ATMEL ATTINY261A 8-bit microcontroller with 2/4/8k bytes in-system programmable flash Datasheet

Features
• High Performance, Low Power AVR® 8-Bit Microcontroller
• Advanced RISC Architecture
•
•
•
•
•
•
•
– 123 Powerful Instructions – Most Single Clock Cycle Execution
– 32 x 8 General Purpose Working Registers
– Fully Static Operation
– Up to 20 MIPS Throughput at 20 MHz
High Endurance Non-volatile Memory Segments
– 2/4/8K Bytes of In-System Self-Programmable Flash Program Memory
• Endurance: 10,000 Write/Erase Cycles
– 128/256/512 Bytes of In-System Programmable EEPROM
• Endurance: 100,000 Write/Erase Cycles
– 128/256/512 Bytes of Internal SRAM
– Data retention: 20 Years at 85°C / 100 Years at 25°C
– In-System Programmable via SPI Port
– Programming Lock for Software Security
Peripheral Features
– One 8/16-bit Timer/Counter with Prescaler
– One 8/10-bit High Speed Timer/Counter with Prescaler
• 3 High Frequency PWM Outputs with Separate Output Compare Registers
• Programmable Dead Time Generator
– 10-bit ADC
• 11 Single-Ended Channels
• 16 Differential ADC Channel Pairs
• 15 Differential ADC Channel Pairs with Programmable Gain (1x, 8x, 20x, 32x)
– On-chip Analog Comparator
– Programmable Watchdog Timer with Separate On-chip Oscillator
– Universal Serial Interface with Start Condition Detector
– Interrupt and Wake-up on Pin Change
Special Microcontroller Features
– debugWIRE On-chip Debug System
– Power-on Reset and Programmable Brown-out Detection
– Internal Calibrated Oscillator
– External and Internal Interrupt Sources
– Four Sleep Modes: Low Power Idle, ADC Noise Reduction, Standby and PowerDown
– On-Chip Temperature Sensor
I/O and Packages
– 16 Programmable I/O Lines
– 20-pin PDIP, 20-pin SOIC, 20-pin TSSOP and 32-pad MLF
Operating Voltage
– 1.8 – 5.5V
Speed Grades
– 0 – 4 MHz @ 1.8 – 5.5V
– 0 – 10 MHz @ 2.7 – 5.5V
– 0 – 20 MHz @ 4.5 – 5.5V
Power Consumption at 1MHz, 1.8V, 25°C
– Active: 200 µA
– Power-Down Mode: 0.1 µA
8-bit
Microcontroller
with 2/4/8K
Bytes In-System
Programmable
Flash
ATtiny261A
ATtiny461A
ATtiny861A
Preliminary
8197A–AVR–10/09
1. Pin Configurations
Figure 1-1.
Pinout ATtiny261A/461A/861A
PDIP/SOIC/TSSOP
(MOSI/DI/SDA/OC1A/PCINT8) PB0
(MISO/DO/OC1A/PCINT9) PB1
(SCK/USCK/SCL/OC1B/PCINT10) PB2
(OC1B/PCINT11) PB3
VCC
GND
(ADC7/OC1D/CLKI/XTAL1/PCINT12) PB4
(ADC8/OC1D/CLKO/XTAL2/PCINT13) PB5
(ADC9/INT0/T0/PCINT14) PB6
(ADC10/RESET/PCINT15) PB7
20
19
18
17
16
15
14
13
12
11
PA0 (ADC0/DI/SDA/PCINT0)
PA1 (ADC1/DO/PCINT1)
PA2 (ADC2/INT1/USCK/SCL/PCINT2)
PA3 (AREF/PCINT3)
AGND
AVCC
PA4 (ADC3/ICP0/PCINT4)
PA5 (ADC4/AIN2/PCINT5)
PA6 (ADC5/AIN0/PCINT6)
PA7 (ADC6/AIN1/PCINT7)
32
31
30
29
28
27
26
25
PB2 (SCK/USCK/SCL/OC1B/PCINT10)
PB1 (MISO/DO/OC1A/PCINT9)
PB0 (MOSI/DI/SDA/OC1A/PCINT8)
NC
NC
NC
PA0 (ADC0/DI/SDA/PCINT0)
PA1 (ADC1/DO/PCINT1)
1
2
3
4
5
6
7
8
9
10
1
2
3
4
5
6
7
8
QFN/MLF
24
23
22
21
20
19
18
17
NC
PA2 (ADC2/INT1/USCK/SCL/PCINT2)
PA3 (AREF/PCINT3)
AGND
NC
NC
AVCC
PA4 (ADC3/ICP0/PCINT4)
NC
(ADC9/INT0/T0/PCINT14) PB6
(ADC10/RESET/PCINT15) PB7
NC
(ADC6/AIN1/PCINT7) PA7
(ADC5/AIN0/PCINT6) PA6
(ADC4/AIN2/PCINT5) PA5
NC
9
10
11
12
13
14
15
16
NC
(OC1B/PCINT11) PB3
NC
VCC
GND
NC
(ADC7/OC1D/CLKI/XTAL1/PCINT12) PB4
(ADC8/OC1D/CLKO/XTAL2/PCINT13) PB5
Note:
2
To ensure mechanical stability the center pad underneath the QFN/MLF package should be soldered to ground on the board.
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1.1
1.1.1
Pin Descriptions
VCC
Supply voltage.
1.1.2
GND
Ground.
1.1.3
AVCC
Analog supply voltage. This is the supply voltage pin for the Analog-to-digital Converter (ADC),
the analog comparator, the Brown-Out Detector (BOD), the internal voltage reference and Port
A. It should be externally connected to VCC, even if some peripherals such as the ADC are not
used. If the ADC is used AVCC should be connected to VCC through a low-pass filter.
1.1.4
AGND
Analog ground.
1.1.5
Port A (PA7:PA0)
An 8-bit, bi-directional I/O port with internal pull-up resistors, individually selectable for each bit.
Output buffers have symmetrical drive characteristics with both high sink and source capability.
As inputs, port pins that are externally pulled low will source current if pull-up resistors have
been activated. Port pins are tri-stated when a reset condition becomes active, even if the clock
is not running.
Port A also serves the functions of various special features of the device, as listed on page 61.
1.1.6
Port B (PB7:PB0)
An 8-bit, bi-directional I/O port with internal pull-up resistors, individually selectable for each bit.
Output buffers have symmetrical drive characteristics with both high sink and source capability.
As inputs, port pins that are externally pulled low will source current if pull-up resistors have
been activated. Port 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 device, as listed on page 64.
1.1.7
RESET
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 and provided the reset pin has not been disabled. The minimum pulse length is given in Table 19-4 on page 187. Shorter pulses are not guaranteed to
generate a reset.
The reset pin can also be used as a (weak) I/O pin.
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2. Overview
ATtiny261A/461A/861A are low-power CMOS 8-bit microcontrollers based on the AVR
enhanced RISC architecture. By executing powerful instructions in a single clock cycle, the
devices achieve throughputs approaching 1 MIPS per MHz allowing the system designer to optimize power consumption versus processing speed.
Block Diagram
Block Diagram
GND
Figure 2-1.
VCC
2.1
Watchdog
Timer
Watchdog
Oscillator
Oscillator
Circuits /
Clock
Generation
Power
Supervision
POR / BOD &
RESET
debugWIRE
Flash
SRAM
PROGRAM
LOGIC
CPU
EEPROM
AVCC
AGND
AREF
Timer/Counter1
A/D Conv.
USI
Analog Comp.
Internal
Bandgap
DATABUS
Timer/Counter0
3
PORT B (8)
11
PORT A (8)
RESET
XTAL[1..2]
PB[0..7]
PA[0..7]
The AVR core combines a rich instruction set with 32 general purpose working registers. All 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.
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ATtiny261A/461A/861A
The ATtiny261A/461A/861A provides the following features: 2/4/8K byte of In-System Programmable Flash, 128/256/512 bytes EEPROM, 128/256/512 bytes SRAM, 16 general purpose I/O
lines, 32 general purpose working registers, an 8-bit Timer/Counter with compare modes, an 8bit high speed Timer/Counter, a Universal Serial Interface, Internal and External Interrupts, an
11-channel, 10-bit ADC, a programmable Watchdog Timer with internal oscillator, and four software selectable power saving modes. Idle mode stops the CPU while allowing the SRAM,
Timer/Counter, ADC, Analog Comparator, and Interrupt system to continue functioning. Powerdown mode saves the register contents, disabling all chip functions until the next Interrupt or
Hardware Reset. 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, allowing very fast start-up combined
with low power consumption.
The device is manufactured using Atmel’s high density non-volatile memory technology. The
On-chip ISP Flash allows the Program memory to be re-programmed In-System through an SPI
serial interface, by a conventional non-volatile memory programmer or by an On-chip boot code
running on the AVR core.
The ATtiny261A/461A/861A AVR is supported by a full suite of program and system development tools including: C Compilers, Macro Assemblers, Program Debugger/Simulators, and
Evaluation kits.
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3. General Information
3.1
Resources
A comprehensive set of drivers, application notes, data sheets and descriptions on development
tools are available for download at http://www.atmel.com/avr.
3.2
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.
For I/O Registers located in the 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, this
means “LDS” and “STS” combined with “SBRS”, “SBRC”, “SBR”, and “CBR”. Note that not all
AVR devices include an extended I/O map.
3.3
Data Retention
Reliability Qualification results show that the projected data retention failure rate is much less
than 1 PPM over 20 years at 85°C or 100 years at 25°C.
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ATtiny261A/461A/861A
4. CPU Core
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.
4.1
Architectural Overview
Figure 4-1.
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
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 In-System Reprogrammable Flash memory.
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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, 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.
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 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.
4.2
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.
4.3
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 neither automatically stored when entering an interrupt routine, nor
restored when returning from an interrupt. This must be handled by software.
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ATtiny261A/461A/861A
4.3.1
SREG – AVR Status Register
Bit
7
6
5
4
3
2
1
0
0x3F (0x5F)
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 for the interrupts to be enabled. 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 I-bit 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.
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4.4
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 4-2 below shows the structure of the 32 general purpose working registers in the CPU.
Figure 4-2.
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
R27
0x1B
X-register Low Byte
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 4-2, 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.
4.4.1
10
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 4-3.
ATtiny261A/461A/861A
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ATtiny261A/461A/861A
Figure 4-3.
The X-, Y-, and Z-registers
15
X-register
XH
7
XL
0
R27 (0x1B)
15
Y-register
0
R26 (0x1A)
YH
7
YL
0
R29 (0x1D)
Z-register
0
7
0
7
0
R28 (0x1C)
15
ZH
7
0
ZL
7
R31 (0x1F)
0
0
R30 (0x1E)
In different addressing modes these address registers function as automatic increment and
automatic decrement (see the instruction set reference for details).
4.5
Stack Pointer
The Stack is mainly used for storing temporary data, local variables and return addresses for
interrupts and subroutine calls. The Stack Pointer Register always points to the top of the Stack,
in the data SRAM Stack area where the subroutine and interrupt stacks are located.
The Stack 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 start of the
SRAM (see Figure 5-2 on page 16). The initial Stack Pointer value equals the last address of the
internal SRAM.
Note that the Stack is implemented as growing from higher to lower memory locations. This
means a Stack PUSH command decreases the Stack Pointer. See Table 4-1.
Table 4-1.
Stack Pointer instructions
Instruction
Stack pointer
Description
PUSH
Decremented by 1
Data is pushed onto the stack
CALL
ICALL
RCALL
Decremented by 2
Return address is pushed onto the stack with a
subroutine call or interrupt
POP
Incremented by 1
Data is popped from the stack
RET
RETI
Incremented by 2
Return address is popped from the stack with return
from subroutine or return from interrupt
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.
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4.5.1
SPH and SPL — Stack Pointer Register
Bit
15
14
13
12
11
10
9
8
0x3E (0x5E)
SP15
SP14
SP13
SP12
SP11
SP10
SP9
SP8
SPH
0x3D (0x5D)
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
RAMEND
RAMEND
RAMEND
RAMEND
RAMEND
RAMEND
RAMEND
RAMEND
RAMEND
RAMEND
RAMEND
RAMEND
RAMEND
RAMEND
RAMEND
RAMEND
Read/Write
Initial Value
4.6
Instruction Execution Timing
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.
Figure 4-4 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 4-4.
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 4-5 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 4-5.
Single Cycle ALU Operation
T1
T2
T3
T4
clkCPU
Total Execution Time
Register Operands Fetch
ALU Operation Execute
Result Write Back
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4.7
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.
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 48. 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 INT0 – the External Interrupt Request
0.
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.
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Assembly Code Example
in r16, SREG
cli
; store SREG value
; disable interrupts during timed sequence
sbi EECR, EEMPE
; start EEPROM write
sbi EECR, EEPE
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<<EEMPE); /* start EEPROM write */
EECR |= (1<<EEPE);
SREG = cSREG; /* restore SREG value (I-bit) */
Note:
See “Code Examples” on page 6.
When using the SEI instruction to enable interrupts, the instruction following SEI will be executed before any pending interrupts, as shown in the following examples.
Assembly Code Example
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) */
Note:
4.7.1
See “Code Examples” on page 6.
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.
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ATtiny261A/461A/861A
5. Memories
This section describes the different memories of the ATtiny261A/461A/861A. The AVR architecture has two main memory spaces, the Data memory and the Program memory space. In
addition, the ATtiny261A/461A/861A features an EEPROM Memory for data storage. All three
memory spaces are linear and regular.
5.1
In-System Re-programmable Flash Program Memory
The ATtiny261A/461A/861A contains 2/4/8K byte 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 1024/2048/4096 x 16.
The F lash memory has an endurance of at least 10,000 write/erase cycles. The
ATtiny261A/461A/861A Program Counter (PC) is 10/11/12 bits wide, thus capable of addressing
the 1024/2048/4096 Program memory locations. “Memory Programming” on page 167 contains
a detailed description on Flash data serial downloading using the SPI pins.
Constant tables can be allocated within the entire address space of program memory (see the
LPM – Load Program memory instruction description).
Timing diagrams for instruction fetch and execution are presented in “Instruction Execution Timing” on page 12.
Figure 5-1.
Program Memory Map
Program Memory
0x0000
0x03FF/0x07FF/0x0FFF
5.2
SRAM Data Memory
Figure 5-2 on page 16 shows how the ATtiny261A/461A/861A SRAM Memory is organized.
The lower data memory locations address both the Register File, the I/O memory and the internal data SRAM. The first 32 locations address the Register File, the next 64 locations the
standard I/O memory, and the last 128/256/512 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.
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8197A–AVR–10/09
When using register indirect addressing modes with automatic pre-decrement and post-increment, the address registers X, Y, and Z are decremented or incremented.
The 32 general purpose working registers, 64 I/O Registers, and the 128/256/512 bytes of internal data SRAM in the ATtiny261A/461A/861A are all accessible through all these addressing
modes. The Register File is described in “General Purpose Register File” on page 10.
Figure 5-2.
Data Memory Map
Data Memory
0x0000 - 0x001F
0x0020 - 0x005F
0x0060
32 Registers
64 I/O Registers
Internal SRAM
(128/256/512 x 8)
0x0DF/0x15F/0x25F
5.2.1
Data Memory 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 illustrated in Figure 5-3.
Figure 5-3.
On-chip Data SRAM Access Cycles
T1
T2
T3
clkCPU
Address
Compute Address
Address valid
Write
Data
WR
Read
Data
RD
Memory Access Instruction
5.3
Next Instruction
EEPROM Data Memory
The ATtiny261A/461A/861A contains 128/256/512 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 Serial data
downloading to the EEPROM, see “Electrical Characteristics” on page 184.
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ATtiny261A/461A/861A
5.3.1
EEPROM Read/Write Access
The EEPROM Access Registers are accessible in the I/O space.
The write access times for the EEPROM are given in Table 5-1 on page 22. 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 19 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 “Atomic Byte Programming” on page 17 and “Split Byte Programming” on page 17 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.
5.3.2
Atomic Byte Programming
Using Atomic Byte Programming is the simplest mode. When writing a byte to the EEPROM, the
user must write the address into the EEARL Register and data into EEDR Register. If the
EEPMn bits are zero, writing EEPE (within four cycles after EEMPE is written) will trigger the
erase/write operation. Both the erase and write cycle are done in one operation and the total
programming time is given in Table 5-1 on page 22. The EEPE bit remains set until the erase
and write operations are completed. While the device is busy with programming, it is not possible to do any other EEPROM operations.
5.3.3
Split Byte Programming
It is possible to split the erase and write cycle in two different operations. This may be useful if
the system requires short access time for some limited period of time (typically if the power supply voltage falls). In order to take advantage of this method, it is required that the locations to be
written have been erased before the write operation. But since the erase and write operations
are split, it is possible to do the erase operations when the system allows doing time-critical
operations (typically after Power-up).
5.3.4
Erase
To erase a byte, the address must be written to EEAR. If the EEPMn bits are 0b01, writing the
EEPE within four cycles after EEMPE is written will trigger the erase operation only (programming time is given in Table 5-1 on page 22). The EEPE bit remains set until the erase operation
completes. While the device is busy programming, it is not possible to do any other EEPROM
operations.
5.3.5
Write
To write a location, the user must write the address into EEAR and the data into EEDR. If the
EEPMn bits are 0b10, writing the EEPE (within four cycles after EEMPE is written) will trigger
the write operation only (programming time is given in Table 5-1 on page 22). The EEPE bit
remains set until the write operation completes. If the location to be written has not been erased
before write, the data that is stored must be considered as lost. While the device is busy with
programming, it is not possible to do any other EEPROM operations.
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The calibrated Oscillator is used to time the EEPROM accesses. Make sure the Oscillator frequency is within the requirements described in “OSCCAL – Oscillator Calibration Register” on
page 32.
5.3.6
Program Examples
The following code examples show one assembly and one C function for erase, write, or atomic
write of 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.
