSC2 only)
When this bit is clear, second I/O pin affected to PSCOUT22 acts as a standard port.
When this bit is set, second I/O pin affected to PSCOUT22 is connected to the PSC
waveform generator A output and is set and clear according to the PSC operation.
• Bit 0 – POENnA: PSC n OUT Part A Output Enable
When this bit is clear, I/O pin affected to PSCOUTn0 acts as a standard port.
When this bit is set, I/O pin affected to PSCOUTn0 is connected to the PSC waveform
generator A output and is set and clear according to the PSC operation.
Output Compare SA Register
– OCRnSAH and OCRnSAL
Bit
7
6
5
4
–
–
–
–
3
2
1
0
OCRnSA[11:8]
OCRnSAH
OCRnSA[7:0]
Output Compare RA Register
– OCRnRAH and OCRnRAL
OCRnSAL
Read/Write
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
Initial Value
0
0
0
0
0
0
0
0
Bit
7
6
5
4
3
2
1
0
–
–
–
–
OCRnRA[11:8]
OCRnRAH
OCRnRA[7:0]
Output Compare SB Register
– OCRnSBH and OCRnSBL
OCRnRAL
Read/Write
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
Initial Value
0
0
0
0
0
0
0
0
Bit
7
6
5
4
3
2
1
0
–
–
–
–
OCRnSB[11:8]
OCRnSBH
OCRnSB[7:0]
OCRnSBL
Read/Write
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
Initial Value
0
0
0
0
0
0
0
0
169
4317A-3–AVR–02/05
Output Compare RB Register
– OCRnRBH and OCRnRBL
Bit
7
6
5
4
3
OCRnRB[15:12]
2
1
0
OCRnRB[11:8]
OCRnRBH
OCRnRB[7:0]
OCRnRBL
Read/Write
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
Initial Value
0
0
0
0
0
0
0
0
Note : n = 0 to 2 according to PSC number.
The Output Compare Registers RA, RB, SA and SB contain a 12-bit value that is continuously compared with the PSC counter value. A match can be used to generate an
Output Compare interrupt, or to generate a waveform output on the associated pin.
The Output Compare Registers RB contains also a 4-bit value that is used for the flank
width modulation.
The Output Compare Registers are 16bit and 12-bit in size. To ensure that both the high
and low bytes are written simultaneously when the CPU writes to these registers, the
access is performed using an 8-bit temporary high byte register (TEMP). This temporary
register is shared by all the other 16-bit registers.
170
AT90PWM2/3
4317A-3–AVR–02/05
AT90PWM2/3
PSC 0 Configuration Register
– PCNF0
PSC 1 Configuration Register
– PCNF1
PSC 2 Configuration Register
– PCNF2
Bit
7
6
5
PFIFTY0
PALOCK0
PLOCK0
Read/Write
R/W
R/W
R/W
R/W
Initial Value
0
0
0
Bit
4
2
1
POP0
PCLKSEL0
-
R/W
R/W
R/W
R/W
0
0
0
0
0
4
3
0
7
6
5
PFIFTY1
PALOCK1
PLOCK1
Read/Write
R/W
R/W
R/W
R/W
Initial Value
0
0
0
Bit
3
PMODE01 PMODE00
0
2
1
POP1
PCLKSEL1
-
R/W
R/W
R/W
R/W
0
0
0
0
0
4
3
PMODE11 PMODE10
7
6
5
PFIFTY2
PALOCK2
PLOCK2
Read/Write
R/W
R/W
R/W
R/W
Initial Value
0
0
0
0
2
1
0
POP2
PCLKSEL2
POME2
R/W
R/W
R/W
R/W
0
0
0
0
PMODE21 PMODE20
PCNF0
PCNF0
PCNF0
The PSC n Configuration Register is used to configure the running mode of the PSC.
• Bit 7 - PFIFTYn: PSC n Fifty
Writing this bit to one, set the PSC in a fifty percent mode where only OCRnRBH/L and
OCRnSBH/L are used. They are duplicated in OCRnRAH/L and OCRnSAH/L during the
update of OCRnRBH/L. This feature is useful to perform fifty percent waveforms.
• Bit 6 - PALOCKn: PSC n Autolock
When this bit is set, the Output Compare Registers RA, SA and SB can be written without disturbing the PSC cycles. The update of the PSC internal registers will be done at
the end of the PSC cycle if the Output Compare Register RB has been the last written.
When set, this bit prevails over LOCK (bit 5)
• Bit 5 – PLOCKn: PSC n Lock
When this bit is set, the Output Compare Registers RA, RB, SA and SB can be written
without disturbing the PSC cycles. The update of the PSC internal registers will be done
if the LOCK bit is released to zero.
• Bit 4:3 – PMODEn1: 0: PSC n Mode
Select the mode of PSC.
Table 64. PSC n Mode Selection
PMODEn1
PMODEn0
Description
0
0
One Ramp Mode
0
1
Two Ramp Mode
1
0
Four Ramp Mode
1
1
Center Aligned Mode
• Bit 2 – POPn: PSC n Output Polarity
If this bit is cleared, the PSC outputs are active Low.
If this bit is set, the PSC outputs are active High.
171
4317A-3–AVR–02/05
• Bit 1 – PCLKSELn: PSC n Input Clock Select
This bit is used to select between CLKPF or CLKPS clocks.
Set this bit to select the fast clock input (CLKPF).
Clear this bit to select the slow clock input (CLKPS).
• Bit 0 – POME2: PSC 2 Output Matrix Enable (PSC2 only)
Set this bit to enable the Output Matrix feature on PSC2 outputs. See “PSC2 Outputs”
on page 163.
When Output Matrix is used, the PSC n Output Polarity POPn has no action on the
outputs.
172
AT90PWM2/3
4317A-3–AVR–02/05
AT90PWM2/3
PSC 0 Control Register –
PCTL0
Bit
7
6
5
4
3
2
1
0
PPRE01
PPRE00
PBFM0
PAOC0B
PAOC0A
PARUN0
PCCYC0
PRUN0
Read/Write
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
Initial Value
0
0
0
0
0
0
0
0
PCTL0
• Bit 7:6 – PPRE01:0 : PSC 0 Prescaler Select
This two bits select the PSC input clock division factor. All generated waveform will be
modified by this factor.
Table 65. PSC 0 Prescaler Selection
PPRE01
PPRE00
Description
0
0
No divider on PSC input clock
0
1
Divide the PSC input clock by 4
1
0
Divide the PSC input clock by 16
1
1
Divide the PSC clock by 64
• Bit 5 – PBFM0 : Balance Flank Width Modulation
When this bit is clear, Flank Width Modulation operates on On-Time 1 only.
When this bit is set, Flank Width Modulation operates on On-Time 0 and On-Time 1.
• Bit 4 – PAOC0B : PSC 0 Asynchronous Output Control B
When this bit is set, Fault input selected to block B can act directly to PSCOUT01 output. See Section “PSC Clock Sources”, page 165
• Bit 3 – PAOC0A : PSC 0 Asynchronous Output Control A
When this bit is set, Fault input selected to block A can act directly to PSCOUT00 output. See Section “PSC Clock Sources”, page 165
• Bit 2 – PARUN0 : PSC 0 Autorun
When this bit is set, the PSC 0 starts with PSC2. That means that PSC 0 starts :
•
when PRUN2 bit in PCTL2 is set,
•
or when PARUN2 bit in PCTL2 is set and PRUN1 bit in PCTL1 register is set.
Thanks to this bit, 2 or 3 PSCs can be synchronized (motor control for example)
• Bit 1 – PCCYC0 : PSC 0 Complete Cycle
When this bit is set, the PSC 0 completes the entire waveform cycle before halt operation requested by clearing PRUN0. This bit is not relevant in slave mode (PARUN0 = 1).
• Bit 0 – PRUN0 : PSC 0 Run
Writing this bit to one starts the PSC 0.
When set, this bit prevails over PARUN0 bit.
173
4317A-3–AVR–02/05
PSC 1 Control Register –
PCTL1
Bit
7
6
5
4
3
2
1
0
PPRE11
PPRE10
PBFM1
PAOC1B
PAOC1A
PARUN1
PCCYC1
PRUN1
Read/Write
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
Initial Value
0
0
0
0
0
0
0
0
PCTL1
• Bit 7:6 – PPRE11:0 : PSC 1 Prescaler Select
This two bits select the PSC input clock division factor.All generated waveform will be
modified by this factor.
Table 66. PSC 1 Prescaler Selection
PPRE11
PPRE10
Description
0
0
No divider on PSC input clock
0
1
Divide the PSC input clock by 4
1
0
Divide the PSC input clock by 16
1
1
Divide the PSC clock by 64
• Bit 5 – PBFM1 : Balance Flank Width Modulation
When this bit is clear, Flank Width Modulation operates on On-Time 1 only.
When this bit is set, Flank Width Modulation operates on On-Time 0 and On-Time 1.
• Bit 4 – PAOC1B : PSC 1 Asynchronous Output Control B
When this bit is set, Fault input selected to block B can act directly to PSCOUT11 output. See Section “PSC Clock Sources”, page 165
• Bit 3 – PAOC1A : PSC 1 Asynchronous Output Control A
When this bit is set, Fault input selected to block A can act directly to PSCOUT10 output. See Section “PSC Clock Sources”, page 165
• Bit 2 – PARUN1 : PSC 1 Autorun
When this bit is set, the PSC 1 starts with PSC0. That means that PSC 1 starts :
•
when PRUN0 bit in PCTL0 register is set,
•
or when PARUN0 bit in PCTL0 is set and PRUN2 bit in PCTL2 register is set.
Thanks to this bit, 2 or 3 PSCs can be synchronized (motor control for example)
• Bit 1 – PCCYC1 : PSC 1 Complete Cycle
When this bit is set, the PSC 1 completes the entire waveform cycle before halt operation requested by clearing PRUN1. This bit is not relevant in slave mode (PARUN1 = 1).
• Bit 0 – PRUN1 : PSC 1 Run
Writing this bit to one starts the PSC 1.
When set, this bit prevails over PARUN1 bit.
174
AT90PWM2/3
4317A-3–AVR–02/05
AT90PWM2/3
PSC 2 Control Register –
PCTL2
Bit
7
6
5
4
3
2
1
0
PPRE21
PPRE20
PBFM2
PAOC2B
PAOC2A
PARUN2
PCCYC2
PRUN2
Read/Write
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
Initial Value
0
0
0
0
0
0
0
0
PCTL2
• Bit 7:6 – PPRE21:0 : PSC 2 Prescaler Select
This two bits select the PSC input clock division factor.All generated waveform will be
modified by this factor.
Table 67. PSC 2 Prescaler Selection
PPRE21
PPRE20
Description
0
0
No divider on PSC input clock
0
1
Divide the PSC input clock by 4
1
0
Divide the PSC input clock by 16
1
1
Divide the PSC clock by 64
• Bit 5 – PBFM2 : Balance Flank Width Modulation
When this bit is clear, Flank Width Modulation operates on On-Time 1 only.
When this bit is set, Flank Width Modulation operates on On-Time 0 and On-Time 1.
• Bit 4 – PAOC2B : PSC 2 Asynchronous Output Control B
When this bit is set, Fault input selected to block B can act directly to PSCOUT21 and
PSCOUT23 outputs. See Section “PSC Clock Sources”, page 165.
• Bit 3 – PAOC2A : PSC 2 Asynchronous Output Control A
When this bit is set, Fault input selected to block A can act directly to PSCOUT20 and
PSCOUT22 outputs. See Section “PSC Clock Sources”, page 165.
• Bit 2 – PARUN2 : PSC 2 Autorun
When this bit is set, the PSC 2 starts with PSC1. That means that PSC 2 starts :
•
when PRUN1 bit in PCTL1 register is set,
•
or when PARUN1 bit in PCTL1 is set and PRUN0 bit in PCTL0 register is set.
• Bit 1 – PCCYC2 : PSC 2 Complete Cycle
When this bit is set, the PSC 2 completes the entire waveform cycle before halt operation requested by clearing PRUN2. This bit is not relevant in slave mode (PARUN2 = 1).
• Bit 0 – PRUN2 : PSC 2 Run
Writing this bit to one starts the PSC 2.
When set, this bit prevails over PARUN2 bit.
175
4317A-3–AVR–02/05
PSC n Input A Control
Register – PFRCnA
Bit
7
PCAEnA
PSC n Input B Control
Register – PFRCnB
6
5
4
3
2
1
0
PISELnA PELEVnA PFLTEnA PRFMnA3 PRFMnA2 PRFMnA1 PRFMnA0
Read/Write
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
Initial Value
0
0
0
0
0
0
0
0
6
5
4
3
2
1
0
Bit
7
PCAEnB
PISELnB PELEVnB PFLTEnB PRFMnB3 PRFMnB2 PRFMnB1 PRFMnB0
Read/Write
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
Initial Value
0
0
0
0
0
0
0
0
PFRCnA
PFRCnB
The Input Control Registers are used to configure the 2 PSC’s Retrigger/Fault block A &
B. The 2 blocks are identical, so they are configured on the same way.
• Bit 7 – PCAEnx : PSC n Capture Enable Input Part x
Writing this bit to one enables the capture function when external event occurs on input
selected as input for Part x (see PISELnx bit in the same register).
• Bit 6 – PISELnx : PSC n Input Select for Part x
Clear this bit to select PSCINn as input of Fault/Retrigger block x.
Set this bit to select Comparator n Output as input of Fault/Retrigger block x.
• Bit 5 –PELEVnx : PSC n Edge Level Selector of Input Part x
When this bit is clear, the falling edge or low level of selected input generates the significative event for retrigger or fault function .
When this bit is set, the rising edge or high level of selected input generates the significative event for retrigger or fault function.
• Bit 4 – PFLTEnx : PSC n Filter Enable on Input Part x
Setting this bit (to one) activates the Input Capture Noise Canceler. When the noise canceler is activated, the input from the retrigger pin is filtered. The filter function requires
four successive equal valued samples of the retrigger pin for changing its output. The
Input Capture is therefore delayed by four oscillator cycles when the noise canceler is
enabled.
• Bit 3:0 – PRFMnx3:0: PSC n Fault Mode
These four bits define the mode of operation of the Fault or Retrigger functions.
(see PSC Functional Specification for more explanations)
Table 68. Level Sensitivity and Fault Mode Operation
PRFMnx3:0
176
Description
0000b
No action, PSC Input is ignored
0001b
PSC Input Mode 1: Stop signal, Jump to Opposite Dead-Time and
Wait
0010b
PSC Input Mode 2: Stop signal, Execute Opposite Dead-Time and
Wait
AT90PWM2/3
4317A-3–AVR–02/05
AT90PWM2/3
PRFMnx3:0
Description
0011b
PSC Input Mode 3: Stop signal, Execute Opposite while Fault active
0100b
PSC Input Mode 4: Deactivate outputs without changing timing.
0101b
PSC Input Mode 5: Stop signal and Insert Dead-Time
0110b
0111b
PSC Input Mode 6: Stop signal, Jump to Opposite Dead-Time and
Wait.
PSC Input Mode 7: Halt PSC and Wait for Software Action
1000b
Edge Retrigger PSC
1001b
PSC Input Mode 9: Fixed Frequency Edge Retrigger PSC
1010b
Reserved (do not use)
1011b
1100b
1101b
1110b
1111b
PSC Input Mode 14: Fixed Frequency Edge Retrigger PSC and Disactivate Output
Reserved (do not use)
177
4317A-3–AVR–02/05
PSC 0 Input Capture Register
– PICR0H and PICR0L
Bit
7
6
5
4
–
–
–
–
3
2
1
0
PICR0[11:8]
PICR0H
PICR0[7:0]
PSC 1 Input Capture Register
– PICR1H and PICR1L
PICR0L
Read/Write
R
R
R
R
R
R
R
R
Initial Value
0
0
0
0
0
0
0
0
Bit
7
6
5
4
3
2
1
0
–
–
–
–
PICR1[11:8]
PICR1H
PICR1[7:0]
PSC 2 Input Capture Register
– PICR2H and PICR2L
PICR1L
Read/Write
R
R
R
R
R
R
R
R
Initial Value
0
0
0
0
0
0
0
0
Bit
7
6
5
4
3
2
1
0
–
–
–
–
PICR2[11:8]
PICR2H
PICR2[7:0]
PICR2L
Read/Write
R
R
R
R
R
R
R
R
Initial Value
0
0
0
0
0
0
0
0
The Input Capture is updated with the PSC counter value each time an event occurs on
the enabled PSC input pin (or optionally on the Analog Comparator output) if the capture
function is enabled (bit PCAEnx in PFRCnx register is set).
The Input Capture Register is 12-bit in size. To ensure that both the high and low bytes
are read simultaneously when the CPU accesses these registers, the access is performed using an 8-bit temporary high byte register (TEMP). This temporary register is
shared by all the other 16-bit or 12-bit registers.
This register is read only and a write operation to this register is not allowed.
PSC2 Specific Register
PSC 2 Output Matrix – POM2
Bit
7
6
5
4
3
2
1
0
POMV2B3
POMV2B2
POMV2B1
POMV2B0
POMV2A3
POMV2A2
POMV2A1
POMV2A0
Read/Write
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
Initial Value
0
0
0
0
0
0
0
0
POM2
• Bit 7 – POMV2B3: Output Matrix Output B Ramp 3
This bit gives the state of the PSCOUT21 (and/or PSCOUT23) during ramp 3
• Bit 6 – POMV2B2: Output Matrix Output B Ramp 2
This bit gives the state of the PSCOUT21 (and/or PSCOUT23) during ramp 2
• Bit 5 – POMV2B1: Output Matrix Output B Ramp 1
This bit gives the state of the PSCOUT21 (and/or PSCOUT23) during ramp 1
• Bit 4 – POMV2B0: Output Matrix Output B Ramp 0
This bit gives the state of the PSCOUT21 (and/or PSCOUT23) during ramp 0
178
AT90PWM2/3
4317A-3–AVR–02/05
AT90PWM2/3
• Bit 3 – POMV2A3: Output Matrix Output A Ramp 3
This bit gives the state of the PSCOUT20 (and/or PSCOUT22) during ramp 3
• Bit 2 – POMV2A2: Output Matrix Output A Ramp 2
This bit gives the state of the PSCOUT20 (and/or PSCOUT22) during ramp 2
• Bit 1 – POMV2A1: Output Matrix Output A Ramp 1
This bit gives the state of the PSCOUT20 (and/or PSCOUT22) during ramp 1
• Bit 0 – POMV2A0: Output Matrix Output A Ramp 0
This bit gives the state of the PSCOUT20 (and/or PSCOUT22) during ramp 0
PSC0 Interrupt Mask Register
– PIM0
PSC1 Interrupt Mask Register
– PIM1
PSC2 Interrupt Mask Register
– PIM2
Bit
7
6
5
4
3
2
1
0
-
-
PSEIE0
PEVE0B
PEVE0A
-
-
PEOPE0
Read/Write
R
R
R/W
R/W
R/W
R
R
R/W
Initial Value
0
0
0
0
0
0
0
0
Bit
7
6
5
4
3
2
1
0
-
-
PSEIE1
PEVE1B
PEVE1A
-
-
PEOPE1
Read/Write
R
R
R/W
R/W
R/W
R
R
R/W
Initial Value
0
0
0
0
0
0
0
0
Bit
7
6
5
4
3
2
1
0
-
-
PSEIE2
PEVE2B
PEVE2A
-
-
PEOPE2
Read/Write
R
R
R/W
R/W
R/W
R
R
R/W
Initial Value
0
0
0
0
0
0
0
0
PIM0
PIM1
PIM2
• Bit 5 – PSEIEn : PSC n Synchro Error Interrupt Enable
When this bit is set, the PSEIn bit (if set) generate an interrupt.
• Bit 4 – PEVEnB : PSC n External Event B Interrupt Enable
When this bit is set, an external event which can generates a capture from Retrigger/Fault block B generates also an interrupt.
• Bit 3 – PEVEnA : PSC n External Event A Interrupt Enable
When this bit is set, an external event which can generates a capture from Retrigger/Fault block A generates also an interrupt.
• Bit 0 – PEOPEn : PSC n End Of Cycle Interrupt Enable
When this bit is set, an interrupt is generated when PSC reaches the end of the whole
cycle.
179
4317A-3–AVR–02/05
PSC0 Interrupt Flag Register –
PIFR0
PSC1 Interrupt Flag Register –
PIFR1
PSC2 Interrupt Flag Register –
PIFR2
Bit
7
6
5
4
3
2
1
0
POAC0B
POAC0A
PSEI0
PEV0B
PEV0A
PRN01
PRN00
PEOP2
Read/Write
R
R
R/W
R/W
R/W
R
R
R/W
Initial Value
0
0
0
0
0
0
0
0
Bit
7
6
5
4
3
2
1
0
POAC1B
POAC1A
PSEI1
PEV1B
PEV1A
PRN11
PRN10
PEOP1
Read/Write
R
R
R/W
R/W
R/W
R
R
R/W
Initial Value
0
0
0
0
0
0
0
0
Bit
7
6
5
4
3
2
1
0
POAC2B
POAC2A
PSEI2
PEV2B
PEV2A
PRN21
PRN20
PEOP2
Read/Write
R
R
R/W
R/W
R/W
R
R
R/W
Initial Value
0
0
0
0
0
0
0
0
PIFR0
PIFR1
PIFR2
• Bit 7 – POACnB : PSC n Output B Activity
This bit is set by hardware each time the output PSCOUTn1 changes from 0 to 1 or from
1 to 0.
Must be cleared by software by writing a one to its location.
This feature is useful to detect that a PSC output doesn’t change due to a freezen external input signal.
• Bit 6 – POACnA : PSC n Output A Activity
This bit is set by hardware each time the output PSCOUTn0 changes from 0 to 1 or from
1 to 0.
Must be cleared by software by writing a one to its location.
This feature is useful to detect that a PSC output doesn’t change due to a freezen external input signal.
• Bit 5 – PSEIn : PSC n Synchro Error Interrupt
This bit is set by hardware when the update (or end of PSC cycle) of the PSCn configured in auto run (PARUNn = 1) does not occur at the same time than the PSCn-1 which
has generated the input run signal. (For PSC0, PSCn-1 is PSC2).
Must be cleared by software by writing a one to its location.
This feature is useful to detect that a PSC doesn’t run at the same speed or with the
same phase than the PSC master.
• Bit 4 – PEVnB : PSC n External Event B Interrupt
This bit is set by hardware when an external event which can generates a capture or a
retrigger from Retrigger/Fault block B occurs.
Must be cleared by software by writing a one to its location.
This bit can be read even if the corresponding interrupt is not enabled (PEVEnB bit = 0).
180
AT90PWM2/3
4317A-3–AVR–02/05
AT90PWM2/3
• Bit 3 – PEVnA : PSC n External Event A Interrupt
This bit is set by hardware when an external event which can generates a capture or a
retrigger from Retrigger/Fault block A occurs.
Must be cleared by software by writing a one to its location.
This bit can be read even if the corresponding interrupt is not enabled (PEVEnA bit = 0).
• Bit 2:1 – PRNn1:0 : PSC n Ramp Number
Memorization of the ramp number when the last PEVnA or PEVnB occured.
Table 69. PSC n Ramp Number Description
PnRN1
PnRN0
Description
0
0
The last event which has generated an interrupt occured during ramp 1
0
1
The last event which has generated an interrupt occured during ramp 2
1
0
The last event which has generated an interrupt occured during ramp 3
1
1
The last event which has generated an interrupt occured during ramp 4
• Bit 0 – PEOPn: End Of PSC n Interrupt
This bit is set by hardware when PSC n achieves its whole cycle.
Must be cleared by software by writing a one to its location.
181
4317A-3–AVR–02/05
Serial Peripheral Interface – SPI
The Serial Peripheral Interface (SPI) allows high-speed synchronous data transfer
between the AT90PWM2/3 and peripheral devices or between several AVR devices.
The AT90PWM2/3 SPI includes the following features:
Features
•
•
•
•
•
•
•
•
Full-duplex, Three-wire Synchronous Data Transfer
Master or Slave Operation
LSB First or MSB First Data Transfer
Seven Programmable Bit Rates
End of Transmission Interrupt Flag
Write Collision Flag Protection
Wake-up from Idle Mode
Double Speed (CK/2) Master SPI Mode
Figure 94. SPI Block Diagram(1)
SPIPS
MISO
MISO
_A
clk IO
MOSI
MOSI
_A
DIVIDER
/2/4/8/16/32/64/128
SCK
SCK
_A
SPI2X
SS
SPI2X
SS_A
Note:
1. Refer to Figure 1 on page 3, and Table 24 on page 70 for SPI pin placement.
The interconnection between Master and Slave CPUs with SPI is shown in Figure 95.
The system consists of two shift Registers, and a Master clock generator. The SPI Master initiates the communication cycle when pulling low the Slave Select SS pin of the
desired Slave. Master and Slave prepare the data to be sent in their respective shift
Registers, and the Master generates the required clock pulses on the SCK line to inter-
182
AT90PWM2/3
4317B–AVR–02/05
AT90PWM2/3
change data. Data is always shifted from Master to Slave on the Master Out – Slave In,
MOSI, line, and from Slave to Master on the Master In – Slave Out, MISO, line. After
each data packet, the Master will synchronize the Slave by pulling high the Slave Select,
SS, line.
When configured as a Master, the SPI interface has no automatic control of the SS line.
This must be handled by user software before communication can start. When this is
done, writing a byte to the SPI Data Register starts the SPI clock generator, and the
hardware shifts the eight bits into the Slave. After shifting one byte, the SPI clock generator stops, setting the end of transmission flag (SPIF). If the SPI Interrupt Enable bit
(SPIE) in the SPCR Register is set, an interrupt is requested. The Master may continue
to shift the next byte by writing it into SPDR, or signal the end of packet by pulling high
the Slave Select, SS line. The last incoming byte will be kept in the Buffer Register for
later use.
When configured as a Slave, the SPI interface will remain sleeping with MISO tri-stated
as long as the SS pin is driven high. In this state, software may update the contents of
the SPI Data Register, SPDR, but the data will not be shifted out by incoming clock
pulses on the SCK pin until the SS pin is driven low. As one byte has been completely
shifted, the end of transmission flag, SPIF is set. If the SPI Interrupt Enable bit, SPIE, in
the SPCR Register is set, an interrupt is requested. The Slave may continue to place
new data to be sent into SPDR before reading the incoming data. The last incoming byte
will be kept in the Buffer Register for later use.
Figure 95. SPI Master-slave Interconnection
SHIFT
ENABLE
The system is single buffered in the transmit direction and double buffered in the receive
direction. This means that bytes to be transmitted cannot be written to the SPI Data
Register before the entire shift cycle is completed. When receiving data, however, a
received character must be read from the SPI Data Register before the next character
has been completely shifted in. Otherwise, the first byte is lost.
In SPI Slave mode, the control logic will sample the incoming signal of the SCK pin. To
ensure correct sampling of the clock signal, the frequency of the SPI clock should never
exceed fclkio/4.
183
4317B–AVR–02/05
When the SPI is enabled, the data direction of the MOSI, MISO, SCK, and SS pins is
overridden according to Table 70. For more details on automatic port overrides, refer to
“Alternate Port Functions” on page 68.
Table 70. SPI Pin Overrides(1)
Pin
Direction, Master SPI
Direction, Slave SPI
MOSI
User Defined
Input
MISO
Input
User Defined
SCK
User Defined
Input
SS
User Defined
Input
Note:
184
1. See “Alternate Functions of Port B” on page 70 for a detailed description of how to
define the direction of the user defined SPI pins.
AT90PWM2/3
4317B–AVR–02/05
AT90PWM2/3
The following code examples show how to initialize the SPI as a Master and how to perform a simple transmission.
DDR_SPI in the examples must be replaced by the actual Data Direction Register controlling the SPI pins. DD_MOSI, DD_MISO and DD_SCK must be replaced by the actual
data direction bits for these pins. E.g. if MOSI is placed on pin PB2, replace DD_MOSI
with DDB2 and DDR_SPI with DDRB.
Assembly Code Example(1)
SPI_MasterInit:
; Set MOSI and SCK output, all others input
ldi
r17,(1<<DD_MOSI)|(1<<DD_SCK)
out
DDR_SPI,r17
; Enable SPI, Master, set clock rate fck/16
ldi
r17,(1<<SPE)|(1<<MSTR)|(1<<SPR0)
out
SPCR,r17
ret
SPI_MasterTransmit:
; Start transmission of data (r16)
out
SPDR,r16
Wait_Transmit:
; Wait for transmission complete
sbis SPSR,SPIF
rjmp Wait_Transmit
ret
C Code Example(1)
void SPI_MasterInit(void)
{
/* Set MOSI and SCK output, all others input */
DDR_SPI = (1<<DD_MOSI)|(1<<DD_SCK);
/* Enable SPI, Master, set clock rate fck/16 */
SPCR = (1<<SPE)|(1<<MSTR)|(1<<SPR0);
}
void SPI_MasterTransmit(char cData)
{
/* Start transmission */
SPDR = cData;
/* Wait for transmission complete */
while(!(SPSR & (1<<SPIF)))
;
}
Note:
1. The example code assumes that the part specific header file is included.
185
4317B–AVR–02/05
The following code examples show how to initialize the SPI as a Slave and how to perform a simple reception.
Assembly Code Example(1)
SPI_SlaveInit:
; Set MISO output, all others input
ldi
r17,(1<<DD_MISO)
out
DDR_SPI,r17
; Enable SPI
ldi
r17,(1<<SPE)
out
SPCR,r17
ret
SPI_SlaveReceive:
; Wait for reception complete
sbis SPSR,SPIF
rjmp SPI_SlaveReceive
; Read received data and return
in
r16,SPDR
ret
C Code Example(1)
void SPI_SlaveInit(void)
{
/* Set MISO output, all others input */
DDR_SPI = (1<<DD_MISO);
/* Enable SPI */
SPCR = (1<<SPE);
}
char SPI_SlaveReceive(void)
{
/* Wait for reception complete */
while(!(SPSR & (1<<SPIF)))
;
/* Return data register */
return SPDR;
}
Note:
186
1. The example code assumes that the part specific header file is included.
AT90PWM2/3
4317B–AVR–02/05
AT90PWM2/3
SS Pin Functionality
Slave Mode
When the SPI is configured as a Slave, the Slave Select (SS) pin is always input. When
SS is held low, the SPI is activated, and MISO becomes an output if configured so by
the user. All other pins are inputs. When SS is driven high, all pins are inputs, and the
SPI is passive, which means that it will not receive incoming data. Note that the SPI
logic will be reset once the SS pin is driven high.
The SS pin is useful for packet/byte synchronization to keep the slave bit counter synchronous with the master clock generator. When the SS pin is driven high, the SPI slave
will immediately reset the send and receive logic, and drop any partially received data in
the Shift Register.
Master Mode
When the SPI is configured as a Master (MSTR in SPCR is set), the user can determine
the direction of the SS pin.
If SS is configured as an output, the pin is a general output pin which does not affect the
SPI system. Typically, the pin will be driving the SS pin of the SPI Slave.
If SS is configured as an input, it must be held high to ensure Master SPI operation. If
the SS pin is driven low by peripheral circuitry when the SPI is configured as a Master
with the SS pin defined as an input, the SPI system interprets this as another master
selecting the SPI as a slave and starting to send data to it. To avoid bus contention, the
SPI system takes the following actions:
1. The MSTR bit in SPCR is cleared and the SPI system becomes a Slave. As a
result of the SPI becoming a Slave, the MOSI and SCK pins become inputs.
2. The SPIF flag in SPSR is set, and if the SPI interrupt is enabled, and the I-bit in
SREG is set, the interrupt routine will be executed.
Thus, when interrupt-driven SPI transmission is used in Master mode, and there exists a
possibility that SS is driven low, the interrupt should always check that the MSTR bit is
still set. If the MSTR bit has been cleared by a slave select, it must be set by the user to
re-enable SPI Master mode.
MCU Control Register –
MCUCR
Bit
7
6
5
4
3
2
1
0
SPIPS
–
–
PUD
–
–
IVSEL
IVCE
Read/Write
R/W
R
R
R/W
R
R
R/W
R/W
Initial Value
0
0
0
0
0
0
0
0
MCUCR
• Bit 7– SPIPS: SPI Pin Redirection
Thanks to SPIPS (SPI Pin Select) in MCUCR Sfr, SPI pins can be redirected.
On 32 pins packages, SPIPS has the following action:
–
When the SPIPS bit is written to zero, the SPI signals are directed on pins
MISO,MOSI, SCK and SS.
–
When the SPIPS bit is written to one,the SPI signals are directed on
alternate SPI pins, MISO_A, MOSI_A, SCK_A and SS_A.
On 24 pins package, SPIPS has the following action:
–
When the SPIPS bit is written to zero, the SPI signals are directed on
alternate SPI pins, MISO_A, MOSI_A, SCK_A and SS_A.
–
When the SPIPS bit is written to one,the SPI signals are directed on pins
MISO,MOSI, SCK and SS.
Note that programming port are always located on alternate SPI port.
187
4317B–AVR–02/05
SPI Control Register – SPCR
Bit
7
6
5
4
3
2
1
0
SPIE
SPE
DORD
MSTR
CPOL
CPHA
SPR1
SPR0
Read/Write
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
Initial Value
0
0
0
0
0
0
0
0
SPCR
• Bit 7 – SPIE: SPI Interrupt Enable
This bit causes the SPI interrupt to be executed if SPIF bit in the SPSR Register is set
and the if the Global Interrupt Enable bit in SREG is set.
• Bit 6 – SPE: SPI Enable
When the SPE bit is written to one, the SPI is enabled. This bit must be set to enable
any SPI operations.
• Bit 5 – DORD: Data Order
When the DORD bit is written to one, the LSB of the data word is transmitted first.
When the DORD bit is written to zero, the MSB of the data word is transmitted first.
• Bit 4 – MSTR: Master/Slave Select
This bit selects Master SPI mode when written to one, and Slave SPI mode when written
logic zero. If SS is configured as an input and is driven low while MSTR is set, MSTR will
be cleared, and SPIF in SPSR will become set. The user will then have to set MSTR to
re-enable SPI Master mode.
• Bit 3 – CPOL: Clock Polarity
When this bit is written to one, SCK is high when idle. When CPOL is written to zero,
SCK is low when idle. Refer to Figure 96 and Figure 97 for an example. The CPOL functionality is summarized below:
Table 71. CPOL Functionality
CPOL
Leading Edge
Trailing Edge
0
Rising
Falling
1
Falling
Rising
• Bit 2 – CPHA: Clock Phase
The settings of the Clock Phase bit (CPHA) determine if data is sampled on the leading
(first) or trailing (last) edge of SCK. Refer to Figure 96 and Figure 97 for an example.
The CPOL functionality is summarized below:
Table 72. CPHA Functionality
CPHA
Leading Edge
Trailing Edge
0
Sample
Setup
1
Setup
Sample
• Bits 1, 0 – SPR1, SPR0: SPI Clock Rate Select 1 and 0
188
AT90PWM2/3
4317B–AVR–02/05
AT90PWM2/3
These two bits control the SCK rate of the device configured as a Master. SPR1 and
SPR0 have no effect on the Slave. The relationship between SCK and the clkIO frequency fclkio is shown in the following table:
Table 73. Relationship Between SCK and the Oscillator Frequency
SPI2X
SPR1
SPR0
0
0
0
0
0
1
0
1
0
0
1
1
1
0
0
1
0
1
1
1
0
1
1
1
SCK Frequency
fclkio/4
fclkio/16
fclkio/64
fclkio/128
fclkio/2
fclkio/8
fclkio/32
fclkio/64
189
4317B–AVR–02/05
SPI Status Register – SPSR
Bit
7
6
5
4
3
2
1
0
SPIF
WCOL
–
–
–
–
–
SPI2X
Read/Write
R
R
R
R
R
R
R
R/W
Initial Value
0
0
0
0
0
0
0
0
SPSR
• Bit 7 – SPIF: SPI Interrupt Flag
When a serial transfer is complete, the SPIF flag is set. An interrupt is generated if SPIE
in SPCR is set and global interrupts are enabled. If SS is an input and is driven low
when the SPI is in Master mode, this will also set the SPIF flag. SPIF is cleared by hardware when executing the corresponding interrupt handling vector. Alternatively, the
SPIF bit is cleared by first reading the SPI Status Register with SPIF set, then accessing
the SPI Data Register (SPDR).
• Bit 6 – WCOL: Write COLlision Flag
The WCOL bit is set if the SPI Data Register (SPDR) is written during a data transfer.
The WCOL bit (and the SPIF bit) are cleared by first reading the SPI Status Register
with WCOL set, and then accessing the SPI Data Register.
• Bit 5..1 – Res: Reserved Bits
These bits are reserved bits in the AT90PWM2/3 and will always read as zero.
• Bit 0 – SPI2X: Double SPI Speed Bit
When this bit is written logic one the SPI speed (SCK Frequency) will be doubled when
the SPI is in Master mode (see Table 73). This means that the minimum SCK period will
be two CPU clock periods. When the SPI is configured as Slave, the SPI is only guaranteed to work at fclkio/4 or lower.
The SPI interface on the AT90PWM2/3 is also used for program memory and EEPROM
downloading or uploading. See Serial Programming Algorithm305 for serial programming and verification.
SPI Data Register – SPDR
Bit
7
6
5
4
3
2
1
0
SPD7
SPD6
SPD5
SPD4
SPD3
SPD2
SPD1
SPD0
Read/Write
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
Initial Value
X
X
X
X
X
X
X
X
SPDR
Undefined
• Bits 7:0 - SPD7:0: SPI Data
The SPI Data Register is a read/write register used for data transfer between the Register File and the SPI Shift Register. Writing to the register initiates data transmission.
Reading the register causes the Shift Register Receive buffer to be read.
190
AT90PWM2/3
4317B–AVR–02/05
AT90PWM2/3
Data Modes
There are four combinations of SCK phase and polarity with respect to serial data,
which are determined by control bits CPHA and CPOL. The SPI data transfer formats
are shown in Figure 96 and Figure 97. Data bits are shifted out and latched in on opposite edges of the SCK signal, ensuring sufficient time for data signals to stabilize. This is
clearly seen by summarizing Table 71 and Table 72, as done below:
Table 74. CPOL Functionality
Leading Edge
Trailing eDge
SPI Mode
CPOL=0, CPHA=0
Sample (Rising)
Setup (Falling)
0
CPOL=0, CPHA=1
Setup (Rising)
Sample (Falling)
1
CPOL=1, CPHA=0
Sample (Falling)
Setup (Rising)
2
CPOL=1, CPHA=1
Setup (Falling)
Sample (Rising)
3
Figure 96. SPI Transfer Format with CPHA = 0
SCK (CPOL = 0)
mode 0
SCK (CPOL = 1)
mode 2
SAMPLE I
MOSI/MISO
CHANGE 0
MOSI PIN
CHANGE 0
MISO PIN
SS
MSB first (DORD = 0) MSB
LSB first (DORD = 1) LSB
Bit 6
Bit 1
Bit 5
Bit 2
Bit 4
Bit 3
Bit 3
Bit 4
Bit 2
Bit 5
Bit 1
Bit 6
LSB
MSB
Figure 97. SPI Transfer Format with CPHA = 1
SCK (CPOL = 0)
mode 1
SCK (CPOL = 1)
mode 3
SAMPLE I
MOSI/MISO
CHANGE 0
MOSI PIN
CHANGE 0
MISO PIN
SS
MSB first (DORD = 0)
LSB first (DORD = 1)
MSB
LSB
Bit 6
Bit 1
Bit 5
Bit 2
Bit 4
Bit 3
Bit 3
Bit 4
Bit 2
Bit 5
Bit 1
Bit 6
LSB
MSB
191
4317B–AVR–02/05
USART
The Universal Synchronous and Asynchronous serial Receiver and Transmitter
(USART) is a highly flexible serial communication device. The main features are:
Features
•
•
•
•
•
•
•
•
•
•
•
•
•
192
Full Duplex Operation (Independent Serial Receive and Transmit Registers)
Asynchronous or Synchronous Operation
Master or Slave Clocked Synchronous Operation
High Resolution Baud Rate Generator
Supports Serial Frames with 5, 6, 7, 8, or 9 Data Bits and 1 or 2 Stop Bits
Odd or Even Parity Generation and Parity Check Supported by Hardware
Data OverRun Detection
Framing Error Detection
Noise Filtering Includes False Start Bit Detection and Digital Low Pass Filter
Three Separate Interrupts on TX Complete, TX Data Register Empty and RX Complete
Multi-processor Communication Mode
Double Speed Asynchronous Communication Mode
USART Extended mode (EUSART) with:
– Independant bit number configuration for transmit and receive
– Supports Serial Frames with 5, 6, 7, 8, 9 or 13, 14, 15, 16, 17 Data Bits and 1 or 2 Stop
Bits
– Biphase Manchester encode/decoder (for DALI Communications)
– Manchester framing error detection
– Bit ordering configuration (MSB or LSB first)
– Sleep mode exit under reception of EUSART frame
AT90PWM2/3
4317B–AVR–02/05
AT90PWM2/3
Overview
A simplified block diagram of the USART Transmitter is shown in Figure 98. CPU accessible I/O Registers and I/O pins are shown in bold.
Figure 98. USART Block Diagram(1)
Clock Generator
UBRR[H:L]
CLKio
BAUD RATE GENERATOR
SYNC LOGIC
PIN
CONTROL
XCK
Transmitter
TX
CONTROL
UDR (Transmit)
DATA BUS
PARITY
GENERATOR
TxD
Receiver
RECEIVE SHIFT REGISTER
UDR
UCSRA
Note:
PIN
CONTROL
TRANSMIT SHIFT REGISTER
CLOCK
RECOVERY
RX
CONTROL
DATA
RECOVERY
PIN
CONTROL
RxD
PARITY
CHECKER
(Receive)
UCSRB
UCSRC
1. Refer to Pin Configurations3, Table 30 on page 75, and Table 28 on page 74 for
USART pin placement.
The dashed boxes in the block diagram separate the three main parts of the USART
(listed from the top): Clock Generator, Transmitter and Receiver. Control registers are
shared by all units. The Clock Generation logic consists of synchronization logic for
external clock input used by synchronous slave operation, and the baud rate generator.
The XCK (Transfer Clock) pin is only used by synchronous transfer mode. The Transmitter consists of a single write buffer, a serial Shift Register, Parity Generator and
Control logic for handling different serial frame formats. The write buffer allows a continuous transfer of data without any delay between frames. The Receiver is the most
complex part of the USART module due to its clock and data recovery units. The recovery units are used for asynchronous data reception. In addition to the recovery units, the
Receiver includes a Parity Checker, Control logic, a Shift Register and a two level
receive buffer (UDR). The Receiver supports the same frame formats as the Transmitter, and can detect Frame Error, Data OverRun and Parity Errors.
193
4317B–AVR–02/05
Clock Generation
The Clock Generation logic generates the base clock for the Transmitter and Receiver.
The USART supports four modes of clock operation: Normal asynchronous, Double
Speed asynchronous, Master synchronous and Slave synchronous mode. The UMSEL
bit in USART Control and Status Register C (UCSRC) selects between asynchronous
and synchronous operation. Double Speed (asynchronous mode only) is controlled by
the U2X found in the UCSRA Register. When using synchronous mode (UMSEL = 1),
the Data Direction Register for the XCK pin (DDR_XCK) controls whether the clock
source is internal (Master mode) or external (Slave mode). The XCK pin is only active
when using synchronous mode.
Figure 99 shows a block diagram of the clock generation logic.
Figure 99. USART Clock Generation Logic, Block Diagram
UBRRn
U2Xn
fclk io
Prescaling
Down-Counter
UBRRn+1
/2
/4
/2
0
1
0
clk io
DDR_XCKn
xn cki
XCKn
Pin
Sync
Register
Edge
Detector
UCPOLn
DDR_XCKn
0
UMSELn
1
xn cko
txn clk
1
1
0
rxn clk
Signal description:
txn clk Transmitter clock (Internal Signal).
rxn clk Receiver base clock (Internal Signal).
xn cki Input from XCK pin (internal Signal). Used for synchronous slave operation.
xn cko Clock output to XCK pin (Internal Signal). Used for synchronous master
operation.
fclkio
Internal Clock Generation –
Baud Rate Generator
System I/O Clock frequency.
Internal clock generation is used for the asynchronous and the synchronous master
modes of operation. The description in this section refers to Figure 99.
The USART Baud Rate Register (UBRR) and the down-counter connected to it function
as a programmable prescaler or baud rate generator. The down-counter, running at system clock (fclkio), is loaded with the UBRR value each time the counter has counted
down to zero or when the UBRRL Register is written. A clock is generated each time the
counter reaches zero. This clock is the baud rate generator clock output (=
fclkio/(UBRR+1)). The Transmitter divides the baud rate generator clock output by 2, 8
or 16 depending on mode. The baud rate generator output is used directly by the
Receiver’s clock and data recovery units. However, the recovery units use a state
machine that uses 2, 8 or 16 states depending on mode set by the state of the UMSEL,
U2X and DDR_XCK bits.