Assembly Code Example
EEPROM_write:
; Wait for completion of previous write
sbic EECR,EEPE
rjmp EEPROM_write
; Set Programming mode
ldi
r16, (0<<EEPM1)|(0<<EEPM0)
out
EECR, r16
; Set up address (r18:r17) in address register
out EEARH, r18
out EEARL, r17
; Write data (r19) to data register
out EEDR, r19
; Write logical one to EEMPE
sbi EECR,EEMPE
; Start eeprom write by setting EEPE
sbi EECR,EEPE
ret
C Code Example
void EEPROM_write(unsigned char ucAddress, unsigned char ucData)
{
/* Wait for completion of previous write */
while(EECR & (1<<EEPE))
;
/* Set Programming mode */
EECR = (0<<EEPM1)|(0<<EEPM0);
/* Set up address and data registers */
EEAR = ucAddress;
EEDR = ucData;
/* Write logical one to EEMPE */
EECR |= (1<<EEMPE);
/* Start eeprom write by setting EEPE */
EECR |= (1<<EEPE);
}
Note:
18
See “Code Examples” on page 6.
ATtiny261A/461A/861A
8197A–AVR–10/09
ATtiny261A/461A/861A
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,EEPE
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 char ucAddress)
{
/* Wait for completion of previous write */
while(EECR & (1<<EEPE))
;
/* Set up address register */
EEAR = ucAddress;
/* Start eeprom read by writing EERE */
EECR |= (1<<EERE);
/* Return data from data register */
return EEDR;
}
Note:
5.3.7
See “Code Examples” on page 6.
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.
EEPROM data corruption can easily be avoided by following this design 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
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8197A–AVR–10/09
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.
5.4
I/O Memory
The I/O space definition of the ATtiny261A/461A/861A is shown in “Register Summary” on page
273.
All I/Os and peripherals are placed in the I/O space. All I/O locations may be accessed using the
LD/LDS/LDD and ST/STS/STD instructions, enabling data transfer 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.
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, 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 on registers in the address
range 0x00 to 0x1F, only.
The I/O and Peripherals Control Registers are explained in later sections.
5.4.1
5.5
5.5.1
General Purpose I/O Registers
The ATtiny261A/461A/861A contains three 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. General Purpose I/O Registers within the address range 0x00 - 0x1F are
directly bit-accessible using the SBI, CBI, SBIS, and SBIC instructions.
Register Description
EEARH – EEPROM Address Register
Bit
7
6
5
4
3
2
1
0
0x1F (0x3F)
–
–
–
–
–
–
–
EEAR8
Read/Write
R
R
R
R
R
R
R
R/W
Initial Value
0
0
0
0
0
0
0
X/0
EEARH
• Bits 7:1 – Res: Reserved Bits
These bits are reserved and will always read as zero.
• Bit 0 – EEAR8: EEPROM Address
This is the most significant EEPROM address bit of ATtiny861A. In devices with less EEPROM,
i.e. ATtiny261A/ATtiny461A, this bit is reserved and will always read zero. The initial value of the
EEPROM Address Register (EEAR) is undefined and a proper value must therefore be written
before the EEPROM is accessed.
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ATtiny261A/461A/861A
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ATtiny261A/461A/861A
5.5.2
EEARL – EEPROM Address Register
Bit
7
6
5
4
3
2
1
0
0x1E (0x3E)
EEAR7
EEAR6
EEAR5
EEAR4
EEAR3
EEAR2
EEAR1
EEAR0
Read/Write
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
Initial Value
X/0
X
X
X
X
X
X
X
EEARL
• Bit 7 – EEAR7: EEPROM Address
This is the most significant EEPROM address bit of ATtiny461A. In devices with less EEPROM,
i.e. ATtiny261A, this bit is reserved and will always read zero. The initial value of the EEPROM
Address Register (EEAR) is undefined and a proper value must therefore be written before the
EEPROM is accessed.
• Bits 6:0 – EEAR6:0: EEPROM Address
These are the (low) bits of the EEPROM Address Register. The EEPROM data bytes are
addressed linearly in the range 0...128/256/512. The initial value of EEAR is undefined and a
proper value must be therefore be written before the EEPROM may be accessed.
5.5.3
EEDR – EEPROM Data Register
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
0x1D (0x3D)
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 operation, the
EEDR contains the data read out from the EEPROM at the address given by EEAR.
5.5.4
EECR – EEPROM Control Register
Bit
7
6
5
4
3
2
1
0
0x1C (0x3C)
–
–
EEPM1
EEPM0
EERIE
EEMPE
EEPE
EERE
Read/Write
R
R
R/W
R/W
R/W
R/W
R/W
R/W
Initial Value
0
0
X
X
0
0
X
0
EECR
• Bit 7 – Res: Reserved Bit
This bit is reserved for future use and will always read zero. For compatibility with future AVR
devices, always write this bit to zero. After reading, mask out this bit.
• Bit 6 – Res: Reserved Bit
This bit is reserved and will always read as zero.
• Bits 5, 4 – EEPM1 and EEPM0: EEPROM Programming Mode Bits
The EEPROM Programming mode bits setting defines which programming action that will be
triggered when writing EEPE. It is possible to program data in one atomic operation (erase the
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8197A–AVR–10/09
old value and program the new value) or to split the Erase and Write operations in two different
operations. The Programming times for the different modes are shown in Table 5-1.
Table 5-1.
EEPROM Mode Bits
EEPM1
EEPM0
Programming
Time
0
0
3.4 ms
Erase and Write in one operation (Atomic Operation)
0
1
1.8 ms
Erase Only
1
0
1.8 ms
Write Only
1
1
–
Operation
Reserved for future use
When EEPE is set, any write to EEPMn will be ignored. During reset, the EEPMn bits will be
reset to 0b00 unless the EEPROM is busy programming.
• 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 Non-volatile memory is ready for programming.
• Bit 2 – EEMPE: EEPROM Master Program Enable
The EEMPE bit determines whether writing EEPE to one will have effect or not.
When EEMPE is set, setting EEPE within four clock cycles will program the EEPROM at the
selected address. If EEMPE is zero, setting EEPE will have no effect. When EEMPE has been
written to one by software, hardware clears the bit to zero after four clock cycles.
• Bit 1 – EEPE: EEPROM Program Enable
The EEPROM Program Enable Signal EEPE is the programming enable signal to the EEPROM.
When EEPE is written, the EEPROM will be programmed according to the EEPMn bits setting.
The EEMPE bit must be written to one before a logical one is written to EEPE, otherwise no
EEPROM write takes place. When the write access time has elapsed, the EEPE bit is cleared
by hardware. When EEPE 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 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 EEPE 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.
5.5.5
GPIOR2 – General Purpose I/O Register 2
Bit
22
7
6
5
4
3
2
1
0
0x0C (0x2C)
MSB
LSB
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
GPIOR2
ATtiny261A/461A/861A
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ATtiny261A/461A/861A
5.5.6
GPIOR1 – General Purpose I/O Register 1
Bit
5.5.7
7
6
5
4
3
2
1
0
0x0B (0x2B)
MSB
LSB
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
5
4
3
2
1
GPIOR1
GPIOR0 – General Purpose I/O Register 0
Bit
7
6
0
0x0A (0x2A)
MSB
LSB
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
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8197A–AVR–10/09
6. Clock System
Figure 6-1 presents the principal clock systems and their distribution. All of the clocks need not
be active at a given time. In order to reduce power consumption, the clocks to modules not being
used can be halted by using different sleep modes, as described in “Power Management and
Sleep Modes” on page 34.
Figure 6-1.
Clock Distribution
General I/O
Modules
General I/O
Modules
ADC
CPU Core
RAM
Flash and
EEPROM
clkADC
clkI/O
AVR Clock
Control Unit
clkCPU
clkFLASH
Reset Logic
Watchdog Timer
Source clock
Watchdog clock
System Clock
Prescaler
Clock
Multiplexer
clkPCK
clkPLL
PLL
Oscillator
6.1
Watchdog
Oscillator
External Clock
Crystal
Oscillator
Low-Frequency
Calibrated RC
Crystal
Oscillator
Oscillator
Calibrated RC
Oscillator
Clock Subsystems
The clock subsystems are detailed in the sections below.
6.1.1
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.
6.1.2
I/O Clock – clkI/O
The I/O clock is used by the majority of the I/O modules, like Timer/Counter. 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.
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ATtiny261A/461A/861A
6.1.3
Flash Clock – clkFLASH
The Flash clock controls operation of the Flash interface. The Flash clock is usually active simultaneously with the CPU clock.
6.1.4
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.
6.1.5
Fast Peripheral Clock – clkPCK
Selected peripherals can be clocked at a frequency higher than the CPU core. The fast peripheral clock is generated by an on-chip PLL circuit.
6.1.6
PLL System Clock – clkADC
The PLL can also be used to generate a system clock. The clock signal can be prescaled to
avoid overclocking the CPU.
6.2
Clock Sources
The device has the following clock source options, selectable by Flash Fuse bits as shown
below. The clock from the selected source is input to the AVR clock generator, and routed to the
appropriate modules.
Table 6-1.
Device Clocking Options Select(1) vs. PB4 and PB5 Functionality
Device Clocking Option
CKSEL3:0
PB4
PB5
External Clock (see page 26)
0000
XTAL1
I/O
High-Frequency PLL Clock (see page 26)
0001
I/O
I/O
Calibrated Internal 8 MHz Oscillator (see page 28)
0010
I/O
I/O
Internal 128 kHz Oscillator (see page 29)
0011
I/O
I/O
Low-Frequency Crystal Oscillator (see page 29)
01xx
XTAL1
XTAL2
Crystal Oscillator / Ceramic Resonator
0.4...0.9 MHz (see page 30)
1000
1001
XTAL1
XTAL2
Crystal Oscillator / Ceramic Resonator
0.9...3.0 MHz (see page 30)
1010
1011
XTAL1
XTAL2
Crystal Oscillator / Ceramic Resonator
3...8 MHz (see page 30)
1100
1101
XTAL1
XTAL2
Crystal Oscillator / Ceramic Resonator
8...20 MHz (see page 30)
1110
1111
XTAL1
XTAL2
Note:
1. For all fuses “1” means unprogrammed and “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 startup, 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 com-
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8197A–AVR–10/09
mencing normal operation. The watchdog oscillator is used for timing this real-time part of the
start-up time. The number of WD oscillator cycles used for each time-out is shown in Table 6-2.
Table 6-2.
6.2.1
Number of Watchdog Oscillator Cycles
Typ Time-out
Number of Cycles
4 ms
512
64 ms
8K (8,192)
External Clock
To drive the device from an external clock source, CLKI should be driven as shown in Figure 62. To run the device on an external clock, the CKSEL Fuses must be programmed to “0000”.
Figure 6-2.
External Clock Drive Configuration
EXTERNAL
CLOCK
SIGNAL
CLKI
GND
When this clock source is selected, start-up times are determined by the SUT Fuses as shown in
Table 6-3.
Table 6-3.
Start-up Times for the External Clock Selection
SUT1:0
Start-up Time from Powerdown and Power-save
Additional Delay from
Reset
00
6 CK
14CK
01
6 CK
14CK + 4 ms
Fast rising power
10
6 CK
14CK + 64 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. See “System Clock Prescaler” on page 31 for details.
6.2.2
26
High-Frequency PLL Clock
The internal PLL generates a clock signal with a frequency eight times higher than the source
input. The PLL uses the output of the internal 8 MHz oscillator as source and the default setting
generates a fast peripheral clock signal of 64 MHz.
ATtiny261A/461A/861A
8197A–AVR–10/09
ATtiny261A/461A/861A
The fast peripheral clock, clkPCK, can be selected as the clock source for Timer/Counter1 and a
prescaled version of the PLL output, clkPLL, can be selected as system clock. See Figure 6-3 for
a detailed illustration on the PLL clock system.
Figure 6-3.
PCK Clocking System
LSM
OSCCAL
PLLE
CKSEL3:0
CLKPS3:0
LOCK
DETECTOR
1/2
8 MHz
OSCILLATOR
4 MHz
clkPCK
8 MHz
PLL
8x
64 / 32 MHz
XTAL1
XTAL2
PLOCK
1/4
16 MHz
8 MHz
PRESCALER
clkPLL
OSCILLATORS
The internal PLL is enabled when CKSEL fuse bits are programmed to ‘0001’and the PLLE bit of
PLLCSR is set. The internal oscillator and the PLL are switched off in power down and stand-by
sleep modes.
When the LSM bit of PLLCSR is set, the PLL switches from using the output of the internal 8
MHz oscillator to using the output divided by two. The frequency of the fast peripheral clock is
effectively divided by two, resulting in a clock frequency of 32 MHz. The LSM bit can not be set if
PLLCLK is used as a system clock.
Since the PLL is locked to the output of the internal 8 MHz oscillator, adjusting the oscillator frequency via the OSCCAL register also changes the frequency of the fast peripheral clock. It is
possible to adjust the frequency of the internal oscillator to well above 8 MHz but the fast peripheral clock will saturate and remain oscillating at about 85 MHz. In this case the PLL is no longer
locked to the internal oscillator clock signal. Therefore, in order to keep the PLL in the correct
operating range, it is recommended to program the OSCCAL registers such that the oscillator
frequency does not exceed 8 MHz.
The PLOCK bit in PLLCSR is set when PLL is locked.
Programming CKSEL fuse bits to ‘0001’, the PLL output divided by four will be used as a system
clock, as shown in Table 6-4.
Table 6-4.
PLLCK Operating Modes
CKSEL3:0
Nominal Frequency
0001
16 MHz
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When the PLL output is selected as clock source, the start-up times are determined by SUT fuse
bits as shown in Table 6-5.
Table 6-5.
6.2.3
Start-up Times for the PLLCK
SUT1:0
Start-up Time from
Power Down
Additional Delay from
Power-On-Reset (VCC = 5.0V)
Recommended
usage
00
14CK + 1K (1024) + 4 ms
4 ms
BOD enabled
01
14CK + 16K (16384) + 4 ms
4 ms
Fast rising power
10
14CK + 1K (1024) + 64 ms
4 ms
Slowly rising power
11
14CK + 16K (16384) + 64 ms
4 ms
Slowly rising power
Calibrated Internal 8 MHz Oscillator
By default, the Internal Oscillator provides an approximately 8 MHz clock signal. Though voltage
and temperature dependent, this clock can be very accurately calibrated by the user. See Table
19-2 on page 186 and “Internal Oscillators” on page 218 for more details. The device is shipped
with the CKDIV8 Fuse programmed. See “System Clock Prescaler” on page 31 for more details.
This clock may be selected as the system clock by programming the CKSEL Fuses as shown in
Table 6-6. If selected, it will operate with no external components. During reset, hardware loads
the pre-programmed calibration value into the OSCCAL Register and thereby automatically calibrates the internal oscillator. The accuracy of this calibration is shown as Factory calibration in
Table 19-2 on page 186.
Table 6-6.
Notes:
Internal Calibrated Oscillator Operating Modes
CKSEL3:0
Nominal Frequency
0010 (1)
8.0 MHz (2)
1. The device is shipped with this option selected.
2. If the oscillator frequency exceeds the specification of the device (depends on VCC), the
CKDIV8 Fuse can be programmed to divide the internal frequency by 8.
When this oscillator is selected, start-up times are determined by SUT fuses as shown in Table
6-7.
Table 6-7.
Start-up Times for the Internal Calibrated Oscillator Clock Selection
SUT1:0
Start-up Time
from Power-down
Additional Delay from
Reset (VCC = 5.0V)
00
6 CK
14CK(1)
01
6 CK
14CK + 4 ms
Fast rising power
6 CK
14CK + 64 ms
Slowly rising power
(2)
10
11
Note:
Recommended
Usage
BOD enabled
Reserved
1. If the RSTDISBL fuse is programmed, this start-up time will be increased to 14CK + 4 ms to
ensure programming mode can be entered.
2. The device is shipped with this option selected.
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It is possible to reach a higher accuracy than factory calibration by changing the OSCCAL register from software. See “OSCCAL – Oscillator Calibration Register” on page 32. The accuracy of
this calibration is shown as User calibration in Table 19-2 on page 186.
When this oscillator is used as device 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 section “Calibration Byte” on page 169.
6.2.4
Internal 128 kHz Oscillator
The 128 kHz internal oscillator is a low power oscillator providing a clock of 128 kHz. The frequency depends on supply voltage, temperature and batch variations. This clock may be select
as the system clock by programming the CKSEL Fuses to “0011”.
When this clock source is selected, start-up times are determined by the SUT Fuses as shown in
Table 6-8.
Table 6-8.
SUT1:0
Start-up Times for the 128 kHz Internal Oscillator
Start-up Time from Powerdown and Power-save
Additional Delay from
Reset
14CK
Recommended Usage
BOD enabled
00
6 CK
01
6 CK
14CK + 4 ms
Fast rising power
10
6 CK
14CK + 64 ms
Slowly rising power
11
Note:
6.2.5
(1)
Reserved
1. If the RSTDISBL fuse is programmed, this start-up time will be increased to 14CK + 4 ms to
ensure programming mode can be entered.
Low-Frequency Crystal Oscillator
To use a 32.768 kHz watch crystal as the clock source for the device, the low-frequency crystal
oscillator must be selected by setting CKSEL fuses to ‘0100’. The crystal should be connected
as shown in Figure 6-4. To find suitable capacitors please consult the manufacturer’s datasheet.
When this oscillator is selected, start-up times are determined by the SUT fuses as shown in
Table 6-9.
Table 6-9.
SUT1:0
Start-up Times for the Low Frequency Crystal Oscillator Clock Selection
Start-up Time
from Power Down
00
1K (1024) CK
01
10
Additional Delay
from Reset
(1)
4 ms
Fast rising power or BOD enabled
1K (1024) CK(1)
64 ms
Slowly rising power
32K (32768) CK
64 ms
Stable frequency at start-up
11
Notes:
Recommended usage
Reserved
1. These options should be used only if frequency stability at start-up is not important.
Table 6-10.
Capacitance for Low-Frequency Crystal Oscillator
Device
32 kHz Osc. Type
Cap (Xtal1/Tosc1)
Cap (Xtal2/Tosc2)
ATtiny261A/461A/861A
System Osc.
16 pF
6 pF
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6.2.6
Crystal Oscillator / Ceramic Resonator
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 6-4. Either a quartz crystal or a
ceramic resonator may be used.