194
AT90PWM2/3
4317B–AVR–02/05
AT90PWM2/3
Table 75 contains equations for calculating the baud rate (in bits per second) and for
calculating the UBRR value for each mode of operation using an internally generated
clock source.
Table 75. Equations for Calculating Baud Rate Register Setting
Equation for Calculating
Baud Rate(1)
Equation for Calculating
UBRR Value
Asynchronous Normal
mode (U2X = 0)
f CLKio
BAUD = -----------------------------------------16 ( UBRRn + 1 )
f CLKio
UBRRn = ------------------------ – 1
16BAUD
Asynchronous Double
Speed mode (U2X = 1)
f CLKio
BAUD = --------------------------------------8 ( UBRRn + 1 )
f CLKio
UBRRn = -------------------- – 1
8BAUD
Synchronous Master
mode
f CLKio
BAUD = --------------------------------------2 ( UBRRn + 1 )
f CLKio
UBRRn = -------------------- – 1
2BAUD
Operating Mode
Note:
1. The baud rate is defined to be the transfer rate in bit per second (bps)
BAUD Baud rate (in bits per second, bps).
fclkio
System I/O Clock frequency.
UBRR Contents of the UBRRH and UBRRL Registers, (0-4095).
Some examples of UBRR values for some system clock frequencies are found in Table
83 (see page 217).
Double Speed Operation
(U2X)
The transfer rate can be doubled by setting the U2X bit in UCSRA. Setting this bit only
has effect for the asynchronous operation. Set this bit to zero when using synchronous
operation.
Setting this bit will reduce the divisor of the baud rate divider from 16 to 8, effectively
doubling the transfer rate for asynchronous communication. Note however that the
Receiver will in this case only use half the number of samples (reduced from 16 to 8) for
data sampling and clock recovery, and therefore a more accurate baud rate setting and
system clock are required when this mode is used. For the Transmitter, there are no
downsides.
External Clock
External clocking is used by the synchronous slave modes of operation. The description
in this section refers to Figure 99 for details.
External clock input from the XCK pin is sampled by a synchronization register to minimize the chance of meta-stability. The output from the synchronization register must
then pass through an edge detector before it can be used by the Transmitter and
Receiver. This process introduces a two CPU clock period delay and therefore the maximum external XCK clock frequency is limited by the following equation:
f CLKio
f XCKn < ---------------4
Note that fclkio depends on the stability of the system clock source. It is therefore recommended to add some margin to avoid possible loss of data due to frequency variations.
195
4317B–AVR–02/05
Synchronous Clock Operation When synchronous mode is used (UMSEL = 1), the XCK pin will be used as either clock
input (Slave) or clock output (Master). The dependency between the clock edges and
data sampling or data change is the same. The basic principle is that data input (on
RxD) is sampled at the opposite XCK clock edge of the edge the data output (TxDn) is
changed.
Figure 100. Synchronous Mode XCK Timing.
UCPOLn = 1
XCKn
RxDn / TxDn
Sample
UCPOLn = 0
XCKn
RxDn / TxDn
Sample
The UCPOL bit UCRSnC selects which XCK clock edge is used for data sampling and
which is used for data change. As Figure 100 shows, when UCPOL is zero the data will
be changed at rising XCK edge and sampled at falling XCK edge. If UCPOL is set, the
data will be changed at falling XCK edge and sampled at rising XCK edge.
Serial Frame
A serial frame is defined to be one character of data bits with synchronization bits (start
and stop bits), and optionally a parity bit for error checking.
Frame Formats
The USART accepts all 30 combinations of the following as valid frame formats:
•
1 start bit
•
5, 6, 7, 8, or 9 data bits
•
no, even or odd parity bit
•
1 or 2 stop bits
A frame starts with the start bit followed by the least significant data bit. Then the next
data bits, up to a total of nine, are succeeding, ending with the most significant bit. If
enabled, the parity bit is inserted after the data bits, before the stop bits. When a complete frame is transmitted, it can be directly followed by a new frame, or the
communication line can be set to an idle (high) state. Figure 101 illustrates the possible
combinations of the frame formats. Bits inside brackets are optional.
Figure 101. Frame Formats
FRAME
(IDLE)
196
St
0
1
2
St
Start bit, always low.
(n)
Data bits (0 to 8).
3
4
[5]
[6]
[7]
[8]
[P]
Sp1 [Sp2]
(St / IDLE)
AT90PWM2/3
4317B–AVR–02/05
AT90PWM2/3
P
Parity bit. Can be odd or even.
Sp
Stop bit, always high.
IDLE
No transfers on the communication line (RxD or TxD). An IDLE line must be
high.
The frame format used by the USART is set by the UCSZ2:0, UPM1:0 and USBS bits in
UCSRB and UCSRC. The Receiver and Transmitter use the same setting. Note that
changing the setting of any of these bits will corrupt all ongoing communication for both
the Receiver and Transmitter.
The USART Character SiZe (UCSZ2:0) bits select the number of data bits in the frame.
The USART Parity mode (UPM1:0) bits enable and set the type of parity bit. The selection between one or two stop bits is done by the USART Stop Bit Select (USBS) bit. The
Receiver ignores the second stop bit. An FE (Frame Error) will therefore only be
detected in the cases where the first stop bit is zero.
Parity Bit Calculation
The parity bit is calculated by doing an exclusive-or of all the data bits. If odd parity is
used, the result of the exclusive or is inverted. The relation between the parity bit and
data bits is as follows:
P even = d n – 1 ⊕ … ⊕ d 3 ⊕ d 2 ⊕ d 1 ⊕ d 0 ⊕ 0
P odd = d n – 1 ⊕ … ⊕ d 3 ⊕ d 2 ⊕ d 1 ⊕ d 0 ⊕ 1
Peven
Parity bit using even parity
Podd
Parity bit using odd parity
dn
Data bit n of the character
If used, the parity bit is located between the last data bit and first stop bit of a serial
frame.
USART Initialization
The USART has to be initialized before any communication can take place.
The configuration between the USART or EUSART mode should be done before any
other configuration.
The initialization process normally consists of setting the baud rate, setting frame format
and enabling the Transmitter or the Receiver depending on the usage.
For interrupt driven USART operation, the Global Interrupt Flag should be cleared (and
interrupts globally disabled) when doing the initialization.
Before doing a re-initialization with changed baud rate or frame format, be sure that
there are no ongoing transmissions during the period the registers are changed. The
TXC flag can be used to check that the Transmitter has completed all transfers, and the
RXC flag can be used to check that there are no unread data in the receive buffer. Note
that the TXC flag must be cleared before each transmission (before UDR is written) if it
is used for this purpose.
197
4317B–AVR–02/05
The following simple USART initialization code examples show one assembly and one
C function that are equal in functionality. The examples assume asynchronous operation using polling (no interrupts enabled) and a fixed frame format. The baud rate is
given as a function parameter. For the assembly code, the baud rate parameter is
assumed to be stored in the r17:r16 Registers.
Assembly Code Example(1)
USART_Init:
; Set baud rate
out
UBRRH, r17
out
UBRRL, r16
; Set frame format: 8data, no parity & 2 stop bits
ldi
r16, (0<<UMSEL)|(0<<UPM0)|(1<<USBS)|(3<<UCSZ0)
out
UCSRC,r16
; Enable receiver and transmitter
ldi
r16, (1<<RXEN0)|(1<<TXEN0)
out
UCSRB,r16
ret
C Code Example(1)
void USART_Init( unsigned int baud )
{
/* Set baud rate */
UBRRH = (unsigned char)(baud>>8);
UBRRL = (unsigned char)baud;
/* Set frame format: 8data, no parity & 2 stop bits */
UCSRC = (0<<UMSEL)|(0<<UPM0)|(1<<USBS)|(3<<UCSZ0);
/* Enable receiver and transmitter */
UCSRB = (1<<RXEN0)|(1<<TXEN0);
}
Note:
1. The example code assumes that the part specific header file is included.
For I/O Registers located in extended I/O map, “IN”, “OUT”, “SBIS”, “SBIC”, “CBI”,
and “SBI” instructions must be replaced with instructions that allow access to
extended I/O. Typically “LDS” and “STS” combined with “SBRS”, “SBRC”, “SBR”, and
“CBR”.
More advanced initialization routines can be made that include frame format as parameters, disable interrupts and so on. However, many applications use a fixed setting of the
baud and control registers, and for these types of applications the initialization code can
be placed directly in the main routine, or be combined with initialization code for other
I/O modules.
198
AT90PWM2/3
4317B–AVR–02/05
AT90PWM2/3
Data Transmission –
USART Transmitter
The USART Transmitter is enabled by setting the Transmit Enable (TXEN) bit in the
UCSRB Register. When the Transmitter is enabled, the normal port operation of the
TxDn pin is overridden by the USART and given the function as the Transmitter’s serial
output. The baud rate, mode of operation and frame format must be set up once before
doing any transmissions. If synchronous operation is used, the clock on the XCK pin will
be overridden and used as transmission clock.
Sending Frames with 5 to 8
Data Bit
A data transmission is initiated by loading the transmit buffer with the data to be transmitted. The CPU can load the transmit buffer by writing to the UDR I/O location. The
buffered data in the transmit buffer will be moved to the Shift Register when the Shift
Register is ready to send a new frame. The Shift Register is loaded with new data if it is
in idle state (no ongoing transmission) or immediately after the last stop bit of the previous frame is transmitted. When the Shift Register is loaded with new data, it will transfer
one complete frame at the rate given by the Baud Register, U2X bit or by XCK depending on mode of operation.
The following code examples show a simple USART transmit function based on polling
of the Data Register Empty (UDRE) flag. When using frames with less than eight bits,
the most significant bits written to the UDR are ignored. The USART has to be initialized
before the function can be used. For the assembly code, the data to be sent is assumed
to be stored in Register R16.
Assembly Code Example(1)
USART_Transmit:
; Wait for empty transmit buffer
sbis UCSRA,UDRE
rjmp USART_Transmit
; Put data (r16) into buffer, sends the data
out
UDR,r16
ret
C Code Example(1)
void USART_Transmit( unsigned char data )
{
/* Wait for empty transmit buffer */
while ( !( UCSRA & (1<<UDRE)) )
;
/* Put data into buffer, sends the data */
UDR = data;
}
Note:
1. The example code assumes that the part specific header file is included.
For I/O Registers located in extended I/O map, “IN”, “OUT”, “SBIS”, “SBIC”, “CBI”,
and “SBI” instructions must be replaced with instructions that allow access to
extended I/O. Typically “LDS” and “STS” combined with “SBRS”, “SBRC”, “SBR”, and
“CBR”.
The function simply waits for the transmit buffer to be empty by checking the UDRE flag,
before loading it with new data to be transmitted. If the Data Register Empty interrupt is
utilized, the interrupt routine writes the data into the buffer.
199
4317B–AVR–02/05
Sending Frames with 9 Data
Bit
If 9-bit characters are used (UCSZ = 7), the ninth bit must be written to the TXB8 bit in
UCSRB before the low byte of the character is written to UDR. The following code
examples show a transmit function that handles 9-bit characters. For the assembly
code, the data to be sent is assumed to be stored in registers R17:R16.
Assembly Code Example(1)(2)
USART_Transmit:
; Wait for empty transmit buffer
sbis UCSRA,UDRE
rjmp USART_Transmit
; Copy 9th bit from r17 to TXB80
cbi
UCSRB,TXB80
sbrc r17,0
sbi
UCSRB,TXB80
; Put LSB data (r16) into buffer, sends the data
out
UDR,r16
ret
C Code Example(1)(2)
void USART_Transmit( unsigned int data )
{
/* Wait for empty transmit buffer */
while ( !( UCSRA & (1<<UDRE))) )
;
/* Copy 9th bit to TXB8 */
UCSRB &= ~(1<<TXB80);
if ( data & 0x0100 )
UCSRB |= (1<<TXB80);
/* Put data into buffer, sends the data */
UDR = data;
}
Notes:
1. These transmit functions are written to be general functions. They can be optimized if
the contents of the UCSRB is static. For example, only the TXB80 bit of the UCSRB0
Register is used after initialization.
2. The example code assumes that the part specific header file is included.
For I/O Registers located in extended I/O map, “IN”, “OUT”, “SBIS”, “SBIC”, “CBI”,
and “SBI” instructions must be replaced with instructions that allow access to
extended I/O. Typically “LDS” and “STS” combined with “SBRS”, “SBRC”, “SBR”, and
“CBR”.
The ninth bit can be used for indicating an address frame when using multi processor
communication mode or for other protocol handling as for example synchronization.
Transmitter Flags and
Interrupts
The USART Transmitter has two flags that indicate its state: USART Data Register
Empty (UDRE) and Transmit Complete (TXC). Both flags can be used for generating
interrupts.
The Data Register Empty (UDRE) flag indicates whether the transmit buffer is ready to
receive new data. This bit is set when the transmit buffer is empty, and cleared when the
transmit buffer contains data to be transmitted that has not yet been moved into the Shift
200
AT90PWM2/3
4317B–AVR–02/05
AT90PWM2/3
Register. For compatibility with future devices, always write this bit to zero when writing
the UCSRA Register.
When the Data Register Empty Interrupt Enable (UDRIE) bit in UCSRB is written to one,
the USART Data Register Empty Interrupt will be executed as long as UDRE is set (provided that global interrupts are enabled). UDRE is cleared by writing UDR. When
interrupt-driven data transmission is used, the Data Register Empty interrupt routine
must either write new data to UDR in order to clear UDRE or disable the Data Register
Empty interrupt, otherwise a new interrupt will occur once the interrupt routine
terminates.
The Transmit Complete (TXC) flag bit is set one when the entire frame in the Transmit
Shift Register has been shifted out and there are no new data currently present in the
transmit buffer. The TXC flag bit is automatically cleared when a transmit complete interrupt is executed, or it can be cleared by writing a one to its bit location. The TXC flag is
useful in half-duplex communication interfaces (like the RS-485 standard), where a
transmitting application must enter receive mode and free the communication bus
immediately after completing the transmission.
When the Transmit Complete Interrupt Enable (TXCIE) bit in UCSRB is set, the USART
Transmit Complete Interrupt will be executed when the TXC flag becomes set (provided
that global interrupts are enabled). When the transmit complete interrupt is used, the
interrupt handling routine does not have to clear the TXC flag, this is done automatically
when the interrupt is executed.
Parity Generator
The Parity Generator calculates the parity bit for the serial frame data. When parity bit is
enabled (UPM1 = 1), the transmitter control logic inserts the parity bit between the last
data bit and the first stop bit of the frame that is sent.
Disabling the Transmitter
The disabling of the Transmitter (setting the TXEN to zero) will not become effective
until ongoing and pending transmissions are completed, i.e., when the Transmit Shift
Register and Transmit Buffer Register do not contain data to be transmitted. When disabled, the Transmitter will no longer override the TxD pin.
Data Reception – USART
Receiver
The USART Receiver is enabled by writing the Receive Enable (RXEN) bit in the
UCSRB Register to one. When the Receiver is enabled, the normal pin operation of the
RxD pin is overridden by the USART and given the function as the Receiver’s serial
input. The baud rate, mode of operation and frame format must be set up once before
any serial reception can be done. If synchronous operation is used, the clock on the
XCK pin will be used as transfer clock.
Receiving Frames with 5 to 8
Data Bits
The Receiver starts data reception when it detects a valid start bit. Each bit that follows
the start bit will be sampled at the baud rate or XCK clock, and shifted into the Receive
Shift Register until the first stop bit of a frame is received. A second stop bit will be
ignored by the Receiver. When the first stop bit is received, i.e., a complete serial frame
is present in the Receive Shift Register, the contents of the Shift Register will be moved
into the receive buffer. The receive buffer can then be read by reading the UDR I/O
location.
201
4317B–AVR–02/05
The following code example shows a simple USART receive function based on polling
of the Receive Complete (RXC) flag. When using frames with less than eight bits the
most significant bits of the data read from the UDR will be masked to zero. The USART
has to be initialized before the function can be used.
Assembly Code Example(1)
USART_Receive:
; Wait for data to be received
sbis UCSRA, RXC
rjmp USART_Receive
; Get and return received data from buffer
in
r16, UDR
ret
C Code Example(1)
unsigned char USART_Receive( void )
{
/* Wait for data to be received */
while ( !(UCSRA & (1<<RXC)) )
;
/* Get and return received data from buffer */
return UDR;
}
Note:
1. The example code assumes that the part specific header file is included.
For I/O Registers located in extended I/O map, “IN”, “OUT”, “SBIS”, “SBIC”, “CBI”,
and “SBI” instructions must be replaced with instructions that allow access to
extended I/O. Typically “LDS” and “STS” combined with “SBRS”, “SBRC”, “SBR”, and
“CBR”.
The function simply waits for data to be present in the receive buffer by checking the
RXC flag, before reading the buffer and returning the value.
Receiving Frames with 9 Data
Bits
202
If 9-bit characters are used (UCSZ=7) the ninth bit must be read from the RXB8 bit in
UCSRB before reading the low bits from the UDR. This rule applies to the FE, DOR and
UPE Status Flags as well. Read status from UCSRA, then data from UDR. Reading the
UDR I/O location will change the state of the receive buffer FIFO and consequently the
TXB8, FE, DOR and UPE bits, which all are stored in the FIFO, will change.
AT90PWM2/3
4317B–AVR–02/05
AT90PWM2/3
The following code example shows a simple USART receive function that handles both
nine bit characters and the status bits.
Assembly Code Example(1)
USART_Receive:
; Wait for data to be received
sbis UCSRA, RXC0
rjmp USART_Receive
; Get status and 9th bit, then data from buffer
in
r18, UCSRA
in
r17, UCSRB
in
r16, UDR
; If error, return -1
andi r18,(1<<FE0)|(1<<DOR0)|(1<<UPE0)
breq USART_ReceiveNoError
ldi
r17, HIGH(-1)
ldi
r16, LOW(-1)
USART_ReceiveNoError:
; Filter the 9th bit, then return
lsr
r17
andi r17, 0x01
ret
C Code Example(1)
unsigned int USART_Receive( void )
{
unsigned char status, resh, resl;
/* Wait for data to be received */
while ( !(UCSRA & (1<<RXC0)) )
;
/* Get status and 9th bit, then data */
/* from buffer */
status = UCSRA;
resh = UCSRB;
resl = UDR;
/* If error, return -1 */
if ( status & (1<<FE0)|(1<<DOR0)|(1<<UPE0) )
return -1;
/* Filter the 9th bit, then return */
resh = (resh >> 1) & 0x01;
return ((resh << 8) | resl);
}
Note:
1. The example code assumes that the part specific header file is included.
For I/O Registers located in extended I/O map, “IN”, “OUT”, “SBIS”, “SBIC”, “CBI”,
and “SBI” instructions must be replaced with instructions that allow access to
203
4317B–AVR–02/05
extended I/O. Typically “LDS” and “STS” combined with “SBRS”, “SBRC”, “SBR”, and
“CBR”.
The receive function example reads all the I/O Registers into the Register File before
any computation is done. This gives an optimal receive buffer utilization since the buffer
location read will be free to accept new data as early as possible.
Receive Complete Flag and
Interrupt
The USART Receiver has one flag that indicates the Receiver state.
The Receive Complete (RXC) flag indicates if there are unread data present in the
receive buffer. This flag is one when unread data exist in the receive buffer, and zero
when the receive buffer is empty (i.e., does not contain any unread data). If the Receiver
is disabled (RXEN = 0), the receive buffer will be flushed and consequently the RXC bit
will become zero.
When the Receive Complete Interrupt Enable (RXCIE) in UCSRB is set, the USART
Receive Complete interrupt will be executed as long as the RXC flag is set (provided
that global interrupts are enabled). When interrupt-driven data reception is used, the
receive complete routine must read the received data from UDR in order to clear the
RXC flag, otherwise a new interrupt will occur once the interrupt routine terminates.
Receiver Error Flags
The USART Receiver has three error flags: Frame Error (FE), Data OverRun (DOR) and
Parity Error (UPE). All can be accessed by reading UCSRA. Common for the error flags
is that they are located in the receive buffer together with the frame for which they indicate the error status. Due to the buffering of the error flags, the UCSRA must be read
before the receive buffer (UDR), since reading the UDR I/O location changes the buffer
read location. Another equality for the error flags is that they can not be altered by software doing a write to the flag location. However, all flags must be set to zero when the
UCSRA is written for upward compatibility of future USART implementations. None of
the error flags can generate interrupts.
The Frame Error (FE) flag indicates the state of the first stop bit of the next readable
frame stored in the receive buffer. The FE flag is zero when the stop bit was correctly
read (as one), and the FE flag will be one when the stop bit was incorrect (zero). This
flag can be used for detecting out-of-sync conditions, detecting break conditions and
protocol handling. The FE flag is not affected by the setting of the USBS bit in UCSRC
since the Receiver ignores all, except for the first, stop bits. For compatibility with future
devices, always set this bit to zero when writing to UCSRA.
204
AT90PWM2/3
4317B–AVR–02/05
AT90PWM2/3
The Data OverRun (DOR) flag indicates data loss due to a receiver buffer full condition.
A Data OverRun occurs when the receive buffer is full (two characters), it is a new character waiting in the Receive Shift Register, and a new start bit is detected. If the DOR
flag is set there was one or more serial frame lost between the frame last read from
UDR, and the next frame read from UDR. For compatibility with future devices, always
write this bit to zero when writing to UCSRA. The DOR flag is cleared when the frame
received was successfully moved from the Shift Register to the receive buffer.
The following example (See Figure 102.) represents a Data OverRun condition. As the
receive buffer is full with CH1 and CH2, CH3 is lost. When a Data OverRun condition is
detected, the OverRun error is memorized. When the two characters CH1 and CH2 are
read from the receive buffer, the DOR bit is set (and not before) and RxC remains set to
warn the application about the overrun error.
Figure 102. Data OverRun example
RxD
CH1
CH2
CH3
DOR
RxC
t
Software Access
to Receive buffer
RxC=1
UDR=CH1
DOR=0
RxC=1
UDR=CH2
DOR=0
RxC=1
UDR=XX
DOR=1
The Parity Error (UPE) Flag indicates that the next frame in the receive buffer had a Parity Error when received. If Parity Check is not enabled the UPE bit will always be read
zero. For compatibility with future devices, always set this bit to zero when writing to
UCSRA. For more details see “Parity Bit Calculation” on page 197 and “Parity Checker”
on page 205.
Parity Checker
The Parity Checker is active when the high USART Parity mode (UPM1) bit is set. Type
of Parity Check to be performed (odd or even) is selected by the UPM0 bit. When
enabled, the Parity Checker calculates the parity of the data bits in incoming frames and
compares the result with the parity bit from the serial frame. The result of the check is
stored in the receive buffer together with the received data and stop bits. The Parity
Error (UPE) flag can then be read by software to check if the frame had a Parity Error.
The UPE bit is set if the next character that can be read from the receive buffer had a
Parity Error when received and the Parity Checking was enabled at that point (UPM1 =
1). This bit is valid until the receive buffer (UDR) is read.
205
4317B–AVR–02/05
Disabling the Receiver
In contrast to the Transmitter, disabling of the Receiver will be immediate. Data from
ongoing receptions will therefore be lost. When disabled (i.e., the RXEN is set to zero)
the Receiver will no longer override the normal function of the RxD port pin. The
Receiver buffer FIFO will be flushed when the Receiver is disabled. Remaining data in
the buffer will be lost
Flushing the Receive Buffer
The receiver buffer FIFO will be flushed when the Receiver is disabled, i.e., the buffer
will be emptied of its contents. Unread data will be lost. If the buffer has to be flushed
during normal operation, due to for instance an error condition, read the UDR I/O location until the RXC flag is cleared.
The following code example shows how to flush the receive buffer.
Assembly Code Example(1)
USART_Flush:
sbis UCSRA, RXC0
ret
in
r16, UDR
rjmp USART_Flush
C Code Example(1)
void USART_Flush( void )
{
unsigned char dummy;
while ( UCSRA & (1<<RXC0) ) dummy = UDR;
}
Note:
1. The example code assumes that the part specific header file is included.
For I/O Registers located in extended I/O map, “IN”, “OUT”, “SBIS”, “SBIC”, “CBI”,
and “SBI” instructions must be replaced with instructions that allow access to
extended I/O. Typically “LDS” and “STS” combined with “SBRS”, “SBRC”, “SBR”, and
“CBR”.
Asynchronous Data
Reception
The USART includes a clock recovery and a data recovery unit for handling asynchronous data reception. The clock recovery logic is used for synchronizing the internally
generated baud rate clock to the incoming asynchronous serial frames at the RxD pin.
The data recovery logic samples and low pass filters each incoming bit, thereby improving the noise immunity of the Receiver. The asynchronous reception operational range
depends on the accuracy of the internal baud rate clock, the rate of the incoming
frames, and the frame size in number of bits.
Asynchronous Clock
Recovery
The clock recovery logic synchronizes internal clock to the incoming serial frames. Figure 103 illustrates the sampling process of the start bit of an incoming frame. The
sample rate is 16 times the baud rate for Normal mode, and eight times the baud rate for
Double Speed mode. The horizontal arrows illustrate the synchronization variation due
to the sampling process. Note the larger time variation when using the Double Speed
mode (U2X = 1) of operation. Samples denoted zero are samples done when the RxD
line is idle (i.e., no communication activity).
206
AT90PWM2/3
4317B–AVR–02/05
AT90PWM2/3
Figure 103. Start Bit Sampling
RxDn
IDLE
START
BIT 0
Sample
(U2Xn = 0)
0
0
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
1
2
3
Sample
(U2Xn = 1)
0
1
2
3
4
5
6
7
8
1
2
When the clock recovery logic detects a high (idle) to low (start) transition on the RxD
line, the start bit detection sequence is initiated. Let sample 1 denote the first zero-sample as shown in the figure. The clock recovery logic then uses samples 8, 9, and 10 for
Normal mode, and samples 4, 5, and 6 for Double Speed mode (indicated with sample
numbers inside boxes on the figure), to decide if a valid start bit is received. If two or
more of these three samples have logical high levels (the majority wins), the start bit is
rejected as a noise spike and the Receiver starts looking for the next high to low-transition. If however, a valid start bit is detected, the clock recovery logic is synchronized and
the data recovery can begin. The synchronization process is repeated for each start bit.
Asynchronous Data Recovery
When the receiver clock is synchronized to the start bit, the data recovery can begin.
The data recovery unit uses a state machine that has 16 states for each bit in Normal
mode and eight states for each bit in Double Speed mode. Figure 104 shows the sampling of the data bits and the parity bit. Each of the samples is given a number that is
equal to the state of the recovery unit.
Figure 104. Sampling of Data and Parity Bit
RxDn
BIT x
Sample
(U2Xn = 0)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
1
Sample
(U2Xn = 1)
1
2
3
4
5
6
7
8
1
The decision of the logic level of the received bit is taken by doing a majority voting of
the logic value to the three samples in the center of the received bit. The center samples
are emphasized on the figure by having the sample number inside boxes. The majority
voting process is done as follows: If two or all three samples have high levels, the
received bit is registered to be a logic 1. If two or all three samples have low levels, the
received bit is registered to be a logic 0. This majority voting process acts as a low pass
filter for the incoming signal on the RxD pin. The recovery process is then repeated until
a complete frame is received. Including the first stop bit. Note that the Receiver only
uses the first stop bit of a frame.
207
4317B–AVR–02/05
Figure 105 shows the sampling of the stop bit and the earliest possible beginning of the
start bit of the next frame.
Figure 105. Stop Bit Sampling and Next Start Bit Sampling
RxDn
STOP 1
(A)
(B)
(C)
Sample
(U2Xn = 0)
1
2
3
4
5
6
7
8
9
10
0/1
0/1
0/1
Sample
(U2Xn = 1)
1
2
3
4
5
6
0/1
The same majority voting is done to the stop bit as done for the other bits in the frame. If
the stop bit is registered to have a logic 0 value, the Frame Error (FE) flag will be set.
A new high to low transition indicating the start bit of a new frame can come right after
the last of the bits used for majority voting. For Normal Speed mode, the first low level
sample can be at point marked (A) in Figure 105. For Double Speed mode the first low
level must be delayed to (B). (C) marks a stop bit of full length. The early start bit detection influences the operational range of the Receiver.
Asynchronous Operational
Range
The operational range of the Receiver is dependent on the mismatch between the
received bit rate and the internally generated baud rate. If the Transmitter is sending
frames at too fast or too slow bit rates, or the internally generated baud rate of the
Receiver does not have a similar (see Table 76) base frequency, the Receiver will not
be able to synchronize the frames to the start bit.
The following equations can be used to calculate the ratio of the incoming data rate and
internal receiver baud rate.
( D + 1 )S
R slow = ------------------------------------------S – 1 + D ⋅ S + SF
( D + 2 )S
R fast = ----------------------------------( D + 1 )S + S M
D
Sum of character size and parity size (D = 5 to 10 bit)
S
Samples per bit. S = 16 for Normal Speed mode and S = 8 for Double Speed
mode.
SF
First sample number used for majority voting. SF = 8 for normal speed and SF = 4
for Double Speed mode.
SM
Middle sample number used for majority voting. SM = 9 for normal speed and
SM = 5 for Double Speed mode.
Rslow is the ratio of the slowest incoming data rate that can be accepted in relation to the
receiver baud rate.
Rfast is the ratio of the fastest incoming data rate that can be accepted in relation to the
receiver baud rate.
Table 76 and Table 77 list the maximum receiver baud rate error that can be tolerated.
Note that Normal Speed mode has higher toleration of baud rate variations.
208
AT90PWM2/3
4317B–AVR–02/05
AT90PWM2/3
Table 76. Recommended Maximum Receiver Baud Rate Error for Normal Speed Mode
(U2X = 0)
D
# (Data+Parity Bit)
Rslow (%)
Rfast (%)
Max Total Error (%)
Recommended Max
Receiver Error (%)
5
93.20
106.67
+6.67/-6.8
± 3.0
6
94.12
105.79
+5.79/-5.88
± 2.5
7
94.81
105.11
+5.11/-5.19
± 2.0
8
95.36
104.58
+4.58/-4.54
± 2.0
9
95.81
104.14
+4.14/-4.19
± 1.5
10
96.17
103.78
+3.78/-3.83
± 1.5
Table 77. Recommended Maximum Receiver Baud Rate Error for Double Speed Mode
(U2X = 1)
D
# (Data+Parity Bit)
Rslow (%)
Rfast (%)
Max Total Error (%)
Recommended Max
Receiver Error (%)
5
94.12
105.66
+5.66/-5.88
± 2.5
6
94.92
104.92
+4.92/-5.08
± 2.0
7
95.52
104,35
+4.35/-4.48
± 1.5
8
96.00
103.90
+3.90/-4.00
± 1.5
9
96.39
103.53
+3.53/-3.61
± 1.5
10
96.70
103.23
+3.23/-3.30
± 1.0
The recommendations of the maximum receiver baud rate error was made under the
assumption that the Receiver and Transmitter equally divides the maximum total error.
There are two possible sources for the receivers baud rate error. The Receiver’s system
clock (XTAL) will always have some minor instability over the supply voltage range and
the temperature range. When using a crystal to generate the system clock, this is rarely
a problem, but for a resonator the system clock may differ more than 2% depending of
the resonators tolerance. The second source for the error is more controllable. The baud
rate generator can not always do an exact division of the system frequency to get the
baud rate wanted. In this case an UBRR value that gives an acceptable low error can be
used if possible.
Multi-processor
Communication Mode
This mode is available only in USART mode, not in EUSART.
MPCM Protocol
If the Receiver is set up to receive frames that contain 5 to 8 data bits, then the first stop
bit indicates if the frame contains data or address information. If the Receiver is set up
Setting the Multi-processor Communication mode (MPCM) bit in UCSRA enables a filtering function of incoming frames received by the USART Receiver. Frames that do not
contain address information will be ignored and not put into the receive buffer. This
effectively reduces the number of incoming frames that has to be handled by the CPU,
in a system with multiple MCUs that communicate via the same serial bus. The Transmitter is unaffected by the MPCM setting, but has to be used differently when it is a part
of a system utilizing the Multi-processor Communication mode.
209
4317B–AVR–02/05
for frames with nine data bits, then the ninth bit (RXB8) is used for identifying address
and data frames. When the frame type bit (the first stop or the ninth bit) is one, the frame
contains an address. When the frame type bit is zero the frame is a data frame.
The Multi-processor Communication mode enables several slave MCUs to receive data
from a master MCU. This is done by first decoding an address frame to find out which
MCU has been addressed. If a particular slave MCU has been addressed, it will receive
the following data frames as normal, while the other slave MCUs will ignore the received
frames until another address frame is received.
Using MPCM
For an MCU to act as a master MCU, it can use a 9-bit character frame format (UCSZ =
7). The ninth bit (TXB8) must be set when an address frame (TXB8 = 1) or cleared when
a data frame (TXBn = 0) is being transmitted. The slave MCUs must in this case be set
to use a 9-bit character frame format.
The following procedure should be used to exchange data in Multi-processor Communication mode:
1. All Slave MCUs are in Multi-processor Communication mode (MPCM in
UCSRA is set).
2. The Master MCU sends an address frame, and all slaves receive and read this
frame. In the Slave MCUs, the RXC flag in UCSRA will be set as normal.
3. Each Slave MCU reads the UDR Register and determines if it has been
selected. If so, it clears the MPCM bit in UCSRA, otherwise it waits for the next
address byte and keeps the MPCM setting.
4. The addressed MCU will receive all data frames until a new address frame is
received. The other Slave MCUs, which still have the MPCM bit set, will ignore
the data frames.
5. When the last data frame is received by the addressed MCU, the addressed
MCU sets the MPCM bit and waits for a new address frame from master. The
process then repeats from 2.
Using any of the 5- to 8-bit character frame formats is possible, but impractical since the
Receiver must change between using N and N+1 character frame formats. This makes
full-duplex operation difficult since the Transmitter and Receiver use the same character
size setting. If 5- to 8-bit character frames are used, the Transmitter must be set to use
two stop bit (USBS = 1) since the first stop bit is used for indicating the frame type.
210
AT90PWM2/3
4317B–AVR–02/05
AT90PWM2/3
USART Register
Description
USART I/O Data Register –
UDR
Bit
7
6
5
4
3
2
1
0
RXB[7:0]
UDR (Read)
TXB[7:0]
UDR (Write)
Read/Write
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
Initial Value
0
0
0
0
0
0
0
0
• Bit 7:0 – RxB7:0: Receive Data Buffer (read access)
• Bit 7:0 – TxB7:0: Transmit Data Buffer (write access)
The USART Transmit Data Buffer Register and USART Receive Data Buffer Registers
share the same I/O address referred to as USART Data Register or UDR. The Transmit
Data Buffer Register (TXBn) will be the destination for data written to the UDR Register
location. Reading the UDR Register location will return the contents of the Receive Data
Buffer Register (RXBn).
For 5-, 6-, or 7-bit characters the upper unused bits will be ignored by the Transmitter
and set to zero by the Receiver.
The transmit buffer can only be written when the UDRE flag in the UCSRA Register is
set. Data written to UDR when the UDRE flag is not set, will be ignored by the USART
Transmitter. When data is written to the transmit buffer, and the Transmitter is enabled,
the Transmitter will load the data into the Transmit Shift Register when the Shift Register
is empty. Then the data will be serially transmitted on the TxDn pin.
The receive buffer consists of a two level FIFO. The FIFO will change its state whenever
the receive buffer is accessed.
This register is available in both USART and EUSART modes.
USART Control and Status
Register A – UCSRA
Bit
Read/Write
Initial Value
0
7
6
5
4
3
2
1
0
RXC
TXC
UDRE
FE
DOR
UPE
U2X
MPCM
R
R/W
R
R
R
R
R/W
R/W
0
1
0
0
0
0
UCSRA
0
• Bit 7 – RXC: USART Receive Complete
This flag bit is set when there are unread data in the receive buffer and cleared when the
receive buffer is empty (i.e., does not contain any unread data). If the Receiver is disabled, the receive buffer will be flushed and consequently the RXC bit will become zero.
The RXC flag can be used to generate a Receive Complete interrupt (see description of
the RXCIE bit).
This bit is available in both USART and EUSART modes.
• Bit 6 – TXC: USART Transmit Complete
This flag bit is set when the entire frame in the Transmit Shift Register has been shifted
out and there are no new data currently present in the transmit buffer (UDR). The TXC
flag bit is automatically cleared when a transmit complete interrupt is executed, or it can
be cleared by writing a one to its bit location. The TXC flag can generate a Transmit
Complete interrupt (see description of the TXCIE bit).
This bit is available in both USART and EUSART modes.
• Bit 5 – UDRE: USART Data Register Empty
211
4317B–AVR–02/05
The UDRE flag indicates if the transmit buffer (UDR) is ready to receive new data. If
UDRE is one, the buffer is empty, and therefore ready to be written. The UDRE flag can
generate a Data Register Empty interrupt (see description of the UDRIE bit).
UDRE is set after a reset to indicate that the Transmitter is ready.
This bit is available in both USART and EUSART modes.
• Bit 4 – FE: Frame Error
This bit is set if the next character in the receive buffer had a Frame Error when
received. I.e., when the first stop bit of the next character in the receive buffer is zero.
This bit is valid until the receive buffer (UDR) is read. The FE bit is zero when the stop
bit of received data is one. Always set this bit to zero when writing to UCSRA.
This bit is also valid in EUSART mode only when data bits are level encoded (in
Manchester mode the FEM bit allows to detect a framing error).
• Bit 3 – DOR: Data OverRun
This bit is set if a Data OverRun condition is detected. A Data OverRun occurs when the
receive buffer is full (two characters), it is a new character waiting in the Receive Shift
Register, and a new start bit is detected. This bit is valid until the receive buffer (UDR) is
read. Always set this bit to zero when writing to UCSRA.
This bit is available in both USART and EUSART modes.
• Bit 2 – UPE: USART Parity Error
This bit is set if the next character in the receive buffer had a Parity Error when received
and the Parity Checking was enabled at that point (UPM1 = 1). This bit is valid until the
receive buffer (UDR) is read. Always set this bit to zero when writing to UCSRA.
This bit is also valid in EUSART mode only when data bits are level encoded (there is no
parity in Manchester mode).
• Bit 1 – U2X: Double the USART Transmission Speed
This bit only has effect for the asynchronous operation. Write this bit to zero when using
synchronous operation.
Writing this bit to one will reduce the divisor of the baud rate divider from 16 to 8 effectively doubling the transfer rate for asynchronous communication.
This bit is available in both USART and EUSART modes.
• Bit 0 – MPCM: Multi-processor Communication Mode
This bit enables the Multi-processor Communication mode. When the MPCM bit is written to one, all the incoming frames received by the USART Receiver that do not contain
address information will be ignored. The Transmitter is unaffected by the MPCM setting.
For more detailed information see “Multi-processor Communication Mode” on page 209.
This mode is unavailable when the EUSART mode is set.
212
AT90PWM2/3
4317B–AVR–02/05
AT90PWM2/3
USART Control and Status
Register B – UCSRB
Bit
7
6
5
4
3
2
1
0
RXCIE
TXCIE
UDRIE
RXEN
TXEN
UCSZ2
RXB8
TXB8
Read/Write
R/W
R/W
R/W
R/W
R/W
R/W
R
R/W
Initial Value
0
0
0
0
0
0
0
0
UCSRB
• Bit 7 – RXCIE: RX Complete Interrupt Enable
Writing this bit to one enables interrupt on the RXC flag. A USART Receive Complete
interrupt will be generated only if the RXCIE bit is written to one, the Global Interrupt
Flag in SREG is written to one and the RXC bit in UCSRA is set.
This bit is available for both USART and EUSART modes.
• Bit 6 – TXCIE: TX Complete Interrupt Enable
Writing this bit to one enables interrupt on the TXC flag. A USART Transmit Complete
interrupt will be generated only if the TXCIE bit is written to one, the Global Interrupt
Flag in SREG is written to one and the TXC bit in UCSRA is set.
This bit is available for both USART and EUSART mode.
• Bit 5 – UDRIE: USART Data Register Empty Interrupt Enable
Writing this bit to one enables interrupt on the UDRE flag. A Data Register Empty interrupt will be generated only if the UDRIE bit is written to one, the Global Interrupt Flag in
SREG is written to one and the UDRE bit in UCSRA is set.
This bit is available for both USART and EUSART mode.
• Bit 4 – RXEN: Receiver Enable
Writing this bit to one enables the USART Receiver. The Receiver will override normal
port operation for the RxD pin when enabled. Disabling the Receiver will flush the
receive buffer invalidating the FE, DOR, and UPE Flags.
This bit is available for both USART and EUSART mode.
• Bit 3 – TXEN: Transmitter Enable
Writing this bit to one enables the USART Transmitter. The Transmitter will override normal port operation for the TxDn pin when enabled. The disabling of the Transmitter
(writing TXEN to zero) will not become effective until ongoing and pending transmissions are completed, i.e., when the Transmit Shift Register and Transmit Buffer Register
do not contain data to be transmitted. When disabled, the Transmitter will no longer
override the TxDn port.
This bit is available for both USART and EUSART mode.
• Bit 2 – UCSZ2: Character Size
The UCSZ2 bits combined with the UCSZ1:0 bit in UCSRC sets the number of data bits
(Character SiZe) in a frame the Receiver and Transmitter use.
This bit have no effect when the EUSART mode is enable.
• Bit 1 – RXB8: Receive Data Bit 8
RXB8 is the ninth data bit of the received character when operating with serial frames
with nine data bits. Must be read before reading the low bits from UDR.
When the EUSART mode is enable and configured in 17 bits receive mode, this bit contains the seventeenth bit (see EUSART section).
• Bit 0 – TXB8: Transmit Data Bit 8
213
4317B–AVR–02/05
TXB8 is the ninth data bit in the character to be transmitted when operating with serial
frames with nine data bits. Must be written before writing the low bits to UDR.
When the EUSART mode is enable and configured in 17 bits transmit mode, this bit contains the seventeenth bit (See EUSART section).
USART Control and Status
Register C – UCSRC
Bit
7
6
5
4
3
2
1
0
-
UMSEL0
UPM1
UPM0
USBS
UCSZ1
UCSZ0
UCPOL
Read/Write
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
Initial Value
0
0
0
0
0
1
1
0
UCSRC
• Bit 7 – Reserved Bit
This bit is reserved for future use. For compatibilty with future devices, this bit must be
written to zero when USCRC is written.
• Bit 6 – UMSEL: USART Mode Select
This bit selects between asynchronous and synchronous mode of operation.
Table 78. UMSEL Bit Settings
UMSEL
Mode
0
Asynchronous Operation
1
Synchronous Operation
When configured in EUSART mode, the synchronous mode should not be set with
Manchester mode (See EUSART section).
• Bit 5:4 – UPM1:0: Parity Mode
These bits enable and set type of parity generation and check. If enabled, the Transmitter will automatically generate and send the parity of the transmitted data bits within
each frame. The Receiver will generate a parity value for the incoming data and compare it to the UPM setting. If a mismatch is detected, the UPE Flag in UCSRA will be set.
Table 79. UPM Bits Settings
UPM1
UPM0
Parity Mode
0
0
Disabled
0
1
Reserved
1
0
Enabled, Even Parity
1
1
Enabled, Odd Parity
This setting is available in EUSART mode only when data bits are level encoded (in
Manchester the parity checker and generator are not available).
214
AT90PWM2/3
4317B–AVR–02/05
AT90PWM2/3
• Bit 3 – USBS: Stop Bit Select
This bit selects the number of stop bits to be inserted by the Transmitter. The Receiver
ignores this setting.
In EUSART mode, the USBS bit has the same behavior and the EUSB bit of the
EUSART allows to configure the number of stop bit for the receiver in this mode.
Table 80. USBS Bit Settings
USBS
Stop Bit(s)
0
1-bit
1
2-bit
• Bit 2:1 – UCSZ1:0: Character Size
The UCSZ1:0 bits combined with the UCSZ2 bit in UCSRB sets the number of data bits
(Character SiZe) in a frame the Receiver and Transmitter use.
Table 81. UCSZ Bits Settings
UCSZ2
UCSZ1
UCSZ0
Character Size
0
0
0
5-bit
0
0
1
6-bit
0
1
0
7-bit
0
1
1
8-bit
1
0
0
Reserved
1
0
1
Reserved
1
1
0
Reserved
1
1
1
9-bit
When the EUSART mode is set, these bits have no effect.
• Bit 0 – UCPOL: Clock Polarity
This bit is used for synchronous mode only. Write this bit to zero when asynchronous
mode is used. The UCPOL bit sets the relationship between data output change and
data input sample, and the synchronous clock (XCK).
Table 82. UCPOL Bit Settings
Transmitted Data Changed
(Output of TxDn Pin)
Received Data Sampled
(Input on RxD Pin)
0
Rising XCK Edge
Falling XCK Edge
1
Falling XCK Edge
Rising XCK Edge
UCPOL
215
4317B–AVR–02/05
USART Baud Rate Registers –
UBRRL and UBRRH
Bit
15
14
13
12
–
–
–
–
11
10
9
8
UBRR[11:8]
UBRRH
UBRR[7:0]
7
Read/Write
Initial Value
6
5
4
3
UBRRL
2
1
0
R
R
R
R
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
• Bit 15:12 – Reserved Bits
These bits are reserved for future use. For compatibility with future devices, these bit
must be written to zero when UBRRH is written.
• Bit 11:0 – UBRR11:0: USART Baud Rate Register
This is a 12-bit register which contains the USART baud rate. The UBRRH contains the
four most significant bits, and the UBRRL contains the eight least significant bits of the
USART baud rate. Ongoing transmissions by the Transmitter and Receiver will be corrupted if the baud rate is changed. Writing UBRRL will trigger an immediate update of
the baud rate prescaler.
216
AT90PWM2/3
4317B–AVR–02/05
AT90PWM2/3
Examples of Baud Rate
Setting
For standard crystal, resonator and external oscillator frequencies, the most commonly
used baud rates for asynchronous operation can be generated by using the UBRR settings in Table 83 up to Table 86. UBRR values which yield an actual baud rate differing
less than 0.5% from the target baud rate, are bold in the table. Higher error ratings are
acceptable, but the Receiver will have less noise resistance when the error ratings are
high, especially for large serial frames (see “Asynchronous Operational Range” on page
208). The error values are calculated using the following equation:
BaudRate Closest Match
Error[%] = ⎛ 1 – --------------------------------------------------------⎞ • 100%
⎝
⎠
BaudRate
Table 83. Examples of UBRR Settings for Commonly Frequencies
fclkio = 1.0000 MHz
fclkio = 1.8432 MHz
fclkio = 2.0000 MHz
Baud
Rate
(bps)
UBRR
2400
25
0.2%
51
0.2%
47
0.0%
95
0.0%
51
0.2%
103
0.2%
4800
12
0.2%
25
0.2%
23
0.0%
47
0.0%
25
0.2%
51
0.2%
9600
6
-7.0%
12
0.2%
11
0.0%
23
0.0%
12
0.2%
25
0.2%
14.4k
3
8.5%
8
-3.5%
7
0.0%
15
0.0%
8
-3.5%
16
2.1%
19.2k
2
8.5%
6
-7.0%
5
0.0%
11
0.0%
6
-7.0%
12
0.2%
28.8k
1
8.5%
3
8.5%
3
0.0%
7
0.0%
3
8.5%
8
-3.5%
38.4k
1
-18.6%
2
8.5%
2
0.0%
5
0.0%
2
8.5%
6
-7.0%
57.6k
0
8.5%
1
8.5%
1
0.0%
3
0.0%
1
8.5%
3
8.5%
76.8k
–
–
1
-18.6%
1
-25.0%
2
0.0%
1
-18.6%
2
8.5%
115.2k
–
–
0
8.5%
0
0.0%
1
0.0%
0
8.5%
1
8.5%
230.4k
–
–
–
–
–
–
0
0.0%
–
–
–
–
250k
–
–
–
–
–
–
–
–
–
–
–
–
500k
–
–
–
–
–
–
–
–
–
–
–
–
1M
–
–
–
–
–
–
–
–
–
–
–
–
Max.
1.
U2X = 0
(1)
U2X = 1
Error
UBRR
62.5 kbps
U2X = 0
Error
125 kbps
UBRR
U2X = 1
Error
115.2 kbps
UBRR
U2X = 0
Error
230.4 Kbps
UBRR
U2X = 1
Error
125 kpbs
UBRR
Error
250 kbps
UBRR = 0, Error = 0.0%
217
4317B–AVR–02/05
Table 84. Examples of UBRR Settings for Commonly Frequencies (Continued)
fclkio = 3.6864 MHz
fclkio = 4.0000 MHz
fclkio = 7.3728 MHz
Baud
Rate
(bps)
UBRR
2400
95
0.0%
191
0.0%
103
0.2%
207
0.2%
191
0.0%
383
0.0%
4800
47
0.0%
95
0.0%
51
0.2%
103
0.2%
95
0.0%
191
0.0%
9600
23
0.0%
47
0.0%
25
0.2%
51
0.2%
47
0.0%
95
0.0%
14.4k
15
0.0%
31
0.0%
16
2.1%
34
-0.8%
31
0.0%
63
0.0%
19.2k
11
0.0%
23
0.0%
12
0.2%
25
0.2%
23
0.0%
47
0.0%
28.8k
7
0.0%
15
0.0%
8
-3.5%
16
2.1%
15
0.0%
31
0.0%
38.4k
5
0.0%
11
0.0%
6
-7.0%
12
0.2%
11
0.0%
23
0.0%
57.6k
3
0.0%
7
0.0%
3
8.5%
8
-3.5%
7
0.0%
15
0.0%
76.8k
2
0.0%
5
0.0%
2
8.5%
6
-7.0%
5
0.0%
11
0.0%
115.2k
1
0.0%
3
0.0%
1
8.5%
3
8.5%
3
0.0%
7
0.0%
230.4k
0
0.0%
1
0.0%
0
8.5%
1
8.5%
1
0.0%
3
0.0%
250k
0
-7.8%
1
-7.8%
0
0.0%
1
0.0%
1
-7.8%
3
-7.8%
500k
–
–
0
-7.8%
–
–
0
0.0%
0
-7.8%
1
-7.8%
1M
–
–
–
–
–
–
–
–
–
–
0
-7.8%
Max. (1)
1.
218
U2X = 0
U2X = 1
Error
UBRR
230.4 kbps
U2X = 0
Error
460.8 kbps
UBRR
U2X = 1
Error
250 kbps
UBRR
U2X = 0
Error
0.5 Mbps
UBRR
U2X = 1
Error
460.8 kpbs
UBRR
Error
921.6 kbps
UBRR = 0, Error = 0.0%
AT90PWM2/3
4317B–AVR–02/05
AT90PWM2/3
Table 85. Examples of UBRR Settings for Commonly Frequencies (Continued)
fclkio = 8.0000 MHz
fclkio = 10.000 MHz
fclkio = 11.0592 MHz
Baud
Rate
(bps)
UBRR
2400
207
0.2%
416
-0.1%
259
0.2%
520
0.0%
287
0.0%
575
0.0%
4800
103
0.2%
207
0.2%
129
0.2%
259
0.2%
143
0.0%
287
0.0%
9600
51
0.2%
103
0.2%
64
0.2%
129
0.2%
71
0.0%
143
0.0%
14.4k
34
-0.8%
68
0.6%
42
0.9%
86
0.2%
47
0.0%
95
0.0%
19.2k
25
0.2%
51
0.2%
32
-1.4%
64
0.2%
35
0.0%
71
0.0%
28.8k
16
2.1%
34
-0.8%
21
-1.4%
42
0.9%
23
0.0%
47
0.0%
38.4k
12
0.2%
25
0.2%
15
1.8%
32
-1.4%
17
0.0%
35
0.0%
57.6k
8
-3.5%
16
2.1%
10
-1.5%
21
-1.4%
11
0.0%
23
0.0%
76.8k
6
-7.0%
12
0.2%
7
1.9%
15
1.8%
8
0.0%
17
0.0%
115.2k
3
8.5%
8
-3.5%
4
9.6%
10
-1.5%
5
0.0%
11
0.0%
230.4k
1
8.5%
3
8.5%
2
-16.8%
4
9.6%
2
0.0%
5
0.0%
250k
1
0.0%
3
0.0%
2
-33.3%
4
0.0%
2
-7.8%
5
-7.8%
500k
0
0.0%
1
0.0%
–
–
2
-33.3%
–
–
2
-7.8%
1M
–
–
0
0.0%
–
–
–
–
–
–
–
–
U2X = 0
Max. (1)
1.
U2X = 1
Error
UBRR
0.5 Mbps
Error
1 Mbps
U2X = 0
UBRR
U2X = 1
Error
625 kbps
UBRR
U2X = 0
Error
1.25 Mbps
UBRR
U2X = 1
Error
691.2 kbps
UBRR
Error
1.3824 Mbps
UBRR = 0, Error = 0.0%
219
4317B–AVR–02/05
Table 86. Examples of UBRR Settings for Commonly Frequencies (Continued)
fclkio = 12.0000 MHz
fclkio = 14.7456 MHz
fclkio = 16.0000 MHz
Baud
Rate
(bps)
UBRR
2400
312
-0.2%
624
0.0%
383
0.0%
767
0.0%
416
-0.1%
832
0.0%
4800
155
0.2%
312
-0.2%
191
0.0%
383
0.0%
207
0.2%
416
-0.1%
9600
77
0.2%
155
0.2%
95
0.0%
191
0.0%
103
0.2%
207
0.2%
14.4k
51
0.2%
103
0.2%
63
0.0%
127
0.0%
68
0.6%
138
-0.1%
19.2k
38
0.2%
77
0.2%
47
0.0%
95
0.0%
51
0.2%
103
0.2%
28.8k
25
0.2%
51
0.2%
31
0.0%
63
0.0%
34
-0.8%
68
0.6%
38.4k
19
-2.5%
38
0.2%
23
0.0%
47
0.0%
25
0.2%
51
0.2%
57.6k
12
0.2%
25
0.2%
15
0.0%
31
0.0%
16
2.1%
34
-0.8%
76.8k
9
-2.7%
19
-2.5%
11
0.0%
23
0.0%
12
0.2%
25
0.2%
115.2k
6
-8.9%
12
0.2%
7
0.0%
15
0.0%
8
-3.5%
16
2.1%
230.4k
2
11.3%
6
-8.9%
3
0.0%
7
0.0%
3
8.5%
8
-3.5%
250k
2
0.0%
5
0.0%
3
-7.8%
6
5.3%
3
0.0%
7
0.0%
500k
–
–
2
0.0%
1
-7.8%
3
-7.8%
1
0.0%
3
0.0%
1M
–
–
–
–
0
-7.8%
1
-7.8%
0
0.0%
1
0.0%
Max. (1)
1.
220
U2X = 0
U2X = 1
Error
UBRR
750 kbps
U2X = 0
Error
1.5 Mbps
UBRR
Error
921.6 kbps
U2X = 1
UBRR
Error
1.8432 Mbps
U2X = 0
UBRR
Error
1 Mbps
U2X = 1
UBRR
Error
2 Mbps
UBRR = 0, Error = 0.0%
AT90PWM2/3
4317B–AVR–02/05
AT90PWM2/3
EUSART (Extended
USART)
The Extended Universal Synchronous and Asynchronous serial Receiver and Transmitter (EUSART) provides functionnal extensions to the USART.
Features
•
•
•
•
•
•
Overview
A simplified block diagram of the EUSART Transmitter is shown in Figure 106. CPU
accessible I/O Registers and I/O pins are shown in bold.
Independant bit number configuration for transmit and receive
Supports Serial Frames with 5, 6, 7, 8, 9 or 13, 14, 15, 16, 17 Data Bits and 1 or 2 Stop Bits
Biphase Manchester encode/decoder (for DALI Communications)
Manchester framing error detection
Bit ordering
Autoadaptative baud rate synchronization with received Manchester data.
Figure 106. EUSART Block Diagram
Clock Generator
UBRR[H:L]
CLKio
BAUD RATE GENERATOR
SYNC LOGIC
PIN
CONTROL
XCK
Transmitter
DATA BUS
EUDR
(Transmit)
TX
CONTROL
UDR
(Transmit)
PARITY
GENERATOR
MANCHESTER
ENCODER
PIN
CONTROL
TRANSMIT SHIFT REGISTER
TxD
Receiver
CLOCK
RECOVERY
RECEIVE SHIFT REGISTER
EUDR
(Receive)
UDR
(Receive)
RX
CONTROL
MANCHESTER
DECODER
DATA
RECOVERY
PIN
CONTROL
RxD
PARITY
CHECKER
UCSRA
UCSRB
UCSRC
EUCSRA
EUCSRB
EUCSRC
221
4317B–AVR–02/05
The EUSART is actived with the EUSART bit of EUCSRB register. Until this bit is not
set, the USART will behave as standard USART, all the functionnalities of the EUSART
are not accessible.
The EUSART supports more serial frame formats than the standard USART interface:
•
•
Asynchonous frames
–
Standard bit level encoded
–
Manchester bit encoded
Synchronous frames
–
In this mode only the Standard bit level encoded is available
Serial Frames
A serial frame is defined to be one character of data bits with synchronization bits (start
and stop bits), and optionally a parity bit for error checking.
Frame Formats
The EUSART allows to receive and transmit serial frame with the following format:
•
1 start bit
•
5, 6, 7, 8, 9, 13, 14,15,16,17 data bits
•
data bits and start bit level encoded or Manchester encoded
•
data transmition MSB or LSB first (bit ordering)
•
no, even or odd parity bit
•
1 or 2 stop bits:
–
Stop bits insertion for transmition
–
Stop bits value read access in reception
The frame format used by the EUSART can be configured through the following
USART/EUSART registers:
•
UTxS3:0 and URxS3:0 (EUCSRA of EUSART register) select the number of data
bits per frame
•
UPM1:0 bits enable and set the type of parity bit (when configured in Manchester
mode, the parity should be fixed to none).
USBS (UCSRC register of USART) and EUSBS (EUCSRB register of EUSART) select
the number of stop bits to be processed respectively by the transmiter and the receiver.
The receiver stores the two stop bit values when configured in Manchester mode. When
configured in level encoded mode, the second stop bit is ignored (behavior similar as
the USART).
Parity Bit Calculation
The parity bit behavior is similar to the USART mode, except for the Manchester
encoded mode, where no parity bit can be inserted or detected (should be configured to
none with the UPM1:0 bits. The parity bit is calculated by doing an exclusive-or of all the
data bits. If odd parity is used, the result of the exclusive or is inverted. The relation
between the parity bit and data bits is as follows:
P even = d n – 1 ⊕ … ⊕ d 3 ⊕ d 2 ⊕ d 1 ⊕ d 0 ⊕ 0
P odd = d n – 1 ⊕ … ⊕ d 3 ⊕ d 2 ⊕ d 1 ⊕ d 0 ⊕ 1
Peven
Parity bit using even parity
Podd
Parity bit using odd parity
dn
Data bit n of the character
If used, the parity bit is located between the last data bit and first stop bit of a serial
frame.
222
AT90PWM2/3
4317B–AVR–02/05
AT90PWM2/3
Manchester encoding
Manchester encoding (also know as Biphase Code) is a synchronous clock encoding
technique used to encode the clock and data of a synchronous bit stream. In this technique, the actual binary data to be transmitted are not sent as a sequence of logic 1's
and 0's as in level encoded way as in standard USART (known technically as Non
Return to Zero (NRZ)). Instead, the bits are translated into a slightly different format that
has a number of advantages over using straight binary encoding (i.e. NRZ).
Manchester encoding follows the rules:
•
If the original data is a Logic 1, the Manchester code is: 0 to 1 (upward transition at
bit center)
•
If the original data is a Logic 0, the Manchester code is: 1 to 0 (downward transition
at bit center)
Figure 107. Manchester Bi-phase levels
Logical 0
Manchester frame
Logical 1
The USART supports Manchester encoded frames with the following characteristics:
•
One start bit Manchester encoded (logical ‘1’)
•
5, 6, 7, 8, 9, 13, 14,15,16,17 data bits in transmission or reception (MSB or LSB
first)
•
The number of data bit in a frame is independently configurable in reception and
transmission mode.
•
One or Two stop bits (level encoded)
Figure 108. Manchester Frame example
Encoder Clock
Manchester Data
Binary Data
1 0 0 1 1 1 1 0 1 0 0 1 0 1 0 1 0
Start
Bit
Data Bits
(up to 17 data bit)
Stop
Bits
223
4317B–AVR–02/05
Manchester decoder
When configured in Manchester mode, the EUSART receiver is able to receive serial
frame using a 17-bit shift register, an edge detector and several data/control registers.
The Manchester decoder receives a frame from the RxD pin of the EUSART interface
and loads the received data in the EUSART data register (UDR and EUDR).
The bit order of the data bits in the frame is configurable to handle MSB or LSB first.
The polarity of the bi-phase start is not configurable. The start bit a logical ‘1’ (rising
edge at bit center).
The polarity of the stop bits is not configurable, the interface allows to read the 2 stops
bits value by software.
The Manchester decoder is enable when the EUSART is configured in Manchester
mode and the RXEN of USCRB set (global USART receive enable).
The number of data bits to be received can be configured with the URxS bits of
EUSCRA register.
The Manchester decoder provides a special mode where 16 or 17 data bits can be
received. In this mode the Manchester decoder can automatically detects if the seventeenth bit is Manchester encoded or not (seventeenth data bit or first stop bit). If the
receiver detects a valid data bit (Manchester transition) during the seventeenth bit time
of the frame, the receiver will process the frame as a 17-bit frame lenght and set the
F1617 bit of EUSCRC register.
In Manchester mode, the clock used for sampling the EUSART input signal is programmed by the baudrate generator.
The Manchester decoder performs an autoadaptative synchronization with the received
data.
The edge detector of the Manchester decoder is based upon a 16 bits up/down counter
which maximum value can be configured through the MUBRRH and MUBRRL registers.
Typically the maximum counter value is given by the following formula:
MUBRR[H:L]=FCLKIO / (2*baud rate frequency)
224
AT90PWM2/3
4317B–AVR–02/05
AT90PWM2/3
Each time bit in the Manchester serial frame is divided into two phases (See Figure
109). The counter counts during the first phase and counts down during the second one.
When the data bit transition is detected, the counter memorises the N1 counter value
and start counting down.
When the counter reachs the zero value, it starts counting up again and the N1/2 value
allows to open the next detection window. This detection window defines the time zone
where the next data bit edge is sampled.
Figure 109. Manchester Decoder operation
Data Clock
Start Bit
Bit 1
Bit 2
N1
N2
N3
Manchester
Data
Manchester
Decoder
Counter
N1/2
N2/2
N2/2
N3/2
Detection
Window
Internal
Manchester
Clock
Decoded
Data-
225
4317B–AVR–02/05
Manchester Framing error
detection
When configured in Manchester mode, the framing error (FE) of the USCRA register is
not used, the EUSART generates a dedicated Frame Error Manchester (FEM) when a
data data bit is not detected during the detection window (See Figure 110).
Figure 110. Manchester Frame error detection
Internal
Manchester
Clock
Bit 1
Start Bit
Bit 2
Bit 1
Start Bit
Bit 2
Data bit shift
Data bit shift
Manchester
Data
N3
Counter
Overflow
N1
Manchester
Decoder
Counter
N1
N2
N1/2
N2/2
N2
N1/2
N2/2
N3
Detection
Window
Manchester
Framing error
Manchester
Framing error
When a Manchester framing error is detected the FEM bit and RxC bit are set at the
same time. This allows the application to execute the reception complete interrupt subroute when this error conditon is detected.
When a Manchester framing error is detected, the EUSART receiver immediately enters
in a new start bit detection phase. Thus when a Manchester framing error is detected
within a frame, the receiver will process the rest of the frame as a new incomming frame
and generate other FEM errors.
226
AT90PWM2/3
4317B–AVR–02/05
AT90PWM2/3
Configuring the EUSART
Data Transmission – EUSART Transmitter
The EUSART Transmitter is enabled in the same way as standard USART, by setting
the Transmit Enable (TXEN) bit in the UCSRB Register. When the Transmitter is
enabled, the normal port operation of the TxDn pin is overridden by the EUSART and
given the function as the Transmitter’s serial output. The baud rate, mode of operation
and frame format must be set up once before doing any transmissions. If synchronous
operation is used, the clock on the XCK pin will be overridden and used as transmission
clock.
Sending Frames with 5 to 8
Data Bit
In this mode the behavior is the same as the standard USART (See “Sending Frames
with 5 to 8 Data Bit” in USART section).
Sending Frames with 9, 13, 14,
15 or 16 Data Bit
In these configurations the most significant bits (9, 13, 14, 15 or 16) should be loaded in
the EUDR register before the low byte of the character is written to UDR. The write operation in the UDR register allows to start the transmission.
Assembly Code Example(1)
EUSART_Transmit:
; Wait for empty transmit buffer
sbis UCSRA,UDRE
rjmp EUSART_Transmit
; Put LSB data (r16) and MSN data (r15) into buffer, sends the
data
out
EUDR,r15
out
UDR,r16
ret
C Code Example(1)
void EUSART_Transmit( unsigned int data )
{
/* Wait for empty transmit buffer */
while ( !( UCSRA & (1<<UDRE))) )
/* Put data into buffer, sends the data */
EUDR = data>>8;
UDR = data;
}
Note:
The example code assumes that the part specific header file is included.
For I/O Registers located in extended I/O map, “IN”, “OUT”, “SBIS”, “SBIC”, “CBI”, and
“SBI” instructions must be replaced with instructions that allow access to extended I/O.
Typically “LDS” and “STS” combined with “SBRS”, “SBRC”, “SBR”, and “CBR”.
227
4317B–AVR–02/05
Sending 17 Data Bit Frames
In this configuration the seventeenth bit shoud be loaded in the RXB8 bit register, the
rest of the most significant bits (9, 10, 11, 12, 13, 14, 15 and 16) should be loaded in the
EUDR register, before the low byte of the character is written to UDR.
Transmitter Flags and
Interrupts
The behavior of the EUSART is the same as in USART mode (See “Receive Complete
Flag and Interrupt”).
The interrupts generation and handling for transmission in EUSART mode are the same
as in USART mode.
Disabling the Transmitter
The disabling of the Transmitter (setting the TXEN to zero) will not become effective
until ongoing and pending transmissions are completed, i.e., when the Transmit Shift
Register and Transmit Buffer Register do not contain data to be transmitted.
Data Reception – EUSART Receiver
Data Reception –
EUSART Receiver
The EUSART Receiver is enabled by writing the Receive Enable (RXEN) bit in the
UCSRB Register to one (same as USART). When the Receiver is enabled, the normal
pin operation of the RxD pin is overridden by the EUSART and given the function as the
Receiver’s serial input. The baud rate, mode of operation and frame format must be set
up once before any serial reception can be done. If synchronous operation is used, the
clock on the XCK pin will be used as transfer clock.
Receiving Frames with 5 to 8
Data Bits
In this mode the behavior is the same as the standard USART (See “Receiving Frames
with 5 to 8 Data Bits” in USART section).
Receiving Frames with 9, 13,
14, 15 or 16 Data Bits
In these configurations the most significant bits (9, 13, 14, 15 or 16) should be read in
the EUDR register before reading the of the character in the UDR register.
Read status from EUCSRC, then data from UDR.
228
AT90PWM2/3
4317B–AVR–02/05
AT90PWM2/3
The following code example shows a simple EUSART receive function.
Assembly Code Example(1)
EUSART_Receive:
; Wait for data to be received
sbis UCSRA, RXC
rjmp EUSART_Receive
; Get MSB (r15), LSB (r16)
in
r15, EUDR
in
r16, UDR
ret
C Code Example(1)
unsigned int EUSART_Receive( void )
{
unsigneg int rx_data
/* Wait for data to be received */
while ( !(UCSRA & (1<<RXC)) )
;
/* Get and return received data from buffer */
rx_data=EUDR;
rx_data=rx_data<<8+UDR;
return rx_data;
}
Note:
The example code assumes that the part specific header file is included.
For I/O Registers located in extended I/O map, “IN”, “OUT”, “SBIS”, “SBIC”, “CBI”, and
“SBI” instructions must be replaced with instructions that allow access to extended I/O.
Typically “LDS” and “STS” combined with “SBRS”, “SBRC”, “SBR”, and “CBR”.
Receiving 17 Data Bit Frames
In this configuration the seventeenth bit shoud be read from the RXB8 bit register, the
rest of the most significant bits (9, 10, 11, 12, 13, 14, 15 and 16) should be read from the
EUDR register, before the low byte of the character is read from UDR.
Receive Complete Flag and
Interrupt
The EUSART Receiver has the same USART flag that indicates the Receiver state.
Receiver Error Flags
When the EUSART is not configured in Manchester mode, the EUSART has the three
same errors flags as standard mode: Frame Error (FE), Data OverRun (DOR) and Parity
Error (UPE). All can be accessed by reading UCSRA. (See “Receiver Error Flags” in
USART section).
See “Receive Complete Flag and Interrupt” in USART section.
When the EUSART is configured in Machester mode, the EUSART has two errors flags:
Data OverRun (DOR), and Manchester framing error (FEM bit of EUCSRC).
All the receiver error flags are valid only when the RxC bit is set and until the UDR register is read.
229
4317B–AVR–02/05
Parity Checker
The parity checker of the EUSART is available only when data bits are level encoded
and behaves as is USART mode (See Parity checker of the USART).
OverRun
The Data OverRun (DOR bit of USCRA) flag indicates data loss due to a receiver buffer
full condition. This flag operates as in USART mode (See USART section).
EUSART Registers
Description
USART I/O Data Register –
UDR
Bit
7
6
5
4
3
2
1
0
RXB[7:0]
UDR (Read)
TXB[7:0]
UDR (Write)
Read/Write
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
Initial Value
0
0
0
0
0
0
0
0
• Bit 7:0 – RxB7:0: Receive Data Buffer (read access)
• Bit 7:0 – TxB7:0: Transmit Data Buffer (write access)
This register is common to the USART and EUSART interfaces for Transmit Data Buffer
Register and Receive Data Buffer Register. See description for UDR register in USART.
EUSART I/O Data Register –
EUDR
Bit
7
6
5
4
3
2
1
0
RXB[15:8]
EUDR (Read)
TXB[15:8]
EUDR (Write)
Read/Write
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
Initial Value
0
0
0
0
0
0
0
0
• Bit 7:0 – RxB15:8: Receive Data Buffer (read access)
• Bit 7:0 – TxB15:8: Transmit Data Buffer (write access)
This register provide an extension to the UDR register when EUSART is used with more
than 8 bits.
UDR/EUDR data access with
character size up to 8 bits
When the EUSART is used with 8 or less bits, only the UDR register is used for dta
access.
UDR/EUDR data access with 9
bits per character
When the EUSART is used with 9 bits character, the behavior is different of the standart
USART mode, the UDR register is used in combinaison with the first bit of EUDR
(EUDR:0) for data access, the RxB8/TxB8 bit is not used.
Figure 111. 9 bits communication data access
Data 8:0
EUDR
230
8 7
0
UDR
AT90PWM2/3
4317B–AVR–02/05
AT90PWM2/3
UDR/EUDR data access from
13 to 17 bits per character
When the EUSART is used in 13, 14, 15, 16 or 17 bits per character mode, the
EUDR/UDR registers are used in combinaison with the RxB8/TxB8 bit for data access.
For 13, 14, 15 or 16 bit character the upper unused bits in EUDR will be ignored by the
Transmitter and set to zero by the Receiver. In transmitter mode, the data should be
written MSB first. The data transmission starts when the UDR register is written.
In these modes, the RxB8/TxB8 registers are not used.
Figure 112. 13, 14, 15 and 16 bits communication data access
Data 15:0
15
8 7
0
EUDR
UDR
For 17 bit character the seventeenth bit is locate in RxB8 or TXB8 register. In transmitter
mode, the data should be written MSB first. The data transmission starts when the UDR
register is written.
Figure 113. 17 bits communication data access
Data 16:0
16 15
8 7
RxB8 (receive)
or TxB8 (transmit)
EUSART Control and Status
Register A – EUCSRA
Bit
0
EUDR
UDR
7
6
5
4
3
2
1
0
UTxS3
UTxS2
UTxS1
UTxS0
UTxS3
URxS2
URxS1
URxS0
Read/Write
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
Initial Value
0
0
1
1
0
0
1
1
EUCSRA
• Bit 7:4 – EUSART Transmit Character Size
231
4317B–AVR–02/05
The UTxS3:0 bits sets the number of data bits (Character Size) in a frame the Transmitter use.
Table 87. UTxS Bits Settings
UTxS3
UTxS2
UTxS1
UTxS0
Transmit Character Size
0
0
0
0
5-bit
0
0
0
1
6-bit
0
0
1
0
7-bit
0
0
1
1
8-bit
0
1
0
0
Reserved
0
1
0
1
Reserved
0
1
1
0
Reserved
0
1
1
1
9-bit
1
0
0
0
13-bit
1
0
0
1
14-bit
1
0
1
0
15-bit
1
0
1
1
16-bit
1
1
0
0
Reserved
1
1
0
1
Reserved
1
1
1
0
Reserved
1
1
1
1
17-bit
• Bit 3:0 – EUSART Receive Character Size
The UTxS3:0 bits sets the number of data bits (Character Size) in a frame the Receiver
use.
Table 88. URxS Bits Settings
232
URxS3
URxS2
URxS1
URxS0
Receive Character Size
0
0
0
0
5-bit
0
0
0
1
6-bit
0
0
1
0
7-bit
0
0
1
1
8-bit
0
1
0
0
Reserved
0
1
0
1
Reserved
0
1
1
0
Reserved
0
1
1
1
9-bit
1
0
0
0
13-bit
1
0
0
1
14-bit
1
0
1
0
15-bit
1
0
1
1
16-bit
AT90PWM2/3
4317B–AVR–02/05
AT90PWM2/3
Table 88. URxS Bits Settings
EUSART Control Register B –
EUCSRB
URxS3
URxS2
URxS1
URxS0
1
1
0
0
Reserved
1
1
0
1
Reserved
1
1
1
0
16 OR 17 bit (for Manchester
encoded only mode)
1
1
1
1
17-bit
Bit
Receive Character Size
7
6
5
4
3
2
1
0
-
-
-
EUSART
EUSBS
-
EMCH
BODR
Read/Write
R
R
R
R/W
R/W
R
R/W
R/W
Initial Value
0
0
0
0
0
0
0
0
EUCSRB
• Bit 7:5 –Reserved Bits
These bits are reserved for future use. For compatibilty with future devices, these bits
must be written to zero when EUSCRB is written.
• Bit 4 – EUSART Enable Bit
Set to enable the EUSART mode, clear to operate as standard USART.
• Bit 3– EUSBS Enable Bit
This bit selects the number of stop bits detected by the receiver.
Table 89. EUSBS Bit Settings
EUSBS
Note:
Receiver Stop Bit(s)
0
1-bit
1
2-bit
The number of stop bit inserted by the Transmitter in EUSART mode is configurable
throught the USBS bit of in the of the USART.
• Bit 2–Reserved Bit
This bit is reserved for future use. For compatibilty with future devices, this bit must be
written to zero when EUSCRB is written.
• Bit 1 – Manchester mode
When set the EUSART operates in manchester encoder/decoder mode (Manchester
encoded frames). When cleared the EUSART detected and transmit level encoded
frames.
Table 90. USART/EUSART modes selection summary
UMSEL
EMCH
EUSART
Mode
0
X
0
Asynchronous up to 9 bits level encoded (standard
asynchronous USART mode)
0
X
0
Synchronous up to 9 bits level encoded (standard
synchronous USART mode)
0
0
1
Asynchronous up to 17 bits level encoded
233
4317B–AVR–02/05
Table 90. USART/EUSART modes selection summary
UMSEL
EMCH
EUSART
Mode
0
1
1
Asynchronous up to 17 bits Manchester encoded
1
0
1
Synchronous up to 17 bits level encoded
1
1
1
Reserved
As in Manchester mode the parity checker and generator are unavailable, the parity
should be configured to none ( write UPM1:0 to 00 in UCSRC), see Table 79.
• Bit 0 –Bit Order
This bit allows to change the bit ordering in the transmit and received frames.
Clear to transmit and receive LSB first (standard USART mode)
Set to transmit and receive MSB first.
EUSART Status Register C –
EUCSRC
Bit
7
6
5
4
3
2
1
0
-
-
-
-
FEM
F1617
STP1
STP0
Read/Write
R
R
R
R
R
R
R
R
Initial Value
0
0
0
0
0
0
0
0
EUCSRC
• Bit 7:4 –Reserved Bits
These bits are reserved for future use. For compatibilty with future devices, these bits
must be written to zero when EUSCRC is written.
• Bit 3 –Frame Error Manchester
This bit is set by hardware when a framing error is detected in manchester mode. This
bit is valid when the RxC bit is set and until the receive buffer (UDR) is read.
• Bit 2 –F1617
When the receiver is configured for 16 or 17 bits in Manchester encoded mode, this bit
indicates if the received frame is 16 or 17 bits lenght.
Cleared: indicates that the received frame is 16 bits lenght.
Set: Indicates that the received frame is 17 bits lenght.
This bit is valid when the RxC bit is set and until the receive buffer (UDR) is read.
• Bit 1:0 –Stop bits values
When Manchester mode is activated, these bits contains the stop bits value of the previous received frame.
When the data bits in the serial frame are standard level encoded, these bits are not
updated.
Manchester receiver Baud
Rate Registers – MUBRRL and
MUBRRH
Bit
15
14
13
12
11
10
9
8
MUBRR[15:8]
MUBRRH
MUBRR[7:0]
7
Read/Write
Initial Value
234
6
5
4
3
MUBRRL
2
1
0
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
AT90PWM2/3
4317B–AVR–02/05
AT90PWM2/3
• Bit 15:0 – MUBRR15:0: Manchester Receiver Baud Rate Register
This is a 16-bit register which contains the maximum value for the Machester receiver
counter. The MUBRRH contains the eight most significant bits, and the MUBRRL contains the eight least significant bits. Ongoing transmissions by the Receiver will be
corrupted if the baud rate is changed.
MUBRR[H:L]=FCLKIO / (2*baud rate frequency)
Table 91. Examples of MUBRR Settings for Commonly Frequencies
1 MHz
fclkio =
1.8432
MHz
fclkio =
2.0000
MHz
fclkio =
7.3728
MHz
fclkio =
8.0000
MHz
fclkio =
11.0592
MHz
fclkio =
14.7456
MHz
fclkio =
1200
416
768
832
1536
1664
3072
3328
4608
6144
6656
2400
208
384
416
768
832
1536
1664
2304
3072
3328
4800
104
192
208
384
416
768
832
1152
1536
1664
9600
52
96
104
192
208
384
416
576
768
832
14.4k
35
64
63
128
127
256
254
384
512
507
19.2k
26
48
52
96
104
192
208
288
384
416
28.8k
17
32
35
64
70
128
139
192
256
278
38.4k
13
24
26
48
52
96
104
144
192
208
57.6k
9
16
17
32
35
64
70
96
128
139
76.8k
6
12
13
24
26
48
52
72
96
104
115.2k
4
8
9
16
17
28
35
48
64
70
4
4
8
9
16
17
24
32
35
250k
8
16
22
30
32
500k
4
8
11
15
16
4
5
8
8
Baud Rate
(bps)
fclkio =
230.4k
1M
fclkio =
fclkio =
3.6864MH
4.000 MHz
z
16.000
MHz
235
4317B–AVR–02/05
Analog Comparator
The Analog Comparator compares the input values on the positive pin ACMPx and negative pin ACMPM.
Overview
The AT90PWM2/3 features three fast analog comparators.
Each comparator has a dedicated input on the positive input, and the negative input can
be configured as:
•
a steady value among the 4 internal reference levels defined by the Vref selected
thanks to the REFS1:0 bits in ADMUX register.
•
a value generated from the internal DAC
•
an external analog input ACMPM.
When the voltage on the positive ACMPn pin is higher than the voltage selected by the
ACnM multiplexer on the negative input, the Analog Comparator output, ACnO, is set.
The comparator is a clocked comparator. A new comparison is done on the falling edge
of CLKI/O or CLKI/O/2 ( Depending on ACCKDIV fit of ACSR register, See “Analog Comparator Status Register – ACSR” on page 240.).
Each comparator can trigger a separate interrupt, exclusive to the Analog Comparator.
In addition, the user can select Interrupt triggering on comparator output rise, fall or
toggle.
The interrupt flags can also be used to synchronize ADC or DAC conversions.
Moreover, the comparator’s output of the comparator 1 can be set to trigger the
Timer/Counter1 Input Capture function.
A block diagram of the three comparators and their surrounding logic is shown in Figure
114.
236
AT90PWM2/3
4317B–AVR–02/05
AT90PWM2/3
Figure 114. Analog Comparator Block Diagram(1)(2)
AC0O
CLK I/O (/2)
AC0IF
+
ACMP0
Interrupt Sensitivity Control
Analog Comparator 0 Interrupt
AC0IE
AC0IS1
AC0EN
AC0M
2 1 0
AC0IS0
AC1O
CLK I/O (/2)
AC1IF
+
ACMP1
Interrupt Sensitivity Control
Analog Comparator 1 Interrupt
AC1IE
AC1IS1
AC1EN
AC1IS0
T1 Capture Trigger
AC1ICE
AC2O
AC1M
2 1 0
CLK I/O (/2)
AC2IF
+
ACMP2
Interrupt Sensitivity Control
Analog Comparator 2 Interrupt
AC0IE
AC2EN
AC2IS1
AC2IS0
ACMPM
Vref
DAC
DAC
Result
AC2M
2 1 0
DACEN
Aref
AVcc
Internal 2.56V
Reference
REFS0
Notes:
Analog Comparator
Register Description
Analog Comparator 0 Control
Register – AC0CON
/1.60
/2.13
/3.20
REFS1
/6.40
1. ADC multiplexer output: see Table 101 on page 257.
2. Refer to Figure 1 on page 3 and for Analog Comparator pin placement.
3. The voltage on Vref is defined in Table 100.ADC Voltage Reference Selection257
Each analog comparator has its own control register.
A dedicated register has been designed to consign the outputs and the flags of the 3
analog comparators.
Bit
7
6
5
4
3
2
1
0
AC0EN
AC0IE
AC0IS1
AC0IS0
-
AC0M2
AC0M1
AC0M0
Read/Write
R/W
R/W
R/W
R/W
-
R/W
R/W
R/W
Initial Value
0
0
0
0
0
0
0
0
AC0CON
• Bit 7– AC0EN: Analog Comparator 0 Enable Bit
Set this bit to enable the analog comparator 0.
Clear this bit to disable the analog comparator 0.
• Bit 6– AC0IE: Analog Comparator 0 Interrupt Enable bit
Set this bit to enable the analog comparator 0 interrupt.
Clear this bit to disable the analog comparator 0 interrupt.
• Bit 5, 4– AC0IS1, AC0IS0: Analog Comparator 0 Interrupt Select bit
237
4317B–AVR–02/05
These 2 bits determine the sensitivity of the interrupt trigger.
The different setting are shown in Table 92.
Table 92. Interrupt sensitivity selection
AC0IS1
AC0IS0
Description
0
0
Comparator Interrupt on output toggle
0
1
Reserved
1
0
Comparator interrupt on output falling edge
1
1
Comparator interrupt on output rising edge
• Bit 2, 1, 0– AC0M2, AC0M1, AC0M0: Analog Comparator 0 Multiplexer register
These 3 bits determine the input of the negative input of the analog comparator.
The different setting are shown in Table 93.
Table 93. Analog Comparator 0 negative input selection
AC0M2
Analog Comparator 1Control
Register – AC1CON
AC0M1
AC0M0
Description
0
0
0
“Vref”/6.40
0
0
1
“Vref”/3.20
0
1
0
“Vref”/2.13
0
1
1
“Vref”/1.60
1
0
0
Analog Comparator Negative Input (ACMPM pin)
1
0
1
DAC result
1
1
0
Reserved
1
1
1
Reserved
Bit
7
6
5
4
3
2
1
0
AC1EN
AC1IE
AC1IS1
AC1IS0
AC1ICE
AC1M2
AC1M1
AC1M0
Read/Write
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
Initial Value
0
0
0
0
0
0
0
0
AC1CON
• Bit 7– AC1EN: Analog Comparator 1 Enable Bit
Set this bit to enable the analog comparator 1.
Clear this bit to disable the analog comparator 1.
• Bit 6– AC1IE: Analog Comparator 1 Interrupt Enable bit
Set this bit to enable the analog comparator 1 interrupt.
Clear this bit to disable the analog comparator 1 interrupt.
• Bit 5, 4– AC1IS1, AC1IS0: Analog Comparator 1 Interrupt Select bit
238
AT90PWM2/3
4317B–AVR–02/05
AT90PWM2/3
These 2 bits determine the sensitivity of the interrupt trigger.
The different setting are shown in Table 92.
Table 94. Interrupt sensitivity selection
AC1IS1
AC1IS0
Description
0
0
Comparator Interrupt on output toggle
0
1
Reserved
1
0
Comparator interrupt on output falling edge
1
1
Comparator interrupt on output rising edge
• Bit 3– AC1ICE: Analog Comparator 1 Interrupt Capture Enable bit
Set this bit to enable the input capture of the Timer/Counter1 on the analog comparator
event. The comparator output is in this case directly connected to the input capture
front-end logic, making the comparator utilize the noise canceler and edge select features of the Timer/Counter1 Input Capture interrupt. To make the comparator trigger the
Timer/Counter1 Input Capture interrupt, the ICIE1 bit in the Timer Interrupt Mask Register (TIMSK1) must be set.
In case ICES1 bit (“Timer/Counter1 Control Register B – TCCR1B” on page 127) is set
high, the rising edge of AC1O is the capture/trigger event of the Timer/Counter1, in case
ICES1 is set to zero, it is the falling edge which is taken into account.
Clear this bit to disable this function. In this case, no connection between the Analog
Comparator and the input capture function exists.
• Bit 2, 1, 0– AC1M2, AC1M1, AC1M0: Analog Comparator 1 Multiplexer register
These 3 bits determine the input of the negative input of the analog comparator.
The different setting are shown in Table 95.
Table 95. Analog Comparator 1 negative input selection
AC1M2
Analog Comparator 2 Control
Register – AC2CON
AC1M1
AC1M0
Description
0
0
0
“Vref”/6.40
0
0
1
“Vref”/3.20
0
1
0
“Vref”/2.13
0
1
1
“Vref”/1.60
1
0
0
Analog Comparator Negative Input (ACMPM pin)
1
0
1
DAC result
1
1
0
Reserved
1
1
1
Reserved
Bit
7
6
5
4
AC2EN
AC2IE
AC2IS1
AC2IS0
Read/Write
R/W
R/W
R/W
R/W
Initial Value
0
0
0
0
3
2
1
0
AC2M2
AC2M1
AC2M0
-
R/W
R/W
R/W
0
0
0
0
AC2CON
• Bit 7– AC2EN: Analog Comparator 2 Enable Bit
Set this bit to enable the analog comparator 2.
Clear this bit to disable the analog comparator 2.
239
4317B–AVR–02/05
• Bit 6– AC2IE: Analog Comparator 2 Interrupt Enable bit
Set this bit to enable the analog comparator 2 interrupt.
Clear this bit to disable the analog comparator 2 interrupt.
• Bit 5, 4– AC2IS1, AC2IS0: Analog Comparator 2 Interrupt Select bit
These 2 bits determine the sensitivity of the interrupt trigger.
The different setting are shown in Table 92.
Table 96. Interrupt sensitivity selection
AC2IS1
AC2IS0
Description
0
0
Comparator Interrupt on output toggle
0
1
Reserved
1
0
Comparator interrupt on output falling edge
1
1
Comparator interrupt on output rising edge
• Bit 2, 1, 0– AC2M2, AC2M1, AC2M0: Analog Comparator 2 Multiplexer register
These 3 bits determine the input of the negative input of the analog comparator.
The different setting are shown in Table 97.
Table 97. Analog Comparator 2 negative input selection
AC2M2
Analog Comparator Status
Register – ACSR
AC2M1
AC2M0
Description
0
0
0
“Vref”/6.40
0
0
1
“Vref”/3.20
0
1
0
“Vref”/2.13
0
1
1
“Vref”/1.60
1
0
0
Analog Comparator Negative Input (ACMPM pin)
1
0
1
DAC result
1
1
0
Reserved
1
1
1
Reserved
Bit
7
6
5
4
3
2
1
0
ACCKDIV
AC2IF
AC1IF
AC0IF
-
AC2O
AC1O
AC0O
Read/Write
R
R
R
R
-
R
R
R
Initial Value
0
0
0
0
0
0
0
0
ACSR
• Bit 7– ACCKDIV: Analog Comparator Clock Divider
The analog comparators can work with a clock up to 8MHz.
Set this bit in case the clock frequency of the microcontroller is higher than 8 MHz to
insert a divider by 2 between the clock of the microcontroller and the clock of the analog
comparators.
Clear this bit to have the same clock frequency for the microcontroller and the analog
comparators.
• Bit 6– AC2IF: Analog Comparator 2 Interrupt Flag Bit
This bit is set by hardware when comparator 2 output event triggers off the interrupt
mode defined by AC2IS1 and AC2IS0 bits in AC2CON register.
This bit is cleared by hardware when the corresponding interrupt vector is executed in
240
AT90PWM2/3
4317B–AVR–02/05
AT90PWM2/3
case the AC2IE in AC2CON register is set. Anyway, this bit is cleared by writing a logical one on it.
This bit can also be used to synchronize ADC or DAC conversions.
• Bit 5– AC1IF: Analog Comparator 1 Interrupt Flag Bit
This bit is set by hardware when comparator 1 output event triggers off the interrupt
mode defined by AC1IS1 and AC1IS0 bits in AC1CON register.
This bit is cleared by hardware when the corresponding interrupt vector is executed in
case the AC1IE in AC1CON register is set. Anyway, this bit is cleared by writing a logical one on it.