Figure 6-4.
Crystal Oscillator Connections
C2
C1
XTAL2
XTAL1
GND
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 6-11. For ceramic resonators, the capacitor values given by
the manufacturer should be used.
Table 6-11.
Crystal Oscillator Operating Modes
CKSEL3:1
Frequency Range (MHz)
Recommended C1 and C2 Value (pF)
0.4 - 0.9
–
101
0.9 - 3.0
12 - 22
110
3.0 - 8.0
12 - 22
111
8.0 -
12 - 22
(1)
100
Notes:
1. This option should not be used with crystals, only with ceramic resonators.
The Oscillator can operate in three different modes, each optimized for a specific frequency
range. The operating mode is selected by fuses CKSEL3:1 as shown in Table 6-11.
The CKSEL0 Fuse together with the SUT1:0 Fuses select the start-up times as shown in Table
6-12.
Table 6-12.
30
Start-up Times for the Crystal Oscillator Clock Selection
CKSEL0
SUT1:0
Start-up Time from
Power-down and
Power-save
Additional Delay
from Reset
(VCC = 5.0V)
0
00
258 CK(1)
14CK + 4 ms
Ceramic resonator,
fast rising power
0
01
258 CK(1)
14CK + 64 ms
Ceramic resonator,
slowly rising power
0
10
1K (1024) CK(2)
14CK
Ceramic resonator,
BOD enabled
Recommended Usage
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ATtiny261A/461A/861A
Table 6-12.
Start-up Times for the Crystal Oscillator Clock Selection (Continued)
CKSEL0
SUT1:0
Start-up Time from
Power-down and
Power-save
0
11
1K (1024)CK(2)
14CK + 4 ms
Ceramic resonator,
fast rising power
1
00
1K (1024)CK(2)
14CK + 64 ms
Ceramic resonator,
slowly rising power
1
01
16K (16384) CK
14CK
Crystal Oscillator,
BOD enabled
1
10
16K (16384) CK
14CK + 4 ms
Crystal Oscillator,
fast rising power
1
11
16K (16384) CK
14CK + 64 ms
Crystal Oscillator,
slowly rising power
Notes:
Additional Delay
from Reset
(VCC = 5.0V)
Recommended Usage
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.
6.2.7
Default Clock Source
The device is shipped with CKSEL = “0010”, SUT = “10”, and CKDIV8 programmed. The default
clock source setting is therefore the Internal Oscillator running at 8 MHz 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 High-voltage Programmer.
It should be noted that unprogramming the CKDIV8 fuse may result in overclocking. At low voltages the devices are rated for clock frequencies below that of the internal oscillator. See Section
19.3 on page 185 for maximum operating frequency versus supply voltage.
6.3
System Clock Prescaler
The system clock can be divided by setting the “CLKPR – Clock Prescale Register” on page 32.
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 6-13 on page 33.
6.3.1
Switching Time
When switching between prescaler settings, the System Clock Prescaler ensures that no
glitches occur in the clock system and 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 another cannot be exactly predicted.
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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, two active clock edges are produced. Here, T1 is
the previous clock period, and T2 is the period corresponding to the new prescaler setting.
6.4
Clock Output Buffer
The device can output the system clock on the CLKO pin. To enable the output, the CKOUT
Fuse has to be programmed. This mode is suitable when the chip clock is used to drive other circuits on the system. Note that the clock will not be output during reset and the normal operation
of I/O pin will be overridden when the fuse is programmed. Any clock source, including the internal oscillator, can be selected when the clock is output on CLKO. If the System Clock Prescaler
is used, it is the divided system clock that is output.
6.5
6.5.1
Register Description
OSCCAL – Oscillator Calibration Register
Bit
7
6
5
4
3
2
1
0
0x31 (0x51)
CAL7
CAL6
CAL5
CAL4
CAL3
CAL2
CAL1
CAL0
Read/Write
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
Initial Value
OSCCAL
Device Specific Calibration Value
• Bits 7:0 – CAL7:0: Oscillator Calibration Value
The Oscillator Calibration Register is used to trim the Calibrated Internal Oscillator to remove
process variations from the oscillator frequency. A pre-programmed calibration value is automatically written to this register during chip reset, giving the Factory calibrated frequency as
specified in Table 19-2 on page 186. The application software can write this register to change
the oscillator frequency. The oscillator can be calibrated to frequencies as specified in Table 192 on page 186. 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 CAL7:0 bits are used to tune the frequency of the oscillator. A setting of 0x00 gives the lowest frequency, and a setting of 0xFF gives the highest.
6.5.2
CLKPR – Clock Prescale Register
Bit
7
6
5
4
3
2
1
0
0x28 (0x48)
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
See Bit Description
CLKPR
• 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 the 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 6:4 – Res: Reserved Bits
These bits are reserved and will always read as zero.
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ATtiny261A/461A/861A
• 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 6-13.
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.
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 eight 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 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 6-13.
Clock Prescaler Select
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
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7. Power Management and Sleep Modes
The high performance and industry leading code efficiency makes the AVR microcontrollers an
ideal choise for low power applications. In addition, 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.
7.1
Sleep Modes
Figure 6-1 on page 24 presents the different clock systems and their distribution. The figure is
helpful in selecting an appropriate sleep mode. Table 7-1 shows the different sleep modes and
their wake up sources.
Table 7-1.
Active Clock Domains and Wake-up Sources in Different Sleep Modes
ADC Noise Reduct.
clkPCK
clkPLL
Main Clock
Source Enabled
INT0, INT1 and
Pin Change
SPM/EEPROM
Ready Interrupt
ADC
Interrupt
USI
Interrupt
Other
I/O
Watchdog
Interrupt
X
X
X
X(2)
X
X
X
X
X
X
X
X
Power-down
Standby
Note:
Wake-up Sources
clkADC
Idle
Osc.
clkIO
clkFLASH
Sleep Mode
clkCPU
Active Clock Domains
(2)
X
X
(1)
X
X
X
X
X
X(1)
X
X
(1)
X
X
X
1. For INT0 and INT1, only level interrupt.
2. When PLL selected as system clock.
To enter any of the sleep modes, the SE bit in MCUCR must be written to logic one and a
SLEEP instruction must be executed. The SM1:0 bits in the MCUCR Register select which sleep
mode (Idle, ADC Noise Reduction, Power-down, or Standby) will be activated by the SLEEP
instruction. See Table 7-2 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.
Note that if a level triggered interrupt is used for wake-up the changed level must be held for
some time to wake up the MCU (and for the MCU to enter the interrupt service routine). See
“External Interrupts” on page 49 for details.
7.1.1
Idle Mode
When bits SM1:0 are written to 00, the SLEEP instruction makes the MCU enter Idle mode,
stopping the CPU but allowing Analog Comparator, ADC, Timer/Counter, Watchdog, and the
interrupt system to continue operating. This sleep mode basically halts clkCPU and clkFLASH, while
allowing the other clocks to run.
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ATtiny261A/461A/861A
Idle mode enables the MCU to wake up from external triggered interrupts as well as internal
ones like the Timer Overflow. 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.
7.1.2
ADC Noise Reduction Mode
When the SM1:0 bits are written to 01, the SLEEP instruction makes the MCU enter ADC Noise
Reduction mode, stopping the CPU but allowing the ADC, the external interrupts, and the
Watchdog to continue operating (if enabled). This sleep mode halts clkI/O, clkCPU, and clkFLASH,
while allowing the other clocks to run.
This mode 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
form the ADC Conversion Complete interrupt, only an External Reset, a Watchdog Reset, a
Brown-out Reset, an SPM/EEPROM ready interrupt, an external level interrupt on INT0 or a pin
change interrupt can wake up the MCU from ADC Noise Reduction mode.
7.1.3
Power-Down Mode
When the SM1:0 bits are written to 10, the SLEEP instruction makes the MCU enter Powerdown mode. In this mode, the 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, an external level interrupt on INT0, or a pin change interrupt can wake up the MCU. This
sleep mode halts all generated clocks, allowing operation of asynchronous modules, only.
7.1.4
Standby Mode
When the SM1:0 bits are written to 11 and an external crystal/resonator clock option is selected,
the SLEEP instruction makes the MCU enter Standby mode. This mode is identical to Powerdown with the exception that the Oscillator is kept running. From Standby mode, the device
wakes up in six clock cycles.
7.2
Software BOD Disable
When the Brown-out Detector (BOD) is enabled by BODLEVEL fuses (see Table 18-4 on page
168), the BOD is actively monitoring the supply voltage during a sleep period. It is possible to
save power by disabling the BOD by software in Power-Down sleep mode. The sleep mode
power consumption will then be at the same level as when BOD is globally disabled by fuses.
If BOD is disabled by software, the BOD function is turned off immediately after entering the
sleep mode. Upon wake-up from sleep, BOD is automatically enabled again. This ensures safe
operation in case the VCC level has dropped during the sleep period.
When the BOD has been disabled, the wake-up time from sleep mode will be approximately
60µs to ensure that the BOD is working correctly before the MCU continues executing code.
BOD disable is controlled by the BODS (BOD Sleep) bit of BOD Control Register, see “MCUCR
– MCU Control Register” on page 37. Writing this bit to one turns off BOD in Power-Down and
Stand-By, while writing a zero keeps the BOD active. The default setting is zero, i.e. BOD active.
Writing to the BODS bit is controlled by a timed sequence and an enable bit, see “MCUCR –
MCU Control Register” on page 37.
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7.3
Power Reduction Register
The Power Reduction Register (PRR), see “PRR – Power Reduction Register” on page 38, 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.
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. See “Supply Current
of I/O modules” on page 193 for examples. In all other sleep modes, the clock is already
stopped.
7.4
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.
7.4.1
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 the 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 “AC – Analog Comparator” on page 135 for details on how
to configure the Analog Comparator.
7.4.2
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 “ADC – Analog to Digital Converter” on
page 140 for details on ADC operation.
7.4.3
Brown-out Detector
If the Brown-out Detector is not needed in 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 41 for details on how to
configure the Brown-out Detector.
7.4.4
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 42 for details on the start-up time.
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7.4.5
Watchdog Timer
If the Watchdog Timer is not needed in the application, this 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 42 for details on how to configure the Watchdog Timer.
7.4.6
Port Pins
When entering a sleep mode, all port pins should be configured to use minimum power. The
most important thing 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 “Digital Input Enable and Sleep Modes” on page 57 for details on
which pins are enabled. If the input buffer is enabled and the input signal is left floating or has 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 (DIDR0, DIDR1).
Refer to “DIDR0 – Digital Input Disable Register 0” on page 159 or “DIDR1 – Digital Input Disable Register 1” on page 159 for details.
7.5
7.5.1
Register Description
MCUCR – MCU Control Register
The MCU Control Register contains control bits for power management.
Bit
7
6
5
4
3
2
1
0
0x35 (0x55)
BODS
PUD
SE
SM1
SM0
BODSE
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
MCUCR
• Bit 7 – BODS: BOD Sleep
In order to disable BOD during sleep the BODS bit must be written to logic one. This is controlled
by a timed sequence and the enable bit, BODSE. First, both BODS and BODSE must be set to
one. Second, within four clock cycles, BODS must be set to one and BODSE must be set to
zero. The BODS bit is active three clock cycles after it is set. A sleep instruction must be executed while BODS is active in order to turn off the BOD for the actual sleep mode. The BODS bit
is automatically cleared after three clock cycles.
• Bit 5 – 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.
• Bits 4, 3 – SM1:0: Sleep Mode Select Bits 2:0
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These bits select between the three available sleep modes as shown in Table 7-2.
Table 7-2.
Sleep Mode Select
SM1
SM0
Sleep Mode
0
0
Idle
0
1
ADC Noise Reduction
1
0
Power-down
1
1
Standby
• Bit 2 – BODSE: BOD Sleep Enable
The BODSE bit enables setting of BODS control bit, as explained on BODS bit description. BOD
disable is controlled by a timed sequence.
7.5.2
PRR – Power Reduction Register
The Power Reduction Register provides a method to reduce power consumption by allowing
peripheral clock signals to be disabled.
Bit
7
6
5
4
3
2
1
0x36 (0x56)
–
-
-
-
PRTIM1
PRTIM0
PRUSI
0
PRADC
Read/Write
R
R
R
R
R/W
R/W
R/W
R/W
Initial Value
0
0
0
0
0
0
0
0
PRR
• Bits 7, 6, 5, 4 – Res: Reserved Bits
These bits are reserved and will always read zero.
• Bit 3 – PRTIM1: Power Reduction Timer/Counter1
Writing a logic one to this bit shuts down the Timer/Counter1 module. When the Timer/Counter1
is enabled, operation will continue like before the shutdown.
• Bit 2 – PRTIM0: Power Reduction Timer/Counter0
Writing a logic one to this bit shuts down the Timer/Counter0 module. When the Timer/Counter0
is enabled, operation will continue like before the shutdown.
• Bit 1 – PRUSI: Power Reduction USI
Writing a logic one to this bit shuts down the USI by stopping the clock to the module. When
waking up the USI again, the USI should be re initialized to ensure proper operation.
• Bit 0 – PRADC: Power Reduction ADC
Writing a logic one to this bit shuts down the ADC. The ADC must be disabled before shut down.
Also analog comparator needs this clock.
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ATtiny261A/461A/861A
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ATtiny261A/461A/861A
8. System Control and Reset
8.1
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 RJMP – Relative
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. The circuit diagram in Figure 8-1 shows the reset logic. Electrical parameters of the
reset circuitry are given in Table 19-4 on page 187.
Figure 8-1.
Reset Logic
DATA BUS
PORF
BORF
EXTRF
WDRF
MCU Status
Register (MCUSR)
Power-on Reset
Circuit
Brown-out
Reset Circuit
BODLEVEL [1..0]
Pull-up Resistor
SPIKE
FILTER
Watchdog
Oscillator
Clock
Generator
CK
Delay Counters
TIMEOUT
CKSEL[1:0]
SUT[1:0]
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 25.
39
8197A–AVR–10/09
8.2
Reset Sources
The ATtiny261A/461A/861A has four 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.
8.2.1
Power-on Reset
A Power-on Reset (POR) pulse is generated by an On-chip detection circuit. The detection level
is defined in “System and Reset Characteristics” on page 187. 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 VCC rise. The RESET signal is activated again, without any delay,
when VCC decreases below the detection level.
Figure 8-2.
MCU Start-up, RESET Tied to VCC
VPOT
VCC
VRST
RESET
tTOUT
TIME-OUT
INTERNAL
RESET
Figure 8-3.
MCU Start-up, RESET Extended Externally
VCC
RESET
TIME-OUT
VPOT
VRST
tTOUT
INTERNAL
RESET
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ATtiny261A/461A/861A
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ATtiny261A/461A/861A
8.2.2
External Reset
An External Reset is generated by a low level on the RESET pin if enabled. Reset pulses longer
than the minimum pulse width (see “System and Reset Characteristics” on page 187) 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.
Figure 8-4.
External Reset During Operation
CC
8.2.3
Brown-out Detection
A Brown-out Detection (BOD) circuit monitors 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.
When the BOD is enabled, and VCC decreases to a value below the trigger level (VBOT- in Figure
8-5), the Brown-out Reset is immediately activated. When VCC increases above the trigger level
(VBOT+ in Figure 8-5), the delay counter starts the MCU after the Time-out 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 “System and Reset Characteristics” on page 187.
Figure 8-5.
Brown-out Reset During Operation
VCC
VBOT-
VBOT+
RESET
TIME-OUT
tTOUT
INTERNAL
RESET
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8197A–AVR–10/09
8.2.4
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
“Watchdog Timer” on page 42 for details on operation of the Watchdog Timer.
Figure 8-6.
Watchdog Reset During Operation
CC
CK
8.3
Internal Voltage Reference
ATtiny261A/461A/861A features an internal bandgap reference. This reference is used for
Brown-out Detection, and it can be used as an input to the Analog Comparator or the ADC. The
bandgap voltage varies with supply voltage and temperature, as can be seen in Figure 20-45 on
page 217.
8.3.1
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 “System and Reset Characteristics” on page 187. 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 bits).
2. When the bandgap reference is connected to the Analog Comparator (by setting the
ACBG bit in ACSR).
3. When the ADC is enabled.
Thus, when the BOD is not enabled, after setting the ACBG bit or enabling the ADC, the user
must always allow the reference to start up before the output from the Analog Comparator or
ADC is used. To reduce power consumption in Power-down mode, the user can avoid the three
conditions above to ensure that the reference is turned off before entering Power-down mode.
8.4
Watchdog Timer
The Watchdog Timer is clocked from an on-chip oscillator, which runs at 128 kHz. By controlling
the Watchdog Timer prescaler, the Watchdog Reset interval can be adjusted as shown in Table
8-3 on page 47. The WDR – Watchdog Reset – instruction resets the Watchdog Timer. The
Watchdog Timer is also reset when it is disabled and when a device reset occurs. Ten different
clock cycle periods can be selected to determine the reset period. If the reset period expires
without another Watchdog Reset, the device resets and executes from the Reset Vector. For
timing details on the Watchdog Reset, refer to Table 8-3 on page 47.
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ATtiny261A/461A/861A
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ATtiny261A/461A/861A
The Wathdog Timer can also be configured to generate an interrupt instead of a reset. This can
be very helpful when using the Watchdog to wake-up from Power-down.
To prevent unintentional disabling of the Watchdog or unintentional change of time-out period,
two different safety levels are selected by the fuse WDTON as shown in Table 8-1 Refer to
“Timed Sequences for Changing the Configuration of the Watchdog Timer” on page 43 for
details.
Table 8-1.
WDT Configuration as a Function of the Fuse Settings of WDTON
Safety
Level
WDTON
WDT Initial
State
How to Disable the
WDT
How to Change Timeout
Unprogrammed
1
Disabled
Timed sequence
No limitations
Programmed
2
Enabled
Always enabled
Timed sequence
Watchdog Timer
OSC/512K
OSC/1024K
OSC/256K
OSC/64K
OSC/128K
OSC/8K
OSC/4K
OSC/2K
WATCHDOG
RESET
OSC/32K
WATCHDOG
PRESCALER
128 kHz
OSCILLATOR
OSC/16K
Figure 8-7.