This bit can also be used to synchronize ADC or DAC conversions.
• Bit 5– AC0IF: Analog Comparator 0 Interrupt Flag Bit
This bit is set by hardware when comparator 0 output event triggers off the interrupt
mode defined by AC0IS1 and AC0IS0 bits in AC0CON register.
This bit is cleared by hardware when the corresponding interrupt vector is executed in
case the AC0IE in AC0CON register is set. Anyway, this bit is cleared by writing a logical one on it.
This bit can also be used to synchronize ADC or DAC conversions.
• Bit 2– AC2O: Analog Comparator 2 Output Bit
AC2O bit is directly the output of the Analog comparator 2.
Set when the output of the comparator is high.
Cleared when the output comparator is low.
• Bit 1– AC1O: Analog Comparator 1 Output Bit
AC1O bit is directly the output of the Analog comparator 1.
Set when the output of the comparator is high.
Cleared when the output comparator is low.
• Bit 0– AC0O: Analog Comparator 0 Output Bit
AC0O bit is directly the output of the Analog comparator 0.
Set when the output of the comparator is high.
Cleared when the output comparator is low.
Digital Input Disable Register
0 – DIDR0
Bit
7
6
5
4
3
2
1
0
ADC7D
ADC6D
ADC5D
ADC4D
ADC3D
ACMPM
ADC2D
ACMP2D
ADC1D
ADC0D
Read/Write
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
Initial Value
0
0
0
0
0
0
0
0
DIDR0
• Bit 3:2 – ACMPM and ACMP2D: ACMPM and ACMP2 Digital Input Disable
When this bit is written logic one, the digital input buffer on the corresponding Analog pin
is disabled. The corresponding PIN Register bit will always read as zero when this bit is
set. When an analog signal is applied to one of these pins and the digital input from this
pin is not needed, this bit should be written logic one to reduce power consumption in
the digital input buffer.
Digital Input Disable Register
1– DIDR1
Bit
7
6
5
-
-
ACMP0D
4
3
AMP0PD AMP0ND
2
1
0
ADC10D
ACMP1D
ADC9D
AMP1PD
ADC8D
AMP1ND
Read/Write
-
-
R/W
R/W
R/W
R/W
R/W
R/W
Initial Value
0
0
0
0
0
0
0
0
DIDR1
• Bit 5, 2: ACMP0D and ACMP1 Digital Input Disable
241
4317B–AVR–02/05
When this bit is written logic one, the digital input buffer on the corresponding analog pin
is disabled. The corresponding PIN Register bit will always read as zero when this bit is
set. When an analog signal is applied to one of these pins and the digital input from this
pin is not needed, this bit should be written logic one to reduce power consumption in
the digital input buffer.
242
AT90PWM2/3
4317B–AVR–02/05
AT90PWM2/3
Analog to Digital Converter - ADC
Features
•
•
•
•
•
•
•
•
•
•
•
•
•
•
10-bit Resolution
0.5 LSB Integral Non-linearity
± 2 LSB Absolute Accuracy
8- 250 µs Conversion Time
Up to 120 kSPS at Maximum Resolution
11 Multiplexed Single Ended Input Channels
Two Differential input channels with accurate (5%) programmable gain 5, 10, 20 and 40
Optional Left Adjustment for ADC Result Readout
0 - VCC ADC Input Voltage Range
Selectable 2.56 V ADC Reference Voltage
Free Running or Single Conversion Mode
ADC Start Conversion by Auto Triggering on Interrupt Sources
Interrupt on ADC Conversion Complete
Sleep Mode Noise Canceler
The AT90PWM2/3 features a 10-bit successive approximation ADC. The ADC is connected to an 15-channel Analog Multiplexer which allows eleven single-ended input.
The single-ended voltage inputs refer to 0V (GND).
The device also supports 2 differential voltage input combinations which are equipped
with a programmable gain stage, providing amplification steps of 14dB (5x), 20 dB (10x),
26 dB (20x), or 32dB (40x) on the differential input voltage before the A/D conversion.
On the amplified channels, 8-bit resolution can be expected.
The ADC contains a Sample and Hold circuit which ensures that the input voltage to the
ADC is held at a constant level during conversion. A block diagram of the ADC is shown
in Figure 115.
The ADC has a separate analog supply voltage pin, AVCC. AVCC must not differ more
than ± 0.3V from VCC. See the paragraph “ADC Noise Canceler” on page 250 on how to
connect this pin.
Internal reference voltages of nominally 2.56V or AVCC are provided On-chip. The voltage reference may be externally decoupled at the AREF pin by a capacitor for better
noise performance.
243
4317B–AVR–02/05
Figure 115. Analog to Digital Converter Block Schematic
AREF
AVCC
Internal 2.56V
Reference
REFS0
ADC0
ADC1
ADC2
ADC3
ADC4
ADC5
ADC6
ADC7
AMP1-/ADC8
AMP1+/ADC9
ADC10
AMP0AMP0+
REFS1
Coarse/Fine DAC
10
+
-
+
CONTROL
REFS0
CK
AMP1CSR
ADLAR
-
MUX3
MUX2
MUX1
MUX0
Sources
-
ADCL
Edge
Detector
-
ADASCR
ADEN
ADSC
ADATE
ADIF
ADIE
PRESCALER
ADPS2
ADPS1
ADPS0
ADCSRA
ADMUX
-
10
ADC CONVERSION
COMPLETE IRQ
GND
Bandgap
REFS1
ADCH
CKADC CKADC
+
AMP0CSR
10
SAR
ADTS3
ADATE
ADTS2
ADTS1
ADTS0
ADCSRB
244
AT90PWM2/3
4317B–AVR–02/05
AT90PWM2/3
Operation
The ADC converts an analog input voltage to a 10-bit digital value through successive
approximation. The minimum value represents GND and the maximum value represents
the voltage on the AREF pin minus 1 LSB. Optionally, AVCC or an internal 2.56V reference voltage may be connected to the AREF pin by writing to the REFSn bits in the
ADMUX Register. The internal voltage reference may thus be decoupled by an external
capacitor at the AREF pin to improve noise immunity.
The analog input channel are selected by writing to the MUX bits in ADMUX. Any of the
ADC input pins, as well as GND and a fixed bandgap voltage reference, can be selected
as single ended inputs to the ADC.
The ADC is enabled by setting the ADC Enable bit, ADEN in ADCSRA. Voltage reference is set by the REFS1 and REFS0 bits in ADMUX register, whatever the ADC is
enabled or not. The ADC does not consume power when ADEN is cleared, so it is recommended to switch off the ADC before entering power saving sleep modes.
The ADC generates a 10-bit result which is presented in the ADC Data Registers,
ADCH and ADCL. By default, the result is presented right adjusted, but can optionally
be presented left adjusted by setting the ADLAR bit in ADMUX.
If the result is left adjusted and no more than 8-bit precision is required, it is sufficient to
read ADCH. Otherwise, ADCL must be read first, then ADCH, to ensure that the content
of the Data Registers belongs to the same conversion. Once ADCL is read, ADC access
to Data Registers is blocked. This means that if ADCL has been read, and a conversion
completed before ADCH is read, neither register is updated and the result from the conversion is lost. When ADCH is read, ADC access to the ADCH and ADCL Registers is
re-enabled.
The ADC has its own interrupt which can be triggered when a conversion completes.
The ADC access to the Data Registers is prohibited between reading of ADCH and
ADCL, the interrupt will trigger even if the result is lost.
Starting a Conversion
A single conversion is started by writing a logical one to the ADC Start Conversion bit,
ADSC. This bit stays high as long as the conversion is in progress and will be cleared by
hardware when the conversion is completed. If a different data channel is selected while
a conversion is in progress, the ADC will finish the current conversion before performing
the channel change.
Alternatively, a conversion can be triggered automatically by various sources. Auto Triggering is enabled by setting the ADC Auto Trigger Enable bit, ADATE in ADCSRA. The
trigger source is selected by setting the ADC Trigger Select bits, ADTS in ADCSRB
(See description of the ADTS bits for a list of the trigger sources). When a positive edge
occurs on the selected trigger signal, the ADC prescaler is reset and a conversion is
started. This provides a method of starting conversions at fixed intervals. If the trigger
signal is still set when the conversion completes, a new conversion will not be started. If
another positive edge occurs on the trigger signal during conversion, the edge will be
ignored. Note that an interrupt flag will be set even if the specific interrupt is disabled or
the Global Interrupt Enable bit in SREG is cleared. A conversion can thus be triggered
without causing an interrupt. However, the interrupt flag must be cleared in order to trigger a new conversion at the next interrupt event.
245
4317B–AVR–02/05
Figure 116. ADC Auto Trigger Logic
ADTS[2:0]
PRESCALER
START
CLKADC
ADATE
ADIF
SOURCE 1
.
.
.
.
CONVERSION
LOGIC
EDGE
DETECTOR
SOURCE n
ADSC
Using the ADC Interrupt Flag as a trigger source makes the ADC start a new conversion
as soon as the ongoing conversion has finished. The ADC then operates in Free Running mode, constantly sampling and updating the ADC Data Register. The first
conversion must be started by writing a logical one to the ADSC bit in ADCSRA. In this
mode the ADC will perform successive conversions independently of whether the ADC
Interrupt Flag, ADIF is cleared or not. The free running mode is not allowed on the
amplified channels.
If Auto Triggering is enabled, single conversions can be started by writing ADSC in
ADCSRA to one. ADSC can also be used to determine if a conversion is in progress.
The ADSC bit will be read as one during a conversion, independently of how the conversion was started.
Prescaling and
Conversion Timing
Figure 117. ADC Prescaler
ADEN
START
Reset
7-BIT ADC PRESCALER
CK/64
CK/128
CK/32
CK/8
CK/16
CK/4
CK/2
CK
ADPS0
ADPS1
ADPS2
ADC CLOCK SOURCE
By default, the successive approximation circuitry requires an input clock frequency
between 50 kHz and 2 MHz to get maximum resolution. If a lower resolution than 10 bits
is needed, the input clock frequency to the ADC can be higher than 2 MHz to get a
higher sample rate.
The ADC module contains a prescaler, which generates an acceptable ADC clock frequency from any CPU frequency above 100 kHz. The prescaling is set by the ADPS bits
in ADCSRA. The prescaler starts counting from the moment the ADC is switched on by
setting the ADEN bit in ADCSRA. The prescaler keeps running for as long as the ADEN
bit is set, and is continuously reset when ADEN is low.
246
AT90PWM2/3
4317B–AVR–02/05
AT90PWM2/3
When initiating a single ended conversion by setting the ADSC bit in ADCSRA, the conversion starts at the following rising edge of the ADC clock cycle. See “Changing
Channel or Reference Selection” on page 248 for details on differential conversion
timing.
A normal conversion takes 13 ADC clock cycles. The first conversion after the ADC is
switched on (ADEN in ADCSRA is set) takes 25 ADC clock cycles in order to initialize
the analog circuitry.
The actual sample-and-hold takes place 3.5 ADC clock cycles after the start of a normal
conversion and 13.5 ADC clock cycles after the start of an first conversion. When a conversion is complete, the result is written to the ADC Data Registers, and ADIF is set. In
Single Conversion mode, ADSC is cleared simultaneously. The software may then set
ADSC again, and a new conversion will be initiated on the first rising ADC clock edge.
When Auto Triggering is used, the prescaler is reset when the trigger event occurs. This
assures a fixed delay from the trigger event to the start of conversion. In this mode, the
sample-and-hold takes place two ADC clock cycles after the rising edge on the trigger
source signal. Three additional CPU clock cycles are used for synchronization logic.
In Free Running mode, a new conversion will be started immediately after the conversion completes, while ADSC remains high. For a summary of conversion times, see
Table 98.
Figure 118. ADC Timing Diagram, First Conversion (Single Conversion Mode)
Next
Conversion
First Conversion
Cycle Number
1
2
12
13
14
16
15
17
18
19
20
21
22
24
23
25
1
2
3
ADC Clock
ADEN
ADSC
ADIF
Sign and MSB of Result
ADCH
LSB of Result
ADCL
MUX and REFS
Update
MUX
and REFS
Update
Conversion
Complete
Sample & Hold
Figure 119. ADC Timing Diagram, Single Conversion
One Conversion
Cycle Number
1
2
3
4
5
6
7
8
9
10
11
12
Next Conversion
13
14
15
16
1
2
3
ADC Clock
ADSC
ADIF
ADCH
Sign and MSB of Result
ADCL
LSB of Result
Sample & Hold
MUX and REFS
Update
Conversion
Complete
MUX and REFS
Update
247
4317B–AVR–02/05
Figure 120. ADC Timing Diagram, Auto Triggered Conversion
One Conversion
Cycle Number
1
2
3
4
5
6
7
Next Conversion
8
13
14
15
16
1
2
ADC Clock
Trigger
Source
ADATE
ADIF
ADCH
Sign and MSB of Result
ADCL
LSB of Result
Prescaler
Reset
Sample &
Hold
Prescaler
Reset
Conversion
Complete
MUX and REFS
Update
Figure 121. ADC Timing Diagram, Free Running Conversion
One Conversion
Cycle Number
14
15
Next Conversion
16
1
2
3
4
ADC Clock
ADSC
ADIF
ADCH
Sign and MSB of Result
ADCL
LSB of Result
Sample & Hold
Conversion
Complete
MUX and REFS
Update
Table 98. ADC Conversion Time
Condition
Sample & Hold
(Cycles from Start of Conversion)
Conversion Time
(Cycles)
Changing Channel or
Reference Selection
248
First
Conversion
Normal
Conversion,
Single Ended
Auto Triggered
Conversion
13.5
3.5
2
25
15.5
16
The MUXn and REFS1:0 bits in the ADMUX Register are single buffered through a temporary register to which the CPU has random access. This ensures that the channels
and reference selection only takes place at a safe point during the conversion. The
channel and reference selection is continuously updated until a conversion is started.
Once the conversion starts, the channel and reference selection is locked to ensure a
sufficient sampling time for the ADC. Continuous updating resumes in the last ADC
clock cycle before the conversion completes (ADIF in ADCSRA is set). Note that the
conversion starts on the following rising ADC clock edge after ADSC is written. The user
is thus advised not to write new channel or reference selection values to ADMUX until
one ADC clock cycle after ADSC is written.
AT90PWM2/3
4317B–AVR–02/05
AT90PWM2/3
If Auto Triggering is used, the exact time of the triggering event can be indeterministic.
Special care must be taken when updating the ADMUX Register, in order to control
which conversion will be affected by the new settings.
If both ADATE and ADEN is written to one, an interrupt event can occur at any time. If
the ADMUX Register is changed in this period, the user cannot tell if the next conversion
is based on the old or the new settings. ADMUX can be safely updated in the following
ways:
1. When ADATE or ADEN is cleared.
2. During conversion, minimum one ADC clock cycle after the trigger event.
3. After a conversion, before the interrupt flag used as trigger source is cleared.
When updating ADMUX in one of these conditions, the new settings will affect the next
ADC conversion.
In order to start a conversion on an amplified channel, there is a dedicated ADASCR bit
in ADCSRB register which wait for the next amplifier trigger event before really starting
the conversion by an hardware setting of the ADSC bit in ADCSRA register.
ADC Input Channels
ADC Voltage Reference
When changing channel selections, the user should observe the following guidelines to
ensure that the correct channel is selected:
•
In Single Conversion mode, always select the channel before starting the
conversion. The channel selection may be changed one ADC clock cycle after
writing one to ADSC. However, the simplest method is to wait for the conversion to
complete before changing the channel selection.
•
In Free Running mode, always select the channel before starting the first
conversion. The channel selection may be changed one ADC clock cycle after
writing one to ADSC. However, the simplest method is to wait for the first conversion
to complete, and then change the channel selection. Since the next conversion has
already started automatically, the next result will reflect the previous channel
selection. Subsequent conversions will reflect the new channel selection.
•
In Free Running mode, because the amplifier clear the ADSC bit at the end of an
amplified conversion, it is not possible to use the free running mode, unless ADSC
bit is set again by soft at the end of each conversion.
The reference voltage for the ADC (VREF) indicates the conversion range for the ADC.
Single ended channels that exceed VREF will result in codes close to 0x3FF. VREF can be
selected as either AVCC, internal 2.56V reference, or external AREF pin.
AVCC is connected to the ADC through a passive switch. The internal 2.56V reference is
generated from the internal bandgap reference (VBG) through an internal amplifier. In
either case, the external AREF pin is directly connected to the ADC, and the reference
voltage can be made more immune to noise by connecting a capacitor between the
AREF pin and ground. VREF can also be measured at the AREF pin with a high impedant
voltmeter. Note that VREF is a high impedant source, and only a capacitive load should
be connected in a system.
If the user has a fixed voltage source connected to the AREF pin, the user may not use
the other reference voltage options in the application, as they will be shorted to the
external voltage. If no external voltage is applied to the AREF pin, the user may switch
between AVCC and 2.56V as reference selection. The first ADC conversion result after
switching reference voltage source may be inaccurate, and the user is advised to discard this result.
249
4317B–AVR–02/05
If differential channels are used, the selected reference should not be closer to AVCC
than indicated in Table 135 on page 315.
ADC Noise Canceler
The ADC features a noise canceler that enables conversion during sleep mode to
reduce noise induced from the CPU core and other I/O peripherals. The noise canceler
can be used with ADC Noise Reduction and Idle mode. To make use of this feature, the
following procedure should be used:
1. Make sure that the ADC is enabled and is not busy converting. Single Conversion mode must be selected and the ADC conversion complete interrupt
must be enabled.
2. Enter ADC Noise Reduction mode (or Idle mode). The ADC will start a conversion once the CPU has been halted.
3. If no other interrupts occur before the ADC conversion completes, the ADC
interrupt will wake up the CPU and execute the ADC Conversion Complete
interrupt routine. If another interrupt wakes up the CPU before the ADC conversion is complete, that interrupt will be executed, and an ADC Conversion
Complete interrupt request will be generated when the ADC conversion
completes. The CPU will remain in active mode until a new sleep command
is executed.
Note that the ADC will not be automatically turned off when entering other sleep modes
than Idle mode and ADC Noise Reduction mode. The user is advised to write zero to
ADEN before entering such sleep modes to avoid excessive power consumption.
If the ADC is enabled in such sleep modes and the user wants to perform differential
conversions, the user is advised to switch the ADC off and on after waking up from
sleep to prompt an extended conversion to get a valid result.
Analog Input Circuitry
The analog input circuitry for single ended channels is illustrated in Figure 122 An analog source applied to ADCn is subjected to the pin capacitance and input leakage of that
pin, regardless of whether that channel is selected as input for the ADC. When the channel is selected, the source must drive the S/H capacitor through the series resistance
(combined resistance in the input path).
The ADC is optimized for analog signals with an output impedance of approximately
10 kΩ or less. If such a source is used, the sampling time will be negligible. If a source
with higher impedance is used, the sampling time will depend on how long time the
source needs to charge the S/H capacitor, with can vary widely. The user is recommended to only use low impedant sources with slowly varying signals, since this
minimizes the required charge transfer to the S/H capacitor.
If differential gain channels are used, the input circuitry looks somewhat different,
although source impedances of a few hundred kΩ or less is recommended.
Signal components higher than the Nyquist frequency (fADC/2) should not be present for
either kind of channels, to avoid distortion from unpredictable signal convolution. The
user is advised to remove high frequency components with a low-pass filter before
applying the signals as inputs to the ADC.
250
AT90PWM2/3
4317B–AVR–02/05
AT90PWM2/3
Figure 122. Analog Input Circuitry
IIH
ADCn
1..100 kΩ
CS/H= 14 pF
IIL
VCC/2
Analog Noise Canceling
Techniques
Digital circuitry inside and outside the device generates EMI which might affect the
accuracy of analog measurements. If conversion accuracy is critical, the noise level can
be reduced by applying the following techniques:
1. Keep analog signal paths as short as possible. Make sure analog tracks run
over the analog ground plane, and keep them well away from high-speed
switching digital tracks.
2. The AVCC pin on the device should be connected to the digital VCC supply
voltage via an LC network as shown in Figure 123.
3. Use the ADC noise canceler function to reduce induced noise from the CPU.
4. If any ADC port pins are used as digital outputs, it is essential that these do
not switch while a conversion is in progress.
Figure 123. ADC Power Connections
VCC
GND
(ADC0) PE2
(ADC1) PD4
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
32
31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
PB7(ADC4)
PB6 (ADC7)
PB5 (ADC6)
PC7 (D2A)
PB4 (AMP0+)
PB3 (AMP0-)
PC6 (ADC10/ACMP1)
AREF
AGND
AVCC
PC5 (ADC9/AMP1+)
PC4 (ADC8/AMP1-)
PB2 (ADC5)
PD7 (ACMP0)
PD6 (ADC3/ACMPM)
PD5 (ADC2/ACMP2)
10µH
100nF
Analog Ground Plane
Offset Compensation
Schemes
The gain stage has a built-in offset cancellation circuitry that nulls the offset of differential measurements as much as possible. The remaining offset in the analog path can be
measured directly by shortening both differential inputs using the AMPxIS bit with both
inputs unconnected. (See “Amplifier 0 Control and Status register – AMP0CSR” on page
251
4317B–AVR–02/05
263. and See “Amplifier 1Control and Status register – AMP1CSR” on page 264.). This
offset residue can be then subtracted in software from the measurement results. Using
this kind of software based offset correction, offset on any channel can be reduced
below one LSB.
ADC Accuracy Definitions
An n-bit single-ended ADC converts a voltage linearly between GND and VREF in 2n
steps (LSBs). The lowest code is read as 0, and the highest code is read as 2n-1.
Several parameters describe the deviation from the ideal behavior:
252
AT90PWM2/3
4317B–AVR–02/05
AT90PWM2/3
•
Offset: The deviation of the first transition (0x000 to 0x001) compared to the ideal
transition (at 0.5 LSB). Ideal value: 0 LSB.
Figure 124. Offset Error
Output Code
Ideal ADC
Actual ADC
Offset
Error
•
VREF Input Voltage
Gain Error: After adjusting for offset, the Gain Error is found as the deviation of the
last transition (0x3FE to 0x3FF) compared to the ideal transition (at 1.5 LSB below
maximum). Ideal value: 0 LSB
Figure 125. Gain Error
Output Code
Gain
Error
Ideal ADC
Actual ADC
VREF Input Voltage
253
4317B–AVR–02/05
•
Integral Non-linearity (INL): After adjusting for offset and gain error, the INL is the
maximum deviation of an actual transition compared to an ideal transition for any
code. Ideal value: 0 LSB.
Figure 126. Integral Non-linearity (INL)
Output Code
INL
Ideal ADC
Actual ADC
VREF
•
Input Voltage
Differential Non-linearity (DNL): The maximum deviation of the actual code width
(the interval between two adjacent transitions) from the ideal code width (1 LSB).
Ideal value: 0 LSB.
Figure 127. Differential Non-linearity (DNL)
Output Code
0x3FF
1 LSB
DNL
0x000
0
254
VREF Input Voltage
•
Quantization Error: Due to the quantization of the input voltage into a finite number
of codes, a range of input voltages (1 LSB wide) will code to the same value. Always
± 0.5 LSB.
•
Absolute Accuracy: The maximum deviation of an actual (unadjusted) transition
compared to an ideal transition for any code. This is the compound effect of offset,
gain error, differential error, non-linearity, and quantization error. Ideal value: ± 0.5
LSB.
AT90PWM2/3
4317B–AVR–02/05
AT90PWM2/3
ADC Conversion Result
After the conversion is complete (ADIF is high), the conversion result can be found in
the ADC Result Registers (ADCL, ADCH).
For single ended conversion, the result is:
V IN ⋅ 1023
ADC = -------------------------V REF
where VIN is the voltage on the selected input pin and VREF the selected voltage reference (see Table 100 on page 257 and Table 101 on page 257). 0x000 represents
analog ground, and 0x3FF represents the selected reference voltage.
If differential channels are used, the result is:
( V POS – V NEG ) ⋅ GAIN ⋅ 512
ADC = -----------------------------------------------------------------------V REF
where VPOS is the voltage on the positive input pin, VNEG the voltage on the negative
input pin, GAIN the selected gain factor and VREF the selected voltage reference. The
result is presented in two’s complement form, from 0x200 (-512d) through 0x1FF
(+511d). Note that if the user wants to perform a quick polarity check of the result, it is
sufficient to read the MSB of the result (ADC9 in ADCH). If the bit is one, the result is
negative, and if this bit is zero, the result is positive. Figure 128 shows the decoding of
the differential input range.
Table 82 shows the resulting output codes if the differential input channel pair (ADCn ADCm) is selected with a reference voltage of VREF.
Figure 128. Differential Measurement Range
Output Code
0x1FF
0x000
- VREF /Gain
0x3FF
0
VREF/Gain Differential Input
Voltage (Volts)
0x200
255
4317B–AVR–02/05
Table 99. Correlation Between Input Voltage and Output Codes
VADCn
Read code
Corresponding decimal value
VADCm + VREF /GAIN
0x1FF
511
VADCm + 0.999 VREF /GAIN
0x1FF
511
VADCm + 0.998 VREF /GAIN
0x1FE
510
...
...
...
VADCm + 0.001 VREF /GAIN
0x001
1
VADCm
0x000
0
VADCm - 0.001 VREF /GAIN
0x3FF
-1
...
...
...
VADCm - 0.999 VREF /GAIN
0x201
-511
VADCm - VREF /GAIN
0x200
-512
Example 1:
–
ADMUX = 0xED (ADC3 - ADC2, 10x gain, 2.56V reference, left adjusted result)
–
Voltage on ADC3 is 300 mV, voltage on ADC2 is 500 mV.
–
ADCR = 512 * 10 * (300 - 500) / 2560 = -400 = 0x270
–
ADCL will thus read 0x00, and ADCH will read 0x9C.
Writing zero to ADLAR right adjusts the result: ADCL = 0x70, ADCH = 0x02.
Example 2:
256
–
ADMUX = 0xFB (ADC3 - ADC2, 1x gain, 2.56V reference, left adjusted result)
–
Voltage on ADC3 is 300 mV, voltage on ADC2 is 500 mV.
–
ADCR = 512 * 1 * (300 - 500) / 2560 = -41 = 0x029.
–
ADCL will thus read 0x40, and ADCH will read 0x0A.
Writing zero to ADLAR right adjusts the result: ADCL = 0x00, ADCH = 0x29.
AT90PWM2/3
4317B–AVR–02/05
AT90PWM2/3
ADC Register Description
The ADC of the AT90PWM2/3 is controlled through 3 different registers. The ADCSRA
and The ADCSRB registers which are the ADC Control and Status registers, and the
ADMUX which allows to select the Vref source and the channel to be converted.
The conversion result is stored on ADCH and ADCL register which contain respectively
the most significant bits and the less significant bits.
ADC Multiplexer Register –
ADMUX
Bit
7
6
5
4
3
2
1
0
REFS1
REFS0
ADLAR
-
MUX3
MUX2
MUX1
MUX0
Read/Write
R/W
R/W
R/W
-
R/W
R/W
R/W
R/W
Initial Value
0
0
0
0
0
0
0
0
ADMUX
• Bit 7, 6 – REFS1, 0: ADC Vref Selection Bits
These 2 bits determine the voltage reference for the ADC.
The different setting are shown in Table 100.
Table 100. ADC Voltage Reference Selection
REFS1
REFS0
Description
0
0
External Vref on AREF pin, Internal Vref is switched off
0
1
AVcc with external capacitor connected on the AREF pin
1
0
Reserved
1
1
Internal 2.56V Reference voltage with external capacitor connected
on the AREF pin
If these bits are changed during a conversion, the change will not take effect until this
conversion is complete (it means while the ADIF bit in ADCSRA register is set).
In case the internal Vref is selected, it is turned ON as soon as an analog feature
needed it is set.
• Bit 5 – ADLAR: ADC Left Adjust Result
Set this bit to left adjust the ADC result.
Clear it to right adjust the ADC result.
The ADLAR bit affects the configuration of the ADC result data registers. Changing this
bit affects the ADC data registers immediately regardless of any on going conversion.
For a complete description of this bit, see Section “ADC Result Data Registers – ADCH
and ADCL”, page 260.
• Bit 3, 2, 1, 0 – MUX3, MUX2, MUX1, MUX0: ADC Channel Selection Bits
These 4 bits determine which analog inputs are connected to the ADC input. The different setting are shown in Table 101.
Table 101. ADC Input Channel Selection
MUX3
MUX2
MUX1
MUX0
Description
0
0
0
0
ADC0
0
0
0
1
ADC1
0
0
1
0
ADC2
0
0
1
1
ADC3
0
1
0
0
ADC4
257
4317B–AVR–02/05
Table 101. ADC Input Channel Selection
MUX3
MUX2
MUX1
MUX0
Description
0
1
0
1
ADC5
0
1
1
0
ADC6
0
1
1
1
ADC7
1
0
0
0
ADC8
1
0
0
1
ADC9
1
0
1
0
ADC10
1
0
1
1
AMP0
1
1
0
0
AMP1 (- is ADC8, + is ADC9)
1
1
0
1
Reserved
1
1
1
0
Bandgap
1
1
1
1
GND
If these bits are changed during a conversion, the change will not take effect until this
conversion is complete (it means while the ADIF bit in ADCSRA register is set).
ADC Control and Status
Register A – ADCSRA
Bit
7
6
5
4
3
2
1
0
ADEN
ADSC
ADATE
ADIF
ADIE
ADPS2
ADPS1
ADPS0
Read/Write
R/W
R/W
R/W
R
R/W
R/W
R/W
R/W
Initial Value
0
0
0
0
0
0
0
0
ADCSRA
• Bit 7 – ADEN: ADC Enable Bit
Set this bit to enable the ADC.
Clear this bit to disable the ADC.
Clearing this bit while a conversion is running will take effect at the end of the
conversion.
• Bit 6– ADSC: ADC Start Conversion Bit
Set this bit to start a conversion in single conversion mode or to start the first conversion
in free running mode.
Cleared by hardware when the conversion is complete. Writing this bit to zero has no
effect.
The first conversion performs the initialization of the ADC.
• Bit 5 – ADATE: ADC Auto trigger Enable Bit
Set this bit to enable the auto triggering mode of the ADC.
Clear it to return in single conversion mode.
In auto trigger mode the trigger source is selected by the ADTS bits in the ADCSRB register. See Table 103 on page 259.
• Bit 4– ADIF: ADC Interrupt Flag
Set by hardware as soon as a conversion is complete and the Data register are updated
with the conversion result.
Cleared by hardware when executing the corresponding interrupt handling vector.
Alternatively, ADIF can be cleared by writing it to logical one.
• Bit 3– ADIE: ADC Interrupt Enable Bit
258
AT90PWM2/3
4317B–AVR–02/05
AT90PWM2/3
Set this bit to activate the ADC end of conversion interrupt.
Clear it to disable the ADC end of conversion interrupt.
• Bit 2, 1, 0– ADPS2, ADPS1, ADPS0: ADC Prescaler Selection Bits
These 3 bits determine the division factor between the system clock frequency and input
clock of the ADC.
The different setting are shown in Table 102.
Table 102. ADC Prescaler Selection
ADPS2
ADC Control and Status
Register B– ADCSRB
ADPS1
ADPS0
Division Factor
0
0
0
2
0
0
1
2
0
1
0
4
0
1
1
8
1
0
0
16
1
0
1
32
1
1
0
64
1
1
1
128
Bit
7
6
5
4
3
2
1
0
ADHSM
-
-
ADASCR
ADTS3
ADTS2
ADTS1
ADTS0
Read/Write
-
-
-
R/W
R/W
R/W
R/W
R/W
Initial Value
0
0
0
0
0
0
0
0
ADCSRB
• Bit 7 – ADHSM: ADC High Speed Mode
Writing this bit to one enables the ADC High Speed mode. Set this bit if you wish to
convert with an ADC clock frequency higher than 200KHz.
• Bit 4– ADASCR: Analog to Digital Conversion on Amplified Channel Start
Conversion Request Bit
Set this to request a conversion on an amplified channel.
Cleared by hardware as soon as the Analog to Digital Conversion is started.
Alternatively, this bit can be cleared by writing it to logical zero.
• Bit 3, 2, 1, 0– ADTS3:ADTS0: ADC Auto Trigger Source Selection Bits
These bits are only necessary in case the ADC works in auto trigger mode. It means if
ADATE bit in ADCSRA register is set.
In accordance with the Table 103, these 3 bits select the interrupt event which will generate the trigger of the start of conversion. The start of conversion will be generated by
the rising edge of the selected interrupt flag whether the interrupt is enabled or not. In
case of trig on PSCnASY event, there is no flag. So in this case a conversion will start
each time the trig event appears and the previous conversion is completed..
Table 103. ADC Auto Trigger Source Selection
ADTS3
ADTS2
ADTS1
ADTS0
Description
0
0
0
0
Free Running Mode
0
0
0
1
Analog Comparator 0
0
0
1
0
External Interrupt Request 0
259
4317B–AVR–02/05
Table 103. ADC Auto Trigger Source Selection
ADTS3
ADC Result Data Registers –
ADCH and ADCL
ADTS2
ADTS1
ADTS0
Description
0
0
1
1
Timer/Counter0 Compare Match
0
1
0
0
Timer/Counter0 Overflow
0
1
0
1
Timer/Counter1 Compare Match B
0
1
1
0
Timer/Counter1 Overflow
0
1
1
1
Timer/Counter1 Capture Event
1
0
0
0
PSC0ASY Event
1
0
0
1
PSC1ASY Event
1
0
1
0
PSC2ASY Event
1
0
1
1
Analog comparator 1
1
1
0
0
Analog comparator 2
1
1
0
1
Reserved
1
1
1
0
Reserved
1
1
1
1
Reserved
When an ADC conversion is complete, the conversion results are stored in these two
result data registers.
When the ADCL register is read, the two ADC result data registers can’t be updated until
the ADCH register has also been read.
Consequently, in 10-bit configuration, the ADCL register must be read first before the
ADCH.
Nevertheless, to work easily with only 8-bit precision, there is the possibility to left adjust
the result thanks to the ADLAR bit in the ADCSRA register. Like this, it is sufficient to
only read ADCH to have the conversion result.
ADLAR = 0
Bit
Read/Write
Initial Value
7
6
5
4
3
2
1
0
-
-
-
-
-
-
ADC9
ADC8
ADCH
ADC7
ADC6
ADC5
ADC4
ADC3
ADC2
ADC1
ADC0
ADCL
R
R
R
R
R
R
R
R
R
R
R
R
R
R
R
R
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
ADLAR = 1
Bit
Read/Write
Initial Value
Digital Input Disable Register
0 – DIDR0
260
Bit
7
6
5
4
3
2
1
0
ADC9
ADC8
ADC7
ADC6
ADC5
ADC4
ADC3
ADC2
ADCH
ADC1
ADC0
-
-
-
-
-
-
ADCL
R
R
R
R
R
R
R
R
R
R
R
R
R
R
R
R
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
7
6
5
4
3
2
1
0
AT90PWM2/3
4317B–AVR–02/05
AT90PWM2/3
ADC7D
ADC6D
ADC5D
ADC4D
ADC3D
ACMPM
ADC2D
ACMP2D
ADC1D
ADC0D
Read/Write
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
Initial Value
0
0
0
0
0
0
0
0
DIDR0
• Bit 7:0 – ADC7D..ADC0D: ACMP2:1 and ADC7:0 Digital Input Disable
When this bit is written logic one, the digital input buffer on the corresponding ADC pin is
disabled. The corresponding PIN Register bit will always read as zero when this bit is
set. When an analog signal is applied to the ADC7..0 pin and the digital input from this
pin is not needed, this bit should be written logic one to reduce power consumption in
the digital input buffer.
Digital Input Disable Register
1– DIDR1
Bit
7
6
5
-
-
ACMP0D
4
3
AMP0PD AMP0ND
2
1
0
ADC10D
ACMP1D
ADC9D
AMP1PD
ADC8D
AMP1ND
Read/Write
-
-
R/W
R/W
R/W
R/W
R/W
R/W
Initial Value
0
0
0
0
0
0
0
0
DIDR1
• Bit 5:0 – ACMP0D, AMP0+D, AMP0-D, ADC10D..ADC8D: ACMP0, AMP1:0 and
ADC10:8 Digital Input Disable
When this bit is written logic one, the digital input buffer on the corresponding ADC pin is
disabled. The corresponding PIN Register bit will always read as zero when this bit is
set. When an analog signal is applied to an analog pin and the digital input from this pin
is not needed, this bit should be written logic one to reduce power consumption in the
digital input buffer.
Amplifier
The AT90PWM2/3 features two differential amplified channels with programmable 5, 10,
20, and 40 gain stage.
Because the amplifier is a switching capacitor amplifier, it needs to be clocked by a synchronization signal called in this document the amplifier synchronization clock. To
ensure an accurate result, the amplifier input needs to have a quite stable input value
during at least 4 Amplifier synchronization clock periods.
Amplified conversions can be synchronized to PSC events (See “Synchronization
Source Description in One/Two/Four Ramp Modes” on page 168 and “Synchronization
Source Description in Centered Mode” on page 169) or to the internal clock CKADC equal
to eighth the ADC clock frequency. In case the synchronization is done the ADC clock
divided by 8, this synchronization is done automatically by the ADC interface in such a
way that the sample-and-hold occurs at a specific phase of CKADC2. A conversion initiated by the user (i.e., all single conversions, and the first free running conversion) when
CKADC2 is low will take the same amount of time as a single ended conversion (13 ADC
clock cycles from the next prescaled clock cycle). A conversion initiated by the user
when CK ADC2 is high will take 14 ADC clock cycles due to the synchronization
mechanism.
The normal way to use the amplifier is to select a synchronization clock via the
AMPxMX3:0 bits in the AMPxCSR register. Then the amplifier can be switched on, and
the amplification is done on each synchronization event.
In order to start an amplified Analog to Digital Conversion on the amplified channel, the
ADMUX must be configured as specified on Table 101 on page 257.
The ADC starting requirement is done by setting the ADASCR (Analog to Digital Conversion on Amplified Channel Start Conversion Request ) bit in the ADCSRB register.
261
4317B–AVR–02/05
Then, the ADSC bit of the ADCSRA Register is set on the next amplifier clock event,
and a conversion is started.
Until the conversion is not achieved, it is not possible to start a conversion on another
channel.
In order to have a better understanding of the functioning of the amplifier synchronization, a timing diagram example is shown Figure 129.
Delta V
4th stable sample
Signal to be
measured
PSC
Block
PSCn_ASY
AMPLI_clk
(Sync Clock)
CK ADC
Amplifier
Block
Amplifier Sample
Enable
Amplifier Hold
Value
Valid sample
ADASCR
ADC
ADSC
ADC
Sampling
ADC Result Ready
Figure 129. Amplifier synchronization timing diagram
It is also possible to auto trigger conversion on the amplified channel. In this case, the
conversion is started at the next amplifier clock event following the last auto trigger
event selected thanks to the ADTS bits in the ADCSRB register. In auto trigger conversion, the free running mode is not possible unless the ADSC bit in ADCSRA is set by
soft after each conversion.
262
AT90PWM2/3
4317B–AVR–02/05
AT90PWM2/3
The block diagram of the two amplifiers is shown on Figure 130.
+
SAMPLING
AMP0+
AMP0-
Toward ADC MUX
(AMP0)
ADCK/8
ASY0
ASY1
ASY2
00
01
10
01
Sampling
Clock
AMP0EN AMP0IS AMP0G1 AMP0G0
-
-
AMP0TS1AMP0TS0
AMP0CSR
+
SAMPLING
AMP1+
AMP1-
Toward ADC MU
(AMP1)
ADCK/8
ASY0
ASY1
ASY2
00
01
10
01
Sampling
Clock
AMP1EN AMP1IS AMP1G1 AMP1G0
-
-
AMP1TS1AMP1TS0
AMP1CSR
Figure 130. Amplifiers block diagram
Amplifier Control
Registers
The configuration of the amplifiers are controlled via two dedicated registers AMP0CSR
and AMP1CSR. Then the start of conversion is done via the ADC control and status
registers.
The conversion result is stored on ADCH and ADCL register which contain respectively
the most significant bits and the less significant bits.
Amplifier 0 Control and Status
register – AMP0CSR
Bit
7
6
5
4
3
2
1
0
AMP0EN
AMP0IS
AMP0G1
AMP0G0
-
-
AMP0TS1
AMP0TS0
Read/Write
R/W
R/W
R/W
R/W
-
-
R/W
R/W
Initial Value
0
0
0
0
0
0
0
0
AMP0CSR
• Bit 7 – AMP0EN: Amplifier 0 Enable Bit
263
4317B–AVR–02/05
Set this bit to enable the Amplifier 0.
Clear this bit to disable the Amplifier 0.
Clearing this bit while a conversion is running will take effect at the end of the
conversion.
• Bit 6– AMP0IS: Amplifier 0 Input Shunt
Set this bit to short-circuit the Amplifier 0 input.
Clear this bit to normally use the Amplifier 0.
• Bit 5, 4– AMP0G1, 0: Amplifier 0 Gain Selection Bits
These 2 bits determine the gain of the amplifier 0.
The different setting are shown in Table 104.
Table 104. Amplifier 0 Gain Selection
REFS1
REFS0
Description
0
0
Gain 5
0
1
Gain 10
1
0
Gain 20
1
1
Gain 40
To ensure an accurate result, after the gain value has been changed, the amplifier input
needs to have a quite stable input value during at least 4 Amplifier synchronization clock
periods.
• Bit 1, 0– AMP0TS1, AMP0TS0: Amplifier 0 Trigger Source Selection Bits
In accordance with the Table 105, these 2 bits select the event which will generate the
trigger for the amplifier 0. This trigger source is necessary to start the conversion on the
amplified channel.
Table 105. AMP0 Auto Trigger Source Selection
Amplifier 1Control and Status
register – AMP1CSR
AMP0TS1
AMP0TS0
0
0
Auto synchronization on ADC Clock/8
0
1
Trig on PSC0_ASY
1
0
Trig on PSC1_ASY
1
1
Trig on PSC2_ASY
Bit
Description
7
6
5
4
3
2
1
0
AMP1EN
AMP1IS
AMP1G1
AMP1G0
-
-
AMP1TS1
AMP1TS0
Read/Write
R/W
R/W
R/W
R/W
-
-
R/W
R/W
Initial Value
0
0
0
0
0
0
0
0
AMP1CSR
• Bit 7 – AMP1EN: Amplifier 1 Enable Bit
Set this bit to enable the Amplifier 1.
Clear this bit to disable the Amplifier 1.
Clearing this bit while a conversion is running will take effect at the end of the
conversion.
• Bit 6– AMP1IS: Amplifier 1 Input Shunt
Set this bit to short-circuit the Amplifier 1 input.
Clear this bit to normally use the Amplifier 1.
264
AT90PWM2/3
4317B–AVR–02/05
AT90PWM2/3
• Bit 5, 4– AMP1G1, 0: Amplifier 1 Gain Selection Bits
These 2 bits determine the gain of the amplifier 0.
The different setting are shown in Table 106.
Table 106. Amplifier 1 Gain Selection
REFS1
REFS0
Description
0
0
Gain 5
0
1
Gain 10
1
0
Gain 20
1
1
Gain 40
To ensure an accurate result, after the gain value has been changed, the amplifier input
needs to have a quite stable input value during at least 4 Amplifier synchronization clock
periods.
• Bit 1, 0– AMP1TS1, AMP1TS0: Amplifier 1 Trigger Source Selection Bits
In accordance with the Table 107, these 2 bits select the event which will generate the
trigger for the amplifier 1. This trigger source is necessary to start the conversion on the
amplified channel.
Table 107. AMP1 Auto Trigger source selection
AMP1TS1
AMP1TS0
Description
0
0
Auto synchronization on ADC Clock/8
0
1
Trig on PSC0_ASY
1
0
Trig on PSC1_ASY
1
1
Trig on PSC2_ASY
265
4317B–AVR–02/05
Digital to Analog Converter - DAC
Features
•
•
•
•
•
10 bits resolution
8 bits linearity
+/- 0.5 LSB accuracy between 100mV and AVcc-100mV
Vout = DAC*Vref/1023
The DAC could be connected to the negative inputs of the analog comparators and/or to
a dedicated output driver.
• The output impedance of the driver is lower than 1KOhms. So the driver is able to load a
1nF capacitance in parallel with a resistor higher than 33K with a time constant around
1us.
The AT90PWM2/3 features a 10-bit Digital to Analog Converter. This DAC can be used
for the analog comparators and/or can be output on the D2A pin of the microcontroller
via a dedicated driver.
The DAC has a separate analog supply voltage pin, AVCC. AVCC must not differ more
than ± 0.3V from VCC. See the paragraph “ADC Noise Canceler” on page 250 on how to
connect this pin.
The reference voltage is the same as the one used for the ADC, See “ADC Multiplexer
Register – ADMUX” on page 257.. These nominally 2.56V Vref or AVCC are provided
On-chip. The voltage reference may be externally decoupled at the AREF pin by a
capacitor for better noise performance.
266
AT90PWM2/3
4317B–AVR–02/05
AT90PWM2/3
Figure 131. Digital to Analog Converter Block Schematic
DAC
Result
D2A pin
VRef
DAC
Output
Driver
10
1
0
10
10
DAC High bits
DAC Low bits
Sources
DACH
Update DAC
Trigger
Edge
Detector
DAATE
DACL
DATS2
DATS1
DATS0
-
DALA
DAOE
DAEN
DACON
267
4317B–AVR–02/05
Operation
The Digital to Analog Converter generates an analog signal proportional to the value of
the DAC registers value.
In order to have an accurate sampling frequency control, there is the possibility to
update the DAC input values through different trigger events.
Starting a Conversion
The DAC is configured thanks to the DACON register. As soon as the DAEN bit in
DACON register is set, the DAC converts the value present on the DACH and DACL
registers in accordance with the register DACON setting.
Alternatively, a conversion can be triggered automatically by various sources. Auto Triggering is enabled by setting the DAC Auto Trigger Enable bit, DAATE in DACON. The
trigger source is selected by setting the DAC Trigger Select bits, DATS in DACON (See
description of the DATS bits for a list of the trigger sources). When a positive edge
occurs on the selected trigger signal, the DAC converts the value present on the DACH
and DACL registers in accordance with the register DACON setting. This provides a
method of starting conversions at fixed intervals. If the trigger signal is still set when the
conversion completes, a new conversion will not be started. If another positive edge
occurs on the trigger signal during conversion, the edge will be ignored. Note that an
interrupt flag will be set even if the specific interrupt is disabled or the Global Interrupt
Enable bit in SREG is cleared. A conversion can thus be triggered without causing an
interrupt. However, the interrupt flag must be cleared in order to trigger a new conversion at the next interrupt event.
DAC Voltage Reference
The reference voltage for the ADC (VREF) indicates the conversion range for the DAC.
VREF can be selected as either AVCC, internal 2.56V reference, or external AREF pin.
AVCC is connected to the DAC through a passive switch. The internal 2.56V reference is
generated from the internal bandgap reference (VBG) through an internal amplifier. In
either case, the external AREF pin is directly connected to the DAC, and the reference
voltage can be made more immune to noise by connecting a capacitor between the
AREF pin and ground. VREF can also be measured at the AREF pin with a high impedant
voltmeter. Note that VREF is a high impedant source, and only a capacitive load should
be connected in a system.
If the user has a fixed voltage source connected to the AREF pin, the user may not use
the other reference voltage options in the application, as they will be shorted to the
external voltage. If no external voltage is applied to the AREF pin, the user may switch
between AVCC and 2.56V as reference selection. The first DAC conversion result after
switching reference voltage source may be inaccurate, and the user is advised to discard this result.
268
AT90PWM2/3
4317B–AVR–02/05
AT90PWM2/3
DAC Register Description
The DAC is controlled via three dedicated registers:
Digital to Analog Conversion
Control Register – DACON
•
The DACON register which is used for DAC configuration
•
DACH and DACL which are used to set the value to be converted.
Bit
7
6
5
4
3
2
1
0
DAATE
DATS2
DATS1
DATS0
-
DALA
DAOE
DAEN
Read/Write
R/W
R/W
R/W
R/W
-
R/W
R/W
R/W
Initial Value
0
0
0
0
0
0
0
0
DACON
• Bit 7 – DAATE: DAC Auto Trigger Enable bit
Set this bit to update the DAC input value on the positive edge of the trigger signal
selected with the DACTS2-0 bit in DACON register.
Clear it to automatically update the DAC input when a value is written on DACH register.
• Bit 6:4 – DATS2, DATS1, DATS0: DAC Trigger Selection bits
These bits are only necessary in case the DAC works in auto trigger mode. It means if
DAATE bit is set.
In accordance with the Table 108, these 3 bits select the interrupt event which will generate the update of the DAC input values. The update will be generated by the rising
edge of the selected interrupt flag whether the interrupt is enabled or not.
Table 108. DAC Auto Trigger source selection
DATS2
DATS1
DATS0
Description
0
0
0
Analog comparator 0
0
0
1
Analog comparator 1
0
1
0
External Interrupt Request 0
0
1
1
Timer/Counter0 Compare Match
1
0
0
Timer/Counter0 Overflow
1
0
1
Timer/Counter1 Compare Match B
1
1
0
Timer/Counter1 Overflow
1
1
1
Timer/Counter1 Capture Event
• Bit 2 – DALA: Digital to Analog Left Adjust
Set this bit to left adjust the DAC input data.
Clear it to right adjust the DAC input data.
The DALA bit affects the configuration of the DAC data registers. Changing this bit
affects the DAC output on the next DACH writing.
• Bit 1 – DAOE: Digital to Analog Output Enable bit
Set this bit to output the conversion result on AD2,
Clear it to use the DAC internally.
• Bit 0 – DAEN: Digital to Analog Enable bit
Set this bit to enable the DAC,
Clear it to disable the DAC.
269
4317B–AVR–02/05
Digital to Analog Converter
input Register – DACH and
DACL
DACH and DACL registers contain the value to be converted into analog voltage.
Writing the DACL register forbid the update of the input value until DACH has not been
written too. So the normal way to write a 10-bit value in the DAC register is firstly to write
DACL the DACH.
In order to work easily with only 8 bits, there is the possibility to left adjust the input
value. Like this it is sufficient to write DACH to update the DAC value.
DALA = 0
Bit
Read/Write
Initial Value
7
6
5
4
3
2
1
0
-
-
-
-
-
-
DAC9
DAC8
DACH
DAC7
DAC6
DAC5
DAC4
DAC3
DAC2
DAC1
DAC0
DACL
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
DALA = 1
Bit
Read/Write
Initial Value
7
6
5
4
3
2
1
0
DAC9
DAC8
DAC7
DAC6
DAC5
DAC4
DAC3
DAC2
DACH
DAC1
DAC0
-
-
-
-
-
-
DACL
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
To work with the 10-bit DAC, two registers have to be updated. In order to avoid intermediate value, the DAC input values which are really converted into analog signal are
buffering into unreachable registers. In normal mode, the update of the shadow register
is done when the register DACH is written.
In case DAATE bit is set, the DAC input values will be updated on the trigger event
selected through DATS bits.
In order to avoid wrong DAC input values, the update can only be done after having written respectively DACL and DACH registers. It is possible to work on 8-bit configuration
by only writing the DACH value. In this case, update is done each trigger event.
In case DAATE bit is cleared, the DAC is in an automatic update mode. Writing the
DACH register automatically update the DAC input values with the DACH and DACL
register values.
It means that whatever is the configuration of the DAATE bit, changing the DACL register has no effect on the DAC output until the DACH register has also been updated. So,
to work with 10 bits, DACL must be written first before DACH. To work with 8-bit configuration, writing DACH allows the update of the DAC.
270
AT90PWM2/3
4317B–AVR–02/05
AT90PWM2/3
debugWIRE On-chip
Debug System
Features
•
•
•
•
•
•
•
•
•
•
Overview
The debugWIRE On-chip debug system uses a One-wire, bi-directional interface to control the program flow, execute AVR instructions in the CPU and to program the different
non-volatile memories.
Physical Interface
When the debugWIRE Enable (DWEN) Fuse is programmed and Lock bits are unprogrammed, the debugWIRE system within the target device is activated. The RESET port
pin is configured as a wire-AND (open-drain) bi-directional I/O pin with pull-up enabled
and becomes the communication gateway between target and emulator.
Complete Program Flow Control
Emulates All On-chip Functions, Both Digital and Analog, except RESET Pin
Real-time Operation
Symbolic Debugging Support (Both at C and Assembler Source Level, or for Other HLLs)
Unlimited Number of Program Break Points (Using Software Break Points)
Non-intrusive Operation
Electrical Characteristics Identical to Real Device
Automatic Configuration System
High-Speed Operation
Programming of Non-volatile Memories
Figure 132. The debugWIRE Setup
1.8 - 5.5V
VCC
dW
dW(RESET)
GND
Figure 132 shows the schematic of a target MCU, with debugWIRE enabled, and the
emulator connector. The system clock is not affected by debugWIRE and will always be
the clock source selected by the CKSEL Fuses.
When designing a system where debugWIRE will be used, the following observations
must be made for correct operation:
•
Pull-up resistors on the dW/(RESET) line must not be smaller than 10kΩ. The pullup resistor is not required for debugWIRE functionality.
•
Connecting the RESET pin directly to VCC will not work.
271
4317B–AVR–02/05
Software Break Points
•
Capacitors connected to the RESET pin must be disconnected when using
debugWire.
•
All external reset sources must be disconnected.
debugWIRE supports Program memory Break Points by the AVR Break instruction. Setting a Break Point in AVR Studio ® will insert a BREAK instruction in the Program
memory. The instruction replaced by the BREAK instruction will be stored. When program execution is continued, the stored instruction will be executed before continuing
from the Program memory. A break can be inserted manually by putting the BREAK
instruction in the program.
The Flash must be re-programmed each time a Break Point is changed. This is automatically handled by AVR Studio through the debugWIRE interface. The use of Break
Points will therefore reduce the Flash Data retention. Devices used for debugging purposes should not be shipped to end customers.
Limitations of
debugWIRE
The debugWIRE communication pin (dW) is physically located on the same pin as
External Reset (RESET). An External Reset source is therefore not supported when the
debugWIRE is enabled.
The debugWIRE system accurately emulates all I/O functions when running at full
speed, i.e., when the program in the CPU is running. When the CPU is stopped, care
must be taken while accessing some of the I/O Registers via the debugger (AVR
Studio).
A programmed DWEN Fuse enables some parts of the clock system to be running in all
sleep modes. This will increase the power consumption while in sleep. Thus, the DWEN
Fuse should be disabled when debugWire is not used.
debugWIRE Related
Register in I/O Memory
The following section describes the registers used with the debugWire.
debugWire Data Register –
DWDR
Bit
7
6
5
4
3
2
1
0
DWDR[7:0]
DWDR
Read/Write
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
Initial Value
0
0
0
0
0
0
0
0
The DWDR Register provides a communication channel from the running program in
the MCU to the debugger. This register is only accessible by the debugWIRE and can
therefore not be used as a general purpose register in the normal operations.
272
AT90PWM2/3
4317B–AVR–02/05
AT90PWM2/3
Boot Loader Support
– Read-While-Write
Self-Programming
In AT90PWM2/3, the Boot Loader Support provides a real Read-While-Write Self-Programming mechanism for downloading and uploading program code by the MCU itself.
This feature allows flexible application software updates controlled by the MCU using a
Flash-resident Boot Loader program. The Boot Loader program can use any available
data interface and associated protocol to read code and write (program) that code into
the Flash memory, or read the code from the program memory. The program code
within the Boot Loader section has the capability to write into the entire Flash, including
the Boot Loader memory. The Boot Loader can thus even modify itself, and it can also
erase itself from the code if the feature is not needed anymore. The size of the Boot
Loader memory is configurable with fuses and the Boot Loader has two separate sets of
Boot Lock bits which can be set independently. This gives the user a unique flexibility to
select different levels of protection.
Boot Loader Features
•
•
•
•
•
•
•
Read-While-Write Self-Programming
Flexible Boot Memory Size
High Security (Separate Boot Lock Bits for a Flexible Protection)
Separate Fuse to Select Reset Vector
Optimized Page(1) Size
Code Efficient Algorithm
Efficient Read-Modify-Write Support
Note:
1. A page is a section in the Flash consisting of several bytes (see Table 127 on page
294) used during programming. The page organization does not affect normal
operation.
Application and Boot
Loader Flash Sections
The Flash memory is organized in two main sections, the Application section and the
Boot Loader section (see Figure 134). The size of the different sections is configured by
the BOOTSZ Fuses as shown in Table 114 on page 286 and Figure 134. These two
sections can have different level of protection since they have different sets of Lock bits.
Application Section
The Application section is the section of the Flash that is used for storing the application
code. The protection level for the Application section can be selected by the application
Boot Lock bits (Boot Lock bits 0), see Table 110 on page 277. The Application section
can never store any Boot Loader code since the SPM instruction is disabled when executed from the Application section.
BLS – Boot Loader Section
While the Application section is used for storing the application code, the The Boot
Loader software must be located in the BLS since the SPM instruction can initiate a programming when executing from the BLS only. The SPM instruction can access the
entire Flash, including the BLS itself. The protection level for the Boot Loader section
can be selected by the Boot Loader Lock bits (Boot Lock bits 1), see Table 111 on page
277.
Read-While-Write and No Whether the CPU supports Read-While-Write or if the CPU is halted during a Boot
Loader software update is dependent on which address that is being programmed. In
Read-While-Write Flash
addition to the two sections that are configurable by the BOOTSZ Fuses as described
Sections
above, the Flash is also divided into two fixed sections, the Read-While-Write (RWW)
section and the No Read-While-Write (NRWW) section. The limit between the RWWand NRWW sections is given in Table 115 on page 286 and Figure 134 on page 276.
The main difference between the two sections is:
•
When erasing or writing a page located inside the RWW section, the NRWW section
can be read during the operation.
•
When erasing or writing a page located inside the NRWW section, the CPU is halted
during the entire operation.
273
4317B–AVR–02/05
Note that the user software can never read any code that is located inside the RWW
section during a Boot Loader software operation. The syntax “Read-While-Write section” refers to which section that is being programmed (erased or written), not which
section that actually is being read during a Boot Loader software update.
RWW – Read-While-Write
Section
If a Boot Loader software update is programming a page inside the RWW section, it is
possible to read code from the Flash, but only code that is located in the NRWW section. During an on-going programming, the software must ensure that the RWW section
never is being read. If the user software is trying to read code that is located inside the
RWW section (i.e., by a call/jmp/lpm or an interrupt) during programming, the software
might end up in an unknown state. To avoid this, the interrupts should either be disabled
or moved to the Boot Loader section. The Boot Loader section is always located in the
NRWW section. The RWW Section Busy bit (RWWSB) in the Store Program Memory
Control and Status Register (SPMCSR) will be read as logical one as long as the RWW
section is blocked for reading. After a programming is completed, the RWWSB must be
cleared by software before reading code located in the RWW section. See “Store Program Memory Control and Status Register – SPMCSR” on page 278. for details on how
to clear RWWSB.
NRWW – No Read-While-Write
Section
The code located in the NRWW section can be read when the Boot Loader software is
updating a page in the RWW section. When the Boot Loader code updates the NRWW
section, the CPU is halted during the entire Page Erase or Page Write operation.
Table 109. Read-While-Write Features
274
Which Section does the Zpointer Address During the
Programming?
Which Section Can
be Read During
Programming?
Is the CPU
Halted?
Read-While-Write
Supported?
RWW Section
NRWW Section
No
Yes
NRWW Section
None
Yes
No
AT90PWM2/3
4317B–AVR–02/05
AT90PWM2/3
Figure 133. Read-While-Write vs. No Read-While-Write
Read-While-Write
(RWW) Section
Z-pointer
Addresses RWW
Section
Z-pointer
Addresses NRWW
Section
No Read-While-Write
(NRWW) Section
CPU is Halted
During the Operation
Code Located in
NRWW Section
Can be Read During
the Operation
275
4317B–AVR–02/05
Figure 134. Memory Sections
Program Memory
BOOTSZ = '10'
Program Memory
BOOTSZ = '11'
0x0000
No Read-While-Write Section
Read-While-Write Section
Application Flash Section
End RWW
Start NRWW
Application Flash Section
Boot Loader Flash Section
End Application
Start Boot Loader
Flashend
No Read-While-Write Section
Read-While-Write Section
0x0000
Program Memory
BOOTSZ = '01'
Application Flash Section
End RWW
Start NRWW
Application Flash Section
End Application
Start Boot Loader
Boot Loader Flash Section
Flashend
Program Memory
BOOTSZ = '00'
No Read-While-Write Section
Boot Loader Lock Bits
Read-While-Write Section
Application Flash Section
End RWW
Start NRWW
Application Flash Section
End Application
Start Boot Loader
Boot Loader Flash Section
Flashend
Note:
0x0000
No Read-While-Write Section
Read-While-Write Section
0x0000
Application Flash Section
End RWW, End Application
Start NRWW, Start Boot Loader
Boot Loader Flash Section
Flashend
1. The parameters in the figure above are given in Table 114 on page 286.
If no Boot Loader capability is needed, the entire Flash is available for application code.
The Boot Loader has two separate sets of Boot Lock bits which can be set independently. This gives the user a unique flexibility to select different levels of protection.
The user can select:
•
To protect the entire Flash from a software update by the MCU.
•
To protect only the Boot Loader Flash section from a software update by the MCU.
•
To protect only the Application Flash section from a software update by the MCU.
•
Allow software update in the entire Flash.
See Table 110 and Table 111 for further details. The Boot Lock bits can be set in software and in Serial or Parallel Programming mode, but they can be cleared by a Chip
Erase command only. The general Write Lock (Lock Bit mode 2) does not control the
programming of the Flash memory by SPM instruction. Similarly, the general
Read/Write Lock (Lock Bit mode 1) does not control reading nor writing by LPM/SPM, if
it is attempted.
276
AT90PWM2/3
4317B–AVR–02/05
AT90PWM2/3
Table 110. Boot Lock Bit0 Protection Modes (Application Section)(1)
BLB0 Mode
BLB02
BLB01
1
1
1
No restrictions for SPM or LPM accessing the Application
section.
2
1
0
SPM is not allowed to write to the Application section.
3
0
0
SPM is not allowed to write to the Application section, and
LPM executing from the Boot Loader section is not
allowed to read from the Application section. If Interrupt
Vectors are placed in the Boot Loader section, interrupts
are disabled while executing from the Application section.
4
0
1
LPM executing from the Boot Loader section is not
allowed to read from the Application section. If Interrupt
Vectors are placed in the Boot Loader section, interrupts
are disabled while executing from the Application section.
Note:
Protection
1. “1” means unprogrammed, “0” means programmed
Table 111. Boot Lock Bit1 Protection Modes (Boot Loader Section)(1)
BLB1 Mode
BLB12
BLB11
1
1
1
No restrictions for SPM or LPM accessing the Boot Loader
section.
2
1
0
SPM is not allowed to write to the Boot Loader section.
3
0
0
SPM is not allowed to write to the Boot Loader section,
and LPM executing from the Application section is not
allowed to read from the Boot Loader section. If Interrupt
Vectors are placed in the Application section, interrupts
are disabled while executing from the Boot Loader
section.
4
0
1
LPM executing from the Application section is not allowed
to read from the Boot Loader section. If Interrupt Vectors
are placed in the Application section, interrupts are
disabled while executing from the Boot Loader section.
Note:
Protection
1. “1” means unprogrammed, “0” means programmed
Entering the Boot Loader Entering the Boot Loader takes place by a jump or call from the application program.
This may be initiated by a trigger such as a command received via USART, or SPI interProgram
face. Alternatively, the Boot Reset Fuse can be programmed so that the Reset Vector is
pointing to the Boot Flash start address after a reset. In this case, the Boot Loader is
started after a reset. After the application code is loaded, the program can start executing the application code. Note that the fuses cannot be changed by the MCU itself. This
means that once the Boot Reset Fuse is programmed, the Reset Vector will always
point to the Boot Loader Reset and the fuse can only be changed through the serial or
parallel programming interface.
Table 112. Boot Reset Fuse(1)
BOOTRST
Note:
Reset Address
1
Reset Vector = Application Reset (address 0x0000)
0
Reset Vector = Boot Loader Reset (see Table 114 on page 286)
1. “1” means unprogrammed, “0” means programmed
277
4317B–AVR–02/05
Store Program Memory
Control and Status Register –
SPMCSR
The Store Program Memory Control and Status Register contains the control bits
needed to control the Boot Loader operations.
Bit
7
6
5
4
3
2
1
0
SPMIE
RWWSB
–
RWWSRE
BLBSET
PGWRT
PGERS
SELFPRGEN
Read/Write
R/W
R
R
R/W
R/W
R/W
R/W
R/W
Initial Value
0
0
0
0
0
0
0
0
SPMCSR
• Bit 7 – SPMIE: SPM Interrupt Enable
When the SPMIE bit is written to one, and the I-bit in the Status Register is set (one), the
SPM ready interrupt will be enabled. The SPM ready Interrupt will be executed as long
as the SELFPRGEN bit in the SPMCSR Register is cleared.
• Bit 6 – RWWSB: Read-While-Write Section Busy
When a Self-Programming (Page Erase or Page Write) operation to the RWW section is
initiated, the RWWSB will be set (one) by hardware. When the RWWSB bit is set, the
RWW section cannot be accessed. The RWWSB bit will be cleared if the RWWSRE bit
is written to one after a Self-Programming operation is completed. Alternatively the
RWWSB bit will automatically be cleared if a page load operation is initiated.
• Bit 5 – Res: Reserved Bit
This bit is a reserved bit in the AT90PWM2/3 and always read as zero.
• Bit 4 – RWWSRE: Read-While-Write Section Read Enable
When programming (Page Erase or Page Write) to the RWW section, the RWW section
is blocked for reading (the RWWSB will be set by hardware). To re-enable the RWW
section, the user software must wait until the programming is completed (SELFPRGEN
will be cleared). Then, if the RWWSRE bit is written to one at the same time as SELFPRGEN, the next SPM instruction within four clock cycles re-enables the RWW section.
The RWW section cannot be re-enabled while the Flash is busy with a Page Erase or a
Page Write (SELFPRGEN is set). If the RWWSRE bit is written while the Flash is being
loaded, the Flash load operation will abort and the data loaded will be lost.
• Bit 3 – BLBSET: Boot Lock Bit Set
If this bit is written to one at the same time as SELFPRGEN, the next SPM instruction
within four clock cycles sets Boot Lock bits and Memory Lock bits, according to the data
in R0. The data in R1 and the address in the Z-pointer are ignored. The BLBSET bit will
automatically be cleared upon completion of the Lock bit set, or if no SPM instruction is
executed within four clock cycles.
An LPM instruction within three cycles after BLBSET and SELFPRGEN are set in the
SPMCSR Register, will read either the Lock bits or the Fuse bits (depending on Z0 in
the Z-pointer) into the destination register. See “Reading the Fuse and Lock Bits from
Software” on page 282 for details.
• Bit 2 – PGWRT: Page Write
If this bit is written to one at the same time as SELFPRGEN, the next SPM instruction
within four clock cycles executes Page Write, with the data stored in the temporary
buffer. The page address is taken from the high part of the Z-pointer. The data in R1 and
R0 are ignored. The PGWRT bit will auto-clear upon completion of a Page Write, or if no
SPM instruction is executed within four clock cycles. The CPU is halted during the entire
Page Write operation if the NRWW section is addressed.
• Bit 1 – PGERS: Page Erase
If this bit is written to one at the same time as SELFPRGEN, the next SPM instruction
within four clock cycles executes Page Erase. The page address is taken from the high
278
AT90PWM2/3
4317B–AVR–02/05
AT90PWM2/3
part of the Z-pointer. The data in R1 and R0 are ignored. The PGERS bit will auto-clear
upon completion of a Page Erase, or if no SPM instruction is executed within four clock
cycles. The CPU is halted during the entire Page Write operation if the NRWW section is
addressed.
• Bit 0 – SELFPRGEN: Self Programming Enable
This bit enables the SPM instruction for the next four clock cycles. If written to one
together with either RWWSRE, BLBSET, PGWRT or PGERS, the following SPM
instruction will have a special meaning, see description above. If only SELFPRGEN is
written, the following SPM instruction will store the value in R1:R0 in the temporary page
buffer addressed by the Z-pointer. The LSB of the Z-pointer is ignored. The SELFPRGEN bit will auto-clear upon completion of an SPM instruction, or if no SPM
instruction is executed within four clock cycles. During Page Erase and Page Write, the
SELFPRGEN bit remains high until the operation is completed.
Writing any other combination than “10001”, “01001”, “00101”, “00011” or “00001” in the
lower five bits will have no effect.
Addressing the Flash
During SelfProgramming
The Z-pointer is used to address the SPM commands.
Bit
15
14
13
12
11
10
9
8
ZH (R31)
Z15
Z14
Z13
Z12
Z11
Z10
Z9
Z8
ZL (R30)
Z7
Z6
Z5
Z4
Z3
Z2
Z1
Z0
7
6
5
4
3
2
1
0
Since the Flash is organized in pages (see Table 127 on page 294), the Program
Counter can be treated as having two different sections. One section, consisting of the
least significant bits, is addressing the words within a page, while the most significant
bits are addressing the pages. This is1 shown in Figure 135. Note that the Page Erase
and Page Write operations are addressed independently. Therefore it is of major importance that the Boot Loader software addresses the same page in both the Page Erase
and Page Write operation. Once a programming operation is initiated, the address is
latched and the Z-pointer can be used for other operations.
The only SPM operation that does not use the Z-pointer is Setting the Boot Loader Lock
bits. The content of the Z-pointer is ignored and will have no effect on the operation. The
LPM instruction does also use the Z-pointer to store the address. Since this instruction
addresses the Flash byte-by-byte, also the LSB (bit Z0) of the Z-pointer is used.
279
4317B–AVR–02/05
Figure 135. Addressing the Flash During SPM(1)
BIT
15
ZPCMSB
ZPAGEMSB
Z - REGISTER
1 0
0
PCMSB
PROGRAM
COUNTER
PAGEMSB
PCPAGE
PCWORD
PAGE ADDRESS
WITHIN THE FLASH
WORD ADDRESS
WITHIN A PAGE
PROGRAM MEMORY
PAGE
PAGE
INSTRUCTION WORD
PCWORD[PAGEMSB:0]:
00
01
02
PAGEEND
Note:
Self-Programming the
Flash
1. The different variables used in Figure 135 are listed in Table 116 on page 286.
The program memory is updated in a page by page fashion. Before programming a
page with the data stored in the temporary page buffer, the page must be erased. The
temporary page buffer is filled one word at a time using SPM and the buffer can be filled
either before the Page Erase command or between a Page Erase and a Page Write
operation:
Alternative 1, fill the buffer before a Page Erase
•
Fill temporary page buffer
•
Perform a Page Erase
•
Perform a Page Write
Alternative 2, fill the buffer after Page Erase
•
Perform a Page Erase
•
Fill temporary page buffer
•
Perform a Page Write
If only a part of the page needs to be changed, the rest of the page must be stored (for
example in the temporary page buffer) before the erase, and then be rewritten. When
using alternative 1, the Boot Loader provides an effective Read-Modify-Write feature
which allows the user software to first read the page, do the necessary changes, and
then write back the modified data. If alternative 2 is used, it is not possible to read the
old data while loading since the page is already erased. The temporary page buffer can
be accessed in a random sequence. It is essential that the page address used in both
the Page Erase and Page Write operation is addressing the same page. See “Simple
Assembly Code Example for a Boot Loader” on page 284 for an assembly code
example.
280
AT90PWM2/3
4317B–AVR–02/05
AT90PWM2/3
Performing Page Erase by
SPM
Filling the Temporary Buffer
(Page Loading)
To execute Page Erase, set up the address in the Z-pointer, write “X0000011” to
SPMCSR and execute SPM within four clock cycles after writing SPMCSR. The data in
R1 and R0 is ignored. The page address must be written to PCPAGE in the Z-register.
Other bits in the Z-pointer will be ignored during this operation.
•
Page Erase to the RWW section: The NRWW section can be read during the Page
Erase.
•
Page Erase to the NRWW section: The CPU is halted during the operation.
To write an instruction word, set up the address in the Z-pointer and data in R1:R0, write
“00000001” to SPMCSR and execute SPM within four clock cycles after writing
SPMCSR. The content of PCWORD in the Z-register is used to address the data in the
temporary buffer. The temporary buffer will auto-erase after a Page Write operation or
by writing the RWWSRE bit in SPMCSR. It is also erased after a system reset. Note that
it is not possible to write more than one time to each address without erasing the temporary buffer.
If the EEPROM is written in the middle of an SPM Page Load operation, all data loaded
will be lost.
Performing a Page Write
To execute Page Write, set up the address in the Z-pointer, write “X0000101” to
SPMCSR and execute SPM within four clock cycles after writing SPMCSR. The data in
R1 and R0 is ignored. The page address must be written to PCPAGE. Other bits in the
Z-pointer must be written to zero during this operation.
•
Page Write to the RWW section: The NRWW section can be read during the Page
Write.
•
Page Write to the NRWW section: The CPU is halted during the operation.
Using the SPM Interrupt
If the SPM interrupt is enabled, the SPM interrupt will generate a constant interrupt
when the SELFPRGEN bit in SPMCSR is cleared. This means that the interrupt can be
used instead of polling the SPMCSR Register in software. When using the SPM interrupt, the Interrupt Vectors should be moved to the BLS section to avoid that an interrupt
is accessing the RWW section when it is blocked for reading. How to move the interrupts is described in XXXXXXXX.
Consideration While Updating
BLS
Special care must be taken if the user allows the Boot Loader section to be updated by
leaving Boot Lock bit11 unprogrammed. An accidental write to the Boot Loader itself can
corrupt the entire Boot Loader, and further software updates might be impossible. If it is
not necessary to change the Boot Loader software itself, it is recommended to program
the Boot Lock bit11 to protect the Boot Loader software from any internal software
changes.
Prevent Reading the RWW
Section During SelfProgramming
During Self-Programming (either Page Erase or Page Write), the RWW section is
always blocked for reading. The user software itself must prevent that this section is
addressed during the self programming operation. The RWWSB in the SPMCSR will be
set as long as the RWW section is busy. During Self-Programming the Interrupt Vector
table should be moved to the BLS as described in XXXXXXX, or the interrupts must be
disabled. Before addressing the RWW section after the programming is completed, the
user software must clear the RWWSB by writing the RWWSRE. See “Simple Assembly
Code Example for a Boot Loader” on page 284 for an example.
281
4317B–AVR–02/05
Setting the Boot Loader Lock
Bits by SPM
To set the Boot Loader Lock bits, write the desired data to R0, write “X0001001” to
SPMCSR and execute SPM within four clock cycles after writing SPMCSR. The only
accessible Lock bits are the Boot Lock bits that may prevent the Application and Boot
Loader section from any software update by the MCU.
Bit
7
6
5
4
3
2
1
0
R0
1
1
BLB12
BLB11
BLB02
BLB01
1
1
See Table 110 and Table 111 for how the different settings of the Boot Loader bits affect
the Flash access.
If bits 5..2 in R0 are cleared (zero), the corresponding Boot Lock bit will be programmed
if an SPM instruction is executed within four cycles after BLBSET and SELFPRGEN are
set in SPMCSR. The Z-pointer is don’t care during this operation, but for future compatibility it is recommended to load the Z-pointer with 0x0001 (same as used for reading the
lOck bits). For future compatibility it is also recommended to set bits 7, 6, 1, and 0 in R0
to “1” when writing the Lock bits. When programming the Lock bits the entire Flash can
be read during the operation.
EEPROM Write Prevents
Writing to SPMCSR
Note that an EEPROM write operation will block all software programming to Flash.
Reading the Fuses and Lock bits from software will also be prevented during the
EEPROM write operation. It is recommended that the user checks the status bit (EEPE)
in the EECR Register and verifies that the bit is cleared before writing to the SPMCSR
Register.
Reading the Fuse and Lock
Bits from Software
It is possible to read both the Fuse and Lock bits from software. To read the Lock bits,
load the Z-pointer with 0x0001 and set the BLBSET and SELFPRGEN bits in SPMCSR.
When an LPM instruction is executed within three CPU cycles after the BLBSET and
SELFPRGEN bits are set in SPMCSR, the value of the Lock bits will be loaded in the
destination register. The BLBSET and SELFPRGEN bits will auto-clear upon completion
of reading the Lock bits or if no LPM instruction is executed within three CPU cycles or
no SPM instruction is executed within four CPU cycles. When BLBSET and SELFPRGEN are cleared, LPM will work as described in the Instruction set Manual.
Bit
7
6
5
4
3
2
1
0
Rd
–
–
BLB12
BLB11
BLB02
BLB01
LB2
LB1
The algorithm for reading the Fuse Low byte is similar to the one described above for
reading the Lock bits. To read the Fuse Low byte, load the Z-pointer with 0x0000 and
set the BLBSET and SELFPRGEN bits in SPMCSR. When an LPM instruction is executed within three cycles after the BLBSET and SELFPRGEN bits are set in the
SPMCSR, the value of the Fuse Low byte (FLB) will be loaded in the destination register
as shown below. Refer to Table 120 on page 289 for a detailed description and mapping
of the Fuse Low byte.
Bit
7
6
5
4
3
2
1
0
Rd
FLB7
FLB6
FLB5
FLB4
FLB3
FLB2
FLB1
FLB0
Similarly, when reading the Fuse High byte, load 0x0003 in the Z-pointer. When an LPM
instruction is executed within three cycles after the BLBSET and SELFPRGEN bits are
set in the SPMCSR, the value of the Fuse High byte (FHB) will be loaded in the destination register as shown below. Refer to Table 121 on page 290 for detailed description
and mapping of the Fuse High byte.
282
Bit
7
6
5
4
3
2
1
0
Rd
FHB7
FHB6
FHB5
FHB4
FHB3
FHB2
FHB1
FHB0
AT90PWM2/3
4317B–AVR–02/05
AT90PWM2/3
When reading the Extended Fuse byte, load 0x0002 in the Z-pointer. When an LPM
instruction is executed within three cycles after the BLBSET and SELFPRGEN bits are
set in the SPMCSR, the value of the Extended Fuse byte (EFB) will be loaded in the
destination register as shown below. Refer to Table 120 on page 289 for detailed
description and mapping of the Extended Fuse byte.
Bit
7
6
5
4
3
2
1
0
Rd
–
–
–
–
EFB3
EFB2
EFB1
EFB0
Fuse and Lock bits that are programmed, will be read as zero. Fuse and Lock bits that
are unprogrammed, will be read as one.
Preventing Flash Corruption
During periods of low VCC, the Flash program can be corrupted because the supply voltage is too low for the CPU and the Flash to operate properly. These issues are the same
as for board level systems using the Flash, and the same design solutions should be
applied.
A Flash program corruption can be caused by two situations when the voltage is too low.
First, a regular write sequence to the Flash requires a minimum voltage to operate correctly. Secondly, the CPU itself can execute instructions incorrectly, if the supply voltage
for executing instructions is too low.
Flash corruption can easily be avoided by following these design recommendations (one
is sufficient):
1. If there is no need for a Boot Loader update in the system, program the Boot
Loader Lock bits to prevent any Boot Loader software updates.
2. Keep the AVR RESET active (low) during periods of insufficient power supply
voltage. This can be done by enabling the internal Brown-out Detector (BOD) if
the operating voltage matches the detection level. If not, an external low VCC
reset protection circuit can be used. If a reset occurs while a write operation is in
progress, the write operation will be completed provided that the power supply
voltage is sufficient.
3. Keep the AVR core in Power-down sleep mode during periods of low VCC. This
will prevent the CPU from attempting to decode and execute instructions, effectively protecting the SPMCSR Register and thus the Flash from unintentional
writes.
Programming Time for Flash
when Using SPM
The calibrated RC Oscillator is used to time Flash accesses. Table 113 shows the typical programming time for Flash accesses from the CPU.
Table 113. SPM Programming Time
Symbol
Min Programming Time
Max Programming Time
Flash write (Page Erase, Page Write,
and write Lock bits by SPM)
3.7 ms
4.5 ms
283
4317B–AVR–02/05
Simple Assembly Code
Example for a Boot Loader
;-the routine writes one page of data from RAM to Flash
; the first data location in RAM is pointed to by the Y pointer
; the first data location in Flash is pointed to by the Z-pointer
;-error handling is not included
;-the routine must be placed inside the Boot space
; (at least the Do_spm sub routine). Only code inside NRWW section
can
; be read during Self-Programming (Page Erase and Page Write).
;-registers used: r0, r1, temp1 (r16), temp2 (r17), looplo (r24),
; loophi (r25), spmcrval (r20)
; storing and restoring of registers is not included in the routine
; register usage can be optimized at the expense of code size
;-It is assumed that either the interrupt table is moved to the
Boot
; loader section or that the interrupts are disabled.
.equ PAGESIZEB = PAGESIZE*2
;PAGESIZEB is page size in BYTES, not
words
.org SMALLBOOTSTART
Write_page:
; Page Erase
ldi spmcrval, (1<<PGERS) | (1<<SELFPRGEN)
call Do_spm
; re-enable the RWW section
ldi spmcrval, (1<<RWWSRE) | (1<<SELFPRGEN)
call Do_spm
; transfer data from RAM to Flash page buffer
ldi looplo, low(PAGESIZEB)
;init loop variable
ldi loophi, high(PAGESIZEB) ;not required for PAGESIZEB<=256
Wrloop:
ld
r0, Y+
ld
r1, Y+
ldi spmcrval, (1<<SELFPRGEN)
call Do_spm
adiw ZH:ZL, 2
sbiw loophi:looplo, 2
;use subi for PAGESIZEB<=256
brne Wrloop
; execute Page Write
subi ZL, low(PAGESIZEB)
;restore pointer
sbci ZH, high(PAGESIZEB)
;not required for PAGESIZEB<=256
ldi spmcrval, (1<<PGWRT) | (1<<SELFPRGEN)
call Do_spm
; re-enable the RWW section
ldi spmcrval, (1<<RWWSRE) | (1<<SELFPRGEN)
call Do_spm
; read back and check, optional
ldi looplo, low(PAGESIZEB)
;init loop variable
ldi loophi, high(PAGESIZEB) ;not required for PAGESIZEB<=256
subi YL, low(PAGESIZEB)
;restore pointer
sbci YH, high(PAGESIZEB)
Rdloop:
lpm r0, Z+
ld
r1, Y+
cpse r0, r1
jmp Error
284
AT90PWM2/3
4317B–AVR–02/05
AT90PWM2/3
sbiw loophi:looplo, 1
brne Rdloop
;use subi for PAGESIZEB<=256
; return to RWW section
; verify that RWW section is safe to read
Return:
in
temp1, SPMCSR
sbrs temp1, RWWSB
; If RWWSB is set, the RWW section is not
ready yet
ret
; re-enable the RWW section
ldi spmcrval, (1<<RWWSRE) | (1<<SELFPRGEN)
call Do_spm
rjmp Return
Do_spm:
; check for previous SPM complete
Wait_spm:
in
temp1, SPMCSR
sbrc temp1, SELFPRGEN
rjmp Wait_spm
; input: spmcrval determines SPM action
; disable interrupts if enabled, store status
in
temp2, SREG
cli
; check that no EEPROM write access is present
Wait_ee:
sbic EECR, EEPE
rjmp Wait_ee
; SPM timed sequence
out SPMCSR, spmcrval
spm
; restore SREG (to enable interrupts if originally enabled)
out SREG, temp2
ret
285
4317B–AVR–02/05
Boot Loader Parameters
In Table 114 through Table 116, the parameters used in the description of the self programming are given.
Table 114. Boot Size Configuration
Boot
Size
End
Application
Section
Boot Reset
Address
(Start Boot
Loader
Section)
BOOTSZ1
BOOTSZ0
1
1
128
words
4
0x000 0xF7F
0xF80 0xFFF
0xF7F
0xF80
1
0
256
words
8
0x000 0xEFF
0xF00 0xFFF
0xEFF
0xF00
0
1
512
words
16
0x000 0xDFF
0xE00 0xFFF
0xDFF
0xE00
0
0
1024
words
32
0x000 0xBFF
0xC00 0xFFF
0xBFF
0xC00
Note:
Pages
Application
Flash
Section
Boot
Loader
Flash
Section
The different BOOTSZ Fuse configurations are shown in Figure 134.
Table 115. Read-While-Write Limit
Section
Pages
Address
Read-While-Write section (RWW)
96
0x000 - 0xBFF
No Read-While-Write section (NRWW)
32
0xC00 - 0xFFF
For details about these two section, see “NRWW – No Read-While-Write Section” on
page 274 and “RWW – Read-While-Write Section” on page 274
Table 116. Explanation of Different Variables used in Figure 135 and the Mapping to
the Z-pointer
Corresponding
Z-value(1)
Variable
PCMSB
11
Most significant bit in the Program Counter.
(The Program Counter is 12 bits PC[11:0])
PAGEMSB
4
Most significant bit which is used to address the
words within one page (32 words in a page
requires 5 bits PC [4:0]).
ZPCMSB
Z12
Bit in Z-register that is mapped to PCMSB.
Because Z0 is not used, the ZPCMSB equals
PCMSB + 1.
ZPAGEMSB
Z5
Bit in Z-register that is mapped to PAGEMSB.
Because Z0 is not used, the ZPAGEMSB
equals PAGEMSB + 1.
PCPAGE
PC[11:5]
Z12:Z6
Program counter page address: Page select,
for page erase and page write
PCWORD
PC[4:0]
Z5:Z1
Program counter word address: Word select,
for filling temporary buffer (must be zero during
page write operation)
Note:
286
Description
1. Z15:Z13: always ignored
Z0: should be zero for all SPM commands, byte select for the LPM instruction.
See “Addressing the Flash During Self-Programming” on page 279 for details about
the use of Z-pointer during Self-Programming.
AT90PWM2/3
4317B–AVR–02/05
AT90PWM2/3
Memory
Programming
Program And Data
Memory Lock Bits
The AT90PWM2/3 provides six Lock bits which can be left unprogrammed (“1”) or can
be programmed (“0”) to obtain the additional features listed in Table 118. The Lock bits
can only be erased to “1” with the Chip Erase command.
Table 117. Lock Bit Byte(1)
Lock Bit Byte
Description
Default Value
7
–
1 (unprogrammed)
6
–
1 (unprogrammed)
BLB12
5
Boot Lock bit
1 (unprogrammed)
BLB11
4
Boot Lock bit
1 (unprogrammed)
BLB02
3
Boot Lock bit
1 (unprogrammed)
BLB01
2
Boot Lock bit
1 (unprogrammed)
LB2
1
Lock bit
1 (unprogrammed)
LB1
0
Lock bit
1 (unprogrammed)
Notes:
Bit No
1. “1” means unprogrammed, “0” means programmed.
Table 118. Lock Bit Protection Modes(1)(2)
Memory Lock Bits
Protection Type
LB Mode
LB2
LB1
1
1
1
No memory lock features enabled.
0
Further programming of the Flash and EEPROM is
disabled in Parallel and Serial Programming mode. The
Fuse bits are locked in both Serial and Parallel
Programming mode.(1)
0
Further programming and verification of the Flash and
EEPROM is disabled in Parallel and Serial Programming
mode. The Boot Lock bits and Fuse bits are locked in both
Serial and Parallel Programming mode.(1)
2
3
Notes:
1
0
1. Program the Fuse bits and Boot Lock bits before programming the LB1 and LB2.
2. “1” means unprogrammed, “0” means programmed
287
4317B–AVR–02/05
Table 119. Lock Bit Protection Modes(1)(2). Only ATmega88/168.
BLB0 Mode
BLB02
BLB01
1
1
1
No restrictions for SPM or LPM accessing the Application
section.
2
1
0
SPM is not allowed to write to the Application section.
0
SPM is not allowed to write to the Application section, and
LPM executing from the Boot Loader section is not
allowed to read from the Application section. If Interrupt
Vectors are placed in the Boot Loader section, interrupts
are disabled while executing from the Application section.
LPM executing from the Boot Loader section is not
allowed to read from the Application section. If Interrupt
Vectors are placed in the Boot Loader section, interrupts
are disabled while executing from the Application section.
3
4
0
1
BLB1 Mode
BLB12
BLB11
1
1
1
No restrictions for SPM or LPM accessing the Boot Loader
section.
2
1
0
SPM is not allowed to write to the Boot Loader section.
0
SPM is not allowed to write to the Boot Loader section,
and LPM executing from the Application section is not
allowed to read from the Boot Loader section. If Interrupt
Vectors are placed in the Application section, interrupts
are disabled while executing from the Boot Loader
section.
1
LPM executing from the Application section is not allowed
to read from the Boot Loader section. If Interrupt Vectors
are placed in the Application section, interrupts are
disabled while executing from the Boot Loader section.
3
4
Notes:
288
0
0
0
1. Program the Fuse bits and Boot Lock bits before programming the LB1 and LB2.
2. “1” means unprogrammed, “0” means programmed
AT90PWM2/3
4317B–AVR–02/05
AT90PWM2/3
Fuse Bits
The AT90PWM2/3 has three Fuse bytes. Table 120 - Table 122 describe briefly the
functionality of all the fuses and how they are mapped into the Fuse bytes. Note that the
fuses are read as logical zero, “0”, if they are programmed.
Table 120. Extended Fuse Byte
Extended Fuse Byte
Description
Default Value
PSC2RB
7
PSC2 Reset Behaviour
1
PSC1RB
6
PSC1 Reset Behaviour
1
PSC0RB
5
PSC0 Reset Behaviour
1
PSCRV
4
PSCOUT Reset Value
1
–
3
–
1
BOOTSZ1
2
Select Boot Size
(see Table 113 for details)
0 (programmed)(1)
BOOTSZ0
1
Select Boot Size
(see Table 113 for details)
0 (programmed)(1)
BOOTRST
0
Select Reset Vector
1 (unprogrammed)
Note:
PSC Output Behaviour
During Reset
Bit No
1. The default value of BOOTSZ1..0 results in maximum Boot Size. See Table 123 on
page 292 for details.