WDP0
WDP1
WDP2
WDP3
WDE
MCU RESET
8.4.1
8.4.1.1
Timed Sequences for Changing the Configuration of the Watchdog Timer
The sequence for changing configuration differs slightly between the two safety levels. Separate
procedures are described for each level.
Safety Level 1
In this mode, the Watchdog Timer is initially disabled, but can be enabled by writing the WDE bit
to one without any restriction. A timed sequence is needed when disabling an enabled Watchdog Timer. To disable an enabled Watchdog Timer, the following procedure must be followed:
1. In the same operation, write a logic one to 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, in the same operation, write the WDE and WDP bits
as desired, but with the WDCE bit cleared.
8.4.1.2
Safety Level 2
In this mode, the Watchdog Timer is always enabled, and the WDE bit will always read as one. A
timed sequence is needed when changing the Watchdog Time-out period. To change the
Watchdog Time-out, the following procedure must be followed:
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8197A–AVR–10/09
1. In the same operation, write a logical one to WDCE and WDE. Even though the WDE
always is set, the WDE must be written to one to start the timed sequence.
2. Within the next four clock cycles, in the same operation, write the WDP bits as desired,
but with the WDCE bit cleared. The value written to the WDE bit is irrelevant.
8.4.2
Code Examples
The following code example shows one assembly and one C function for turning off the WDT.
The example assumes that interrupts are controlled (e.g., by disabling interrupts globally) so that
no interrupts will occur during execution of these functions.
Assembly Code Example
WDT_off:
wdr
; Clear WDRF in MCUSR
ldi
r16, (0<<WDRF)
out
MCUSR, r16
; Write logical one to WDCE and WDE
; Keep old prescaler setting to prevent unintentional Watchdog Reset
in
r16, WDTCSR
ori r16, (1<<WDCE)|(1<<WDE)
out WDTCSR, r16
; Turn off WDT
ldi r16, (0<<WDE)
out WDTCSR, r16
ret
C Code Example
void WDT_off(void)
{
_WDR();
/* Clear WDRF in MCUSR */
MCUSR = 0x00
/* Write logical one to WDCE and WDE */
WDTCSR |= (1<<WDCE) | (1<<WDE);
/* Turn off WDT */
WDTCSR = 0x00;
}
Note:
44
See “Code Examples” on page 6.
ATtiny261A/461A/861A
8197A–AVR–10/09
ATtiny261A/461A/861A
8.5
8.5.1
Register Description
MCUSR – MCU Status Register
The MCU Status Register provides information on which reset source caused an MCU Reset.
Bit
7
6
5
4
3
2
1
0
0x34 (0x54)
–
–
–
–
WDRF
BORF
EXTRF
PORF
Read/Write
R
R
R
R
R/W
R/W
R/W
R/W
Initial Value
0
0
0
0
See Bit Description
MCUSR
• Bits 7:4 – Res: Reserved Bits
These bits are reserved and will always read zero.
• 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.
• 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.
8.5.2
WDTCR – Watchdog Timer Control Register
Bit
7
6
5
4
3
2
1
0
0x21 (0x41)
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
WDTCR
• Bit 7 – WDIF: Watchdog Timeout 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 Timeout Interrupt Enable
When this bit is written to one, WDE is cleared, and the I-bit in the Status Register is set, the
Watchdog Time-out Interrupt is enabled. In this mode the corresponding interrupt is executed
instead of a reset if a timeout in the Watchdog Timer occurs.
If WDE is set, WDIE is automatically cleared by hardware when a time-out occurs. This is useful
for keeping the Watchdog Reset security while using the interrupt. After the WDIE bit is cleared,
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8197A–AVR–10/09
the next time-out will generate a reset. To avoid the Watchdog Reset, WDIE must be set after
each interrupt.
Table 8-2.
Watchdog Timer Configuration
WDE
WDIE
Watchdog Timer State
Action on Time-out
0
0
Stopped
None
0
1
Running
Interrupt
1
0
Running
Reset
1
1
Running
Interrupt
• Bit 4 – WDCE: Watchdog Change Enable
This bit must be set when the WDE bit is written to logic zero. Otherwise, the Watchdog will not
be disabled. Once written to one, hardware will clear this bit after four clock cycles. Refer to the
description of the WDE bit for a Watchdog disable procedure. This bit must also be set when
changing the prescaler bits. See “Timed Sequences for Changing the Configuration of the
Watchdog Timer” on page 43.
• Bit 3 – WDE: Watchdog Enable
When the WDE is written to logic one, the Watchdog Timer is enabled, and if the WDE is written
to logic zero, the Watchdog Timer function is disabled. WDE can only be cleared if the WDCE bit
has logic level one. To disable an enabled Watchdog Timer, the following procedure must be
followed:
1. In the same operation, write a logic one to WDCE and WDE. A logic one must be written to WDE even though it is set to one before the disable operation starts.
2. Within the next four clock cycles, write a logic 0 to WDE. This disables the Watchdog.
In safety level 2, it is not possible to disable the Watchdog Timer, even with the algorithm
described above. See “Timed Sequences for Changing the Configuration of the Watchdog
Timer” on page 43.
In safety level 1, WDE is overridden by WDRF in MCUSR. See “MCUSR – MCU Status Register” on page 45 for description of WDRF. This means that WDE is always set when WDRF is set.
To clear WDE, WDRF must be cleared before disabling the Watchdog with the procedure
described above. This feature ensures multiple resets during conditions causing failure, and a
safe start-up after the failure.
Note:
If the watchdog timer is not going to be used in the application, it is important to go through a
watchdog disable procedure in the initialization of the device. If the Watchdog is accidentally
enabled, for example by a runaway pointer or brown-out condition, the device will be reset, which
in turn will lead to a new watchdog reset. To avoid this situation, the application software should
always clear the WDRF flag and the WDE control bit in the initialization routine.
• Bits 5, 2:0 – WDP3:0: Watchdog Timer Prescaler 3, 2, 1, and 0
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ATtiny261A/461A/861A
8197A–AVR–10/09
ATtiny261A/461A/861A
The WDP3:0 bits determine the Watchdog Timer prescaling when the Watchdog Timer is
enabled. The different prescaling values and their corresponding Timeout Periods are shown in
Table 8-3.
Table 8-3.
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 (32764) 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
Notes:
Reserved(1)
1. If selected, one of the valid settings below 0b1010 will be used.
47
8197A–AVR–10/09
9. Interrupts
This section describes the specifics of the interrupt handling as performed in
ATtiny261A/461A/861A. For a general explanation of the AVR interrupt handling, refer to “Reset
and Interrupt Handling” on page 13.
9.1
Interrupt Vectors
Interrupt vectors of ATtiny261A/461A/861A are described in Table 9-1 below.
Table 9-1.
Reset and Interrupt Vectors
Vector
No.
Program
Address
Source
Interrupt Definition
1
0x0000
RESET
External Pin, Power-on Reset,
Brown-out Reset, Watchdog Reset
2
0x0001
INT0
External Interrupt Request 0
3
0x0002
PCINT
Pin Change Interrupt Request
4
0x0003
TIMER1_COMPA
Timer/Counter1 Compare Match A
5
0x0004
TIMER1_COMPB
Timer/Counter1 Compare Match B
6
0x0005
TIMER1_OVF
Timer/Counter1 Overflow
7
0x0006
TIMER0_OVF
Timer/Counter0 Overflow
8
0x0007
USI_START
USI Start
9
0x0008
USI_OVF
USI Overflow
10
0x0009
EE_RDY
EEPROM Ready
11
0x000A
ANA_COMP
Analog Comparator
12
0x000B
ADC
ADC Conversion Complete
13
0x000C
WDT
Watchdog Time-out
14
0x000D
INT1
External Interrupt Request 1
15
0x000E
TIMER0_COMPA
Timer/Counter0 Compare Match A
16
0x000F
TIMER0_COMPB
Timer/Counter0 Compare Match B
17
0x0010
TIMER0_CAPT
Timer/Counter1 Capture Event
18
0x0011
TIMER1_COMPD
Timer/Counter1 Compare Match D
19
0x0012
FAULT_PROTECTION
Timer/Counter1 Fault Protection
If the program never enables an interrupt source, the Interrupt Vectors are not used, and regular
program code can be placed at these locations.
The most typical and general program setup for the Reset and Interrupt Vector Addresses in
ATtiny261A/461A/861A is shown in the following program example.
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ATtiny261A/461A/861A
8197A–AVR–10/09
ATtiny261A/461A/861A
Address Labels Code
9.2
Comments
0x0000
rjmp
RESET
; Reset Handler
0x0001
rjmp
EXT_INT0
; IRQ0 Handler
0x0002
rjmp
PCINT
; PCINT Handler
0x0003
rjmp
TIM1_COMPA
; Timer1 CompareA Handler
0x0004
rjmp
TIM1_COMPB
; Timer1 CompareB Handler
0x0005
rjmp
TIM1_OVF
; Timer1 Overflow Handler
0x0006
rjmp
TIM0_OVF
; Timer0 Overflow Handler
0x0007
rjmp
USI_START
; USI Start Handler
0x0008
rjmp
USI_OVF
; USI Overflow Handler
0x0009
rjmp
EE_RDY
; EEPROM Ready Handler
0x000A
rjmp
ANA_COMP
; Analog Comparator Handler
0x000B
rjmp
ADC
; ADC Conversion Handler
0x000C
rjmp
WDT
; WDT Interrupt Handler
0x000D
rjmp
EXT_INT1
; IRQ1 Handler
0x000E
rjmp
TIM0_COMPA
; Timer0 CompareA Handler
0x000F
rjmp
TIM0_COMPB
; Timer0 CompareB Handler
0x0010
rjmp
TIM0_CAPT
; Timer0 Capture Event Handler
0x0011
rjmp
TIM1_COMPD
; Timer1 CompareD Handler
0x0012
rjmp
FAULT_PROTECTION ; Timer1 Fault Protection
0x0013
RESET: ldi
r16, low(RAMEND) ; Main program start
0x0014
ldi
r17, high(RAMEND); Tiny861 have also SPH
0x0015
out
SPL, r16
; Set Stack Pointer to top of RAM
0x0016
out
SPH, r17
; Tiny861 have also SPH
0x0017
sei
0x0018
<instr>
...
...
; Enable interrupts
External Interrupts
The External Interrupts are triggered by the INT0 or INT1 pin or any of the PCINT15:0 pins.
Observe that, if enabled, the interrupts will trigger even if the INT0, INT1 or PCINT15:0 pins are
configured as outputs. This feature provides a way of generating a software interrupt. Pin
change interrupts PCI will trigger if any enabled PCINT15:0 pin toggles. The PCMSK Register
control which pins contribute to the pin change interrupts. Pin change interrupts on PCINT15:0
are detected asynchronously. This implies that these interrupts can be used for waking the part
also from sleep modes other than Idle mode.
The INT0 and INT1 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 MCU Control Register – MCUCR. When the INT0
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 INT0 or INT1 requires
the presence of an I/O clock, described in “Clock Subsystems” on page 24.
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8197A–AVR–10/09
9.2.1
Low Level Interrupt
A low level interrupt on INT0 is detected asynchronously. This means that the interrupt source
can be used for waking the part also from sleep modes other than Idle (the I/O clock is halted in
all sleep modes except Idle).
Note that if a level triggered interrupt is used for wake-up from Power-down, the required level
must be held long enough for the MCU to complete the wake-up to trigger the level interrupt. If
the level disappears before the end of the Start-up Time, the MCU will still wake up, but no interrupt will be generated. The start-up time is defined by the SUT and CKSEL Fuses as described
in “Clock System” on page 24.
If the low level on the interrupt pin is removed before the device has woken up then program
execution will not be diverted to the interrupt service routine but continue from the instruction following the SLEEP command.
9.3
9.3.1
Register Description
MCUCR – MCU Control Register
The MCU Register contains control bits for interrupt sense control.
Bit
7
6
5
4
3
2
1
0
0x35 (0x55)
BODS
PUD
SE
SM1
SM0
BODSE
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
MCUCR
• Bits 1, 0 – ISC01, ISC00: Interrupt Sense Control 0 Bit 1 and Bit 0
The External Interrupt 0 is activated by the external pin INT0 or INT1 if the SREG I-flag and the
corresponding interrupt mask are set. The level and edges on the external INT0 or INT1 pin that
activate the interrupt are defined in Table 9-2. The value on the INT0 or INT1 pin is 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. If low level interrupt is selected, the low level must be held until the completion of the
currently executing instruction to generate an interrupt.
Table 9-2.
9.3.2
Interrupt 0 Sense Control
ISC01
ISC00
Description
0
0
The low level of INT0 or INT1 generates an interrupt request.
0
1
Any logical change on INT0 or INT1 generates an interrupt request.
1
0
The falling edge of INT0 or INT1 generates an interrupt request.
1
1
The rising edge of INT0 or INT1 generates an interrupt request.
GIMSK – General Interrupt Mask Register
Bit
7
6
5
4
3
2
1
0
0x3B (0x5B)
INT1
INT0
PCIE1
PCIE0
–
–
–
–
Read/Write
R/W
R/W
R/W
R/w
R
R
R
R
Initial Value
0
0
0
0
0
0
0
0
GIMSK
• Bit 7 – INT1: External Interrupt Request 1 Enable
When the INT1 bit is set (one) and the I-bit in the Status Register (SREG) is set (one), the external pin interrupt is enabled. The Interrupt Sense Control0 bits 1/0 (ISC01 and ISC00) in the MCU
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Control Register (MCUCR) define whether the external interrupt is activated on rising and/or falling edge of the INT1 pin or level sensed. Activity on the pin will cause an interrupt request even
if INT1 is configured as an output. The corresponding interrupt of External Interrupt Request 1 is
executed from the INT1 Interrupt Vector.
• Bit 6 – INT0: External Interrupt Request 0 Enable
When the INT0 bit is set (one) and the I-bit in the Status Register (SREG) is set (one), the external pin interrupt is enabled. The Interrupt Sense Control0 bits 1/0 (ISC01 and ISC00) in the MCU
Control Register (MCUCR) define whether the external interrupt is activated on rising and/or falling edge of the INT0 pin or level sensed. Activity on the pin will cause an interrupt request even
if INT0 is configured as an output. The corresponding interrupt of External Interrupt Request 0 is
executed from the INT0 Interrupt Vector.
• Bit 5 – PCIE1: Pin Change Interrupt Enable
When the PCIE1 bit is set (one) and the I-bit in the Status Register (SREG) is set (one), pin
change interrupt is enabled. Any change on any enabled PCINT7:0 or PCINT15:12 pin will
cause an interrupt. The corresponding interrupt of Pin Change Interrupt Request is executed
from the PCI Interrupt Vector. PCINT7:0 and PCINT15:12 pins are enabled individually by the
PCMSK0 and PCMSK1 Register.
• Bit 4 – PCIE0: Pin Change Interrupt Enable
When the PCIE0 bit is set (one) and the I-bit in the Status Register (SREG) is set (one), pin
change interrupt is enabled. Any change on any enabled PCINT11:8 pin will cause an interrupt.
The corresponding interrupt of Pin Change Interrupt Request is executed from the PCI Interrupt
Vector. PCINT11:8 pins are enabled individually by the PCMSK1 Register.
• Bits 3:0 – Res: Reserved Bits
These bits are reserved and will always read as zero.
9.3.3
GIFR – General Interrupt Flag Register
Bit
7
6
5
4
3
2
1
0
0x3A (0x5A)
INT1
INTF0
PCIF
–
–
–
–
–
Read/Write
R/W
R/W
R/W
R
R
R
R
R
Initial Value
0
0
0
0
0
0
0
0
GIFR
• Bit 7– INTF1: External Interrupt Flag 1
When an edge or logic change on the INT1 pin triggers an interrupt request, INTF1 becomes set
(one). If the I-bit in SREG and the INT1 bit in GIMSK are set (one), the MCU will jump to the corresponding 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. This flag is always cleared
when INT1 is configured as a level interrupt.
• Bit 6 – INTF0: External Interrupt Flag 0
When an edge or logic change on the INT0 pin triggers an interrupt request, INTF0 becomes set
(one). If the I-bit in SREG and the INT0 bit in GIMSK are set (one), the MCU will jump to the corresponding 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. This flag is always cleared
when INT0 is configured as a level interrupt.
• Bit 5 – PCIF: Pin Change Interrupt Flag
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8197A–AVR–10/09
When a logic change on any PCINT15 pin triggers an interrupt request, PCIF becomes set
(one). If the I-bit in SREG and the PCIE bit in GIMSK are set (one), the MCU will jump to the corresponding 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.
• Bits 4:0 – Res: Reserved Bits
These bits are reserved and will always read as zero.
9.3.4
PCMSK0 – Pin Change Mask Register A
Bit
7
6
5
4
3
2
1
0
0x23 (0x43)
PCINT7
PCINT6
PCINT5
PCINT4
PCINT3
PCINT2
PCINT1
PCINT0
Read/Write
R/W
R/W
R/W
R/w
R/W
R/W
R/W
R/W
Initial Value
1
1
0
0
1
0
0
0
PCMSK0
• Bits 7:0 – PCINT7:0: Pin Change Enable Mask 7:0
Each PCINT7:0 bit selects whether pin change interrupt is enabled on the corresponding I/O pin.
If PCINT7:0 is set and the PCIE1 bit in GIMSK is set, pin change interrupt is enabled on the corresponding I/O pin. If PCINT7:0 is cleared, pin change interrupt on the corresponding I/O pin is
disabled.
9.3.5
PCMSK1 – Pin Change Mask Register B
Bit
7
6
5
4
3
2
1
0
0x22 (0x42)
PCINT15
PCINT14
PCINT13
PCINT12
PCINT11
PCINT10
PCINT9
PCINT8
Read/Write
R/W
R/W
R/W
R/w
R/W
R/W
R/W
R/W
Initial Value
1
1
1
1
1
1
1
1
PCMSK1
• Bits 7:0 – PCINT15:8: Pin Change Enable Mask 15:8
Each PCINT15:8 bit selects whether pin change interrupt is enabled on the corresponding I/O
pin. If PCINT11:8 is set and the PCIE0 bit in GIMSK is set, pin change interrupt is enabled on
the corresponding I/O pin, and if PCINT15:12 is set and the PCIE1 bit in GIMSK is set, pin
change interrupt is enabled on the corresponding I/O pin. If PCINT15:8 is cleared, pin change
interrupt on the corresponding I/O pin is disabled.