For external component safety reason, the state of PSC outputs during Reset can be
programmed by fuses PSCRV, PSC0RB, PSC1RB & PSC2RB.
These fuses are located in the Extended Fuse Byte ( see Table 120)
PSCRV gives the state low or high which will be forced on PSC outputs selected by
PSC0RB, PSC1RB & PSC2RB fuses.
If PSCRV fuse equals 0 (programmed), the selected PSC outputs will be forced to low
state. If PSCRV fuse equals 1 (unprogrammed), the selected PSC outputs will be forced
to high state.
If PSC0RB fuse equals 1 (unprogrammed), PSCOUT00 & PSCOUT01 keep a standard
port behaviour. If PSC0RB fuse equals 0 (programmed), PSCOUT00 & PSCOUT01 are
forced at reset to low level or high level according to PSCRV fuse bit. In this second
case, PSCOUT00 & PSCOUT01 keep the forced state until PSOC0 register is written..
If PSC1RB fuse equals 1 (unprogrammed), PSCOUT10 & PSCOUT11 keep a standard
port behaviour. If PSC1RB fuse equals 0 (programmed), PSCOUT10 & PSCOUT11 are
forced at reset to low level or high level according to PSCRV fuse bit. In this second
case, PSCOUT10 & PSCOUT11 keep the forced state until PSOC1 register is written.
If PSC2RB fuse equals 1 (unprogrammed), PSCOUT20, PSCOUT21, PSCOUT22 &
PSCOUT23 keep a standard port behaviour. If PSC1RB fuse equals 0 (programmed),
PSCOUT20, PSCOUT21, PSCOUT22 & PSCOUT23 are forced at reset to low level or
high level according to PSCRV fuse bit. In this second case, PSCOUT20, PSCOUT21,
PSCOUT22 & PSCOUT23 keep the forced state until PSOC2 register is written.
289
4317B–AVR–02/05
Table 121. Fuse High Byte
High Fuse Byte
Bit No
Description
Default Value
RSTDISBL(1)
7
External Reset Disable
1 (unprogrammed)
DWEN
6
debugWIRE Enable
1 (unprogrammed)
SPIEN(2)
5
Enable Serial Program and
Data Downloading
0 (programmed, SPI
programming enabled)
WDTON(3)
4
Watchdog Timer Always
On
1 (unprogrammed)
EESAVE
3
EEPROM memory is
preserved through the
Chip Erase
1 (unprogrammed),
EEPROM not reserved
BODLEVEL2(4)
2
Brown-out Detector
trigger level
1 (unprogrammed)
BODLEVEL1(4)
1
Brown-out Detector
trigger level
1 (unprogrammed)
BODLEVEL0(4)
0
Brown-out Detector
trigger level
1 (unprogrammed)
Notes:
1.
2.
3.
4.
See “Alternate Functions of Port C” on page 73 for description of RSTDISBL Fuse.
The SPIEN Fuse is not accessible in serial programming mode.
See “Watchdog Timer Configuration” on page 54 for details.
See Table 15 on page 47 for BODLEVEL Fuse decoding.
Table 122. Fuse Low Byte
Low Fuse Byte
Description
Default Value
7
Divide clock by 8
0 (programmed)
CKOUT(3)
6
Clock output
1 (unprogrammed)
SUT1
5
Select start-up time
1 (unprogrammed)(1)
SUT0
4
Select start-up time
0 (programmed)(1)
CKSEL3
3
Select Clock source
0 (programmed)(2)
CKSEL2
2
Select Clock source
0 (programmed)(2)
CKSEL1
1
Select Clock source
1 (unprogrammed)(2)
CKSEL0
0
Select Clock source
0 (programmed)(2)
CKDIV8
Note:
(4)
Bit No
1. The default value of SUT1..0 results in maximum start-up time for the default clock
source. See Table 10 on page 36 for details.
2. The default setting of CKSEL3..0 results in internal RC Oscillator @ 8 MHz. See
Table 10 on page 36 for details.
3. The CKOUT Fuse allows the system clock to be output on PORTB0. See “Clock Output Buffer” on page 36 for details.
4. See “System Clock Prescaler” on page 37 for details.
The status of the Fuse bits is not affected by Chip Erase. Note that the Fuse bits are
locked if Lock bit1 (LB1) is programmed. Program the Fuse bits before programming the
Lock bits.
290
AT90PWM2/3
4317B–AVR–02/05
AT90PWM2/3
Latching of Fuses
The fuse values are latched when the device enters programming mode and changes of
the fuse values will have no effect until the part leaves Programming mode. This does
not apply to the EESAVE Fuse which will take effect once it is programmed. The fuses
are also latched on Power-up in Normal mode.
Signature Bytes
All Atmel microcontrollers have a three-byte signature code which identifies the device.
This code can be read in both serial and parallel mode, also when the device is locked.
The three bytes reside in a separate address space.
Signature Bytes
For the AT90PWM2/3 the signature bytes are:
1. 0x000: 0x1E (indicates manufactured by Atmel).
2. 0x001: 0x93 (indicates 8KB Flash memory).
3. 0x002: 0x81 (indicates AT90PWM2/3 device when 0x001 is 0x93).
Calibration Byte
The AT90PWM2/3 has a byte calibration value for the internal RC Oscillator. This byte
resides in the high byte of address 0x000 in the signature address space. During reset,
this byte is automatically written into the OSCCAL Register to ensure correct frequency
of the calibrated RC Oscillator.
291
4317B–AVR–02/05
Parallel Programming
Parameters, Pin
Mapping, and
Commands
This section describes how to parallel program and verify Flash Program memory,
EEPROM Data memory, Memory Lock bits, and Fuse bits in the AT90PWM2/3. Pulses
are assumed to be at least 250 ns unless otherwise noted.
Signal Names
In this section, some pins of the AT90PWM2/3 are referenced by signal names describing their functionality during parallel programming, see Figure 136 and Table 123. Pins
not described in the following table are referenced by pin names.
The XA1/XA0 pins determine the action executed when the XTAL1 pin is given a positive pulse. The bit coding is shown in Table 125.
When pulsing WR or OE, the command loaded determines the action executed. The different Commands are shown in Table 126.
Figure 136. Parallel Programming
+ 5V
RDY/BSY
PD1
OE
PD2
WR
PD3
BS1
PD4
XA0
PD5
VCC
+ 5V
AVCC
PB[7:0]
PD6
XA1
PAGEL
DATA
PD7
+ 12 V
RESET
PE2
BS2
XTAL1
GND
Table 123. Pin Name Mapping
Signal Name in
Programming Mode
292
Pin Name
I/O
Function
RDY/BSY
PD1
O
0: Device is busy programming, 1: Device
is ready for new command
OE
PD2
I
Output Enable (Active low)
WR
PD3
I
Write Pulse (Active low)
BS1
PD4
I
Byte Select 1 (“0” selects Low byte, “1”
selects High byte)
XA0
PD5
I
XTAL Action Bit 0
XA1
PD6
I
XTAL Action Bit 1
AT90PWM2/3
4317B–AVR–02/05
AT90PWM2/3
Table 123. Pin Name Mapping (Continued)
Signal Name in
Programming Mode
Pin Name
I/O
PAGEL
PD7
I
Program memory and EEPROM Data
Page Load
BS2
PE2
I
Byte Select 2 (“0” selects Low byte, “1”
selects 2’nd High byte)
PB[7:0]
I/O
DATA
Function
Bi-directional Data bus (Output when OE is
low)
Table 124. Pin Values Used to Enter Programming Mode
Pin
Symbol
Value
PAGEL
Prog_enable[3]
0
XA1
Prog_enable[2]
0
XA0
Prog_enable[1]
0
BS1
Prog_enable[0]
0
Table 125. XA1 and XA0 Coding
XA1
XA0
Action when XTAL1 is Pulsed
0
0
Load Flash or EEPROM Address (High or low address byte
determined by BS1).
0
1
Load Data (High or Low data byte for Flash determined by BS1).
1
0
Load Command
1
1
No Action, Idle
Table 126. Command Byte Bit Coding
Command Byte
Command Executed
1000 0000
Chip Erase
0100 0000
Write Fuse bits
0010 0000
Write Lock bits
0001 0000
Write Flash
0001 0001
Write EEPROM
0000 1000
Read Signature Bytes and Calibration byte
0000 0100
Read Fuse and Lock bits
0000 0010
Read Flash
0000 0011
Read EEPROM
293
4317B–AVR–02/05
Table 127. No. of Words in a Page and No. of Pages in the Flash
Device
Flash Size
Page Size
PCWORD
No. of Pages
PCPAG
E
PCMSB
AT90PWM2/3
4K words
(8K bytes)
32 words
PC[4:0]
128
PC[11:5]
11
Table 128. No. of Words in a Page and No. of Pages in the EEPROM
Serial Programming Pin
Mapping
294
Device
EEPROM
Size
Page Size
PCWORD
No. of
Pages
PCPAG
E
EEAMSB
AT90PWM2/3
512 bytes
4 bytes
EEA[1:0]
128
EEA[8:2]
8
Table 129. Pin Mapping Serial Programming
Symbol
Pins
I/O
Description
MOSI_A
PD3
I
Serial Data in
MISO_A
PD2
O
Serial Data out
SCK_A
PD4
I
Serial Clock
AT90PWM2/3
4317B–AVR–02/05
AT90PWM2/3
Parallel Programming
Enter Programming Mode
The following algorithm puts the device in Parallel (High-voltage) > Programming mode:
1. Set Prog_enable pins listed in Table 124. to “0000”, RESET pin to “0” and Vcc to
0V.
2. Apply 4.5 - 5.5V between VCC and GND. Ensure that Vcc reaches at least 1.8V
within the next 20µs.
3. Wait 20 - 60µs, and apply 11.5 - 12.5V to RESET.
4. Keep the Prog_enable pins unchanged for at least 10µs after the High-voltage
has been applied to ensure the Prog_enable Signature has been latched.
5. Wait at least 300µs before giving any parallel programming commands.
6. Exit Programming mode by power the device down or by bringing RESET pin to
0V.
If the rise time of the Vcc is unable to fulfill the requirements listed above, the following
alternative algorithm can be used.
1. Set Prog_enable pins listed in Table 124. to “0000”, RESET pin to “0” and Vcc to
0V.
2. Apply 4.5 - 5.5V between VCC and GND.
3. Monitor Vcc, and as soon as Vcc reaches 0.9 - 1.1V, apply 11.5 - 12.5V to
RESET.
4. Keep the Prog_enable pins unchanged for at least 10µs after the High-voltage
has been applied to ensure the Prog_enable Signature has been latched.
5. Wait until Vcc actually reaches 4.5 -5.5V before giving any parallel programming
commands.
6. Exit Programming mode by power the device down or by bringing RESET pin to
0V.
Considerations for Efficient
Programming
Chip Erase
The loaded command and address are retained in the device during programming. For
efficient programming, the following should be considered.
•
The command needs only be loaded once when writing or reading multiple memory
locations.
•
Skip writing the data value 0xFF, that is the contents of the entire EEPROM (unless
the EESAVE Fuse is programmed) and Flash after a Chip Erase.
•
Address high byte needs only be loaded before programming or reading a new 256
word window in Flash or 256 byte EEPROM. This consideration also applies to
Signature bytes reading.
The Chip Erase will erase the Flash and EEPROM(1) memories plus Lock bits. The Lock
bits are not reset until the program memory has been completely erased. The Fuse bits
are not changed. A Chip Erase must be performed before the Flash and/or EEPROM
are reprogrammed.
Note:
1. The EEPRPOM memory is preserved during Chip Erase if the EESAVE Fuse is
programmed.
Load Command “Chip Erase”
1. Set XA1, XA0 to “10”. This enables command loading.
2. Set BS1 to “0”.
3. Set DATA to “1000 0000”. This is the command for Chip Erase.
4. Give XTAL1 a positive pulse. This loads the command.
295
4317B–AVR–02/05
5. Give WR a negative pulse. This starts the Chip Erase. RDY/BSY goes low.
6. Wait until RDY/BSY goes high before loading a new command.
Programming the Flash
The Flash is organized in pages, see Table 127 on page 294. When programming the
Flash, the program data is latched into a page buffer. This allows one page of program
data to be programmed simultaneously. The following procedure describes how to program the entire Flash memory:
A. Load Command “Write Flash”
1. Set XA1, XA0 to “10”. This enables command loading.
2. Set BS1 to “0”.
3. Set DATA to “0001 0000”. This is the command for Write Flash.
4. Give XTAL1 a positive pulse. This loads the command.
B. Load Address Low byte
1. Set XA1, XA0 to “00”. This enables address loading.
2. Set BS1 to “0”. This selects low address.
3. Set DATA = Address low byte (0x00 - 0xFF).
4. Give XTAL1 a positive pulse. This loads the address low byte.
C. Load Data Low Byte
1. Set XA1, XA0 to “01”. This enables data loading.
2. Set DATA = Data low byte (0x00 - 0xFF).
3. Give XTAL1 a positive pulse. This loads the data byte.
D. Load Data High Byte
1. Set BS1 to “1”. This selects high data byte.
2. Set XA1, XA0 to “01”. This enables data loading.
3. Set DATA = Data high byte (0x00 - 0xFF).
4. Give XTAL1 a positive pulse. This loads the data byte.
E. Latch Data
1. Set BS1 to “1”. This selects high data byte.
2. Give PAGEL a positive pulse. This latches the data bytes. (See Figure 138 for
signal waveforms)
F. Repeat B through E until the entire buffer is filled or until all data within the page is
loaded.
While the lower bits in the address are mapped to words within the page, the higher bits
address the pages within the FLASH. This is illustrated in Figure 137 on page 297. Note
that if less than eight bits are required to address words in the page (pagesize < 256),
the most significant bit(s) in the address low byte are used to address the page when
performing a Page Write.
G. Load Address High byte
1. Set XA1, XA0 to “00”. This enables address loading.
2. Set BS1 to “1”. This selects high address.
3. Set DATA = Address high byte (0x00 - 0xFF).
4. Give XTAL1 a positive pulse. This loads the address high byte.
H. Program Page
296
AT90PWM2/3
4317B–AVR–02/05
AT90PWM2/3
1. Give WR a negative pulse. This starts programming of the entire page of data.
RDY/BSY goes low.
2. Wait until RDY/BSY goes high (See Figure 138 for signal waveforms).
I. Repeat B through H until the entire Flash is programmed or until all data has been
programmed.
J. End Page Programming
1. 1. Set XA1, XA0 to “10”. This enables command loading.
2. Set DATA to “0000 0000”. This is the command for No Operation.
3. Give XTAL1 a positive pulse. This loads the command, and the internal write signals are reset.
Figure 137. Addressing the Flash Which is Organized in Pages(1)
PCMSB
PROGRAM
COUNTER
PAGEMSB
PCPAGE
PCWORD
PAGE ADDRESS
WITHIN THE FLASH
WORD ADDRESS
WITHIN A PAGE
PROGRAM MEMORY
PAGE
PAGE
PCWORD[PAGEMSB:0]:
00
INSTRUCTION WORD
01
02
PAGEEND
Note:
1. PCPAGE and PCWORD are listed in Table 127 on page 294.
Figure 138. Programming the Flash Waveforms(1)
F
DATA
A
B
0x10
ADDR. LOW
C
DATA LOW
D
E
DATA HIGH
XX
B
ADDR. LOW
C
D
DATA LOW
DATA HIGH
E
XX
G
ADDR. HIGH
H
XX
XA1
XA0
BS1
XTAL1
WR
RDY/BSY
RESET +12V
OE
PAGEL
BS2
Note:
1. “XX” is don’t care. The letters refer to the programming description above.
297
4317B–AVR–02/05
Programming the EEPROM
The EEPROM is organized in pages, see Table 128 on page 294. When programming
the EEPROM, the program data is latched into a page buffer. This allows one page of
data to be programmed simultaneously. The programming algorithm for the EEPROM
data memory is as follows (refer to “Programming the Flash” on page 296 for details on
Command, Address and Data loading):
1. A: Load Command “0001 0001”.
2. G: Load Address High Byte (0x00 - 0xFF).
3. B: Load Address Low Byte (0x00 - 0xFF).
4. C: Load Data (0x00 - 0xFF).
5. E: Latch data (give PAGEL a positive pulse).
K: Repeat 3 through 5 until the entire buffer is filled.
L: Program EEPROM page
1. Set BS1 to “0”.
2. Give WR a negative pulse. This starts programming of the EEPROM page.
RDY/BSY goes low.
3. Wait until to RDY/BSY goes high before programming the next page (See Figure
139 for signal waveforms).
Figure 139. Programming the EEPROM Waveforms
K
DATA
A
G
0x11
ADDR. HIGH
B
ADDR. LOW
C
DATA
E
XX
B
ADDR. LOW
C
DATA
E
L
XX
XA1
XA0
BS1
XTAL1
WR
RDY/BSY
RESET +12V
OE
PAGEL
BS2
Reading the Flash
The algorithm for reading the Flash memory is as follows (refer to “Programming the
Flash” on page 296 for details on Command and Address loading):
1. A: Load Command “0000 0010”.
2. G: Load Address High Byte (0x00 - 0xFF).
3. B: Load Address Low Byte (0x00 - 0xFF).
4. Set OE to “0”, and BS1 to “0”. The Flash word low byte can now be read at
DATA.
5. Set BS1 to “1”. The Flash word high byte can now be read at DATA.
6. Set OE to “1”.
Reading the EEPROM
298
The algorithm for reading the EEPROM memory is as follows (refer to “Programming the
Flash” on page 296 for details on Command and Address loading):
AT90PWM2/3
4317B–AVR–02/05
AT90PWM2/3
1. A: Load Command “0000 0011”.
2. G: Load Address High Byte (0x00 - 0xFF).
3. B: Load Address Low Byte (0x00 - 0xFF).
4. Set OE to “0”, and BS1 to “0”. The EEPROM Data byte can now be read at
DATA.
5. Set OE to “1”.
299
4317B–AVR–02/05
Programming the Fuse Low
Bits
The algorithm for programming the Fuse Low bits is as follows (refer to “Programming
the Flash” on page 296 for details on Command and Data loading):
1. A: Load Command “0100 0000”.
2. C: Load Data Low Byte. Bit n = “0” programs and bit n = “1” erases the Fuse bit.
3. Give WR a negative pulse and wait for RDY/BSY to go high.
Programming the Fuse High
Bits
The algorithm for programming the Fuse High bits is as follows (refer to “Programming
the Flash” on page 296 for details on Command and Data loading):
1. A: Load Command “0100 0000”.
2. C: Load Data Low Byte. Bit n = “0” programs and bit n = “1” erases the Fuse bit.
3. Set BS1 to “1” and BS2 to “0”. This selects high data byte.
4. Give WR a negative pulse and wait for RDY/BSY to go high.
5. Set BS1 to “0”. This selects low data byte.
Programming the Extended
Fuse Bits
The algorithm for programming the Extended Fuse bits is as follows (refer to “Programming the Flash” on page 296 for details on Command and Data loading):
1. 1. A: Load Command “0100 0000”.
2. 2. C: Load Data Low Byte. Bit n = “0” programs and bit n = “1” erases the Fuse
bit.
3. 3. Set BS1 to “0” and BS2 to “1”. This selects extended data byte.
4. 4. Give WR a negative pulse and wait for RDY/BSY to go high.
5. 5. Set BS2 to “0”. This selects low data byte.
Figure 140. Programming the FUSES Waveforms
Write Fuse Low byte
DATA
A
C
0x40
DATA
XX
Write Fuse high byte
A
C
0x40
DATA
XX
Write Extended Fuse byte
A
C
0x40
DATA
XX
XA1
XA0
BS1
BS2
XTAL1
WR
RDY/BSY
RESET +12V
OE
PAGEL
Programming the Lock Bits
The algorithm for programming the Lock bits is as follows (refer to “Programming the
Flash” on page 296 for details on Command and Data loading):
1. A: Load Command “0010 0000”.
2. C: Load Data Low Byte. Bit n = “0” programs the Lock bit. If LB mode 3 is programmed (LB1 and LB2 is programmed), it is not possible to program the Boot
Lock bits by any External Programming mode.
3. Give WR a negative pulse and wait for RDY/BSY to go high.
The Lock bits can only be cleared by executing Chip Erase.
300
AT90PWM2/3
4317B–AVR–02/05
AT90PWM2/3
Reading the Fuse and Lock
Bits
The algorithm for reading the Fuse and Lock bits is as follows (refer to “Programming
the Flash” on page 296 for details on Command loading):
1. A: Load Command “0000 0100”.
2. Set OE to “0”, BS2 to “0” and BS1 to “0”. The status of the Fuse Low bits can
now be read at DATA (“0” means programmed).
3. Set OE to “0”, BS2 to “1” and BS1 to “1”. The status of the Fuse High bits can
now be read at DATA (“0” means programmed).
4. Set OE to “0”, BS2 to “1”, and BS1 to “0”. The status of the Extended Fuse bits
can now be read at DATA (“0” means programmed).
5. Set OE to “0”, BS2 to “0” and BS1 to “1”. The status of the Lock bits can now be
read at DATA (“0” means programmed).
6. Set OE to “1”.
Figure 141. Mapping Between BS1, BS2 and the Fuse and Lock Bits During Read
Fuse Low Byte
0
Extended Fuse Byte
1
0
DATA
BS2
0
Lock Bits
1
Fuse High Byte
1
BS1
BS2
Reading the Signature Bytes
The algorithm for reading the Signature bytes is as follows (refer to “Programming the
Flash” on page 296 for details on Command and Address loading):
1. A: Load Command “0000 1000”.
2. B: Load Address Low Byte (0x00 - 0x02).
3. Set OE to “0”, and BS1 to “0”. The selected Signature byte can now be read at
DATA.
4. Set OE to “1”.
Reading the Calibration Byte
The algorithm for reading the Calibration byte is as follows (refer to “Programming the
Flash” on page 296 for details on Command and Address loading):
1. A: Load Command “0000 1000”.
2. B: Load Address Low Byte, 0x00.
3. Set OE to “0”, and BS1 to “1”. The Calibration byte can now be read at DATA.
4. Set OE to “1”.
301
4317B–AVR–02/05
Parallel Programming
Characteristics
Figure 142. Parallel Programming Timing, Including some General Timing
Requirements
tXLWL
tXHXL
XTAL1
tDVXH
tXLDX
Data & Contol
(DATA, XA0/1, BS1, BS2)
tPLBX t BVWL
tBVPH
PAGEL
tWLBX
tPHPL
tWLWH
WR
tPLWL
WLRL
RDY/BSY
tWLRH
Figure 143. Parallel Programming Timing, Loading Sequence with Timing
Requirements(1)
LOAD ADDRESS
(LOW BYTE)
LOAD DATA LOAD DATA
(HIGH BYTE)
LOAD DATA
(LOW BYTE)
t XLXH
tXLPH
LOAD ADDRESS
(LOW BYTE)
tPLXH
XTAL1
BS1
PAGEL
DATA
ADDR0 (Low Byte)
DATA (Low Byte)
DATA (High Byte)
ADDR1 (Low Byte)
XA0
XA1
Note:
302
1. The timing requirements shown in Figure 142 (i.e., tDVXH, tXHXL, and tXLDX) also apply
to loading operation.
AT90PWM2/3
4317B–AVR–02/05
AT90PWM2/3
Figure 144. Parallel Programming Timing, Reading Sequence (within the Same Page)
with Timing Requirements(1)
LOAD ADDRESS
(LOW BYTE)
READ DATA
(LOW BYTE)
READ DATA
(HIGH BYTE)
LOAD ADDRESS
(LOW BYTE)
tXLOL
XTAL1
tBVDV
BS1
tOLDV
OE
tOHDZ
DATA
ADDR0 (Low Byte)
ADDR1 (Low Byte)
DATA (High Byte)
DATA (Low Byte)
XA0
XA1
Note:
1. The timing requirements shown in Figure 142 (i.e., tDVXH, tXHXL, and tXLDX) also apply
to reading operation.
Table 130. Parallel Programming Characteristics, VCC = 5V ± 10%
Symbol
Parameter
Min
VPP
Programming Enable Voltage
11.5
IPP
Programming Enable Current
tDVXH
Data and Control Valid before XTAL1 High
67
ns
tXLXH
XTAL1 Low to XTAL1 High
200
ns
tXHXL
XTAL1 Pulse Width High
150
ns
tXLDX
Data and Control Hold after XTAL1 Low
67
ns
tXLWL
XTAL1 Low to WR Low
0
ns
tXLPH
XTAL1 Low to PAGEL high
0
ns
tPLXH
PAGEL low to XTAL1 high
150
ns
tBVPH
BS1 Valid before PAGEL High
67
ns
tPHPL
PAGEL Pulse Width High
150
ns
tPLBX
BS1 Hold after PAGEL Low
67
ns
tWLBX
BS2/1 Hold after WR Low
67
ns
tPLWL
PAGEL Low to WR Low
67
ns
tBVWL
BS1 Valid to WR Low
67
ns
tWLWH
WR Pulse Width Low
150
ns
tWLRL
WR Low to RDY/BSY Low
tWLRH
WR Low to RDY/BSY High
(1)
(2)
tWLRH_CE
WR Low to RDY/BSY High for Chip Erase
tXLOL
XTAL1 Low to OE Low
Typ
Max
Units
12.5
V
250
µA
0
1
µs
3.7
4.5
ms
7.5
9
ms
0
ns
303
4317B–AVR–02/05
Table 130. Parallel Programming Characteristics, VCC = 5V ± 10% (Continued)
Symbol
Parameter
tBVDV
BS1 Valid to DATA valid
tOLDV
tOHDZ
Notes:
Serial Downloading
Min
Max
Units
250
ns
OE Low to DATA Valid
250
ns
OE High to DATA Tri-stated
250
ns
0
Typ
1.
tWLRH is valid for the Write Flash, Write EEPROM, Write Fuse bits and Write Lock
bits commands.
2. tWLRH_CE is valid for the Chip Erase command.
Both the Flash and EEPROM memory arrays can be programmed using the serial SPI
bus while RESET is pulled to GND. The serial interface consists of pins SCK, MOSI
(input) and MISO (output). After RESET is set low, the Programming Enable instruction
needs to be executed first before program/erase operations can be executed. NOTE, in
Table 129 on page 294, the pin mapping for SPI programming is listed. Not all parts use
the SPI pins dedicated for the internal SPI interface.
Figure 145. Serial Programming and Verify(1)
+1.8 - 5.5V
VCC
+1.8 - 5.5V(2)
MOSI_A
AVCC
MISO_A
SCK_A
XTAL1
RESET
GND
Notes:
1. If the device is clocked by the internal Oscillator, it is no need to connect a clock
source to the XTAL1 pin.
2. VCC - 0.3V < AVCC < VCC + 0.3V, however, AVCC should always be within 1.8 - 5.5V
When programming the EEPROM, an auto-erase cycle is built into the self-timed programming operation (in the Serial mode ONLY) and there is no need to first execute the
Chip Erase instruction. The Chip Erase operation turns the content of every memory
location in both the Program and EEPROM arrays into 0xFF.
Depending on CKSEL Fuses, a valid clock must be present. The minimum low and high
periods for the serial clock (SCK) input are defined as follows:
Low:> 2 CPU clock cycles for fck < 12 MHz, 3 CPU clock cycles for fck >= 12 MHz
High:> 2 CPU clock cycles for fck < 12 MHz, 3 CPU clock cycles for fck >= 12 MHz
304
AT90PWM2/3
4317B–AVR–02/05
AT90PWM2/3
Serial Programming
Algorithm
When writing serial data to the AT90PWM2/3, data is clocked on the rising edge of SCK.
When reading data from the AT90PWM2/3, data is clocked on the falling edge of SCK.
See Figure 146 for timing details.
To program and verify the AT90PWM2/3 in the serial programming mode, the following
sequence is recommended (See four byte instruction formats in Table 132):
1. Power-up sequence:
Apply power between VCC and GND while RESET and SCK are set to “0”. In
some systems, the programmer can not guarantee that SCK is held low during
power-up. In this case, RESET must be given a positive pulse of at least two
CPU clock cycles duration after SCK has been set to “0”.
2. Wait for at least 20 ms and enable serial programming by sending the Programming Enable serial instruction to pin MOSI.
3. The serial programming instructions will not work if the communication is out of
synchronization. When in sync. the second byte (0x53), will echo back when
issuing the third byte of the Programming Enable instruction. Whether the echo
is correct or not, all four bytes of the instruction must be transmitted. If the 0x53
did not echo back, give RESET a positive pulse and issue a new Programming
Enable command.
4. The Flash is programmed one page at a time. The memory page is loaded one
byte at a time by supplying the 6 LSB of the address and data together with the
Load Program Memory Page instruction. To ensure correct loading of the page,
the data low byte must be loaded before data high byte is applied for a given
address. The Program Memory Page is stored by loading the Write Program
Memory Page instruction with the 8 MSB of the address. If polling is not used,
the user must wait at least tWD_FLASH before issuing the next page. (See Table
131.) Accessing the serial programming interface before the Flash write operation completes can result in incorrect programming.
5. The EEPROM array is programmed one byte at a time by supplying the address
and data together with the appropriate Write instruction. An EEPROM memory
location is first automatically erased before new data is written. If polling is not
used, the user must wait at least tWD_EEPROM before issuing the next byte. (See
Table 131.) In a chip erased device, no 0xFFs in the data file(s) need to be
programmed.
6. Any memory location can be verified by using the Read instruction which returns
the content at the selected address at serial output MISO.
7. At the end of the programming session, RESET can be set high to commence
normal operation.
8. Power-off sequence (if needed):
Set RESET to “1”.
Turn VCC power off.
Data Polling Flash
When a page is being programmed into the Flash, reading an address location within
the page being programmed will give the value 0xFF. At the time the device is ready for
a new page, the programmed value will read correctly. This is used to determine when
the next page can be written. Note that the entire page is written simultaneously and any
address within the page can be used for polling. Data polling of the Flash will not work
for the value 0xFF, so when programming this value, the user will have to wait for at
least tWD_FLASH before programming the next page. As a chip-erased device contains
0xFF in all locations, programming of addresses that are meant to contain 0xFF, can be
skipped. See Table 131 for tWD_FLASH value.
305
4317B–AVR–02/05
Data Polling EEPROM
When a new byte has been written and is being programmed into EEPROM, reading the
address location being programmed will give the value 0xFF. At the time the device is
ready for a new byte, the programmed value will read correctly. This is used to determine when the next byte can be written. This will not work for the value 0xFF, but the
user should have the following in mind: As a chip-erased device contains 0xFF in all
locations, programming of addresses that are meant to contain 0xFF, can be skipped.
This does not apply if the EEPROM is re-programmed without chip erasing the device.
In this case, data polling cannot be used for the value 0xFF, and the user will have to
wait at least t WD_EEPROM before programming the next byte. See Table 131 for
tWD_EEPROM value.
Table 131. Minimum Wait Delay Before Writing the Next Flash or EEPROM Location
Symbol
Minimum Wait Delay
tWD_FLASH
4.5 ms
tWD_EEPROM
3.6 ms
tWD_ERASE
9.0 ms
Figure 146. Serial Programming Waveforms
SERIAL DATA INPUT
(MOSI)
MSB
LSB
SERIAL DATA OUTPUT
(MISO)
MSB
LSB
SERIAL CLOCK INPUT
(SCK)
SAMPLE
Table 132. Serial Programming Instruction Set
Instruction Format
Instruction
Byte 1
Byte 2
Byte 3
Byte4
Programming Enable
1010 1100
0101 0011
xxxx xxxx
xxxx xxxx
Enable Serial Programming after
RESET goes low.
Chip Erase
1010 1100
100x xxxx
xxxx xxxx
xxxx xxxx
Chip Erase EEPROM and Flash.
Read Program Memory
0010 H000
000a aaaa
bbbb bbbb
oooo oooo
Read H (high or low) data o from
Program memory at word address a:b.
Load Program Memory Page
0100 H000
000x xxxx
xxbb bbbb
iiii iiii
Write H (high or low) data i to Program
Memory page at word address b. Data
low byte must be loaded before Data
high byte is applied within the same
address.
Write Program Memory Page
0100 1100
000a aaaa
bbxx xxxx
xxxx xxxx
Write Program Memory Page at
address a:b.
Read EEPROM Memory
1010 0000
000x xxaa
bbbb bbbb
oooo oooo
Read data o from EEPROM memory at
address a:b.
306
Operation
AT90PWM2/3
4317B–AVR–02/05
AT90PWM2/3
Table 132. Serial Programming Instruction Set (Continued)
Instruction Format
Instruction
Byte 1
Byte 2
Byte 3
Byte4
Write EEPROM Memory
1100 0000
000x xxaa
bbbb bbbb
iiii iiii
Write data i to EEPROM memory at
address a:b.
Load EEPROM Memory
Page (page access)
1100 0001
0000 0000
0000 00bb
iiii iiii
Load data i to EEPROM memory page
buffer. After data is loaded, program
EEPROM page.
Write EEPROM Memory
Page (page access)
1100 0010
00xx xxaa
bbbb bb00
xxxx xxxx
Read Lock bits
0101 1000
0000 0000
xxxx xxxx
xxoo oooo
Read Lock bits. “0” = programmed, “1”
= unprogrammed. See Table 117 on
page 287 for details.
Write Lock bits
1010 1100
111x xxxx
xxxx xxxx
11ii iiii
Write Lock bits. Set bits = “0” to
program Lock bits. See Table 117 on
page 287 for details.
Read Signature Byte
0011 0000
000x xxxx
xxxx xxbb
oooo oooo
Read Signature Byte o at address b.
Write Fuse bits
1010 1100
1010 0000
xxxx xxxx
iiii iiii
Set bits = “0” to program, “1” to
unprogram. See Table XXX on page
XXX for details.
Write Fuse High bits
1010 1100
1010 1000
xxxx xxxx
iiii iiii
Set bits = “0” to program, “1” to
unprogram. See Table 121 on page
290 for details.
Write Extended Fuse Bits
1010 1100
1010 0100
xxxx xxxx
xxxx xxii
Set bits = “0” to program, “1” to
unprogram. See Table 120 on page
289 for details.
Read Fuse bits
0101 0000
0000 0000
xxxx xxxx
oooo oooo
Read Fuse bits. “0” = programmed, “1”
= unprogrammed. See Table XXX on
page XXX for details.
Read Fuse High bits
0101 1000
0000 1000
xxxx xxxx
oooo oooo
Read Fuse High bits. “0” = programmed, “1” = unprogrammed. See
Table 121 on page 290 for details.
Read Extended Fuse Bits
0101 0000
0000 1000
xxxx xxxx
oooo oooo
Read Extended Fuse bits. “0” = programmed, “1” = unprogrammed. See
Table 120 on page 289 for details.
Read Calibration Byte
0011 1000
000x xxxx
0000 0000
oooo oooo
Read Calibration Byte
Poll RDY/BSY
1111 0000
0000 0000
xxxx xxxx
xxxx xxxo
If o = “1”, a programming operation is
still busy. Wait until this bit returns to
“0” before applying another command.
Note:
Operation
Write EEPROM page at address a:b.
a = address high bits, b = address low bits, H = 0 - Low byte, 1 - High Byte, o = data out, i = data in, x = don’t care
SPI Serial Programming
Characteristics
For characteristics of the SPI module see “SPI Serial Programming Characteristics” on
page 307.
307
4317B–AVR–02/05
Electrical Characteristics(1)
Absolute Maximum Ratings*
Operating Temperature.................................. -40°C to +105°C
Storage Temperature ..................................... -65°C to +150°C
Voltage on any Pin except RESET
with respect to Ground ................................-1.0V to VCC+0.5V
Voltage on RESET with respect to Ground......-1.0V to +13.0V
*NOTICE:
Stresses beyond those listed under “Absolute
Maximum Ratings” may cause permanent damage to the device. This is a stress rating only and
functional operation of the device at these or
other conditions beyond those indicated in the
operational sections of this specification is not
implied. Exposure to absolute maximum rating
conditions for extended periods may affect
device reliability.
Maximum Operating Voltage .......................................... 56.0V
DC Current per I/O Pin ............................................... 40.0 mA
DC Current VCC and GND Pins................................ 200.0 mA
Note:
308
1. Electrical Characteristics for this product have not yet been finalized. Please consider
all values listed herein as preliminary and non-contractual.
AT90PWM2/3
4317B–AVR–02/05
AT90PWM2/3
DC Characteristics
TA = -45°C to +105°C, VCC = 2.7V to 5.5V (unless otherwise noted)
Symbol
Parameter
Condition
Min.
Typ.
Max.
(1)
Units
VIL
Input Low Voltage
Except XTAL1 pin
TBD
TBD
V
VIL1
Input Low Voltage
XTAL1 pin, External
Clock Selected
TBD
TBD(1)
V
VIH
Input High Voltage
Except XTAL1 and
RESET pins
TBD(2)
TBD
V
VIH1
Input High Voltage
XTAL1 pin, External
Clock Selected
TBD(2)
TBD
V
VIH2
Input High Voltage
RESET pin
TBD(2)
TBD
V
VOL
Output Low Voltage(3)
(Ports A, B, C, D, E, F; G)
IOL = 20 mA, VCC = 5V
IOL = 10 mA, VCC = 3V
TBD
V
VOH
Output High Voltage(4)
(Ports A, B, C, D,
IOH = -20 mA, VCC = 5V
IOH = -10 mA, VCC = 3V
IIL
Input Leakage
Current I/O Pin
VCC = 5.5V, pin low
(absolute value)
TBD
µA
IIH
Input Leakage
Current I/O Pin
VCC = 5.5V, pin high
(absolute value)
TBD
nA
RRST
Reset Pull-up Resistor
TBD
TBD
kΩ
Rpu
I/O Pin Pull-up Resistor
TBD
TBD
kΩ
Active 8 MHz, VCC = 3V
TBD
mA
Active 16 MHz, VCC = 5V
TBD
mA
Idle 8 MHz, VCC = 3V
TBD
mA
Idle 16 MHz, VCC = 5V
TBD
mA
Power Supply Current
ICC
Power-down mode(5)
V
WDT enabled, VCC = 3V
TBD
TBD
µA
WDT disabled, VCC = 3V
TBD
TBD
µA
TBD
mV
TBD
nA
VACIO
Analog Comparator
Input Offset Voltage
VCC = 5V
Vin = VCC/2
IACLK
Analog Comparator
Input Leakage Current
VCC = 5V
Vin = VCC/2
tACID
Analog Comparator
Propagation Delay
VCC = 2.7V
VCC = 5.0V
Note:
TBD
TBD
TBD
TBD
ns
1. “Max” means the highest value where the pin is guaranteed to be read as low
2. “Min” means the lowest value where the pin is guaranteed to be read as high
3. Although each I/O port can sink more than the test conditions (20 mA at VCC = 5V, 10 mA at VCC = 3V) under steady state
conditions (non-transient), the following must be observed:
TQFP and MLF Package:
1] The sum of all IOL, for all ports, should not exceed 400 mA.
2] The sum of all IOL, for ports A0 - A7, G2, C3 - C7 should not exceed 300 mA.
3] The sum of all IOL, for ports C0 - C2, G0 - G1, D0 - D7, XTAL2 should not exceed 150 mA.
4] The sum of all IOL, for ports B0 - B7, G3 - G4, E0 - E7 should not exceed 150 mA.
5] The sum of all IOL, for ports F0 - F7, should not exceed 200 mA.
If IOL exceeds the test condition, VOL may exceed the related specification. Pins are not guaranteed to sink current greater
than the listed test condition.
309
4317B–AVR–02/05
4. Although each I/O port can source more than the test conditions (20 mA at Vcc = 5V, 10 mA at Vcc = 3V) under steady state
conditions (non-transient), the following must be observed:
TQFP and MLF Package:
1] The sum of all IOH, for all ports, should not exceed 400 mA.
2] The sum of all IOH, for ports A0 - A7, G2, C3 - C7 should not exceed 300 mA.
3] The sum of all IOH, for ports C0 - C2, G0 - G1, D0 - D7, XTAL2 should not exceed 150 mA.
4] The sum of all IOH, for ports B0 - B7, G3 - G4, E0 - E7 should not exceed 150 mA.
5] The sum of all IOH, for ports F0 - F7, should not exceed 200 mA.
If IOH exceeds the test condition, VOH may exceed the related specification. Pins are not guaranteed to source current
greater than the listed test condition.
5. Minimum VCC for Power-down is 2.5V.
310
AT90PWM2/3
4317B–AVR–02/05
AT90PWM2/3
External Clock Drive Characteristics
Figure 147. External Clock Drive Waveforms
V IH1
V IL1
Table 133. External Clock Drive
VCC = 2.7 - 5.5V
Maximum Speed vs. VCC
VCC = 4.5 - 5.5V
Min.
Max.
Min.
Max.
Units
0
TBD
0
TBD
MHz
Symbol
Parameter
1/tCLCL
Oscillator Frequency
tCLCL
Clock Period
TBD
TBD
ns
tCHCX
High Time
TBD
TBD
ns
tCLCX
Low Time
TBD
TBD
ns
tCLCH
Rise Time
TBD
TBD
µs
tCHCL
Fall Time
TBD
TBD
µs
∆tCLCL
Change in period from one clock
cycle to the next
2
2
%
Maximum frequency is depending on VCC. As shown in Figure 148 , the Maximum Frequency vs. VCC curve is linear between x.xV < VCC < 4.5V. To calculate the maximum
frequency at a given voltage in this interval, use this equation:
( V – 0,9 )
Frequency = ---------------------0,15
At 3 Volt, this gives:
( 3 – 0,9 )
Frequency = ---------------------- = 14
0,15
Thus, when VCC = 3V, maximum frequency will be 14 MHz.
To calculate required voltage for a maximum frequency, use this equation::
Voltage = 0,9 + 0,15 • f
311
4317B–AVR–02/05
At 19 MHz this gives:
Voltage = 0,9 + 0,15 • 19 = 3,75V
Thus, a maximum frequency of 19 MHz requires VCC = 3.75 V.
Figure 148. Maximum Frequency vs. VCC, AT90PWM2/3
16Mhz
X Mhz
Safe Operating Area
2.7V
312
5.5V
AT90PWM2/3
4317B–AVR–02/05
AT90PWM2/3
SPI Timing Characteristics
See Figure 149 and Figure 150 for details.
Table 134. SPI Timing Parameters
Description
Mode
Min.
Typ.
Max.
1
SCK period
Master
See Table 73
2
SCK high/low
Master
50% duty cycle
3
Rise/Fall time
Master
TBD
4
Setup
Master
TBD
5
Hold
Master
TBD
6
Out to SCK
Master
0.5 • tsck
7
SCK to out
Master
TBD
8
SCK to out high
Master
TBD
9
SS low to out
Slave
TBD
10
SCK period
Slave
4 • tck
11
SCK high/low
Slave
2 • tck
12
Rise/Fall time
Slave
13
Setup
Slave
TBD
14
Hold
Slave
TBD
15
SCK to out
Slave
16
SCK to SS high
Slave
17
SS high to tri-state
Slave
18
SS low to SCK
Slave
ns
TBD
TBD
TBD
TBD
TBD
Figure 149. SPI Interface Timing Requirements (Master Mode)
SS
6
1
SCK
(CPOL = 0)
2
2
SCK
(CPOL = 1)
4
MISO
(Data Input)
5
3
MSB
...
LSB
7
MOSI
(Data Output)
MSB
8
...
LSB
313
4317B–AVR–02/05
Figure 150. SPI Interface Timing Requirements (Slave Mode)
SS
10
9
16
SCK
(CPOL = 0)
11
11
SCK
(CPOL = 1)
13
MOSI
(Data Input)
14
12
MSB
...
LSB
15
MISO
(Data Output)
314
MSB
17
...
LSB
X
AT90PWM2/3
4317B–AVR–02/05
AT90PWM2/3
ADC Characteristics
Table 135. ADC Characteristics - TA = -40°C to +90°C, VCC = 2.7V to 5.5V (unless otherwise noted)
Symbol
Parameter
Resolution
Condition
Min(1)
Typ(1)
Max(1)
Units
Single Ended Conversion
10
Bits
Differential Conversion
Gain = 10x or 20x
8
Bits
Single Ended Conversion
VREF = 4V
ADC clock = 200 kHz
1
TBD
LSB
Single Ended Conversion
VREF = 4V
ADC clock = 2 MHz
TBD
TBD
LSB
Absolute accuracy
Integral Non-linearity
VREF = 4V
0.5
LSB
Differential Non-linearity
VREF = 4V
0.5
LSB
Zero Error (Offset)
VREF = 4V
1
LSB
Conversion Time
Single Conversion
Clock Frequency
AVCC
VREF
VIN
8
260
50
Analog Supply Voltage
VCC - 0.3
µs
2000
(2)
VCC + 0.3
kHz
(3)
V
Single Ended Conversion
2.0
AVCC
V
Differential Conversion
2.0
AVCC - 0.2
V
Single ended channels
GND
VREF
Differential channels
TBD
TBD
Reference Voltage
Input voltage
Single ended channels
TBD
kHz
4
kHz
Input bandwidth
Differential channels
VINT
Internal Voltage Reference
2.4
2.56
2.8
V
RREF
Reference Input Resistance
TBD
TBD
TBD
kΩ
RAIN
Analog Input Resistance
TBD
MΩ
IHSM
Increased current
consumption
TBD
µA
Note:
1. Values are guidelines only. Actual values are TBD.
2. Minimum for AVCC is 2.7 V.
3. Maximum for AVCC is 5.5 V.
315
4317B–AVR–02/05
Table 136. ADC Characteristics - TA = -45°C to +105°C, VCC = 2.7V to 5.5V (unless otherwise noted)
Symbol
Parameter
Resolution
Condition
Min(1)
Typ(1)
Max(1)
Units
Single Ended Conversion
10
Bits
Differential Conversion
Gain = 1x or 20x
8
Bits
Differential Conversion
Gain = 200x
7
Bits
Single Ended Conversion
VREF = 4V
ADC clock = 200 kHz
1
TBD
LSB
Single Ended Conversion
VREF = 4V
ADC clock = 2 MHz
TBD
TBD
LSB
Absolute accuracy
Integral Non-linearity
VREF = 4V
0.5
LSB
Differential Non-linearity
VREF = 4V
0.5
LSB
Zero Error (Offset)
VREF = 4V
1
LSB
Conversion Time
Single Conversion
Clock Frequency
AVCC
VREF
VIN
8
260
50
Analog Supply Voltage
VCC - 0.3
µs
2000
(2)
VCC + 0.3
kHz
(3)
V
Single Ended Conversion
2.0
AVCC
V
Differential Conversion
2.0
AVCC - 0.2
V
Single ended channels
GND
VREF
Differential channels
TBD
TBD
Reference Voltage
Input voltage
Single ended channels
TBD
kHz
Differential channels
TBD
kHz
Input bandwidth
VINT
Internal Voltage Reference
2.4
2.56
2.8
V
RREF
Reference Input Resistance
TBD
TBD
TBD
kΩ
RAIN
Analog Input Resistance
TBD
MΩ
IHSM
Increased current
consumption i
TBD
µA
316
AT90PWM2/3
4317B–AVR–02/05
AT90PWM2/3
Parallel Programming Characteristics
Figure 151. Parallel Programming Timing, Including some General Timing
Requirements
tXLWL
tXHXL
XTAL1
tDVXH
tXLDX
tBVPH
tPLBX t BVWL
Data & Contol
(DATA, XA0/1, BS1, BS2)
PAGEL
tWLBX
tPHPL
tWLWH
WR
tPLWL
WLRL
RDY/BSY
tWLRH
Figure 152. Parallel Programming Timing, Loading Sequence with Timing
Requirements(1)
LOAD ADDRESS
(LOW BYTE)
LOAD DATA LOAD DATA
(HIGH BYTE)
LOAD DATA
(LOW BYTE)
t XLXH
tXLPH
LOAD ADDRESS
(LOW BYTE)
tPLXH
XTAL1
BS1
PAGEL
DATA
ADDR0 (Low Byte)
DATA (Low Byte)
DATA (High Byte)
ADDR1 (Low Byte)
XA0
XA1
Note:
1. The timing requirements shown in Figure 151 (i.e., tDVXH, tXHXL, and tXLDX) also apply
to loading operation.
317
4317B–AVR–02/05
Figure 153. Parallel Programming Timing, Reading Sequence (within the Same Page)
with Timing Requirements(1)
LOAD ADDRESS
(LOW BYTE)
READ DATA
(LOW BYTE)
READ DATA
(HIGH BYTE)
LOAD ADDRESS
(LOW BYTE)
tXLOL
XTAL1
tBVDV
BS1
tOLDV
OE
tOHDZ
DATA
ADDR0 (Low Byte)
DATA (High Byte)
DATA (Low Byte)
ADDR1 (Low Byte)
XA0
XA1
Note:
1. The timing requirements shown in Figure 151 (i.e., tDVXH, tXHXL, and tXLDX) also apply
to reading operation.
Table 137. Parallel Programming Characteristics, VCC = 5V ± 10%
Symbol
Parameter
Min.
VPP
Programming Enable Voltage
TBD
IPP
Programming Enable Current
tDVXH
Data and Control Valid before XTAL1 High
TBD
ns
tXLXH
XTAL1 Low to XTAL1 High
TBD
ns
tXHXL
XTAL1 Pulse Width High
TBD
ns
tXLDX
Data and Control Hold after XTAL1 Low
TBD
ns
tXLWL
XTAL1 Low to WR Low
TBD
ns
tXLPH
XTAL1 Low to PAGEL high
TBD
ns
tPLXH
PAGEL low to XTAL1 high
TBD
ns
tBVPH
BS1 Valid before PAGEL High
TBD
ns
tPHPL
PAGEL Pulse Width High
TBD
ns
tPLBX
BS1 Hold after PAGEL Low
TBD
ns
tWLBX
BS2/1 Hold after WR Low
TBD
ns
tPLWL
PAGEL Low to WR Low
TBD
ns
tBVWL
BS1 Valid to WR Low
TBD
ns
tWLWH
WR Pulse Width Low
TBD
ns
tWLRL
WR Low to RDY/BSY Low
tWLRH
318
WR Low to RDY/BSY High
(1)
tWLRH_CE
WR Low to RDY/BSY High for Chip Erase
tXLOL
XTAL1 Low to OE Low
(2)
Typ.
Max.
Units
TBD
V
TBD
µA
TBD
TBD
µs
TBD
TBD
ms
TBD
TBD
ms
TBD
ns
AT90PWM2/3
4317B–AVR–02/05
AT90PWM2/3
Table 137. Parallel Programming Characteristics, VCC = 5V ± 10% (Continued)
Symbol
Parameter
Min.
tBVDV
BS1 Valid to DATA valid
TBD
tOLDV
tOHDZ
Notes:
Typ.
Max.
Units
TBD
ns
OE Low to DATA Valid
TBD
ns
OE High to DATA Tri-stated
TBD
ns
1.
tWLRH is valid for the Write Flash, Write EEPROM, Write Fuse bits and Write Lock
bits commands.
2. tWLRH_CE is valid for the Chip Erase command.
319
4317B–AVR–02/05
Serial Programming Characteristics
Figure 154. Serial Programming Timing
MOSI / PDI
tSHOX
tOVSH
SCK
tSLSH
tSHSL
MISO / PDO
tSLIV
Table 138. Serial Programming Characteristics, TA = -40°C to 85°C, VCC = 2.7V - 5.5V
(Unless Otherwise Noted)
Symbol
Parameter
Min.
1/tCLCL
Oscillator Frequency (AT90PWM2/3L)
TBD
tCLCL
Oscillator Period (AT90PWM2/3L)
TBD
1/tCLCL
Oscillator Frequency
(AT90PWM2/3, VCC = 4.5V - 5.5V)
TBD
tCLCL
Oscillator Period
(AT90PWM2/3, VCC = 4.5V - 5.5V)
TBD
ns
tSHSL
SCK Pulse Width High
2 tCLCL*
ns
tSLSH
SCK Pulse Width Low
2 tCLCL*
ns
tOVSH
MOSI Setup to SCK High
tCLCL
ns
tSHOX
MOSI Hold after SCK High
2 tCLCL
ns
tSLIV
SCK Low to MISO Valid
Note:
320
TBD
Typ.
Max.
Units
TBD
MHz
ns
TBD
TBD
TBD
MHz
ns
1. 2 tCLCL for fck < 12 MHz, 3 tCLCL for fck >= 12 MHz
AT90PWM2/3
4317B–AVR–02/05
AT90PWM2/3
AT90PWM2/3 Typical
Characteristics –
Preliminary Data
The following charts show typical behavior. These figures are not tested during manufacturing. All current consumption measurements are performed with all I/O pins
configured as inputs and with internal pull-ups enabled. A sine wave generator with railto-rail output is used as clock source.
All Active- and Idle current consumption measurements are done with all bits in the PRR
register set and thus, the corresponding I/O modules are turned off. Also the Analog
Comparator is disabled during these measurements. Table 139 on page 327 and Table
140 on page 327 show the additional current consumption compared to ICC Active and
ICC Idle for every I/O module controlled by the Power Reduction Register. See “Power
Reduction Register” on page 37 for details.
The power consumption in Power-down mode is independent of clock selection.
The current consumption is a function of several factors such as: operating voltage,
operating frequency, loading of I/O pins, switching rate of I/O pins, code executed and
ambient temperature. The dominating factors are operating voltage and frequency.
The current drawn from capacitive loaded pins may be estimated (for one pin) as
CL*VCC*f where CL = load capacitance, VCC = operating voltage and f = average switching frequency of I/O pin.
The parts are characterized at frequencies higher than test limits. Parts are not guaranteed to function properly at frequencies higher than the ordering code indicates.
The difference between current consumption in Power-down mode with Watchdog
Timer enabled and Power-down mode with Watchdog Timer disabled represents the differential current drawn by the Watchdog Timer.
Active Supply Current
Figure 155. Active Supply Current vs. Frequency (0.1 - 1.0 MHz)
ACTIVE SUPPLY CURRENT vs. FREQUENCY
0.1 - 1.0 MHz
1.2
5.5 V
1
TE
A
PL
TE
M
C
E
T
RA
A
CH
E
B
O
T
ICC (mA)
0.8
0.6
0.4
0.2
5.0 V
D
ZE
I
R
4.5 V
4.0 V
3.3 V
2.7 V
1.8 V
0
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
Frequency (MHz)
321
4317B–AVR–02/05
Figure 156. Active Supply Current vs. Frequency (1 - 24 MHz)
ACTIVE SUPPLY CURRENT vs. FREQUENCY
1 - 24 MHz
18
16
5.5V
14
ICC (mA)
12
TE
A
PL
M
CT
A
TE
AR
H
C
BE
2.7V
TO
10
8
6
4
2
5.0V
D
E
Z
I
ER
4.5V
4.0V
3.3V
1.8V
0
0
4
8
12
16
20
24
Frequency (MHz)
Figure 157. Active Supply Current vs. VCC (Internal RC Oscillator, 128 kHz)
ACTIVE SUPPLY CURRENT vs. VCC
INTERNAL RC OSCILLATOR, 128 KHz
0.14
-40 °C
25 °C
85 °C
0.12
ED
E
Z
T
I
LA
ER
P
T
M
AC
TE
R
HA
C
BE
O
T
ICC (mA)
0.1
0.08
0.06
0.04
0.02
0
1.5
2
2.5
3
3.5
4
4.5
5
5.5
VCC (V)
322
AT90PWM2/3
4317B–AVR–02/05
AT90PWM2/3
Figure 158. Active Supply Current vs. VCC (Internal RC Oscillator, 1 MHz)
ACTIVE SUPPLY CURRENT vs. VCC
INTERNAL RC OSCILLATOR, 1 MHz
1.4
25 °C
-40 °C
85 °C
1.2
ED
E
Z
T
I
LA
ER
P
T
M
AC
TE
R
HA
C
BE
O
T
ICC (mA)
1
0.8
0.6
0.4
0.2
0
1.5
2
2.5
3
3.5
4
4.5
5
5.5
VCC (V)
Figure 159. Active Supply Current vs. VCC (Internal RC Oscillator, 8 MHz)
ACTIVE SUPPLY CURRENT vs. VCC
INTERNAL RC OSCILLATOR, 8 MHz
7
25 °C
-40 °C
85 °C
6
E
AT
ICC (mA)
5
PL
M
CT
E
A
T
AR
H
C
BE
TO
4
3
2
IZE
R
E
D
1
0
1.5
2
2.5
3
3.5
4
4.5
5
5.5
VCC (V)
323
4317B–AVR–02/05
Figure 160. Active Supply Current vs. VCC (32 kHz External Oscillator)
ACTIVE SUPPLY CURRENT vs. VCC
32 kHz EXTERNAL OSCILLATOR
60
25 °C
50
TE
IZE
A
R
PL
TE
M
C
TE
RA
A
CH
E
B
TO
ICC (uA)
40
30
20
10
D
0
1.5
2
2.5
3
3.5
4
4.5
5
5.5
VCC (V)
Idle Supply Current
Figure 161. Idle Supply Current vs. Frequency (0.1 - 1.0 MHz)
IDLE SUPPLY CURRENT vs. FREQUENCY
0.1 - 1.0 MHz
0.18
5.5 V
0.16
ED
E
Z
T
I
LA
ER
P
T
M
AC
TE
R
HA
C
BE
TO
0.14
ICC (mA)
0.12
0.1
0.08
0.06
0.04
5.0 V
4.5 V
4.0 V
3.3 V
2.7 V
1.8 V
0.02
0
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
Frequency (MHz)
324
AT90PWM2/3
4317B–AVR–02/05
AT90PWM2/3
Figure 162. Idle Supply Current vs. Frequency (1 - 24 MHz)
IDLE SUPPLY CURRENT vs. FREQUENCY
1 - 24 MHz
4.5
ED
E
Z
T
I
LA
ER
P
T
M
AC
TE
R
HA
C
BE
O
T
4
3.5
ICC (mA)
3
2.5
2
1.5
5.5V
5.0V
4.5V
4.0V
3.3V
1
2.7V
0.5
1.8V
0
0
4
8
12
16
20
24
Frequency (MHz)
Figure 163. Idle Supply Current vs. VCC (Internal RC Oscillator, 128 kHz)
IDLE SUPPLY CURRENT vs. VCC
INTERNAL RC OSCILLATOR, 128 KHz
0.03
E
IZ
AT
R
L
P
TE
M
C
TE
RA
A
CH
E
B
TO
0.025
ICC (mA)
0.02
0.015
0.01
-40 °C
85 °C
25 °C
ED
0.005
0
1.5
2
2.5
3
3.5
4
4.5
5
5.5
VCC (V)
325
4317B–AVR–02/05
Figure 164. Idle Supply Current vs. VCC (Internal RC Oscillator, 1 MHz)
IDLE SUPPLY CURRENT vs. VCC
INTERNAL RC OSCILLATOR, 1 MHz
0.35
E
AT
PL
M
CT
E
A
T
AR
H
C
BE
TO
0.3
ICC (mA)
0.25
0.2
0.15
ED
Z
I
ER
85 °C
25 °C
-40 °C
0.1
0.05
0
1.5
2
2.5
3
3.5
4
4.5
5
5.5
VCC (V)
Figure 165. Idle Supply Current vs. VCC (Internal RC Oscillator, 8 MHz)
IDLE SUPPLY CURRENT vs. VCC
INTERNAL RC OSCILLATOR, 8 MHz
1.6
TE
A
PL
TE
M
C
TE
RA
A
CH
E
B
O
T
1.4
1.2
ICC (mA)
1
0.8
0.6
85 °C
25 °C
-40 °C
D
ZE
I
R
0.4
0.2
0
1.5
2
2.5
3
3.5
4
4.5
5
5.5
VCC (V)
326
AT90PWM2/3
4317B–AVR–02/05
AT90PWM2/3
Figure 166. Idle Supply Current vs. VCC (32 kHz External Oscillator)
IDLE SUPPLY CURRENT vs. VCC
32 kHz EXTERNAL OSCILLATOR
30
E
AT
25
PL
M
CT
E
A
T
AR
H
C
E
B
TO
ICC (uA)
20
15
10
IZE
R
E
D
25 °C
5
0
1.5
2
2.5
3
3.5
4
4.5
5
5.5
VCC (V)
Using the Power Reduction
Register
The tables and formulas below can be used to calculate the additional current consumption for the different I/O modules in Active and Idle mode. The enabling or disabling of
the I/O modules are controlled by the Power Reduction Register. See “Power Reduction
Register” on page 41 for details.
Table 139.
Additional Current Consumption for the different I/O modules (absolute values)
PRR bit
Typical numbers
VCC = 3V, F = 4MHz
VCC = 5V, F = 8MHz
PRUSART0
51 uA
220 uA
PRPSC
75 uA
315 uA
PRD2A
72 uA
300 uA
PRTIM1
32 uA
130 uA
PRTIM0
24 uA
100 uA
PRSPI
95 uA
400 uA
PRADC
75 uA
315 uA
Table 140.
Additional Current Consumption (percentage) in Active and Idle mode
PRR bit
Additional Current consumption
compared to Active with external
clock
(see Figure 155 and Figure 156)
Additional Current consumption
compared to Idle with external
clock
(see Figure 161 and Figure 162)
PRUSART0
3.3%
18%
PRPSC
PRD2A
327
4317B–AVR–02/05
Table 140.
Additional Current Consumption (percentage) in Active and Idle mode (Continued)
PRR bit
Additional Current consumption
compared to Active with external
clock
(see Figure 155 and Figure 156)
Additional Current consumption
compared to Idle with external
clock
(see Figure 161 and Figure 162)
PRTIM1
2.0%
11%
PRTIM0
1.6%
8.5%
PRSPI
6.1%
33%
PRADC
4.9%
26%
It is possible to calculate the typical current consumption based on the numbers from
Table 2 for other VCC and frequency settings than listed in Table 1.
Example 1
Calculate the expected current consumption in idle mode with USART0, TIMER1, and
TWI enabled at VCC = 3.0V and F = 1MHz. From Table 2, third column, we see that we
need to add 18% for the USART0, 26% for the TWI, and 11% for the TIMER1 module.
Reading from Figure 3, we find that the idle current consumption is ~0,075mA at VCC =
3.0V and F = 1MHz. The total current consumption in idle mode with USART0, TIMER1,
and TWI enabled, gives:
I CC total ≈ 0,075mA • ( 1 + 0,18 + 0,26 + 0,11 ) ≈ 0,116mA
Example 2
Same conditions as in example 1, but in active mode instead. From Table 2, second column we see that we need to add 3.3% for the USART0, 4.8% for the TWI, and 2.0% for
the TIMER1 module. Reading from Figure 1, we find that the active current consumption
is ~0,42mA at VCC = 3.0V and F = 1MHz. The total current consumption in idle mode
with USART0, TIMER1, and TWI enabled, gives:
I CC total ≈ 0,42mA • ( 1 + 0,033 + 0,048 + 0,02 ) ≈ 0,46mA
Example 3
All I/O modules should be enabled. Calculate the expected current consumption in
active mode at VCC = 3.6V and F = 10MHz. We find the active current consumption without the I/O modules to be ~ 4.0mA (from Figure 2). Then, by using the numbers from
Table 2 - second column, we find the total current consumption:
I CC total ≈ 4,0mA • ( 1 + 0,033 + 0,048 + 0,047 + 0,02 + 0,016 + 0,061 + 0,049 ) ≈ 5,1mA
328
AT90PWM2/3
4317B–AVR–02/05
AT90PWM2/3
Power-Down Supply
Current
Figure 167. Power-Down Supply Current vs. VCC (Watchdog Timer Disabled)
POWER-DOWN SUPPLY CURRENT vs. VCC
WATCHDOG TIMER DISABLED
2.5
TE
IZE
A
R
PL
TE
M
C
TE
RA
A
H
C
BE
O
T
ICC (uA)
2
1.5
1
D
85 °C
25 °C
-40 °C
0.5
0
1.5
2
2.5
3
3.5
4
4.5
5
5.5
VCC (V)
Figure 168. Power-Down Supply Current vs. VCC (Watchdog Timer Enabled)
POWER-DOWN SUPPLY CURRENT vs. VCC
WATCHDOG TIMER ENABLED
12
ED
E
Z
T
I
LA
ER
P
T
M
AC
TE
R
HA
C
BE
O
T
10
ICC (uA)
8
6
4
85 °C
-40 °C
25 °C
2
0
1.5
2
2.5
3
3.5
4
4.5
5
5.5
VCC (V)
329
4317B–AVR–02/05
Power-Save Supply
Current
Figure 169. Power-Save Supply Current vs. VCC (Watchdog Timer Disabled)
POWER-SAVE SUPPLY CURRENT vs. VCC
WATCHDOG TIMER DISABLED
12
TE
IZE
A
R
PL
TE
M
C
TE
RA
A
CH
E
B
O
T
10
ICC (uA)
8
6
4
D
25 °C
2
0
1.5
2
2.5
3
3.5
4
4.5
5
5.5
VCC (V)
Standby Supply Current
Figure 170. Standby Supply Current vs. VCC (Low Power Crystal Oscillator)
STANDBY SUPPLY CURRENT vs. VCC
Low Power Crystal Oscillator
E
AT
180
PL
M
CT
A
TE
AR
H
C
BE
TO
160
140
ICC (uA)
120
100
80
D
E
Z
I
ER
6 MHz Xtal
6 MHz Res.
4 MHz Res.
4 MHz Xtal
2 MHz Xtal
2 MHz Res.
455kHz Res.
1 MHz Res.
60
40
20
32 kHz Xtal
0
1.5
2
2.5
3
3.5
4
4.5
5
5.5
VCC (V)
330
AT90PWM2/3
4317B–AVR–02/05
AT90PWM2/3
Figure 171. Standby Supply Current vs. VCC (Full Swing Crystal Oscillator)
STANDBY SUPPLY CURRENT vs. VCC
Full Swing Crystal Oscillator
500
450
TE
A
PL
TE
M
C
TE
RA
A
H
C
BE
O
T
400
ICC (uA)
350
300
250
200
150
16 MHz Xtal
ED
Z
I
R
12 MHz Xtal
6 MHz Xtal
(ckopt)
4 MHz Xtal
(ckopt)
2 MHz Xtal
(ckopt)
100
50
0
1.5
2
2.5
3
3.5
4
4.5
5
5.5
VCC (V)
Pin Pull-up
Figure 172. I/O Pin Pull-Up Resistor Current vs. Input Voltage (VCC = 5V)
I/O PIN PULL-UP RESISTOR CURRENT vs. INPUT VOLTAGE
VCC = 5V
160
140
25 °C
85 °C
120
-40 °C
IOP (uA)
100
80
60
40
ED
E
Z
T
I
LA
ER
P
T
M
AC
TE
R
HA
C
BE
TO
20
0
0
1
2
3
4
5
6
VOP (V)
331
4317B–AVR–02/05
Figure 173. I/O Pin Pull-Up Resistor Current vs. Input Voltage (VCC = 2.7V)
I/O PIN PULL-UP RESISTOR CURRENT vs. INPUT VOLTAGE
VCC = 2.7V
90
80
25 °C
85 °C
70
IOP (uA)
60
E
AT
-40 °C
PL
M
CT
E
A
T
AR
H
C
BE
TO
50
40
30
20
ED
Z
I
ER
10
0
0
0.5
1
1.5
2
2.5
3
VOP (V)
Figure 174. Reset Pull-Up Resistor Current vs. Reset Pin Voltage (VCC = 5V)
RESET PULL-UP RESISTOR CURRENT vs. RESET PIN VOLTAGE
VCC = 5V
120
-40ºC
25ºC
ED
E
Z
T
I
LA
ER
P
T
M
AC
TE
R
HA
C
BE
TO
100
85ºC
IRESET (uA)
80
60
40
20
0
0
1
2
3
4
5
6
VRESET (V)
332
AT90PWM2/3
4317B–AVR–02/05
AT90PWM2/3
Figure 175. Reset Pull-Up Resistor Current vs. Reset Pin Voltage (VCC = 2.7V)
RESET PULL-UP RESISTOR CURRENT vs. RESET PIN VOLTAGE
VCC = 2.7V
70
60
ED
E
Z
T
I
LA
ER
P
T
M
AC
TE
R
HA
C
BE
TO
25 °C
-40 °C
IRESET (uA)
50
85 °C
40
30
20
10
0
0
0.5
1
1.5
2
2.5
3
VRESET (V)
Pin Driver Strength
Figure 176. I/O Pin Source Current vs. Output Voltage (VCC = 5V)
I/O PIN SOURCE CURRENT vs. OUTPUT VOLTAGE
VCC = 5V
90
80
-40 °C
70
25 °C
D
85 °C
E
E
Z
T
RI
LA
E
P
M
CT
E
A
T
AR
H
C
BE
TO
IOH (mA)
60
50
40
30
20
10
0
0
1
2
3
4
5
6
VOH (V)
333
4317B–AVR–02/05
Figure 177. I/O Pin Source Current vs. Output Voltage (VCC = 2.7V)
I/O PIN SOURCE CURRENT vs. OUTPUT VOLTAGE
VCC = 2.7V
35
30
-40 °C
25 °C
85 °C
IOH (mA)
25
20
15
10
D
E
E
Z
T
RI
LA
E
P
M
CT
E
A
T
AR
H
C
BE
TO
5
0
0
0.5
1
1.5
2
2.5
3
VOH (V)
Figure 178. I/O Pin Source Current vs. Output Voltage (VCC = 1.8V)
I/O PIN SOURCE CURRENT vs. OUTPUT VOLTAGE
VCC = 1.8V
9
25 °C -40 °C
8
85 °C
7
IOH (mA)
6
5
4
3
2
ED
E
Z
T
I
LA
ER
P
T
M
AC
TE
R
HA
C
BE
TO
1
0
0
0.2
0.4
0.6
0.8
1
1.2
1.4
1.6
1.8
2
VOH (V)
334
AT90PWM2/3
4317B–AVR–02/05
AT90PWM2/3
Figure 179. I/O Pin Sink Current vs. Output Voltage (VCC = 5V)
I/O PIN SINK CURRENT vs. OUTPUT VOLTAGE
VCC = 5V
80
TE
70
LA
P
TE
M
C
TE
RA
A
CH
E
B
TO
60
IOL (mA)
50
40
30
25 °C
ED
Z
I
R
85 °C
20
10
0
0
0.5
1
1.5
2
2.5
VOL (V)
Figure 180. I/O Pin Sink Current vs. Output Voltage (VCC = 2.7V)
I/O PIN SINK CURRENT vs. OUTPUT VOLTAGE
VCC = 2.7V
40
35
-40 °C
30
25 °C
D
E
85
°C
E
Z
T
I
LA
ER
P
T
M
AC
TE
R
HA
C
BE
TO
IOL (mA)
25
20
15
10
5
0
0
0.5
1
1.5
2
2.5
VOL (V)
335
4317B–AVR–02/05
Figure 181. I/O Pin Sink Current vs. Output Voltage (VCC = 1.8V)
I/O PIN SINK CURRENT vs. OUTPUT VOLTAGE
VCC = 1.8V
14
12
-40 °C
25 °C
ED
E
Z
T
I
85 °C
LA
ER
P
T
M
AC
TE
R
HA
C
BE
O
T
IOL (mA)
10
8
6
4
2
0
0
0.2
0.4
0.6
0.8
1
1.2
1.4
1.6
1.8
2
VOL (V)
Pin Thresholds and
Hysteresis
Figure 182. I/O Pin Input Threshold Voltage vs. VCC (VIH, I/O Pin Read As '1')
I/O PIN INPUT THRESHOLD VOLTAGE vs. VCC
VIH, IO PIN READ AS '1'
25 °C
85 °C
-40 °C
3
2.5
ED
E
Z
T
I
LA
ER
P
T
M
AC
TE
R
HA
C
BE
TO
Threshold (V)
2
1.5
1
0.5
0
1.5
2
2.5
3
3.5
4
4.5
5
5.5
VCC (V)
336
AT90PWM2/3
4317B–AVR–02/05
AT90PWM2/3
Figure 183. I/O Pin Input Threshold Voltage vs. VCC (VIL, I/O Pin Read As '0')
I/O PIN INPUT THRESHOLD VOLTAGE vs. VCC
VIL, IO PIN READ AS '0'
3
85 °C
-40 °C
25 °C
2.5
TE
IZE
A
R
PL
TE
M
C
TE
RA
A
H
C
BE
O
T
Threshold (V)
2
1.5
1
0.5
D
0
1.5
2
2.5
3
3.5
4
4.5
5
5.5
VCC (V)
Figure 184. Reset Input Threshold Voltage vs. VCC (VIH, Reset Pin Read As '1')
RESET INPUT THRESHOLD VOLTAGE vs. VCC
VIH, IO PIN READ AS '1'
3
2.5
ED
E
Z
T
I
LA
ER
P
T
M
AC
TE
R
HA
C
BE
TO
2
Threshold (V)
25 °C
85 °C
-40 °C
1.5
1
0.5
0
1.5
2
2.5
3
3.5
4
4.5
5
5.5
VCC (V)
337
4317B–AVR–02/05
Figure 185. Reset Input Threshold Voltage vs. VCC (VIL, Reset Pin Read As '0')
RESET INPUT THRESHOLD VOLTAGE vs. VCC
VIL, IO PIN READ AS '0'
3
-40 °C
85 °C
25 °C
2.5
E
AT
Threshold (V)
2
PL
M
CT
A
TE
AR
H
C
BE
TO
1.5
1
0.5
IZE
R
E
D
0
1.5
2
2.5
3
3.5
4
4.5
5
5.5
VCC (V)
Figure 186. Reset Input Pin Hysteresis vs. VCC
RESET PIN INPUT HYSTERESIS vs. VCC
600
Input Hysteresis (mV)
500
ED
E
Z
T
I
LA
ER
P
T
M
AC
TE
R
HA
C
BE
TO
400
300
200
100
VIL
0
2
2.5
3
3.5
4
4.5
5
5.5
VCC (V)
338
AT90PWM2/3
4317B–AVR–02/05
AT90PWM2/3
BOD Thresholds and
Analog Comparator
Offset
Figure 187. BOD Thresholds vs. Temperature (BODLEVEL Is 4.0V)
BOD THRESHOLDS vs. TEMPERATURE
BODLEVEL IS 4.0V
4.5
D
E
E
Z
T
RI
LA Rising Vcc
E
P
M
CT
A
TE
AR
H
C
BE
TO
4.45
Threshold (V)
4.4
4.35
4.3
Falling Vcc
4.25
4.2
-50
-40
-30
-20
-10
0
10
20
30
40
50
60
70
80
90
100
90
100
Temperature (C)
Figure 188. BOD Thresholds vs. Temperature (BODLEVEL Is 2.7V)
BOD THRESHOLDS vs. TEMPERATURE
BODLEVEL IS 2.7V
2.9
ED
E
Z
T
I
LARising VccTER
P
M
AC
TE
R
HA
C
BE
TO
Falling Vcc
2.85
Threshold (V)
2.8
2.75
2.7
2.65
2.6
-50
-40
-30
-20
-10
0
10
20
30
40
50
60
70
80
Temperature (C)
339
4317B–AVR–02/05
Figure 189. BOD Thresholds vs. Temperature (BODLEVEL Is 1.8V)
BOD THRESHOLDS vs. TEMPERATURE
BODLEVEL IS 1.8V
1.86
ED
E
Z
T
I
LARising VccTER
P
M
AC
TE
R
HA
C
BE
O
T
Threshold (V)
1.84
1.82
1.8
Falling Vcc
1.78
1.76
-50
-40
-30
-20
-10
0
10
20
30
40
50
60
70
80
90
100
Temperature (C)
Figure 190. Bandgap Voltage vs. VCC
BANDGAP VOLTAGE vs. V CC
Bandgap Voltage (V)
1.1
E
AT
1.095
PL
M
CT
E
A
T
AR
H
C
BE
TO
1.09
1.085
E
Z
I
ER
D
-40 C
85 C
1.08
1.5
2
2.5
3
3.5
4
4.5
5
5.5
6
VCC (V)
340
AT90PWM2/3
4317B–AVR–02/05
AT90PWM2/3
Figure 191. Analog Comparator Offset Voltage vs. Common Mode Voltage (VCC=5V)
ANALOG COMPARATOR OFFSET VOLTAGE vs. COMMON MODE VOLTAGE
VCC =5V
Analog comparator offset voltage (V)
0.009
0.008
85 C
ED
E
Z
T
I
LA
ER
P
T
M
AC
TE
R
HA
C
BE
O
T
0.007
0.006
0.005
0.004
0.003
0.002
-40 C
0.001
0
0
0.5
1
1.5
2
2.5
3
3.5
4
4.5
5
Common Mode Voltage (V)
Figure 192. Analog Comparator Offset Voltage vs. Common Mode Voltage (VCC=2.7V)
ANALOG COMPARATOR OFFSET VOLTAGE vs. COMMON MODE VOLTAGE
VCC=5V
4
TE
LA
P
TE
M
C
TE
RA
A
CH
E
B
O
T
3
2.5
(mV)
Analog comparator offset voltage
3.5
2
1.5
D
ZE
I
R
85 C
-40 C
1
0.5
0
0
0.5
1
1.5
2
2.5
Common Mode Voltage (V)
341
4317B–AVR–02/05
Internal Oscillator Speed Figure 193. Watchdog Oscillator Frequency vs. VCC
WATCHDOG OSCILLATOR FREQUENCY vs. VCC
120
ED
E
Z
T
I
LA
ER
P
T
M
AC
TE
R
HA
C
BE
O
T
FRC (kHz)
115
110
105
100
-40 °C
25 °C
85 °C
95
1.5
2
2.5
3
3.5
4
4.5
5
5.5
VCC (V)
Figure 194. Calibrated 8 MHz RC Oscillator Frequency vs. Temperature
CALIBRATED 8 MHz RC OSCILLATOR FREQUENCY vs. TEMPERATURE
8.4
8.3
8.1
FRC (MHz)
5.0 V
2.7 V
1.8 V
ED
E
Z
T
I
LA
ER
P
T
M
AC
TE
R
HA
C
BE
TO
8.2
8
7.9
7.8
7.7
7.6
7.5
7.4
-50
-40
-30
-20
-10
0
10
20
30
40
50
60
70
80
90
100
Temperature (C)
342
AT90PWM2/3
4317B–AVR–02/05
AT90PWM2/3
Figure 195. Calibrated 8 MHz RC Oscillator Frequency vs. VCC
CALIBRATED 8MHz RC OSCILLATOR FREQUENCY vs. VCC
8.6
8.4
ED
E
Z
T
I
LA
ER
P
T
M
AC
TE
R
HA
C
BE
TO
FRC (MHz)
8.2
8
7.8
85 ˚C
25 ˚C
-40 ˚C
7.6
7.4
1.5
2
2.5
3
3.5
4
4.5
5
5.5
VCC (V)
Figure 196. Calibrated 8 MHz RC Oscillator Frequency vs. Osccal Value
CALIBRATED 8MHz RC OSCILLATOR FREQUENCY vs. OSCCAL VALUE
13.5
E
AT
PL
M
CT
E
A
T
AR
H
C
E
B
TO
FRC (MHz)
11.5
9.5
7.5
IZE
R
E
85 °C
25 °C
-40 °C
D
5.5
3.5
0
16
32
48
64
80
96
112
128
144 160
176 192
208
224 240
OSCCAL VALUE
343
4317B–AVR–02/05
Current Consumption of
Peripheral Units
Figure 197. Brownout Detector Current vs. VCC
BROWNOUT DETECTOR CURRENT vs. VCC
32
30
TE
LA
P
M
TE
RA
A
CH
E
B
TO
ICC (uA)
28
26
24
22
IZE
R
E
CT
D
-40 ˚C
25 ˚C
85 ˚C
20
18
1.5
2
2.5
3
3.5
4
4.5
5
5.5
VCC (V)
Figure 198. ADC Current vs. VCC (ADC at 50 kHz)
AREF vs. VCC
ADC AT 50 KHz
500
450
-40 °C
ICC (uA)
400
350
TE
300
250
TO
200
B
L
MP
E
AT
AR
H
EC
T
AC
D
ZE
I
ER
25 °C
85 °C
150
1.5
2
2.5
3
3.5
4
4.5
5
5.5
VCC (V)
344
AT90PWM2/3
4317B–AVR–02/05
AT90PWM2/3
Figure 199. Aref Current vs. VCC (ADC at 1 MHz)
AREF vs. VCC
ADC AT 1 MHz
180
85 ˚C
25 ˚C
-40 ˚C
160
ED
E
Z
T
I
LA
ER
P
T
M
AC
TE
R
HA
C
BE
O
T
140
ICC (uA)
120
100
80
60
40
20
0
1.5
2
2.5
3
3.5
4
4.5
5
5.5
VCC (V)
Figure 200. Analog Comparator Current vs. VCC
ANALOG COMPARATOR CURRENT vs. VCC
140
120
Z
TE
A
RI
L
E
MP
CT
E
A
T
AR
H
C
BE
TO
ICC (uA)
100
80
60
40
-40 ˚C
ED
25 ˚C
85 ˚C
20
0
1.5
2
2.5
3
3.5
4
4.5
5
5.5
VCC (V)
345
4317B–AVR–02/05
Figure 201. Programming Current vs. VCC
PROGRAMMING CURRENT vs. Vcc
14
ED
E
Z
T
I
LA
ER
P
T
M
AC
TE
R
HA
C
BE
TO
12
ICC (mA)
10
8
6
4
-40 ˚C
25 ˚C
85 ˚C
2
0
1.5
2
2.5
3
3.5
4
4.5
5
5.5
VCC (V)
Current Consumption in
Reset and Reset Pulse
width
Figure 202. Reset Supply Current vs. VCC (0.1 - 1.0 MHz, Excluding Current through
the Reset Pull-up)
RESET SUPPLY CURRENT vs. VCC
0.1 - 1.0 MHz, EXCLUDING CURRENT THROUGH THE RESET PULL-UP
0.18
5.5 V
0.16
0.14
ICC (mA)
0.12
M
TE
0.1
0.08
0.06
TO
0.04
B
PL
E
AT
HA
C
E
CT
A
R
D
ZE
I
ER
5.0 V
4.5 V
4.0 V
3.3 V
2.7 V
1.8 V
0.02
0
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
Frequency (MHz)
346
AT90PWM2/3
4317B–AVR–02/05
AT90PWM2/3
Figure 203. Reset Supply Current vs. VCC (1 - 24 MHz, Excluding Current through the
Reset Pull-up)
RESET SUPPLY CURRENT vs. VCC
1 - 24 MHz, EXCLUDING CURRENT THROUGH THE RESET PULL-UP
4.5
D
E
E
Z
T
RI
LA
E
P
M
CT
A
TE
AR
H
C
BE
TO
4
3.5
ICC (mA)
3
2.5
2
1.5
5.5V
5.0V
4.5V
4.0V
3.3V
1
2.7V
0.5
1.8V
0
0
4
8
12
16
20
24
Frequency (MHz)
Figure 204. Reset Pulse Width vs. VCC
RESET PULSE WIDTH vs. VCC
2500
ED
E
Z
T
I
LA
ER
P
T
M
AC
TE
R
HA
C
BE
TO
Pulsewidth (ns)
2000
1500
1000
85 ˚C
-40 ˚C
25 ˚C
500
0
1.5
2
2.5
3
3.5
4
4.5
5
5.5
VCC (V)
347
4317B–AVR–02/05
Register Summary
Address
Name
(0xFF)
PICR2H
Bit 7
Bit 6
Bit 5
Bit 4
Bit 3
Bit 2
Bit 1
Bit 0
(0xFE)
PICR2L
(0xFD)
PFRC2B
PCAPE2B
PRTGE2B
PELEV2B
PFLTE2B
PISEL2B
PFM2B2
PFM2B1
PFM2B0
(0xFC)
PFRC2A
PCAPE2A
PRTGE2A
PELEV2A
PFLTE2A
PISEL2A
PFM2A2
PFM2A1
PFM2A0
(0xFB)
PCTL2
PPRE21
PPRE20
PBFM2
PAOC2B
PAOC2A
PARUN2
PCCYC2
PRUN2
(0xFA)
PCNF2
PFIFTY2
PALOCK2
PLOCK2
PMODE21
PMODE20
POP2
PCLKSEL2
POME2
(0xF9)
OCR2RBH
(0xF8)
OCR2RBL
(0xF7)
OCR2SBH
(0xF6)
OCR2SBL
(0xF5)
OCR2RAH
(0xF4)
OCR2RAL
(0xF3)
OCR2SAH
(0xF2)
OCR2SAL
(0xF1)
POM2
POMV2B3
POMV2B2
POMV2B1
POMV2B0
POS23
POS22
PSYNC21
PSYNC20
POEN2B
POMV2A1
POEN2C
POMV2A0
PSOC2
POMV2A3
POEN2D
POMV2A2
(0xF0)
(0xEF)
PICR1H
POEN2A
(0xEE)
PICR1L
(0xED)
PFRC1B
PCAPE1B
PRTGE1B
PELEV1B
PFLTE1B
PISEL1B
PFM1B2
PFM1B1
PFM1B0
(0xEC)
PFRC1A
PCAPE1A
PRTGE1A
PELEV1A
PFLTE1A
PISEL1A
PFM1A2
PFM1A1
PFM1A0
(0xEB)
PCTL1
PPRE11
PPRE10
PBFM1
PAOC1B
PAOC1A
PARUN1
PCCYC1
PRUN1
(0xEA)
PCNF1
PFIFTY1
PALOCK1
PLOCK1
PMODE11
PMODE10
POP1
PCLKSEL1
-
(0xE9)
OCR1RBH
–
–
–
(0xE8)
OCR1RBL
(0xE7)
OCR1SBH
(0xE6)
OCR1SBL
(0xE5)
OCR1RAH
(0xE4)
OCR1RAL
(0xE3)
OCR1SAH
(0xE2)
OCR1SAL
(0xE1)
Reserved
–
–
–
–
(0xE0)
PSOC1
POS11
POS10
PSYNC11
PSYNC10
(0xDF)
PICR0H
POEN1B
–
POEN1A
(0xDE)
PICR0L
(0xDD)
PFRC0B
PCAPE0B
PRTGE0B
PELEV0B
PFLTE0B
PISEL0B
PFM0B2
PFM0B1
PFM0B0
(0xDC)
PFRC0A
PCAPE0A
PRTGE0A
PELEV0A
PFLTE0A
PISEL0A
PFM0A2
PFM0A1
PFM0A0
(0xDB)
PCTL0
PPRE01
PPRE00
PBFM0
PAOC0B
PAOC0A
PARUN0
PCCYC0
PRUN0
(0xDA)
PCNF0
PFIFTY0
PALOCK0
PLOCK0
PMODE01
PMODE00
POP0
PCLKSEL0
-
(0xD9)
OCR0RBH
–
–
–
(0xD8)
OCR0RBL
(0xD7)
OCR0SBH
(0xD6)
OCR0SBL
(0xD5)
OCR0RAH
(0xD4)
OCR0RAL
(0xD3)
OCR0SAH
(0xD2)
OCR0SAL
(0xD1)
Reserved
–
–
–
–
(0xD0)
PSOC0
POS01
POS00
PSYNC01
PSYNC00
POEN0B
–
POEN0A
(0xCF)
Reserved
–
–
–
–
–
–
–
–
(0xCE)
EUDR
EUDR7
EUDR6
EUDR5
EUDR4
EUDR3
EUDR2
EUDR1
EUDR0
(0xCD)
MUBRRH
MUBRR15
MUBRR014
MUBRR13
MUBRR12
MUBRR011
MUBRR010
MUBRR9
MUBRR8
(0xCC)
MUBRRL
MUBRR7
MUBRR6
MUBRR5
MUBRR4
MUBRR3
MUBRR2
MUBRR1
MUBRR0
(0xCB)
Reserved
–
–
–
–
–
–
–
–
(0xCA)
EUCSRC
–
–
–
–
FEM
F1617
STP1
STP0
(0xC9)
EUCSRB
–
–
–
EUSART
EUSBS
–
EMCH
BODR
(0xC8)
EUCSRA
UTxS3
UTxS2
UTxS1
UTxS0
URxS3
URxS2
URxS1
URxS0
(0xC7)
Reserved
–
–
–
–
–
–
–
–
(0xC6)
UDR
UDR07
UDR06
UDR05
UDR04
UDR03
UDR02
UDR01
UDR00
(0xC5)
UBRRH
–
–
–
–
UBRR011
UBRR010
UBRR09
UBRR08
(0xC4)
UBRRL
UBRR07
UBRR06
UBRR05
UBRR04
UBRR03
UBRR02
UBRR01
UBRR00
(0xC3)
Reserved
–
–
–
–
–
–
–
–
(0xC2)
UCSRC
–
UMSEL0
UPM01
UPM00
USBS0
UCSZ01
UCSZ00
UCPOL0
(0xC1)
UCSRB
RXCIE0
TXCIE0
UDRIE0
RXEN0
TXEN0
UCSZ02
RXB80
TXB80
(0xC0)
UCSRA
RXC0
TXC0
UDRE0
FE0
DOR0
UPE0
U2X0
MPCM0
348
Page
AT90PWM2/3
4317B–AVR–02/05
AT90PWM2/3
Address
Name
Bit 7
Bit 6
Bit 5
Bit 4
Bit 3
Bit 2
Bit 1
Bit 0
(0xBF)
Reserved
–
–
–
–
–
–
–
–
(0xBE)
Reserved
–
–
–
–
–
–
–
–
(0xBD)
Reserved
–
–
–
–
–
–
–
–
(0xBC)
Reserved
–
–
–
–
–
–
–
–
(0xBB)
Reserved
–
–
–
–
–
–
–
–
(0xBA)
Reserved
–
–
–
–
–
–
–
–
(0xB9)
Reserved
–
–
–
–
–
–
–
–
(0xB8)
Reserved
–
–
–
–
–
–
–
–
(0xB7)
Reserved
–
–
–
–
–
–
–
–
(0xB6)
Reserved
–
–
–
–
–
–
–
–
(0xB5)
Reserved
–
–
–
–
–
–
–
–
(0xB4)
Reserved
–
–
–
–
–
–
–
–
(0xB3)
Reserved
–
–
–
–
–
–
–
–
(0xB2)
Reserved
–
–
–
–
–
–
–
–
(0xB1)
Reserved
–
–
–
–
–
–
–
–
(0xB0)
Reserved
–
–
–
–
–
–
–
–
(0xAF)
AC2CON
AC2EN
AC2IE
AC2IS1
AC2IS0
AC2SADE-
AC2M2
AC2M1
AC2M0
AC1M0
(0xAE)
AC1CON
AC1EN
AC1IE
AC1IS1
AC1IS0
AC1ICE
AC1M2
AC1M1
(0xAD)
AC0CON
AC0EN
AC0IE
AC0IS1
AC0IS0
-
AC0M2
AC0M1
AC0M0
(0xAC)
DACH
- / DAC9
- / DAC8
- / DAC7
- / DAC6
- / DAC5
- / DAC4
DAC9 / DAC3
DAC8 / DAC2
(0xAB)
DACL
DAC7 / DAC1
DAC6 /DAC0
DAC5 / -
DAC4 / -
DAC3 / -
DAC2 / -
DAC1 / -
DAC0 /
(0xAA)
DACON
DAATE
DATS2
DATS1
DATS0
-
DALA
DAOE
DAEN
(0xA9)
Reserved
–
–
–
–
–
–
–
–
(0xA8)
Reserved
–
–
–
–
–
–
–
–
(0xA7)
Reserved
–
–
–
–
–
–
–
–
(0xA6)
Reserved
(0xA5)
PIM2
–
-
–
-
–
PSEIE2
–
PEVE2B
–
PEVE2A
–
-
–
-
–
PEOPE2
(0xA4)
PIFR2
-
-
PSEI2
PEV2B
PEV2A
PRN21
PRN20
PEOP2
(0xA3)
PIM1
-
-
PSEIE1
PEVE1B
PEVE1A
-
-
PEOPE1
(0xA2)
PIFR1
-
-
PSEI1
PEV1B
PEV1A
PRN11
PRN10
PEOP1
(0xA1)
PIM0
-
-
PSEIE0
PEVE0B
PEVE0A
-
-
PEOPE0
(0xA0)
PIFR0
-
-
PSEI0
PEV0B
PEV0A
PRN01
PRN00
PEOP0
(0x9F)
Reserved
–
–
–
–
–
–
–
–
(0x9E)
Reserved
–
–
–
–
–
–
–
–
(0x9D)
Reserved
–
–
–
–
–
–
–
–
(0x9C)
Reserved
–
–
–
–
–
–
–
–
(0x9B)
Reserved
–
–
–
–
–
–
–
–
(0x9A)
Reserved
–
–
–
–
–
–
–
–
(0x99)
Reserved
–
–
–
–
–
–
–
–
(0x98)
Reserved
–
–
–
–
–
–
–
–
(0x97)
Reserved
–
–
–
–
–
–
–
–
(0x96)
Reserved
–
–
–
–
–
–
–
–
(0x95)
Reserved
–
–
–
–
–
–
–
–
(0x94)
Reserved
–
–
–
–
–
–
–
–
(0x93)
Reserved
–
–
–
–
–
–
–
–
(0x92)
Reserved
–
–
–
–
–
–
–
–
(0x91)
Reserved
–
–
–
–
–
–
–
–
(0x90)
Reserved
–
–
–
–
–
–
–
–
(0x8F)
Reserved
–
–
–
–
–
–
–
–
(0x8E)
Reserved
–
–
–
–
–
–
–
–
(0x8D)
Reserved
–
–
–
–
–
–
–
–
(0x8C)
Reserved
–
–
–
–
–
–
–
–
(0x8B)
OCR1BH
OCR1B15
OCR1B14
OCR1B13
OCR1B12
OCR1B11
OCR1B10
OCR1B9
OCR1B8
(0x8A)
OCR1BL
OCR1B7
OCR1B6
OCR1B5
OCR1B4
OCR1B3
OCR1B2
OCR1B1
OCR1B0
(0x89)
OCR1AH
OCR1A15
OCR1A14
OCR1A13
OCR1A12
OCR1A11
OCR1A10
OCR1A9
OCR1A8
(0x88)
OCR1AL
OCR1A7
OCR1A6
OCR1A5
OCR1A4
OCR1A3
OCR1A2
OCR1A1
OCR1A0
(0x87)
ICR1H
ICR115
ICR114
ICR113
ICR112
ICR111
ICR110
ICR19
ICR18
(0x86)
ICR1L
ICR17
ICR16
ICR15
ICR14
ICR13
ICR12
ICR11
ICR10
(0x85)
TCNT1H
TCNT115
TCNT114
TCNT113
TCNT112
TCNT111
TCNT110
TCNT19
TCNT18
(0x84)
TCNT1L
TCNT17
TCNT16
TCNT15
TCNT14
TCNT13
TCNT12
TCNT11
TCNT10
(0x83)
Reserved
–
–
–
–
–
–
–
–
(0x82)
TCCR1C
FOC1A
FOC1B
–
–
–
–
–
–
(0x81)
TCCR1B
ICNC1
ICES1
–
WGM13
WGM12
CS12
CS11
CS10
(0x80)
TCCR1A
COM1A1
COM1A0
COM1B1
COM1B0
–
–
WGM11
WGM10
(0x7F)
DIDR1
–
–
ACMP0D
AMP0PD
AMP0ND
ADC10D/ACMP1D
ADC9D/AMP1PD
ADC8D/AMP1ND
(0x7E)
DIDR0
ADC7D
ADC6D
ADC5D
ADC4D
ADC3D/ACMPMD
ADC2D/ACMP2D
ADC1D
ADC0D
Page
349
4317B–AVR–02/05
Address
Name
Bit 7
Bit 6
Bit 5
Bit 4
Bit 3
Bit 2
Bit 1
Bit 0
(0x7D)
Reserved
–
–
–
–
–
–
–
–
(0x7C)
ADMUX
REFS1
REFS0
ADLAR
–
MUX3
MUX2
MUX1
MUX0
(0x7B)
ADCSRB
–
–
–
ADAP
ADASCR
ADTS2
ADTS1
ADTS0
(0x7A)
ADCSRA
ADEN
ADSC
ADATE
ADIF
ADIE
ADPS2
ADPS1
ADPS0
(0x79)
ADCH
- / ADC9
- / ADC8
- / ADC7
- / ADC6
- / ADC5
- / ADC4
ADC9 / ADC3
ADC8 / ADC2
(0x78)
ADCL
ADC7 / ADC1
ADC6 / ADC0
ADC5 / -
ADC4 / -
ADC3 / -
ADC2 / -
ADC1 / -
ADC0 /
(0x77)
AMP1CSR
AMP1EN
-
AMP1G1
AMP1G0
-
AMP1TS2
AMP1TS1
AMP1TS0
(0x76)
AMP0CSR
AMP0EN
-
AMP0G1
AMP0G0
-
AMP0TS2
AMP0TS1
AMP0TS0
(0x75)
Reserved
–
–
–
–
–
–
–
–
(0x74)
Reserved
–
–
–
–
–
–
–
–
(0x73)
Reserved
–
–
–
–
–
–
–
–
(0x72)
Reserved
–
–
–
–
–
–
–
–
(0x71)
Reserved
–
–
–
–
–
–
–
–
(0x70)
Reserved
–
–
–
–
–
–
–
–
(0x6F)
TIMSK1
–
–
ICIE1
–
–
OCIE1B
OCIE1A
TOIE1
(0x6E)
TIMSK0
–
–
–
–
–
OCIE0B
OCIE0A
TOIE0
(0x6D)
Reserved
–
–
–
–
–
–
–
–
(0x6C)
Reserved
–
–
–
–
–
–
–
–
(0x6B)
Reserved
–
–
–
–
–
–
–
–
(0x6A)
Reserved
–
–
–
–
–
–
–
–
(0x69)
EICRA
ISC31
ISC30
ISC21
ISC20
ISC11
ISC10
ISC01
ISC00
(0x68)
Reserved
–
–
–
–
–
–
–
–
(0x67)
Reserved
–
–
–
–
–
–
–
–
(0x66)
OSCCAL
–
CAL6
CAL5
CAL4
CAL3
CAL2
CAL1
CAL0
(0x65)
Reserved
–
–
–
–
–
–
–
–
(0x64)
PRR
PRPSC2
PRPSC1
PRPSC0
PRTIM1
PRTIM0
PRSPI
PRUSART
PRADC
(0x63)
Reserved
–
–
–
–
–
–
–
–
(0x62)
Reserved
–
–
–
–
–
–
–
–
(0x61)
CLKPR
CLKPCE
–
–
–
CLKPS3
CLKPS2
CLKPS1
CLKPS0
WDP0
(0x60)
WDTCSR
WDIF
WDIE
WDP3
WDCE
WDE
WDP2
WDP1
0x3F (0x5F)
SREG
I
T
H
S
V
N
Z
C
0x3E (0x5E)
SPH
SP15
SP14
SP13
SP12
SP11
SP10
SP9
SP8
0x3D (0x5D)
SPL
SP7
SP6
SP5
SP4
SP3
SP2
SP1
SP0
0x3C (0x5C)
Reserved
–
–
–
–
–
–
–
–
0x3B (0x5B)
Reserved
–
–
–
–
–
–
–
–
0x3A (0x5A)
Reserved
–
–
–
–
–
–
–
–
0x39 (0x59)
Reserved
–
–
–
–
–
–
–
–
0x38 (0x58)
Reserved
–
–
–
–
–
–
–
–
0x37 (0x57)
SPMCSR
SPMIE
RWWSB
–
RWWSRE
BLBSET
PGWRT
PGERS
SPMEN
0x36 (0x56)
Reserved
–
–
–
–
–
–
–
–
0x35 (0x55)
MCUCR
SPIPS
–
–
PUD
–
–
IVSEL
IVCE
0x34 (0x54)
MCUSR
–
–
–
–
WDRF
BORF
EXTRF
PORF
0x33 (0x53)
SMCR
–
–
–
–
SM2
SM1
SM0
SE
0x32 (0x52)
MSMCR
0x31 (0x51)
MONDR
0x30 (0x50)
ACSR
ACCKDIV
AC2IF
AC1IF
AC0IF
–
AC2O
AC1O
AC0O
0x2F (0x4F)
Reserved
–
–
–
–
–
–
–
–
0x2E (0x4E)
SPDR
SPD7
SPD6
SPD5
SPD4
SPD3
SPD2
SPD1
SPD0
Monitor Stop Mode Control Register
Monitor Data Register
0x2D (0x4D)
SPSR
SPIF
WCOL
–
–
–
–
–
SPI2X
0x2C (0x4C)
SPCR
SPIE
SPE
DORD
MSTR
CPOL
CPHA
SPR1
SPR0
0x2B (0x4B)
Reserved
–
–
–
–
–
–
–
–
0x2A (0x4A)
Reserved
–
–
–
–
–
–
–
–
0x29 (0x49)
PLLCSR
-
-
-
-
-
PLLF
PLLE
PLOCK
0x28 (0x48)
OCR0B
OCR0B7
OCR0B6
OCR0B5
OCR0B4
OCR0B3
OCR0B2
OCR0B1
OCR0B0
0x27 (0x47)
OCR0A
OCR0A7
OCR0A6
OCR0A5
OCR0A4
OCR0A3
OCR0A2
OCR0A1
OCR0A0
0x26 (0x46)
TCNT0
TCNT07
TCNT06
TCNT05
TCNT04
TCNT03
TCNT02
TCNT01
TCNT00
0x25 (0x45)
TCCR0B
FOC0A
FOC0B
–
–
WGM02
CS02
CS01
CS00
0x24 (0x44)
TCCR0A
COM0A1
COM0A0
COM0B1
COM0B0
–
–
WGM01
WGM00
0x23 (0x43)
GTCCR
TSM
ICPSEL1
–
–
–
–
–
PSRSYNC
0x22 (0x42)
EEARH
–
–
–
–
EEAR11
EEAR10
EEAR9
EEAR8
0x21 (0x41)
EEARL
EEAR7
EEAR6
EEAR5
EEAR4
EEAR3
EEAR2
EEAR1
EEAR0
0x20 (0x40)
EEDR
EEDR7
EEDR6
EEDR5
EEDR4
EEDR3
EEDR2
EEDR1
EEDR0
0x1F (0x3F)
EECR
–
–
–
–
EERIE
EEMWE
EEWE
EERE
0x1E (0x3E)
GPIOR0
GPIOR07
GPIOR06
GPIOR05
GPIOR04
GPIOR03
GPIOR02
GPIOR01
GPIOR00
0x1D (0x3D)
EIMSK
–
–
–
–
INT3
INT2
INT1
INT0
0x1C (0x3C)
EIFR
–
–
–
–
INTF3
INTF2
INTF1
INTF0
350
Page
AT90PWM2/3
4317B–AVR–02/05
AT90PWM2/3
Address
Name
Bit 7
Bit 6
Bit 5
Bit 4
Bit 3
Bit 2
Bit 1
Bit 0
0x1B (0x3B)
GPIOR3
GPIOR37
GPIOR36
GPIOR35
GPIOR34
GPIOR33
GPIOR32
GPIOR31
GPIOR30
0x1A (0x3A)
GPIOR2
GPIOR27
GPIOR26
GPIOR25
GPIOR24
GPIOR23
GPIOR22
GPIOR21
GPIOR20
0x19 (0x39)
GPIOR1
GPIOR17
GPIOR16
GPIOR15
GPIOR14
GPIOR13
GPIOR12
GPIOR11
GPIOR10
0x18 (0x38)
Reserved
–
–
–
–
–
–
–
–
0x17 (0x37)
Reserved
–
–
–
–
–
–
–
–
0x16 (0x36)
TIFR1
–
–
ICF1
–
–
OCF1B
OCF1A
TOV1
0x15 (0x35)
TIFR0
–
–
–
–
–
OCF0B
OCF0A
TOV0
0x14 (0x34)
Reserved
–
–
–
–
–
–
–
–
0x13 (0x33)
Reserved
–
–
–
–
–
–
–
–
0x12 (0x32)
Reserved
–
–
–
–
–
–
–
–
0x11 (0x31)
Reserved
–
–
–
–
–
–
–
–
0x10 (0x30)
Reserved
–
–
–
–
–
–
–
–
0x0F (0x2F)
Reserved
–
–
–
–
–
–
–
–
0x0E (0x2E)
PORTE
–
–
–
–
–
PORTE2
PORTE1
PORTE0
0x0D (0x2D)
DDRE
–
–
–
–
–
DDE2
DDE1
DDE0
0x0C (0x2C)
PINE
–
–
–
–
–
PINE2
PINE1
PINE0
0x0B (0x2B)
PORTD
PORTD7
PORTD6
PORTD5
PORTD4
PORTD3
PORTD2
PORTD1
PORTD0
0x0A (0x2A)
DDRD
DDD7
DDD6
DDD5
DDD4
DDD3
DDD2
DDD1
DDD0
0x09 (0x29)
PIND
PIND7
PIND6
PIND5
PIND4
PIND3
PIND2
PIND1
PIND0
0x08 (0x28)
PORTC
PORTC7
PORTC6
PORTC5
PORTC4
PORTC3
PORTC2
PORTC1
PORTC0
0x07 (0x27)
DDRC
DDC7
DDC6
DDC5
DDC4