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10. I/O Ports
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. The pin driver is strong enough to drive LED displays directly. 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 10-1. See “Electrical Characteristics” on page 184 for a complete list of parameters.
Figure 10-1. I/O Pin Equivalent Schematic
RPU
Logic
Pxn
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” on page 67.
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” on page
54. 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 58. 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.
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10.1
Ports as General Digital I/O
The ports are bi-directional I/O ports with optional internal pull-ups. Figure 10-2 shows a functional description of one I/O-port pin, here generically called Pxn.
Figure 10-2. General Digital I/O(1)
PUD
Q
D
DDxn
Q CLR
WDx
RESET
DATA BUS
RDx
1
Q
Pxn
D
0
PORTxn
Q CLR
RESET
WRx
WPx
RRx
SLEEP
SYNCHRONIZER
D
Q
L
Q
D
RPx
Q
PINxn
Q
clk I/O
PUD:
SLEEP:
clkI/O:
Note:
10.1.1
PULLUP DISABLE
SLEEP CONTROL
I/O CLOCK
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.
Configuring the Pin
Each port pin consists of three register bits: DDxn, PORTxn, and PINxn. As shown in “Register
Description” on page 67, 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
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ATtiny261A/461A/861A
be configured as an output pin. The port pins are tri-stated when reset condition becomes active,
even if no clocks are running.
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).
The pull-up resistor is activated, if the PUExn is written logic one. To switch the pull-up resistor
off, PUExn has to be written logic zero.
10.1.2
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.
10.1.3
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}
= 0b10) as an intermediate step.
Table 10-1 summarizes the control signals for the pin value.
Table 10-1.
10.1.4
Port Pin Configurations
DDxn
PORTxn
PUD
(in MCUCR)
I/O
Pull-up
0
0
X
Input
No
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
Reading the Pin Value
Independent of the setting of Data Direction bit DDxn, the port pin can be read through the
PINxn Register bit. As shown in Figure 10-2, 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 10-3 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.
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8197A–AVR–10/09
Figure 10-3. 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
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 10-4. 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 one system clock period.
Figure 10-4. 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
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10.1.5
Digital Input Enable and Sleep Modes
As shown in Figure 10-2, 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 58.
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 mode, as the clamping in these sleep mode produces the requested
logic change.
10.1.6
Unconnected Pins
If some pins are unused, it is recommended to ensure that these pins have a defined level. Even
though most of the digital inputs are disabled in the deep sleep modes as described above, floating inputs should be avoided to reduce current consumption in all other modes where the digital
inputs are enabled (Reset, Active mode and Idle mode).
The simplest method to ensure a defined level of an unused pin, is to enable the internal pull-up.
In this case, the pull-up will be disabled during reset. If low power consumption during reset is
important, it is recommended to use an external pull-up or pulldown. Connecting unused pins
directly to VCC or GND is not recommended, since this may cause excessive currents if the pin is
accidentally configured as an output.
10.1.7
Program Examples
The following code examples show how to set port B pins 0 and 1 high, 2 and 3 low, and define
the port pins from 4 to 5 as input with a pull-up assigned to port pin 4. 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
...
; Define pull-ups and set outputs high
; Define directions for port pins
ldi
r16,(1<<PB4)|(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
...
Note:
Two temporary registers are used to minimize the time from pull-ups are set on pins 0, 1 and 4,
until the direction bits are correctly set, defining bit 2 and 3 as low and redefining bits 0 and 1 as
strong high drivers.
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C Code Example
unsigned char i;
...
/* Define pull-ups and set outputs high */
/* Define directions for port pins */
PORTB = (1<<PB4)|(1<<PB1)|(1<<PB0);
DDRB = (1<<DDB3)|(1<<DDB2)|(1<<DDB1)|(1<<DDB0);
/* Insert nop for synchronization*/
_NOP();
/* Read port pins */
i = PINB;
...
Note:
10.2
See “Code Examples” on page 6.
Alternate Port Functions
Most port pins have alternate functions in addition to being general digital I/Os. Figure 10-5
shows how the port pin control signals from the simplified Figure 10-2 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.
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Figure 10-5. Alternate Port Functions(1)
PUOExn
PUOVxn
1
PUD
0
DDOExn
DDOVxn
1
Q D
DDxn
0
Q CLR
WDx
PVOExn
RESET
RDx
1
DATA BUS
PVOVxn
1
Pxn
Q
0
D
0
PORTxn
PTOExn
Q CLR
DIEOExn
WPx
DIEOVxn
RESET
WRx
1
0
RRx
SLEEP
SYNCHRONIZER
D
SET
Q
D
RPx
Q
PINxn
L
CLR
Q
CLR
Q
clk I/O
DIxn
AIOxn
PUOExn:
PUOVxn:
DDOExn:
DDOVxn:
PVOExn:
PVOVxn:
DIEOExn:
DIEOVxn:
SLEEP:
PTOExn:
Note:
Pxn PULL-UP OVERRIDE ENABLE
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
Pxn DIGITAL INPUT-ENABLE OVERRIDE VALUE
SLEEP CONTROL
Pxn, PORT TOGGLE OVERRIDE ENABLE
PUD:
WDx:
RDx:
RRx:
WRx:
RPx:
WPx:
clkI/O:
DIxn:
AIOxn:
PULLUP DISABLE
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.
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8197A–AVR–10/09
Table 10-2 summarizes the function of the overriding signals. The pin and port indexes from Figure 10-5 are not shown in the succeeding tables. The overriding signals are generated internally
in the modules having the alternate function.
Table 10-2.
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 bidirectionally.
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.
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10.2.1
Alternate Functions of Port A
The Port A pins with alternate function are shown in Table 10-3.
Table 10-3.
Port B Pins Alternate Functions
Port Pin
Alternate Function
PA7
ADC6: ADC Input Channel 6
AIN0:
Analog Comparator Input
PCINT7: Pin Change Interrupt 0, Source 7
PA6
ADC5: ADC Input Channel 5
AIN1:
Analog Comparator Input
PCINT6: Pin Change Interrupt 0, Source 6
PA5
ADC4: ADC Input Channel 4
AIN2:
Analog Comparator Input
PCINT5: Pin Change Interrupt 0, Source 5
PA4
ADC3: ADC Input Channel 3
ICP0:
Timer/Counter0 Input Capture Pin
PCINT4: Pin Change Interrupt 0, Source 4
PA3
AREF: External Analog Reference
PCINT3: Pin Change Interrupt 0, Source 3
ADC2:
INT1:
PA2
ADC Input Channel 2
External Interrupt 1 Input
USCK: USI Clock (Three Wire Mode)
SCL :
USI Clock (Two Wire Mode)
PCINT2: Pin Change Interrupt 0, Source 2
PA1
ADC1: ADC Input Channel 1
DO:
USI Data Output (Three Wire Mode)
PCINT1:Pin Change Interrupt 0, Source 1
PA0
ADC0: ADC Input Channel 0
DI:
USI Data Input (Three Wire Mode)
SDA:
USI Data Input (Two Wire Mode)
PCINT0: Pin Change Interrupt 0, Source 0
• Port A, Bit 7- ADC6/AIN0/PCINT7
• ADC6: Analog to Digital Converter, Channel 6.
• AIN0: Analog Comparator 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.
• PCINT7: Pin Change Interrupt source 8.
• Port A, Bit 6 - ADC5/AIN1/PCINT6
• ADC5: Analog to Digital Converter, Channel 5.
• AIN1: Analog Comparator 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.
• PCINT6: Pin Change Interrupt source 6.
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• Port A, Bit 5 - ADC4/AIN2/PCINT5
• ADC4: Analog to Digital Converter, Channel 4.
• AIN2: Analog Comparator 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.
• PCINT5: Pin Change Interrupt source 5.
• Port A, Bit 4 - ADC3/ICP0/PCINT4
• ADC3: Analog to Digital Converter, Channel 3.
• ICP0: Timer/Counter0 Input Capture Pin.
• PCINT4: Pin Change Interrupt source 4.
• Port A, Bit 3 - AREF/PCINT3
• AREF: External analog reference for ADC. Pullup and output driver are disabled on PA3
when the pin is used as an external reference or internal voltage reference with external
capacitor at the AREF pin.
• PCINT3: Pin Change Interrupt source 3.
• Port A, Bit 2 - ADC2/INT1/USCK/SCL/PCINT2
• ADC2: Analog to Digital Converter, Channel 2.
• INT1: The PA2 pin can serve as an External Interrupt source 1.
• USCK: Three-wire mode Universal Serial Interface Clock.
• SCL: Two-wire mode Serial Clock for USI Two-wire mode.
• PCINT2: Pin Change Interrupt source 2.
• Port A, Bit 1 - ADC1/DO/PCINT1
• ADC1: Analog to Digital Converter, Channel 1.
• DO: Three-wire mode Universal Serial Interface Data output. Three-wire mode Data output
overrides PORTA1 value and it is driven to the port when data direction bit DDA1 is set.
PORTA1 still enables the pull-up, if the direction is input and PORTA1 is set.
• PCINT1: Pin Change Interrupt source 1.
• Port A, Bit 0 - ADC0/DI/SDA/PCINT0
• ADC0: Analog to Digital Converter, Channel 0.
• DI: Data Input in USI Three-wire mode. USI Three-wire mode does not override normal port
functions, so pin must be configure as an input for DI function.
• SDA: Two-wire mode Serial Interface Data.
• PCINT0: Pin Change Interrupt source 0.
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Table 10-4 and Table 10-5 relate the alternate functions of Port A to the overriding signals
shown in Figure 10-5 on page 59.
Table 10-4.
Overriding Signals for Alternate Functions in PA7:PA4
Signal
Name
PA7/ADC6/AIN0/
PCINT7
PA6/ADC5/AIN1/
PCINT6
PA5/ADC4/AIN2/
PCINT5
PA4/ADC3/ICP0/
PCINT4
PUOE
0
0
0
0
PUOV
0
0
0
0
DDOE
0
0
0
0
DDOV
0
0
0
0
PVOE
0
0
0
0
PVOV
0
0
0
0
PTOE
0
0
0
0
DIEOE
PCINT7 • PCIE +
ADC6D
PCINT6 • PCIE +
ADC5D
PCINT5 • PCIE +
ADC4D
PCINT4 • PCIE +
ADC3D
DIEOV
ADC6D
ADC5D
ADC4D
ADC3D
DI
PCINT7
PCINT6
PCINT5
ICP0/PCINT4
AIO
ADC6, AIN0
ADC5, AIN1
ADC4, AIN2
ADC3
Table 10-5.
Overriding Signals for Alternate Functions in PA3:PA0
Signal
Name
PA3/AREF/
PCINT3
PA2/ADC2/INT1/
USCK/SCL/PCINT2
PA1/ADC1/DO/
PCINT1
PA0/ADC0/DI/SDA/
PCINT0
PUOE
0
0
0
0
PUOV
0
0
0
0
DDOE
0
USI_TWO_WIRE •
USIPOS
0
USI_TWO_WIRE •
USIPOS
DDOV
0
(USI_SCL_HOLD +
PORTB2) • DDB2 •
USIPOS
0
(SDA + PORTB0) •
DDRB0 • USIPOS
PVOE
0
USI_TWO_WIRE •
DDRB2
USI_THREE_WI
RE • USIPOS
USI_TWO_WIRE •
DDRB0 • USIPOS
PVOV
0
0
DO • USIPOS
0
PTOE
0
USI_PTOE • USIPOS
0
0
DIEOE
PCINT3 •
PCIE
PCINT2 • PCIE + INT1 +
ADC2D + USISIE •
USIPOS
PCINT1 • PCIE +
ADC1D
PCINT0 • PCIE +
ADC0D + USISIE •
USIPOS
DIEOV
0
ADC2D
ADC1D
ADC0D
DI
PCINT3
USCK/SCL/INT1/ PCINT2
PCINT1
DI/SDA/PCINT0
AIO
AREF
ADC2
ADC1
ADC0
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8197A–AVR–10/09
10.2.2
Alternate Functions of Port B
The Port B pins with alternate function are shown in Table 10-6.
Table 10-6.
Port B Pins Alternate Functions
Port Pin
Alternate Function
PB7
RESET: Reset pin
dW:
debugWire I/O
ADC10: ADC Input Channel 10
PCINT15:Pin Change Interrupt 0, Source 15
PB6
ADC9: ADC Input Channel 9
T0:
Timer/Counter0 Clock Source
INT0:
External Interrupt 0 Input
PCINT14:Pin Change Interrupt 0, Source 14
PB5
XTAL2: Crystal Oscillator Output
CLKO: System Clock Output
OC1D: Timer/Counter1 Compare Match D Output
ADC8: ADC Input Channel 8
PCINT13:Pin Change Interrupt 0, Source 13
PB4
XTAL1: Crystal Oscillator Input
CLKI:
External Clock Input
OC1D: Inverted Timer/Counter1 Compare Match D Output
ADC7: ADC Input Channel 7
PCINT12:Pin Change Interrupt 0, Source 12
PB3
OC1B: Timer/Counter1 Compare Match B Output
PCINT11:Pin Change Interrupt 0, Source 11
PB2
USCK: USI Clock (Three Wire Mode)
SCL :
USI Clock (Two Wire Mode)
OC1B: Inverted Timer/Counter1 Compare Match B Output
PCINT10:Pin Change Interrupt 0, Source 10
PB1
DO:
USI Data Output (Three Wire Mode)
OC1A: Timer/Counter1 Compare Match A Output
PCINT9: Pin Change Interrupt 1, Source 9
PB0
DI:
USI Data Input (Three Wire Mode)
SDA:
USI Data Input (Two Wire Mode)
OC1A: Inverted Timer/Counter1 Compare Match A Output
PCINT8: Pin Change Interrupt 1, Source 8
• Port B, Bit 7 - RESET/ dW/ ADC10/ PCINT15
• 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 PB7 is used as a reset pin, DDB7, PORTB7 and PINB7 will all read 0.
• dW: When the debugWIRE Enable (DWEN) Fuse is programmed and Lock bits are
unprogrammed, 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.
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ATtiny261A/461A/861A
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ATtiny261A/461A/861A
• ADC10: ADC input Channel 10. Note that ADC input channel 10 uses analog power.
• PCINT15: Pin Change Interrupt source 15.
• Port B, Bit 6 - ADC9/ T0/ INT0/ PCINT14
• ADC9: ADC input Channel 9. Note that ADC input channel 9 uses analog power.
• T0: Timer/Counter0 counter source.
• INT0: The PB6 pin can serve as an External Interrupt source 0.
• PCINT14: Pin Change Interrupt source 14.
• Port B, Bit 5 - XTAL2/ CLKO/ ADC8/ PCINT13
• 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.
• CLKO: The divided system clock can be output on the PB5 pin, if the CKOUT Fuse is
programmed, regardless of the PORTB5 and DDB5 settings. It will also be output during
reset.
• OC1D Output Compare Match output: The PB5 pin can serve as an external output for the
Timer/Counter1 Compare Match D when configured as an output (DDA1 set). The OC1D pin
is also the output pin for the PWM mode timer function.
• ADC8: ADC input Channel 8. Note that ADC input channel 8 uses analog power.
• PCINT13: Pin Change Interrupt source 13.
• Port B, Bit 4 - XTAL1/ CLKI/ OC1B/ ADC7/ PCINT12
• XTAL1/CLKI: Chip clock Oscillator pin 1. Used for all chip clock sources except internal
calibrated oscillator. When used as a clock pin, the pin can not be used as an I/O pin.
• OC1D: Inverted Output Compare Match output: The PB4 pin can serve as an external output
for the Timer/Counter1 Compare Match D when configured as an output (DDA0 set). The
OC1D pin is also the inverted output pin for the PWM mode timer function.
• ADC7: ADC input Channel 7. Note that ADC input channel 7 uses analog power.
• PCINT12: Pin Change Interrupt source 12.
• Port B, Bit 3 - OC1B/ PCINT11
• OC1B, Output Compare Match output: The PB3 pin can serve as an external output for the
Timer/Counter1 Compare Match B. The PB3 pin has to be configured as an output (DDB3
set (one)) to serve this function. The OC1B pin is also the output pin for the PWM mode timer
function.
• PCINT11: Pin Change Interrupt source 11.
• Port B, Bit 2 - SCK/ USCK/ SCL/ OC1B/ PCINT10
• USCK: Three-wire mode Universal Serial Interface Clock.
• SCL: Two-wire mode Serial Clock for USI Two-wire mode.
• OC1B: Inverted Output Compare Match output: The PB2 pin can serve as an external output
for the Timer/Counter1 Compare Match B when configured as an output (DDB2 set). The
OC1B pin is also the inverted output pin for the PWM mode timer function.
• PCINT10: Pin Change Interrupt source 10.
• Port B, Bit 1 - MISO/ DO/ OC1A/ PCINT9
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• DO: Three-wire mode Universal Serial Interface Data output. Three-wire mode Data output
overrides PORTB1 value and it is driven to the port when data direction bit DDB1 is set (one).
PORTB1 still enables the pull-up, if the direction is input and PORTB1 is set (one).
• OC1A: Output Compare Match output: The PB1 pin can serve as an external output for the
Timer/Counter1 Compare Match B when configured as an output (DDB1 set). The OC1A pin
is also the output pin for the PWM mode timer function.
• PCINT9: Pin Change Interrupt source 9.
• Port B, Bit 0 - MOSI/ DI/ SDA/ OC1A/ PCINT8
• DI: Data Input in USI Three-wire mode. USI Three-wire mode does not override normal port
functions, so pin must be configure as an input for DI function.
• SDA: Two-wire mode Serial Interface Data.
• OC1A: Inverted Output Compare Match output: The PB0 pin can serve as an external output
for the Timer/Counter1 Compare Match B when configured as an output (DDB0 set). The
OC1A pin is also the inverted output pin for the PWM mode timer function.
• PCINT8: Pin Change Interrupt source 8.
Table 10-7 and Table 10-8 relate the alternate functions of Port B to the overriding signals
shown in Figure 10-5 on page 59.
Table 10-7.
Signal
Name
PB7/RESET/
dW/ADC10/
PCINT15
PB6/ADC9/T0/
INT0/PCINT14
PB5/XTAL2/CLKO/
OC1D/ADC8/
PCINT13(1)
PB4/XTAL1/
OC1D/ADC7/
PCINT12(1)
PUOE
RSTDISBL(1) •
DWEN(1)
0
INTRC • EXTCLK
INTRC
PUOV
1
0
0
0
0
INTRC • EXTCLK
INTRC
(1)
•
DDOE
RSTDISBL
DWEN(1)
DDOV
debugWire Transmit
0
0
0
PVOE
0
0
OC1D Enable
OC1D Enable
PVOV
0
0
OC1D
OC1D
PTOE
0
0
0
0
DIEOE
0
RSTDISBL + (PCINT5
• PCIE + ADC9D)
INTRC • EXTCLK +
PCINT4 • PCIE +
ADC8D
INTRC + PCINT12 •
PCIE + ADC7D
DIEOV
ADC10D
ADC9D
(INTRC • EXTCLK) +
ADC8D
INTRC • ADC7D
DI
PCINT15
T0/INT0/PCINT14
PCINT13
PCINT12
AIO
RESET / ADC10
ADC9
XTAL2, ADC8
XTAL1, ADC7
Note:
66
Overriding Signals for Alternate Functions in PB7:PB4
1. “1” when the Fuse is “0” (Programmed).
ATtiny261A/461A/861A
8197A–AVR–10/09
ATtiny261A/461A/861A
Table 10-8.
Overriding Signals for Alternate Functions in PB3:PB0
Signal
Name
PB3/OC1B/
PB2/SCK/USCK/SCL/O
C1B/PCINT10
PB1/MISO/DO/OC1A/
PCINT9
PB0/MOSI/DI/SDA/
PCINT11
PUOE
0
0
0
0
PUOV
0
0
0
0
DDOE
0
USI_TWO_WIRE •
USIPOS
0
USI_TWO_WIRE •
USIPOS
DDOV
0
(USI_SCL_HOLD +
PORTB2) • DDB2 •
USIPOS
0
(SDA + PORTB0) •
DDB0 • USIPOS
PVOE
OC1B Enable
OC1B Enable + USIPOS
• USI_TWO_WIRE •
DDB2
OC1A Enable +
USIPOS •
USI_THREE_WIRE
PVOV
OC1B
OC1B
OC1A + (DO •
USIPOS)
OC1A
PTOE
0
USITC • USIPOS
0
0
DIEOE
PCINT11 • PCIE
PCINT10 • PCIE +
USISIE • USIPOS
PCINT9 • PCIE
PCINT8 • PCIE +
(USISIE • USIPOS)
DIEOV
0
0
0
0
DI
PCINT11
USCK/SCL/PCINT10
PCINT9
DI/SDA/PCINT8
OC1A/PCINT8
OC1A Enable +
(USI_TWO_WIRE •
DDB0 • USIPOS)
AIO
Note:
10.3
10.3.1
1. INTRC means that one of the internal oscillators is selected (by the CKSEL fuses), EXTCK
means that external clock is selected (by the CKSEL fuses).
Register Description
MCUCR – MCU Control Register
Bit
7
6
5
4
3
2
1
0
0x35 (0x55)
BODS
PUD
SE
SM1
SM0
BODSE
ISC01
ISC00
Read/Write
R/W
R/W
R/W
R/W
R/W
R/W
R
R
Initial Value
0
0
0
0
0
0
0
0
MCUCR
• Bit 6 – 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). See “Configuring the Pin” on page 54 for more details about this feature.
10.3.2
10.3.3
PORTA – Port A Data Register
Bit
7
6
5
4
3
2
1
0
0x1B (0x3B)
PORTA7
PORTA6
PORTA5
PORTA4
PORTA3
PORTA2
PORTA1
PORTA0
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
PORTA
DDRA – Port A Data Direction Register
Bit
7
6
5
4
3
2
1
0
0x1A (0x3A)
DDA7
DDA6
DDA5
DDA4
DDA3
DDA2
DDA1
DDA0
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
DDRA
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8197A–AVR–10/09
10.3.4
10.3.5
10.3.6
10.3.7
68
PINA – Port A Input Pins Address
Bit
7
6
5
4
3
2
1
0x19 (0x39)
PINA7
PINA6
PINA5
PINA4
PINA3
PINA2
PINA1
0
PINA0
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
PINA
PORTB – Port B Data Register
Bit
7
6
5
4
3
2
1
0
0x18 (0x38)
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
PORTB
DDRB – Port B Data Direction Register
Bit
7
6
5
4
3
2
1
0
0x17 (0x37)
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
0
DDRB
PINB – Port B Input Pins Address
Bit
7
6
5
4
3
2
1
0x16 (0x36)
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
PINB
ATtiny261A/461A/861A
8197A–AVR–10/09
ATtiny261A/461A/861A
11. Timer/Counter0
11.1
Features
•
•
•
•
•
11.2
Clear Timer on Compare Match (Auto Reload)
One Input Capture unit
Four Independent Interrupt Sources (TOV0, OCF0A, OCF0B, ICF0)
8-bit Mode with Two Independent Output Compare Units
16-bit Mode with One Independent Output Compare Unit
Overview
Timer/Counter0 is a general purpose 8/16-bit Timer/Counter module, with two/one Output Compare units and Input Capture feature.
The general operation of Timer/Counter0 is described in 8/16-bit mode. A simplified block diagram of the 8/16-bit Timer/Counter is shown in Figure 11-1. CPU accessible I/O Registers,
including I/O bits and I/O pins, are shown in bold. For actual placement of I/O pins, refer to “Pinout ATtiny261A/461A/861A” on page 2. Device-specific I/O Register and bit locations are listed
in the “Register Description” on page 82.
Figure 11-1. 8-/16-bit Timer/Counter Block Diagram
TOVn (Int. Req.)
Count
Clear
Clock Select
Control Logic
Direction
clkTn
Edge
Detector
Tn
( From Prescaler )
TOP
Timer/Counter
TCNTnH
TCNTnL
=
Fixed TOP value
=
OCnA (Int. Req.)
=
DATA BUS
OCnB (Int. Req.)
ICFn (Int. Req.)
OCRnB
( From Analog
Comparator Ouput )
TCCRnA
11.2.1
OCRnA
TCCRnB
Edge
Detector
Noise
Canceler
ICPn
Registers
The Timer/Counter0 Low Byte Register (TCNT0L) and Output Compare Registers (OCR0A and
OCR0B) are 8-bit registers. Interrupt request (abbreviated Int.Req. in Figure 11-1) signals are all
69
8197A–AVR–10/09
visible in the Timer Interrupt Flag Register (TIFR). All interrupts are individually masked with the
Timer Interrupt Mask Register (TIMSK). TIFR and TIMSK are not shown in the figure.
In 16-bit mode one more 8-bit register is available, the Timer/Counter0 High Byte Register
(TCNT0H). Also, in 16-bit mode, there is only one output compare unit as the two Output Compare Registers, OCR0A and OCR0B, are combined to one, 16-bit Output Compare Register,
where OCR0A contains the low byte and OCR0B contains the high byte of the word. When
accessing 16-bit registers, special procedures described in section “Accessing Registers in 16bit Mode” on page 78 must be followed.
11.2.2
Definitions
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. TCNT0L for accessing
Timer/Counter0 counter value, and so on.
The definitions in Table 11-1 are also used extensively throughout the document.
Table 11-1.
11.3
Definitions
Constant
Description
BOTTOM
The counter reaches 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 depends on the mode of operation
Clock Sources
The Timer/Counter can be clocked internally, via the prescaler, or by an external clock source on
the T0 pin. The Clock Select logic is controlled by the Clock Select (CS02:0) bits located in the
Timer/Counter Control Register 0 B (TCCR0B), and controls which clock source and edge the
Timer/Counter uses to increment 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).
11.3.1
Prescaler
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.
See Figure 11-2 for an illustration of the prescaler unit.
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ATtiny261A/461A/861A
8197A–AVR–10/09
ATtiny261A/461A/861A
Figure 11-2. Prescaler for Timer/Counter0
clk I/O
Clear
PSR0
T0
Synchronization
clkT0
Note:
1. The synchronization logic on the input pins (T0) is shown in Figure 11-3.
The prescaled clock has a frequency of fCLK_I/O/8, fCLK_I/O/64, fCLK_I/O/256, or fCLK_I/O/1024. See
Table 11-4 on page 83 for details.
11.3.1.1
11.3.2
Prescaler Reset
The prescaler is free running, i.e. it operates independently of the Clock Select logic of the
Timer/Counter. 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.
External Clock Source
An external clock source applied to the T0 pin can be used as Timer/Counter clock (clkT0). The
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 11-3 shows a functional
equivalent block diagram of the 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 clkT0 pulse for each positive (CSn2:0 = 7) or negative (CSn2:0
= 6) edge it detects. See Table 11-4 on page 83 for details.
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8197A–AVR–10/09
Figure 11-3. T0 Pin Sampling
D
Tn
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 T0 pin to the counter is updated.
Enabling and disabling of the clock input must be done when 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 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.
11.4
Counter Unit
The main part of the 8-bit Timer/Counter is the programmable bi-directional counter unit. Figure
11-4 shows a block diagram of the counter and its surroundings.
Table 11-2.
Counter Unit Block Diagram
TOVn
(Int.Req.)
DATA BUS
Clock Select
count
TCNTn
Control Logic
clkTn
Edge
Detector
Tn
( From Prescaler )
top
Signal description (internal signals):
count
clkTn
top
Increment or decrement TCNT0 by 1.
Timer/Counter clock, referred to as clkT0 in the following.
Signalize that TCNT0 has reached maximum value.
The counter is incremented at each timer clock (clkT0) until it passes its TOP value and then
restarts from BOTTOM. The counting sequence is determined by the setting of the CTC0 bit
located in the Timer/Counter Control Register (TCCR0A). For more details about counting
sequences, see “Modes of Operation” on page 75. clkT0 can be generated from an external or
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ATtiny261A/461A/861A
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 Timer/Counter Overflow Flag (TOV0) is set when the
counter reaches the maximum value and it can be used for generating a CPU interrupt.
11.5
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 ICP0 pin or alternatively, via the analog-comparator unit. The
time-stamps can then be used to calculate frequency, duty-cycle, 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 11-4. The elements of
the block diagram that are not directly a part of the Input Capture unit are gray shaded.
Figure 11-4. Input Capture Unit Block Diagram
DATA BUS
(8-bit)
TEMP (8-bit)
OCR0B (8-bit)
WRITE
TCNT0H (8-bit)
ICR0 (16-bit Register)
ACO*
Analog
Comparator
ICP0
OCR0A (8-bit)
ACIC0*
TCNT0L (8-bit)
TCNT0 (16-bit Counter)
ICNC0
ICES0
Noise
Canceler
Edge
Detector
ICF0 (Int.Req.)
The Output Compare Register OCR0A is a dual-purpose register that is also used as an 8-bit
Input Capture Register ICR0. In 16-bit Input Capture mode the Output Compare Register
OCR0B serves as the high byte of the Input Capture Register ICR0. In 8-bit Input Capture mode
the Output Compare Register OCR0B is free to be used as a normal Output Compare Register,
but in 16-bit Input Capture mode the Output Compare Unit cannot be used as there are no free
Output Compare Register(s). Even though the Input Capture register is called ICR0 in this section, it is refering to the Output Compare Register(s).
When a change of the logic level (an event) occurs on the Input Capture pin (ICP0), 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 value of the counter
(TCNT0) is written to the Input Capture Register (ICR0). The Input Capture Flag (ICF0) is set at
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8197A–AVR–10/09
the same system clock as the TCNT0 value is copied into Input Capture Register. If enabled
(TICIE0=1), the Input Capture Flag generates an Input Capture interrupt. The ICF0 flag is automatically cleared when the interrupt is executed. Alternatively the ICF0 flag can be cleared by
software by writing a logical one to its I/O bit location.
11.5.1
Input Capture Trigger Source
The default trigger source for the Input Capture unit is the Input Capture pin (ICP0).
Timer/Counter0 can alternatively use the Analog Comparator output as trigger source for the
Input Capture unit. The Analog Comparator is selected as trigger source by setting the Analog
Comparator Input Capture Enable (ACIC0) bit in the Timer/Counter Control Register A
(TCCR0A). Be aware that changing trigger source can trigger a capture. The Input Capture Flag
must therefore be cleared after the change.
Both the Input Capture pin (ICP0) and the Analog Comparator output (ACO) inputs are sampled
using the same technique as for the T0 pin (Figure 11-4 on page 83). 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. An Input Capture can also
be triggered by software by controlling the port of the ICP0 pin.
11.5.2
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 (ICNC0) bit in
Timer/Counter Control Register B (TCCR0B). 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
ICR0 Register. The noise canceler uses the system clock and is therefore not affected by the
prescaler.
11.5.3
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 ICR0 Register before the next event occurs, the ICR0 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 ICR0 Register should be read as early in the interrupt handler routine as possible. The maximum interrupt response time is dependent on the
maximum number of clock cycles it takes to handle any of the other interrupt requests.
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 ICR0
Register has been read. After a change of the edge, the Input Capture Flag (ICF0) must be
cleared by software (writing a logical one to the I/O bit location). For measuring frequency only,
the trigger edge change is not required (if an interrupt handler is used).
11.6
Output Compare Unit
The comparator continuously compares Timer/Counter (TCNT0) with the Output Compare Registers (OCR0A and OCR0B), and whenever the Timer/Counter equals to the Output Compare
Regisers, the comparator signals a match. A match will set the Output Compare Flag at the next
timer clock cycle. In 8-bit mode the match can set either the Output Compare Flag OCF0A or
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OCF0B, but in 16-bit mode the match can set only the Output Compare Flag OCF0A as there is
only one Output Compare Unit. 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. Figure 11-5 shows a block diagram of the Output Compare unit.
Figure 11-5. Output Compare Unit, Block Diagram
DATA BUS
TCNTn
OCRnx
= (8/16-bit Comparator )
OCFnx (Int.Req.)
11.6.1
Compare Match Blocking by TCNT0 Write
All CPU write operations to the TCNT0H/L Register will block any Compare Match that occur in
the next timer clock cycle, even when the timer is stopped. This feature allows OCR0A/B to be
initialized to the same value as TCNT0 without triggering an interrupt when the Timer/Counter
clock is enabled.
11.6.2
Using the Output Compare Unit
Since writing TCNT0H/L will block all Compare Matches for one timer clock cycle, there are risks
involved when changing TCNT0H/L when using the Output Compare Unit, independently of
whether the Timer/Counter is running or not. If the value written to TCNT0H/L equals the
OCR0A/B value, the Compare Match will be missed.
11.7
Modes of Operation
The mode of operation, i.e., the behavior of the Timer/Counter and the Output Compare pins, is
defined by the Timer/Counter Width (TCW0), Input Capture Enable (ICEN0) and Wave Generation Mode (CTC0) bits. See “TCCR0A – Timer/Counter0 Control Register A” on page 82.
Table 11-3 summarises the different modes of operation.
Table 11-3.
Modes of operation
Mode
ICEN0
TCW0
CTC0
Mode of Operation
TOP
Update of OCRx at
TOV Flag Set on
0
0
0
0
Normal, 8-bit Mode
0xFF
Immediate
MAX (0xFF)
1
0
0
1
CTC Mode, 8-bit
OCR0A
Immediate
MAX (0xFF)
2
0
1
X
Normal, 16-bit Mode
0xFFFF
Immediate
MAX (0xFFFF)
3
1
0
X
Input Capture Mode, 8-bit
0xFF
Immediate
MAX (0xFF)
4
1
1
X
Input Capture Mode, 16-bit
0xFFFF
Immediate
MAX (0xFFFF)
11.7.1
Normal, 8-bit Mode
In Normal 8-bit mode (see Table 11-3), the counter (TCNT0L) is incrementing until it overruns
when it passes its maximum 8-bit value (MAX = 0xFF) and then restarts from the bottom (0x00).
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The Overflow Flag (TOV0) is set in the same timer clock cycle as when TCNT0L 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 8-bit mode, a new counter value can be written anytime. The Output Compare Unit can
be used to generate interrupts at some given time.
11.7.2
Clear Timer on Compare Match (CTC) 8-bit Mode
In Clear Timer on Compare or CTC mode, see Table 11-3 on page 75, 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 11-6. The counter value (TCNT0)
increases until a Compare Match occurs between TCNT0 and OCR0A, and then counter
(TCNT0) is cleared.
Figure 11-6. CTC Mode, Timing Diagram
OCnx Interrupt Flag Set
TCNTn
Period
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 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. 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.
11.7.3
76
Normal, 16-bit Mode
In 16-bit mode, see Table 11-3 on page 75, the counter (TCNT0H/L) is a incrementing until it
overruns when it passes its maximum 16-bit value (MAX = 0xFFFF) and then restarts from the
bottom (0x0000). The Overflow Flag (TOV0) will be set in the same timer clock cycle as the
TCNT0H/L becomes zero. The TOV0 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 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.
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11.7.4
8-bit Input Capture Mode
The Timer/Counter0 can also be used in an 8-bit Input Capture mode, see Table 11-3 on page
75 for bit settings. For full description, see the section “Input Capture Unit” on page 73.
11.7.5
16-bit Input Capture Mode
The Timer/Counter0 can also be used in a 16-bit Input Capture mode, see Table 11-3 on page
75 for bit settings. For full description, see the section “Input Capture Unit” on page 73.
11.8
Timer/Counter Timing Diagrams
The Timer/Counter is a synchronous design and the timer clock (clkT0) is therefore shown as a
clock enable signal in the following figures. The figures include information on when Interrupt
Flags are set. Figure 11-7 contains timing data for basic Timer/Counter operation. The figure
shows the count sequence close to the MAX value.