DDC3
DDC2
DDC1
DDC0
0x06 (0x26)
PINC
PINC7
PINC6
PINC5
PINC4
PINC3
PINC2
PINC1
PINC0
0x05 (0x25)
PORTB
PORTB7
PORTB6
PORTB5
PORTB4
PORTB3
PORTB2
PORTB1
PORTB0
0x04 (0x24)
DDRB
DDB7
DDB6
DDB5
DDB4
DDB3
DDB2
DDB1
DDB0
0x03 (0x23)
PINB
PINB7
PINB6
PINB5
PINB4
PINB3
PINB2
PINB1
PINB0
0x02 (0x22)
Reserved
–
–
–
–
–
–
–
–
0x01 (0x21)
Reserved
–
–
–
–
–
–
–
–
0x00 (0x20)
Reserved
–
–
–
–
–
–
–
–
Note:
Page
1. For compatibility with future devices, reserved bits should be written to zero if accessed. Reserved I/O memory addresses
should never be written.
2. I/O Registers within the address range 0x00 - 0x1F are directly bit-accessible using the SBI and CBI instructions. In these
registers, the value of single bits can be checked by using the SBIS and SBIC instructions.
3. Some of the status flags are cleared by writing a logical one to them. Note that, unlike most other AVRs, the CBI and SBI
instructions will only operate on the specified bit, and can therefore be used on registers containing such status flags. The
CBI and SBI instructions work with registers 0x00 to 0x1F only.
4. When using the I/O specific commands IN and OUT, the I/O addresses 0x00 - 0x3F must be used. When addressing I/O
Registers as data space using LD and ST instructions, 0x20 must be added to these addresses. The AT90PWM2/3 is a
complex microcontroller with more peripheral units than can be supported within the 64 location reserved in Opcode for the
IN and OUT instructions. For the Extended I/O space from 0x60 - 0xFF in SRAM, only the ST/STS/STD and LD/LDS/LDD
instructions can be used.
351
4317B–AVR–02/05
Instruction Set Summary
Mnemonics
Operands
ADD
Rd, Rr
ADC
Rd, Rr
ADIW
Rdl,K
SUB
Description
Operation
Flags
#Clocks
Add two Registers
Rd ← Rd + Rr
Z,C,N,V,H
1
Add with Carry two Registers
Rd ← Rd + Rr + C
Z,C,N,V,H
1
Add Immediate to Word
Rdh:Rdl ← Rdh:Rdl + K
Z,C,N,V,S
2
Rd, Rr
Subtract two Registers
Rd ← Rd - Rr
Z,C,N,V,H
1
SUBI
Rd, K
Subtract Constant from Register
Rd ← Rd - K
Z,C,N,V,H
1
SBC
Rd, Rr
Subtract with Carry two Registers
Rd ← Rd - Rr - C
Z,C,N,V,H
1
SBCI
Rd, K
Subtract with Carry Constant from Reg.
Rd ← Rd - K - C
Z,C,N,V,H
1
SBIW
Rdl,K
Subtract Immediate from Word
Rdh:Rdl ← Rdh:Rdl - K
Z,C,N,V,S
2
AND
Rd, Rr
Logical AND Registers
Rd ← Rd • Rr
Z,N,V
1
ANDI
Rd, K
Logical AND Register and Constant
Rd ← Rd • K
Z,N,V
1
OR
Rd, Rr
Logical OR Registers
Rd ← Rd v Rr
Z,N,V
1
ORI
Rd, K
Logical OR Register and Constant
Rd ← Rd v K
Z,N,V
1
EOR
Rd, Rr
Exclusive OR Registers
Rd ← Rd ⊕ Rr
Z,N,V
1
COM
Rd
One’s Complement
Rd ← 0xFF − Rd
Z,C,N,V
1
NEG
Rd
Two’s Complement
Rd ← 0x00 − Rd
Z,C,N,V,H
1
SBR
Rd,K
Set Bit(s) in Register
Rd ← Rd v K
Z,N,V
1
CBR
Rd,K
Clear Bit(s) in Register
Rd ← Rd • (0xFF - K)
Z,N,V
1
INC
Rd
Increment
Rd ← Rd + 1
Z,N,V
1
DEC
Rd
Decrement
Rd ← Rd − 1
Z,N,V
1
TST
Rd
Test for Zero or Minus
Rd ← Rd • Rd
Z,N,V
1
CLR
Rd
Clear Register
Rd ← Rd ⊕ Rd
Z,N,V
1
SER
Rd
Set Register
Rd ← 0xFF
None
1
MUL
Rd, Rr
Multiply Unsigned
R1:R0 ← Rd x Rr
Z,C
2
MULS
Rd, Rr
Multiply Signed
R1:R0 ← Rd x Rr
Z,C
2
MULSU
Rd, Rr
Multiply Signed with Unsigned
R1:R0 ← Rd x Rr
Z,C
2
FMUL
Rd, Rr
Fractional Multiply Unsigned
R1:R0 ← (Rd x Rr) << 1
Z,C
2
FMULS
Rd, Rr
Fractional Multiply Signed
R1:R0 ← (Rd x Rr) << 1
Z,C
2
FMULSU
Rd, Rr
Fractional Multiply Signed with Unsigned
R1:R0 ← (Rd x Rr) << 1
Z,C
2
ARITHMETIC AND LOGIC INSTRUCTIONS
BRANCH INSTRUCTIONS
RJMP
k
IJMP
PC ← PC + k + 1
None
2
PC ← Z
None
2
JMP
k
Direct Jump
PC ← k
None
3
RCALL
k
Relative Subroutine Call
PC ← PC + k + 1
None
3
Indirect Call to (Z)
PC ← Z
None
3
Direct Subroutine Call
PC ← k
None
4
RET
Subroutine Return
PC ← STACK
None
4
RETI
Interrupt Return
PC ← STACK
I
4
Compare, Skip if Equal
if (Rd = Rr) PC ← PC + 2 or 3
None
1/2/3
ICALL
CALL
352
Relative Jump
Indirect Jump to (Z)
k
CPSE
Rd,Rr
CP
Rd,Rr
Compare
Rd − Rr
Z, N,V,C,H
1
CPC
Rd,Rr
Compare with Carry
Rd − Rr − C
Z, N,V,C,H
1
CPI
Rd,K
Compare Register with Immediate
Rd − K
Z, N,V,C,H
1
SBRC
Rr, b
Skip if Bit in Register Cleared
if (Rr(b)=0) PC ← PC + 2 or 3
None
1/2/3
SBRS
Rr, b
Skip if Bit in Register is Set
if (Rr(b)=1) PC ← PC + 2 or 3
None
1/2/3
SBIC
P, b
Skip if Bit in I/O Register Cleared
if (P(b)=0) PC ← PC + 2 or 3
None
1/2/3
SBIS
P, b
Skip if Bit in I/O Register is Set
if (P(b)=1) PC ← PC + 2 or 3
None
1/2/3
BRBS
s, k
Branch if Status Flag Set
if (SREG(s) = 1) then PC←PC+k + 1
None
1/2
BRBC
s, k
Branch if Status Flag Cleared
if (SREG(s) = 0) then PC←PC+k + 1
None
1/2
BREQ
k
Branch if Equal
if (Z = 1) then PC ← PC + k + 1
None
1/2
BRNE
k
Branch if Not Equal
if (Z = 0) then PC ← PC + k + 1
None
1/2
BRCS
k
Branch if Carry Set
if (C = 1) then PC ← PC + k + 1
None
1/2
BRCC
k
Branch if Carry Cleared
if (C = 0) then PC ← PC + k + 1
None
1/2
BRSH
k
Branch if Same or Higher
if (C = 0) then PC ← PC + k + 1
None
1/2
BRLO
k
Branch if Lower
if (C = 1) then PC ← PC + k + 1
None
1/2
BRMI
k
Branch if Minus
if (N = 1) then PC ← PC + k + 1
None
1/2
BRPL
k
Branch if Plus
if (N = 0) then PC ← PC + k + 1
None
1/2
BRGE
k
Branch if Greater or Equal, Signed
if (N ⊕ V= 0) then PC ← PC + k + 1
None
1/2
BRLT
k
Branch if Less Than Zero, Signed
if (N ⊕ V= 1) then PC ← PC + k + 1
None
1/2
BRHS
k
Branch if Half Carry Flag Set
if (H = 1) then PC ← PC + k + 1
None
1/2
BRHC
k
Branch if Half Carry Flag Cleared
if (H = 0) then PC ← PC + k + 1
None
1/2
BRTS
k
Branch if T Flag Set
if (T = 1) then PC ← PC + k + 1
None
1/2
BRTC
k
Branch if T Flag Cleared
if (T = 0) then PC ← PC + k + 1
None
1/2
BRVS
k
Branch if Overflow Flag is Set
if (V = 1) then PC ← PC + k + 1
None
1/2
BRVC
k
Branch if Overflow Flag is Cleared
if (V = 0) then PC ← PC + k + 1
None
1/2
AT90PWM2/3
4317B–AVR–02/05
AT90PWM2/3
Mnemonics
Operands
Description
Operation
Flags
#Clocks
BRIE
k
Branch if Interrupt Enabled
if ( I = 1) then PC ← PC + k + 1
None
1/2
BRID
k
Branch if Interrupt Disabled
if ( I = 0) then PC ← PC + k + 1
None
1/2
BIT AND BIT-TEST INSTRUCTIONS
SBI
P,b
Set Bit in I/O Register
I/O(P,b) ← 1
None
2
CBI
P,b
Clear Bit in I/O Register
I/O(P,b) ← 0
None
2
LSL
Rd
Logical Shift Left
Rd(n+1) ← Rd(n), Rd(0) ← 0
Z,C,N,V
1
LSR
Rd
Logical Shift Right
Rd(n) ← Rd(n+1), Rd(7) ← 0
Z,C,N,V
1
ROL
Rd
Rotate Left Through Carry
Rd(0)←C,Rd(n+1)← Rd(n),C←Rd(7)
Z,C,N,V
1
ROR
Rd
Rotate Right Through Carry
Rd(7)←C,Rd(n)← Rd(n+1),C←Rd(0)
Z,C,N,V
1
ASR
Rd
Arithmetic Shift Right
Rd(n) ← Rd(n+1), n=0..6
Z,C,N,V
1
SWAP
Rd
Swap Nibbles
Rd(3..0)←Rd(7..4),Rd(7..4)←Rd(3..0)
None
1
BSET
s
Flag Set
SREG(s) ← 1
SREG(s)
1
BCLR
s
Flag Clear
SREG(s) ← 0
SREG(s)
1
BST
Rr, b
Bit Store from Register to T
T ← Rr(b)
T
1
BLD
Rd, b
Bit load from T to Register
Rd(b) ← T
None
1
SEC
Set Carry
C←1
C
1
CLC
Clear Carry
C←0
C
1
SEN
Set Negative Flag
N←1
N
1
CLN
Clear Negative Flag
N←0
N
1
SEZ
Set Zero Flag
Z←1
Z
1
CLZ
Clear Zero Flag
Z←0
Z
1
SEI
Global Interrupt Enable
I←1
I
1
CLI
Global Interrupt Disable
I←0
I
1
SES
Set Signed Test Flag
S←1
S
1
CLS
Clear Signed Test Flag
S←0
S
1
SEV
Set Twos Complement Overflow.
V←1
V
1
CLV
Clear Twos Complement Overflow
V←0
V
1
SET
Set T in SREG
T←1
T
1
CLT
Clear T in SREG
T←0
T
1
SEH
CLH
Set Half Carry Flag in SREG
Clear Half Carry Flag in SREG
H←1
H←0
H
H
1
1
DATA TRANSFER INSTRUCTIONS
MOV
Rd, Rr
Move Between Registers
1
Rd, Rr
Copy Register Word
Rd ← Rr
Rd+1:Rd ← Rr+1:Rr
None
MOVW
None
1
LDI
Rd, K
Load Immediate
Rd ← K
None
1
LD
Rd, X
Load Indirect
Rd ← (X)
None
2
LD
Rd, X+
Load Indirect and Post-Inc.
Rd ← (X), X ← X + 1
None
2
LD
Rd, - X
Load Indirect and Pre-Dec.
X ← X - 1, Rd ← (X)
None
2
LD
Rd, Y
Load Indirect
Rd ← (Y)
None
2
LD
Rd, Y+
Load Indirect and Post-Inc.
Rd ← (Y), Y ← Y + 1
None
2
LD
Rd, - Y
Load Indirect and Pre-Dec.
Y ← Y - 1, Rd ← (Y)
None
2
LDD
Rd,Y+q
Load Indirect with Displacement
Rd ← (Y + q)
None
2
LD
Rd, Z
Load Indirect
Rd ← (Z)
None
2
LD
Rd, Z+
Load Indirect and Post-Inc.
Rd ← (Z), Z ← Z+1
None
2
LD
Rd, -Z
Load Indirect and Pre-Dec.
Z ← Z - 1, Rd ← (Z)
None
2
LDD
Rd, Z+q
Load Indirect with Displacement
Rd ← (Z + q)
None
2
LDS
Rd, k
Load Direct from SRAM
Rd ← (k)
None
2
ST
X, Rr
Store Indirect
(X) ← Rr
None
2
ST
X+, Rr
Store Indirect and Post-Inc.
(X) ← Rr, X ← X + 1
None
2
ST
- X, Rr
Store Indirect and Pre-Dec.
X ← X - 1, (X) ← Rr
None
2
ST
Y, Rr
Store Indirect
(Y) ← Rr
None
2
ST
Y+, Rr
Store Indirect and Post-Inc.
(Y) ← Rr, Y ← Y + 1
None
2
ST
- Y, Rr
Store Indirect and Pre-Dec.
Y ← Y - 1, (Y) ← Rr
None
2
STD
Y+q,Rr
Store Indirect with Displacement
(Y + q) ← Rr
None
2
ST
Z, Rr
Store Indirect
(Z) ← Rr
None
2
ST
Z+, Rr
Store Indirect and Post-Inc.
(Z) ← Rr, Z ← Z + 1
None
2
ST
-Z, Rr
Store Indirect and Pre-Dec.
Z ← Z - 1, (Z) ← Rr
None
2
STD
Z+q,Rr
Store Indirect with Displacement
(Z + q) ← Rr
None
2
STS
k, Rr
Store Direct to SRAM
(k) ← Rr
None
2
Load Program Memory
R0 ← (Z)
None
3
LPM
LPM
Rd, Z
Load Program Memory
Rd ← (Z)
None
3
LPM
Rd, Z+
Load Program Memory and Post-Inc
Rd ← (Z), Z ← Z+1
None
3
Store Program Memory
(Z) ← R1:R0
None
-
In Port
Rd ← P
None
1
SPM
IN
Rd, P
OUT
P, Rr
Out Port
P ← Rr
None
1
PUSH
Rr
Push Register on Stack
STACK ← Rr
None
2
353
4317B–AVR–02/05
Mnemonics
Operands
Description
Operation
Flags
#Clocks
POP
Rd
Pop Register from Stack
Rd ← STACK
None
2
MCU CONTROL INSTRUCTIONS
354
NOP
No Operation
None
1
SLEEP
Sleep
(see specific descr. for Sleep function)
None
1
WDR
BREAK
Watchdog Reset
Break
(see specific descr. for WDR/timer)
For On-chip Debug Only
None
None
1
N/A
AT90PWM2/3
4317B–AVR–02/05
AT90PWM2/3
Ordering Information
Speed (MHz)
Power Supply
Ordering Code
Package
16
2.7 - 5.5V
AT90PWM3-16SQ
SO32
16
2.7 - 5.5V
AT90PWM3-16MQ
QFN32
16
2.7 - 5.5V
AT90PWM2-16SQ
SO24
Operation Range
Extended (-40°C to
105°C)
Extended (-40°C to
105°C)
Extended (-40°C to
105°C)
Note:
All packages are Pb free, fully LHF
Note:
This device can also be supplied in wafer form. Please contact your local Atmel sales office for detailed ordering information and
minimum quantities.
Package Information
Package Type
SO24
24-Lead, Small Outline Package
SO32
32-Lead, Small Outline Package
QFN32
32-Lead, Quad Flat No lead
355
4317B–AVR–02/05
SO24
356
AT90PWM2/3
4317B–AVR–02/05
AT90PWM2/3
SO32
357
4317B–AVR–02/05
QFN32
358
AT90PWM2/3
4317B–AVR–02/05
AT90PWM2/3
Datasheet Change Log for AT90PWM2/3
Please note that the referring page numbers in this section are referred to this document. The referring revision in this section are referring to the document revision.
Changes from 4317A- to
4317B
1. PSC section is rewritted.
2. Suppression of description of RAMPZ which doesnot exist.
359
4317B–AVR–02/05
Table of Contents
Features................................................................................................. 1
Disclaimer .............................................................................................. 2
Pin Configurations................................................................................ 3
Pin Descriptions.....................................................................................................5
Overview................................................................................................ 8
Block Diagram ...................................................................................................... 8
Pin Descriptions...................................................................................................10
About Code Examples ........................................................................................ 11
AVR CPU Core .................................................................................... 12
Introduction ......................................................................................................... 12
Architectural Overview........................................................................................ 12
ALU – Arithmetic Logic Unit................................................................................ 13
Status Register ....................................................................................................14
General Purpose Register File ........................................................................... 15
Stack Pointer ...................................................................................................... 16
Instruction Execution Timing............................................................................... 16
Reset and Interrupt Handling.............................................................................. 17
Memories ............................................................................................. 20
In-System Reprogrammable Flash Program Memory ........................................ 20
SRAM Data Memory............................................................................................21
EEPROM Data Memory.......................................................................................23
I/O Memory ..........................................................................................................28
General Purpose I/O Registers............................................................................29
System Clock ...................................................................................... 30
Clock Systems and their Distribution .................................................................. 30
Clock Sources..................................................................................................... 31
Default Clock Source .......................................................................................... 31
Low Power Crystal Oscillator...............................................................................32
Calibrated Internal RC Oscillator ........................................................................ 33
PLL ..................................................................................................................... 34
128 kHz Internal Oscillator.................................................................................. 36
External Clock..................................................................................................... 36
Clock Output Buffer ............................................................................................ 36
System Clock Prescaler...................................................................................... 37
Power Management and Sleep Modes.............................................. 39
Idle Mode .............................................................................................................40
ADC Noise Reduction Mode............................................................................... 40
360
AT90PWM2/3
4317B–AVR–02/05
AT90PWM2/3
Power-down Mode..............................................................................................
Standby Mode.....................................................................................................
Power Reduction Register ..................................................................................
Minimizing Power Consumption .........................................................................
40
40
41
42
System Control and Reset ................................................................. 44
Internal Voltage Reference ................................................................................. 49
Watchdog Timer ..................................................................................................50
Interrupts ............................................................................................. 56
Interrupt Vectors in AT90PWM2/3 ...................................................................... 56
I/O-Ports............................................................................................... 62
Introduction ......................................................................................................... 62
Ports as General Digital I/O ................................................................................ 63
Alternate Port Functions ..................................................................................... 68
Register Description for I/O-Ports........................................................................80
External Interrupts.............................................................................. 82
Timer/Counter0 and Timer/Counter1 Prescalers ............................. 84
8-bit Timer/Counter0 with PWM......................................................... 87
Overview............................................................................................................. 87
Timer/Counter Clock Sources............................................................................. 88
Counter Unit........................................................................................................ 88
Output Compare Unit.......................................................................................... 89
Compare Match Output Unit ............................................................................... 91
Modes of Operation .............................................................................................92
Timer/Counter Timing Diagrams......................................................................... 96
8-bit Timer/Counter Register Description ........................................................... 97
16-bit Timer/Counter1 with PWM..................................................... 104
Overview........................................................................................................... 104
Accessing 16-bit Registers ............................................................................... 106
Timer/Counter Clock Sources............................................................................110
Counter Unit...................................................................................................... 110
Input Capture Unit............................................................................................. 111
Output Compare Units ...................................................................................... 112
Compare Match Output Unit ............................................................................. 114
Modes of Operation .......................................................................................... 115
Timer/Counter Timing Diagrams....................................................................... 123
16-bit Timer/Counter Register Description ........................................................125
Power Stage Controller – (PSC0, PSC1 & PSC2)........................... 132
Features............................................................................................................ 132
361
4317B–AVR–02/05
Overview........................................................................................................... 132
PSC Description ............................................................................................... 133
Signal Description............................................................................................. 135
Functional Description .......................................................................................137
Update of Values .............................................................................................. 142
Enhanced Resolution.........................................................................................143
PSC Inputs.........................................................................................................147
PSC Input Mode 1: Stop signal, Jump to Opposite Dead-Time and Wait .........152
PSC Input Mode 2: Stop signal, Execute Opposite Dead-Time and Wait .........153
PSC Input Mode 3: Stop signal, Execute Opposite while Fault active...............154
PSC Input Mode 4: Deactivate outputs without changing timing. ......................155
PSC Input Mode 5: Stop signal and Insert Dead-Time......................................156
PSC Input Mode 6: Stop signal, Jump to Opposite Dead-Time and Wait. ........157
PSC Input Mode 7: Halt PSC and Wait for Software Action ..............................158
PSC Input Mode 8 .............................................................................................159
PSC Input Mode 9: Fixed Frequency Edge Retrigger PSC ...............................160
PSC Input Mode 14: Fixed Frequency Edge Retrigger PSC and Disactivate Output
161
PSC2 Outputs................................................................................................... 163
PSC Synchronization........................................................................................ 163
Analog Synchronization .................................................................................... 164
Interrupt Handling ............................................................................................. 164
PSC Synchronization.........................................................................................165
PSC Clock Sources .......................................................................................... 165
Interrupts............................................................................................................167
PSC Register Definition .....................................................................................168
PSC2 Specific Register .................................................................................... 178
Serial Peripheral Interface – SPI...................................................... 182
Features............................................................................................................ 182
SS Pin Functionality...........................................................................................187
Data Modes .......................................................................................................191
USART ............................................................................................... 192
Features............................................................................................................ 192
Overview........................................................................................................... 193
Clock Generation .............................................................................................. 194
Serial Frame ..................................................................................................... 196
USART Initialization.......................................................................................... 197
Data Transmission – USART Transmitter .........................................................199
Data Reception – USART Receiver...................................................................201
Asynchronous Data Reception ......................................................................... 206
Multi-processor Communication Mode ..............................................................209
USART Register Description .............................................................................211
Examples of Baud Rate Setting........................................................................ 217
362
AT90PWM2/3
4317B–AVR–02/05
AT90PWM2/3
EUSART (Extended USART) ............................................................ 221
Features............................................................................................................ 221
Overview........................................................................................................... 221
Serial Frames ................................................................................................... 222
Configuring the EUSART.................................................................................. 227
Data Reception – EUSART Receiver ................................................................228
EUSART Registers Description .........................................................................230
Analog Comparator .......................................................................... 236
Overview........................................................................................................... 236
Analog Comparator Register Description ......................................................... 237
Analog to Digital Converter - ADC .................................................. 243
Features............................................................................................................
Operation ..........................................................................................................
Starting a Conversion .......................................................................................
Prescaling and Conversion Timing ...................................................................
Changing Channel or Reference Selection ......................................................
ADC Noise Canceler.........................................................................................
ADC Conversion Result....................................................................................
ADC Register Description.................................................................................
Amplifier............................................................................................................
Amplifier Control Registers ...............................................................................
243
245
245
246
248
250
255
257
261
263
Digital to Analog Converter - DAC .................................................. 266
Features............................................................................................................
Operation ..........................................................................................................
Starting a Conversion .......................................................................................
DAC Register Description.................................................................................
266
268
268
269
debugWIRE On-chip Debug System ............................................... 271
Features............................................................................................................
Overview...........................................................................................................
Physical Interface .............................................................................................
Software Break Points ......................................................................................
Limitations of debugWIRE ................................................................................
debugWIRE Related Register in I/O Memory ...................................................
271
271
271
272
272
272
Boot Loader Support – Read-While-Write Self-Programming ...... 273
Boot Loader Features .......................................................................................
Application and Boot Loader Flash Sections ....................................................
Read-While-Write and No Read-While-Write Flash Sections...........................
Boot Loader Lock Bits.......................................................................................
Entering the Boot Loader Program ...................................................................
Addressing the Flash During Self-Programming ..............................................
Self-Programming the Flash .............................................................................
273
273
273
276
277
279
280
363
4317B–AVR–02/05
Memory Programming...................................................................... 287
Program And Data Memory Lock Bits .............................................................. 287
Fuse Bits............................................................................................................289
PSC Output Behaviour During Reset ............................................................... 289
Signature Bytes ................................................................................................ 291
Calibration Byte ................................................................................................ 291
Parallel Programming Parameters, Pin Mapping, and Commands ...................292
Serial Programming Pin Mapping ..................................................................... 294
Parallel Programming ........................................................................................295
Serial Downloading........................................................................................... 304
Electrical Characteristics(1) .............................................................. 308
Absolute Maximum Ratings*............................................................................. 308
DC Characteristics............................................................................................ 309
External Clock Drive Characteristics .................................................................311
Maximum Speed vs. VCC .................................................................................. 311
SPI Timing Characteristics ................................................................................313
ADC Characteristics ..........................................................................................315
Parallel Programming Characteristics ...............................................................317
Serial Programming Characteristics ..................................................................320
AT90PWM2/3 Typical Characteristics – Preliminary Data ............ 321
Active Supply Current .......................................................................................
Idle Supply Current ...........................................................................................
Power-Down Supply Current ............................................................................
Power-Save Supply Current .............................................................................
Standby Supply Current....................................................................................
Pin Pull-up ........................................................................................................
Pin Driver Strength ...........................................................................................
Pin Thresholds and Hysteresis .........................................................................
BOD Thresholds and Analog Comparator Offset .............................................
Internal Oscillator Speed ..................................................................................
Current Consumption of Peripheral Units .........................................................
Current Consumption in Reset and Reset Pulse width.....................................
321
324
329
330
330
331
333
336
339
342
344
346
Register Summary ............................................................................ 348
Instruction Set Summary ................................................................. 352
Ordering Information........................................................................ 355
SO24................................................................................................................. 356
SO32................................................................................................................. 357
QFN32 .............................................................................................................. 358
Datasheet Change Log for AT90PWM2/3 ....................................... 359
Changes from 4317A- to 4317B ....................................................................... 359
364
AT90PWM2/3
4317B–AVR–02/05
Atmel Corporation
2325 Orchard Parkway
San Jose, CA 95131, USA
Tel: 1(408) 441-0311
Fax: 1(408) 487-2600
Regional Headquarters
Europe
Atmel Sarl
Route des Arsenaux 41
Case Postale 80
CH-1705 Fribourg
Switzerland
Tel: (41) 26-426-5555
Fax: (41) 26-426-5500
Asia
Room 1219
Chinachem Golden Plaza
77 Mody Road Tsimshatsui
East Kowloon
Hong Kong
Tel: (852) 2721-9778
Fax: (852) 2722-1369
Japan
9F, Tonetsu Shinkawa Bldg.
1-24-8 Shinkawa
Chuo-ku, Tokyo 104-0033
Japan
Tel: (81) 3-3523-3551
Fax: (81) 3-3523-7581
Atmel Operations
Memory
2325 Orchard Parkway
San Jose, CA 95131, USA
Tel: 1(408) 441-0311
Fax: 1(408) 436-4314
RF/Automotive
Theresienstrasse 2
Postfach 3535
74025 Heilbronn, Germany
Tel: (49) 71-31-67-0
Fax: (49) 71-31-67-2340
Microcontrollers
2325 Orchard Parkway
San Jose, CA 95131, USA
Tel: 1(408) 441-0311
Fax: 1(408) 436-4314
La Chantrerie
BP 70602
44306 Nantes Cedex 3, France
Tel: (33) 2-40-18-18-18
Fax: (33) 2-40-18-19-60
ASIC/ASSP/Smart Cards
1150 East Cheyenne Mtn. Blvd.
Colorado Springs, CO 80906, USA
Tel: 1(719) 576-3300
Fax: 1(719) 540-1759
Biometrics/Imaging/Hi-Rel MPU/
High Speed Converters/RF Datacom
Avenue de Rochepleine
BP 123
38521 Saint-Egreve Cedex, France
Tel: (33) 4-76-58-30-00
Fax: (33) 4-76-58-34-80
Zone Industrielle
13106 Rousset Cedex, France
Tel: (33) 4-42-53-60-00
Fax: (33) 4-42-53-60-01
1150 East Cheyenne Mtn. Blvd.
Colorado Springs, CO 80906, USA
Tel: 1(719) 576-3300
Fax: 1(719) 540-1759
Scottish Enterprise Technology Park
Maxwell Building
East Kilbride G75 0QR, Scotland
Tel: (44) 1355-803-000
Fax: (44) 1355-242-743
Literature Requests
www.atmel.com/literature
Disclaimer: Atmel Corporation makes no warranty for the use of its products, other than those expressly contained in the Company’s standard
warranty which is detailed in Atmel’s Terms and Conditions located on the Company’s web site. The Company assumes no responsibility for any
errors which may appear in this document, reserves the right to change devices or specifications detailed herein at any time without notice, and
does not make any commitment to update the information contained herein. No licenses to patents or other intellectual property of Atmel are
granted by the Company in connection with the sale of Atmel products, expressly or by implication. Atmel’s products are not authorized for use
as critical components in life support devices or systems.
© Atmel Corporation 2005. All rights reserved. Atmel ® logo and combinations thereof and AVR ® are registered trademarks, and Everywhere
You Are sm are the trademarks of Atmel Corporation or its subsidiaries. Other terms and product names may be the trademarks of others.
Printed on recycled paper.
4317B–AVR–02/05