Figure 11-7. Timer/Counter Timing Diagram, no Prescaling
clkI/O
clkTn
(clkI/O /1)
TCNTn
MAX - 1
MAX
BOTTOM
BOTTOM + 1
TOVn
Figure 11-8 shows the same timing data, but with the prescaler enabled.
Figure 11-8. 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 11-9 on page 78 shows the setting of OCF0A and OCF0B in Normal mode.
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Figure 11-9. Timer/Counter Timing Diagram, Setting of OCF0x, with Prescaler (fclk_I/O/8)
clkI/O
clkTn
(clkI/O /8)
TCNTn
OCRnx - 1
OCRnx
OCRnx
OCRnx + 1
OCRnx + 2
OCRnx Value
OCFnx
Figure 11-10 shows the setting of OCF0A and the clearing of TCNT0 in CTC mode.
Figure 11-10. Timer/Counter Timing Diagram, CTC mode, with Prescaler (fclk_I/O/8)
clkPCK
clkTn
(clkPCK /8)
TCNTn
(CTC)
TOP - 1
OCRnx
TOP
BOTTOM
BOTTOM + 1
TOP
OCFnx
11.9
Accessing Registers in 16-bit Mode
In 16-bit mode (the TCW0 bit is set to one) the TCNT0H/L and OCR0A/B or TCNT0L/H and
OCR0B/A 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. The 16-bit
Timer/Counter 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. 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.
There is one exception in the temporary register usage. In the Output Compare mode the 16-bit
Output Compare Register OCR0A/B is read without the temporary register, because the Output
Compare Register contains a fixed value that is only changed by CPU access. However, in 16bit Input Capture mode the ICR0 register formed by the OCR0A and OCR0B registers must be
accessed with 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.
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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 OCR0A/B registers.
Assembly Code Example
...
; Set TCNT0 to 0x01FF
ldi r17,0x01
ldi r16,0xFF
out TCNT0H,r17
out TCNT0L,r16
; Read TCNT0 into r17:r16
in r16,TCNT0L
in r17,TCNT0H
...
C Code Example
unsigned int i;
...
/* Set TCNT0 to 0x01FF */
TCNT0H = 0x01;
TCNT0L = 0xff;
/* Read TCNT0 into i */
i = TCNT0L;
i |= ((unsigned int)TCNT0H << 8);
...
Note:
See “Code Examples” on page 6.
The assembly code example returns the TCNT0H/L 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.
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The following code examples show how to do an atomic read of the TCNT0 register contents.
Reading any of the OCR0 register can be done by using the same principle.
Assembly Code Example
TIM0_ReadTCNT0:
; Save global interrupt flag
in r18,SREG
; Disable interrupts
cli
; Read TCNT0 into r17:r16
in r16,TCNT0L
in r17,TCNT0H
; Restore global interrupt flag
out SREG,r18
ret
C Code Example
unsigned int TIM0_ReadTCNT0( void )
{
unsigned char sreg;
unsigned int i;
/* Save global interrupt flag */
sreg = SREG;
/* Disable interrupts */
_CLI();
/* Read TCNT0 into i */
i = TCNT0L;
i |= ((unsigned int)TCNT0H << 8);
/* Restore global interrupt flag */
SREG = sreg;
return i;
}
Note:
See “Code Examples” on page 6.
The assembly code example returns the TCNT0H/L value in the r17:r16 register pair.
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The following code examples show how to do an atomic write of the TCNT0H/L register contents. Writing any of the OCR0A/B registers can be done by using the same principle.
Assembly Code Example
TIM0_WriteTCNT0:
; Save global interrupt flag
in r18,SREG
; Disable interrupts
cli
; Set TCNT0 to r17:r16
out TCNT0H,r17
out TCNT0L,r16
; Restore global interrupt flag
out SREG,r18
ret
C Code Example
void TIM0_WriteTCNT0( unsigned int i )
{
unsigned char sreg;
/* Save global interrupt flag */
sreg = SREG;
/* Disable interrupts */
_CLI();
/* Set TCNT0 to i */
TCNT0H = (i >> 8);
TCNT0L = (unsigned char)i;
/* Restore global interrupt flag */
SREG = sreg;
}
Note:
See “Code Examples” on page 6.
The assembly code example requires that the r17:r16 register pair contains the value to be written to TCNT0H/L.
11.9.1
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.
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11.10 Register Description
11.10.1
TCCR0A – Timer/Counter0 Control Register A
Bit
7
6
5
4
3
2
1
0
0x15 (0x35)
TCW0
ICEN0
ICNC0
ICES0
ACIC0
–
–
CTC0
Read/Write
R/W
R/W
R/W
R/W
R/W
R
R
R/W
Initial Value
0
0
0
0
0
0
0
0
TCCR0A
• Bit 7– TCW0: Timer/Counter0 Width
When this bit is written to one 16-bit mode is selected as described Figure 11-7 on page 77.
Timer/Counter0 width is set to 16-bits and the Output Compare Registers OCR0A and OCR0B
are combined to form one 16-bit Output Compare Register. Because the 16-bit registers
TCNT0H/L and OCR0B/A are accessed by the AVR CPU via the 8-bit data bus, special procedures must be followed. These procedures are described in section “Accessing Registers in 16bit Mode” on page 78.
• Bit 6– ICEN0: Input Capture Mode Enable
When this bit is written to onem, the Input Capture Mode is enabled.
• Bit 5 – ICNC0: Input Capture Noise Canceler
Setting this bit activates the Input Capture Noise Canceler. When the noise canceler is activated, the input from the Input Capture Pin (ICP0) is filtered. The filter function requires four
successive equal valued samples of the ICP0 pin for changing its output. The Input Capture is
therefore delayed by four System Clock cycles when the noise canceler is enabled.
• Bit 4 – ICES0: Input Capture Edge Select
This bit selects which edge on the Input Capture Pin (ICP0) that is used to trigger a capture
event. When the ICES0 bit is written to zero, a falling (negative) edge is used as trigger, and
when the ICES0 bit is written to one, a rising (positive) edge will trigger the capture. When a capture is triggered according to the ICES0 setting, the counter value is copied into the Input
Capture Register. The event will also set the Input Capture Flag (ICF0), and this can be used to
cause an Input Capture Interrupt, if this interrupt is enabled.
• Bit 3 - ACIC0: Analog Comparator Input Capture Enable
When written logic one, this bit enables the input capture function in Timer/Counter0 to be triggered by the Analog Comparator. 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/Counter0 Input Capture interrupt. When written logic zero, no connection
between the Analog Comparator and the input capture function exists. To make the comparator
trigger the Timer/Counter0 Input Capture interrupt, the TICIE0 bit in the Timer Interrupt Mask
Register (TIMSK) must be set.
• Bits 2:1 – Res: Reserved Bits
These bits are reserved and will always read zero.
• Bit 0 – CTC0: Waveform Generation Mode
This bit controls the counting sequence of the counter, the source for maximum (TOP) counter
value, see Figure 11-7 on page 77. Modes of operation supported by the Timer/Counter unit are:
Normal mode (counter) and Clear Timer on Compare Match (CTC) mode (see “Modes of Operation” on page 75).
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11.10.2
TCCR0B – Timer/Counter0 Control Register B
Bit
7
6
5
4
3
2
1
0
0x33 (0x53)
-
-
-
TSM
PSR0
CS02
CS01
CS01
Read/Write
R
R
R
R/W
R/W
R/W
R/W
R/W
Initial Value
0
0
0
0
0
0
0
0
TCCR0B
• Bit 4 – 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 PSR0 bit is kept, hence keeping the Prescaler Reset signal asserted.
This ensures that the Timer/Counter is halted and can be configured without the risk of advancing during configuration. When the TSM bit is written to zero, the PSR0 bit is cleared by
hardware, and the Timer/Counter start counting.
• Bit 3 – PSR0: Prescaler Reset Timer/Counter0
When this bit is one, the Timer/Counter0 prescaler will be Reset. This bit is normally cleared
immediately by hardware, except if the TSM bit is set.
• Bits 2, 1, 0 – CS02, CS01, CS00: Clock Select0, Bit 2, 1, and 0
The Clock Select0 bits 2, 1, and 0 define the prescaling source of Timer0.
Table 11-4.
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.
11.10.3
TCNT0L – Timer/Counter0 Register Low Byte
Bit
7
6
5
0x32 (0x52)
4
3
2
1
0
TCNT0L[7:0]
TCNT0L
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/Counter0 Register Low Byte, TCNT0L, gives direct access, both for read and write
operations, to the Timer/Counter unit 8-bit counter. Writing to the TCNT0L Register blocks (disables) the Compare Match on the following timer clock. Modifying the counter (TCNT0L) while
the counter is running, introduces a risk of missing a Compare Match between TCNT0L and the
OCR0x Registers. In 16-bit mode the TCNT0L register contains the lower part of the 16-bit
Timer/Counter0 Register.
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11.10.4
TCNT0H – Timer/Counter0 Register High Byte
Bit
7
6
5
0x14 (0x34)
4
3
2
1
0
TCNT0H[7:0]
TCNT0H
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
When 16-bit mode is selected (the TCW0 bit is set to one) the Timer/Counter Register TCNT0H
combined to the Timer/Counter Register TCNT0L gives direct access, both for read and 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 Registers in 16-bit Mode” on page 78
11.10.5
OCR0A – Timer/Counter0 Output Compare Register A
Bit
7
6
5
0x13 (0x33)
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 (TCNT0L). A match can be used to generate an Output Compare interrupt.
In 16-bit mode the OCR0A register contains the low byte of the 16-bit Output Compare Register.
To ensure that both the high and the 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 Registers in
16-bit Mode” on page 78.
11.10.6
OCR0B – Timer/Counter0 Output Compare Register B
Bit
7
6
5
0x12 (0x32)
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 (TCNT0L in 8-bit mode and TCNTH in 16-bit mode). A match can be used to generate an Output Compare interrupt.
In 16-bit mode the OCR0B register contains the high byte of the 16-bit Output Compare Register. To ensure that both the high and the 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 Registers in 16-bit Mode” on page 78.
11.10.7
TIMSK – Timer/Counter0 Interrupt Mask Register
Bit
7
6
5
4
3
2
1
0
0x39 (0x59)
OCIE1D
OCIE1A
OCIE1B
OCIE0A
OCIE0B
TOIE1
TOIE0
TICIE0
Read/Write
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R
Initial Value
0
0
0
0
0
0
0
0
TIMSK
• Bit 4 – 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
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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 3 – 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 – 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.
• Bit 0 – TICIE0: Timer/Counter0, 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 “Interrupts” on page 48.) is executed when the ICF0 flag, located in TIFR, is set.
11.10.8
TIFR – Timer/Counter0 Interrupt Flag Register
Bit
7
6
5
4
3
2
1
0
0x38 (0x58)
OCF1D
OCF1A
OCF1B
OCF0A
OCF0B
TOV1
TOV0
ICF0
Read/Write
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R
Initial Value
0
0
0
0
0
0
0
0
TIFR
• Bit 4– OCF0A: Output Compare Flag 0 A
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.
The OCF0A is also set in 16-bit mode when a Compare Match occurs between the Timer/Counter and 16-bit data in OCR0B/A. The OCF0A is not set in Input Capture mode when the Output
Compare Register OCR0A is used as an Input Capture Register.
• Bit 3 – OCF0B: Output Compare Flag 0 B
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.
The OCF0B is not set in 16-bit Output Compare mode when the Output Compare Register
OCR0B is used as the high byte of the 16-bit Output Compare Register or in 16-bit Input Capture mode when the Output Compare Register OCR0B is used as the high byte of the Input
Capture Register.
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• Bit 1 – 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 (Timer/Counter0 Overflow Interrupt
Enable), and TOV0 are set, the Timer/Counter0 Overflow interrupt is executed.
• Bits 0 – ICF0: Timer/Counter0, Input Capture Flag
This flag is set when a capture event occurs on the ICP0 pin. When the Input Capture Register
(ICR0) is set to be used as the TOP value, the ICF0 flag is set when the counter reaches the
TOP value.
ICF0 is automatically cleared when the Input Capture Interrupt Vector is executed. Alternatively,
ICF0 can be cleared by writing a logic one to its bit location.
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12. Timer/Counter1
12.1
Features
•
•
•
•
•
•
•
•
•
12.2
8/10-Bit Accuracy
Three Independent Output Compare Units
Clear Timer on Compare Match (Auto Reload)
Glitch Free, Phase and Frequency Correct Pulse Width Modulator (PWM)
Variable PWM Period
High Speed Asynchronous and Synchronous Clocking with Dedicated Prescaler
Independent Dead Time Generators for Each PWM Channel
Fault Protection Unit Can Disable PWM Output Pins
Five Independent Interrupt Sources (TOV1, OCF1A, OCD1B, OCF1D, FPF1)
Overview
Timer/Counter1 is a general purpose high speed Timer/Counter module, with three independent
Output Compare Units, and with PWM support.
The Timer/Counter1 features a high resolution and a high accuracy usage with the lower prescaling opportunities. It can also support three accurate and high speed Pulse Width Modulators
using clock speeds up to 64 MHz. In PWM mode Timer/Counter1 and the output compare registers serve as triple stand-alone PWMs with non-overlapping non-inverted and inverted outputs.
Similarly, the high prescaling opportunities make this unit useful for lower speed functions or
exact timing functions with infrequent actions. A simplified block diagram of the Timer/Counter1
is shown in Figure 12-1.
Figure 12-1. Timer/Counter1 Block Diagram
TOV1
OCF1A
OCF1B
OCF1D
OC1A
OC1A
OC1B
OC1B
FAULT_PROTECTION
DEAD TIME GENERATOR
DEAD TIME GENERATOR
DEAD TIME GENERATOR
OC1D
OC1D
OCW1A
OCW1B
FPF1
FPIE1
WGM11
OC1OE0
WGM10
FPAC1
FPF1
OC1OE3
OC1OE1
FPES1
OC1OE4
OC1OE2
FPIE1
FPEN1
FPNC1
T/C CONTROL
REGISTER C (TCCR1D)
OC1OE5
COM1D0
PWM1D
FOC1D
COM1D1
COM1B0
COM1B1
COM1A1
T/C CONTROL
REGISTER C (TCCR1C)
COM1A0
CS10
CS11
CS13
CS12
PSR1
PSR1
T/C CONTROL
REGISTER B (TCCR1B)
PSR1
PWM1B
FOC1B
FOC1A
PWM1A
COM1B1
COM1B0
T/C CONTROL
REGISTER A (TCCR1A)
COM1A0
OCF1B
OCF1D
TOV1
T/C INT. FLAG
REGISTER (TIFR)
COM1A1
T/C INT. MASK
REGISTER (TIMSK)
OCF1A
OCIE1D
OCIE1A
OCIE1B
TOIE1
OCW1D
CLK
TIMER/COUNTER1
(TCNT1)
COUNT
TIMER/COUNTER1 CONTROL LOGIC
CLEAR
DIRECTION
10-BIT COMPARATOR
10-BIT COMPARATOR
10-BIT OUTPUT
COMPARE REGISTER A
10-BIT OUTPUT
COMPARE REGISTER B
8-BIT OUTPUT COMPARE
REGISTER A (OCR1A)
8-BIT OUTPUT COMPARE
REGISTER B (OCR1B)
10-BIT COMPARATOR
10-BIT COMPARATOR
10-BIT OUTPUT
COMPARE REGISTER C
10-BIT OUTPUT
COMPARE REGISTER D
8-BIT OUTPUT COMPARE
REGISTER C (OCR1C)
8-BIT OUTPUT COMPARE
REGISTER D (OCR1D)
T/C CONTROL
REGISTER D (TCCR1E)
2-BIT HIGH BYTE
REGISTER (TC1H)
8-BIT DATABUS
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For actual placement of the I/O pins, refer to “Pinout ATtiny261A/461A/861A” on page 2. The
device-specific I/O register and bit locations are listed in the “Register Description” on page 110.
12.2.1
Speed
The maximum speed of the Timer/Counter1 is 64 MHz. However, if a supply voltage below 2.7
volts is used, it is recommended to use the Low Speed Mode (LSM), because the
Timer/Counter1 is not running fast enough on low voltage levels. In the Low Speed Mode the
fast peripheral clock is scaled down to 32 MHz. For more details about the Low Speed Mode,
see “PLLCSR – PLL Control and Status Register” on page 118.
12.2.2
Accuracy
The Timer/Counter1 is a 10-bit Timer/Counter module that can alternatively be used as an 8-bit
Timer/Counter. The Timer/Counter1 registers are basically 8-bit registers, but on top of that
there is a 2-bit High Byte Register (TC1H) that can be used as a common temporary buffer to
access the two MSBs of the 10-bit Timer/Counter1 registers by the AVR CPU via the 8-bit data
bus, if the 10-bit accuracy is used. Whereas, if the two MSBs of the 10-bit registers are written to
zero the Timer/Counter1 is working as an 8-bit Timer/Counter. When reading the low byte of any
8-bit register the two MSBs are written to the TC1H register, and when writing the low byte of
any 8-bit register the two MSBs are written from the TC1H register. Special procedures must be
followed when accessing the 10-bit Timer/Counter1 values via the 8-bit data bus. These procedures are described in the section “Accessing 10-Bit Registers” on page 106.
12.2.3
Registers
The Timer/Counter (TCNT1) and Output Compare Registers (OCR1A, OCR1B, OCR1C and
OCR1D) are 8-bit registers that are used as a data source to be compared with the TCNT1 contents. The OCR1A, OCR1B and OCR1D registers determine the action on the OC1A, OC1B and
OC1D pins and they can also generate the compare match interrupts. The OCR1C holds the
Timer/Counter TOP value, i.e. the clear on compare match value. The Timer/Counter1 High
Byte Register (TC1H) is a 2-bit register that is used as a common temporary buffer to access the
MSB bits of the Timer/Counter1 registers, if the 10-bit accuracy is used.
Interrupt request (overflow TOV1, and compare matches OCF1A, OCF1B, OCF1D and fault protection FPF1) signals are visible in the Timer Interrupt Flag Register (TIFR) and Timer/Counter1
Control Register D (TCCR1D). The interrupts are individually masked with the Timer Interrupt
Mask Register (TIMSK) and the FPIE1 bit in the Timer/Counter1 Control Register D (TCCR1D).
Control signals are found in the Timer/Counter Control Registers TCCR1A, TCCR1B, TCCR1C,
TCCR1D and TCCR1E.
12.2.4
Synchronization
In asynchronous clocking mode the Timer/Counter1 and the prescaler allow running the CPU
from any clock source while the prescaler is operating on the fast peripheral clock (PCK) having
frequency of 64 MHz (or 32 MHz in Low Speed Mode). This is possible because there is a synchronization boundary between the CPU clock domain and the fast peripheral clock domain.
Figure 12-2 shows Timer/Counter 1 synchronization register block diagram and describes synchronization delays in between registers. Note that all clock gating details are not shown in the
figure.
The Timer/Counter1 register values go through the internal synchronization registers, which
cause the input synchronization delay, before affecting the counter operation. The registers
TCCR1A, TCCR1B, TCCR1C, TCCR1D, OCR1A, OCR1B, OCR1C and OCR1D can be read
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back right after writing the register. The read back values are delayed for the Timer/Counter1
(TCNT1) register, Timer/Counter1 High Byte Register (TC1H) and flags (OCF1A, OCF1B,
OCF1D and TOV1), because of the input and output synchronization.
The system clock frequency must be lower than half of the PCK frequency, because the synchronization mechanism of the asynchronous Timer/Counter1 needs at least two edges of the
PCK when the system clock is high. If the frequency of the system clock is too high, it is a risk
that data or control values are lost.
Figure 12-2. Timer/Counter1 Synchronization Register Block Diagram.
8-BIT DATABUS
IO-registers
Input synchronization
registers
OCR1A
OCR1A_SI
OCR1B
OCR1B_SI
OCR1C
OCR1C_SI
Timer/Counter1
Output synchronization
registers
TCNT1
TCNT1_SO
TC1H
TC1H_SO
OCR1D
OCR1D_SI
TCCR1A
TCCR1A_SI
TCCR1B
TCCR1B_SI
TCCR1C
TCCR1C_SI
TCCR1D
TCCR1D_SI
TCNT1
TCNT1_SI
TC1H
TC1H_SI
OCF1A
OCF1A_SI
OCF1A
OCF1A_SO
TCNT1
OCF1B
OCF1B_SO
OCF1D
OCF1D_SO
OCF1B
OCF1B_SI
OCF1D
OCF1D_SI
TOV1
TOV1_SI
TOV1
TOV1_SO
PCKE
CK
S
A
S
PCK
SYNC
MODE
ASYNC
MODE
12.2.5
A
1/2 CK Delay
~1/2 CK Delay
1 CK Delay
1 CK Delay
1/2 CK Delay
1 PCK Delay
1 PCK Delay
~1 CK Delay
Definitions
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, B, C or D. However, when using the register or bit
defines in a program, the precise form must be used, i.e., TCNT1 for accessing Timer/Counter1
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counter value and so on. The definitions in Table 12-1 are used extensively throughout the
document.
Table 12-1.
12.3
Definitions
Constant
Description
BOTTOM
The counter reaches 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 depends on the mode of operation
Clock Sources
The Timer/Counter is clocked internally, either from CK or PCK. See bits CSxx in Table 12-17 on
page 114 and bit PCKE in “PLLCSR – PLL Control and Status Register” on page 118.
12.3.1
Prescaler
Figure 12-3 shows the Timer/Counter1 prescaler that supports two clocking modes, a synchronous clocking mode and an asynchronous clocking mode. The synchronous clocking mode uses
the system clock (CK) as a clock timebase and asynchronous mode uses the fast peripheral
clock (PCK) as a clock time base. The PCKE bit from the PLLCSR register enables the asynchronous mode when it is set (‘1’).
Figure 12-3. Timer/Counter1 Prescaler
T1CK/16384
T1CK/8192
T1CK/4096
T1CK/2048
T1CK/1024
T1CK/512
T1CK/256
T1CK/128
T1CK/64
T1CK/32
0
T1CK/16
14-BIT
T/C PRESCALER
T1CK/8
T1CK
T1CK/4
CK
S
PCK 64/32 MHz A
T1CK/2
PSR1
T1CK
PCKE
CS10
CS11
CS12
CS13
TIMER/COUNTER1 COUNT ENABLE
In the asynchronous clocking mode the clock selections are from PCK to PCK/16384 and stop,
and in the synchronous clocking mode the clock selections are from CK to CK/16384 and stop.
The clock options are illustrated in Figure 12-3 and desribed in “TCCR1B – Timer/Counter1
Control Register B” on page 113.
The frequency of the fast peripheral clock is 64 MHz or 32 MHz in Low Speed mode (the LSM bit
in PLLCSR register is set to one). The Low Speed Mode is recommended to use when the supply voltage below 2.7 volts are used.
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12.3.1.1
Prescaler Reset
Setting the PSR1 bit in TCCR1B register resets the prescaler. It is possible to use the Prescaler
Reset for synchronizing the Timer/Counter to program execution.
12.3.1.2
Prescaler Initialization for Asynchronous Mode
To change Timer/Counter1 to the asynchronous mode follow the procedure below:
1. Enable PLL.
2. Wait 100 µs for PLL to stabilize.
3. Poll the PLOCK bit until it is set.
4. Set the PCKE bit in the PLLCSR register which enables the asynchronous mode.
12.4
Counter Unit
The main part of the Timer/Counter1 is the programmable bi-directional counter unit. Figure 124 shows a block diagram of the counter and its surroundings.
Figure 12-4. Counter Unit Block Diagram
DATA BUS
TOV1
clkT1
Timer/Counter1 Count Enable
( From Prescaler )
count
TCNT1
clear
Control Logic
direction
PCKE
PCK
CK
bottom
top
Signal description (internal signals):
count
direction
clear
clkTn
top
bottom
TCNT1 increment or decrement enable.
Select between increment and decrement.
Clear TCNT1 (set all bits to zero).
Timer/Counter clock, referred to as clkT1 in the following.
Signalize that TCNT1 has reached maximum value.
Signalize that TCNT1 has reached minimum value (zero).
Depending on the mode of operation used, the counter is cleared, incremented, or decremented
at each timer clock (clkT1). The timer clock is generated from an synchronous system clock or an
asynchronous PLL clock using the Clock Select bits (CS13:0) and the PCK Enable bit (PCKE).
When no clock source is selected (CS13:0 = 0) the timer is stopped. However, the TCNT1 value
can be accessed by the CPU, regardless of whether clkT1 is present or not. A CPU write overrides (has priority over) all counter clear or count operations.
The counting sequence of the Timer/Counter1 is determined by bits WGM11:10, PWM1A and
PWM1B, located in the Timer/Counter1 Control Registers (TCCR1A, TCCR1C and TCCR1D).
For more details about advanced counting sequences and waveform generation, see “Modes of
Operation” on page 97. The Timer/Counter Overflow Flag (TOV1) is set according to the mode
of operation and can be used for generating a CPU interrupt.
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12.4.1
Counter Initialization for Asynchronous Mode
To set Timer/Counter1 to asynchronous mode follow the procedure below:
1. Enable PLL.
2. Wait 100 µs for PLL to stabilize.
3. Poll the PLOCK bit until it is set.
4. Set the PCKE bit in the PLLCSR register which enables the asynchronous mode.
12.5
Output Compare Unit
The comparator continuously compares TCNT1 with the Output Compare Registers (OCR1A,
OCR1B, OCR1C and OCR1D). Whenever TCNT1 equals to the Output Compare Register, the
comparator signals a match. A match will set the Output Compare Flag (OCF1A, OCF1B or
OCF1D) 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 bits PWM1A, PWM1B, WGM11:10 and
COM1x1:0. 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 “Modes of Operation” on
page 97.). Figure 12-5 shows a block diagram of the Output Compare unit.
Figure 12-5. Output Compare Unit, Block Diagram
8-BIT DATA BUS
TCNTn
TCnH
OCRnx
10-BIT OCRnx
10-BIT TCNTn
= (10-bit Comparator )
OCFnx (Int.Req.)
TOP
BOTTOM
PWMnx
Waveform Generator
FOCn
WGM10
COMnX1:0
OCWnx
The OCR1x Registers are double buffered when using any of the Pulse Width Modulation
(PWM) modes. For the normal mode of operation, the double buffering is disabled. The double
buffering synchronizes the update of the OCR1x Compare Registers to either top or bottom of
the counting sequence. The synchronization prevents the occurrence of odd-length, non-sym-
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metrical PWM pulses, thereby making the output glitch-free. See Figure 12-6 for an example.
During the time between the write and the update operation, a read from OCR1A, OCR1B,
OCR1C or OCR1D will read the contents of the temporary location. This means that the most
recently written value always will read out of OCR1A, OCR1B, OCR1C or OCR1D.
Figure 12-6. Effects of Unsynchronized OCR Latching
Compare Value changes
Counter Value
Compare Value
Output Compare
Waveform OCWnx
Synchronized WFnx Latch
Compare Value changes
Counter Value
Compare Value
Unsynchronized WFnx Latch
Glitch
Output Compare
Wafeform OCWnx
12.5.1
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 (FOC1x) bit. Forcing Compare Match will not set the
OCF1x Flag or reload/clear the timer, but the Waveform Output (OCW1x) will be updated as if a
real Compare Match had occurred (the COM1x1:0 bits settings define whether the Waveform
Output (OCW1x) is set, cleared or toggled).
12.5.2
Compare Match Blocking by TCNT1 Write
All CPU write operations to the TCNT1 Register will block any Compare Match that occur in the
next timer clock cycle, even when the timer is stopped. This feature allows OCR1x to be initialized to the same value as TCNT1 without triggering an interrupt when the Timer/Counter clock is
enabled.
12.5.3
Using the Output Compare Unit
Since writing TCNT1 in any mode of operation will block all Compare Matches for one timer
clock cycle, there are risks involved when changing TCNT1 when using the Output Compare
Unit, independently of whether the Timer/Counter is running or not. If the value written to TCNT1
equals the OCR1x value, the Compare Match will be missed, resulting in incorrect waveform
generation. Similarly, do not write the TCNT1 value equal to BOTTOM when the counter is
down-counting.
The setup of the Waveform Output (OCW1x) should be performed before setting the Data Direction Register for the port pin to output. The easiest way of setting the OCW1x value is to use the
Force Output Compare (FOC1x) strobe bits in Normal mode. The OC1x keeps its value even
when changing between Waveform Generation modes.
Be aware that the COM1x1:0 bits are not double buffered together with the compare value.
Changing the COM1x1:0 bits will take effect immediately.
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12.6
Dead Time Generator
The Dead Time Generator is provided for the Timer/Counter1 PWM output pairs to allow driving
external power control switches safely. The Dead Time Generator is a separate block that can
be used to insert dead times (non-overlapping times) for the Timer/Counter1 complementary
output pairs OC1x and OC1x when the PWM mode is enabled and the COM1x1:0 bits are set to
“01”. See Figure 12-7 below.
Figure 12-7. Block Diagram of Waveform Generator and Dead Time Generator.
top
bottom
Waveform Generator
OCWnx
OCnx
pin
OCnx
OCnx
pin
Dead Time Generator
FOCn
PWMnx WGM10 COMnx
OCnx
CK OR PCK
CLOCK
DTPSn
DTnH
DTnL
The tasks are shared as follows: the Waveform Generator generates the output (OCW1x) and
the Dead Time Generator generates the non-overlapping PWM output pair from the output.
Three Dead Time Generators are provided, one for each PWM output. The non-overlap time is
adjustable and the PWM output and it’s complementary output are adjusted separately, and
independently for both PWM outputs.
The Dead Time Generation is based on 4-bit down counters that count the dead time, as shown
in Figure 12-8.
Figure 12-8. Dead Time Generator
PWM1X
COMPARATOR
OCnx
CK OR PCK
CLOCK
DEAD TIME
PRE-SCALER
CLOCK CONTROL
4-BIT COUNTER
DTnL
DTnH
DTPSn
OCnx
PWM1X
TCCRnB REGISTER
DTn I/O REGISTER
OCWnx
DATA BUS (8-bit)
There is a dedicated prescaler in front of the Dead Time Generator that can divide the
Timer/Counter1 clock (PCK or CK) by 1, 2, 4 or 8. This provides for large range of dead times
that can be generated. The prescaler is controlled by two control bits DTPS11:10. The block has
also a rising and falling edge detector that is used to start the dead time counting period.
Depending on the edge, one of the transitions on the rising edges, OC1x or OC1x is delayed
until the counter has counted to zero. The comparator is used to compare the counter with zero
and stop the dead time insertion when zero has been reached. The counter is loaded with a 4-bit
DT1H or DT1L value from DT1 I/O register, depending on the edge of the Waveform Output
(OCW1x) when the dead time insertion is started. The Output Compare Output are delayed by
one timer clock cycle at minimum from the Waveform Output when the Dead Time is adjusted to
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zero. The outputs OC1x and OC1x are inverted, if the PWM Inversion Mode bit PWM1X is set.
This will also cause both outputs to be high during the dead time.
The length of the counting period is user adjustable by selecting the dead time prescaler setting
by using the DTPS11:10 control bits, and selecting then the dead time value in I/O register DT1.
The DT1 register consists of two 4-bit fields, DT1H and DT1L that control the dead time periods
of the PWM output and its' complementary output separately in terms of the number of prescaled dead time generator clock cycles. Thus the rising edge of OC1x and OC1x can have
different dead time periods as the tnon-overlap / rising edge is adjusted by the 4-bit DT1H value and the
tnon-overlap / falling edge is adjusted by the 4-bit DT1L value.
Figure 12-9. The Complementary Output Pair, COM1x1:0 = 1
OCWnx
OCnx
OCnx
(COMnx = 1)
t non-overlap / rising edge
12.7
t non-overlap / falling edge
Compare Match Output Unit
The Compare Output Mode (COM1x1:0) bits have two functions. The Waveform Generator uses
the COM1x1:0 bits for defining the inverted or non-inverted Waveform Output (OCW1x) at the
next Compare Match. Also, the COM1x1:0 bits control the OC1x and OC1x pin output source.
Figure 12-10 on page 96 shows a simplified schematic of the logic affected by the COM1x1:0 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 COM1x1:0 bits
are shown.
In Normal Mode (non-PWM) the Dead Time Generator is disabled and it is working like a synchronizer: the Output Compare (OC1x) is delayed from the Waveform Output (OCW1x) by one
timer clock cycle. Whereas in Fast PWM Mode and in Phase and Frequency Correct PWM
Mode when the COM1x1:0 bits are set to “01” both the non-inverted and the inverted Output
Compare output are generated, and an user programmable Dead Time delay is inserted for
these complementary output pairs (OC1x and OC1x). The functionality in PWM modes is similar
to Normal mode when any other COM1x1:0 bit setup is used. When referring to the OC1x state,
the reference is for the Output Compare output (OC1x) from the Dead Time Generator, not the
OC1x pin. If a system reset occur, the OC1x is reset to “0”.
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Figure 12-10. Compare Match Output Unit, Schematic
WGM11
clk I/O
OC1OE1:0
COM1A1:0
Output Compare
Pin Configuration
D Q
PORTB0
0
D Q
PORTB1
1
1
D Q
DDRB0
OC1A
PIN
0
OCW1A
clk Tn
Dead Time Q
Generator A Q
OC1A
1
OC1A
0
D Q
DDRB1
WGM11
OC1OE3:2
COM1B1:0
OC1A
PIN
Output Compare
Pin Configuration
DATA BUS
D Q
PORTB2
2
1
0
D Q
DDRB2
D Q
PORTB3
1
OC1B
PIN
0
OCW1B
clk Tn
Dead Time Q
Generator B Q
OC1B
1
OC1B
1
0
0
D Q
DDRB3
WGM11
OC1OE5:4
COM1D1:0
OC1B
PIN
Output Compare
Pin Configuration
D Q
PORTB4
2
1
0
D Q
DDRB4
D Q
PORTB5
1
OC1D
PIN
0
OCW1D
clk Tn
Dead Time Q
Generator D Q
OC1D
OC1D
1
0
1
0
OC1D
PIN
D Q
DDRB5
The general I/O port function is overridden by the Output Compare (OC1x / OC1x) from the
Dead Time Generator if either of the COM1x1:0 bits are set. However, the OC1x 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 OC1x and OC1x pins (DDR_OC1x and DDR_OC1x) must be set as
output before the OC1x and OC1x values are visible on the pin. The port override function is
independent of the Output Compare mode.
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The design of the Output Compare Pin Configuration logic allows initialization of the OC1x state
before the output is enabled. Note that some COM1x1:0 bit settings are reserved for certain
modes of operation. For Output Compare Pin Configurations refer to Table 12-2 on page 98,
Table 12-3 on page 100, Table 12-4 on page 102, Table 12-5 on page 103, Table 12-6 on page
103, and Table 12-7 on page 104.
12.7.1
12.8
Compare Output Mode and Waveform Generation
The Waveform Generator uses the COM1x1:0 bits differently in Normal mode and PWM modes.
For all modes, setting the COM1x1:0 = 0 tells the Waveform Generator that no action on the
OCW1x Output is to be performed on the next Compare Match. For compare output actions in
the non-PWM modes refer to Table 12-8 on page 110. For fast PWM mode, refer to Table 12-9
on page 110, and for the Phase and Frequency Correct PWM refer to Table 12-10 on page 111.
A change of the COM1x1:0 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
FOC1x 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 waveform generation mode bits (PWM1A, PWM1B, and
WGM11:10) and compare output mode bits (COM1x1:0). The Compare Output mode bits do not
affect the counting sequence, while the Waveform Generation mode bits do. The COM1x1:0 bits
control whether the PWM output generated should be inverted, non-inverted or complementary.
For non-PWM modes the COM1x1:0 bits control whether the output should be set, cleared, or
toggled at a Compare Match.
12.8.1
Normal Mode
The simplest mode of operation is Normal mode (PWM1A/PWM1B = 0), where the counter
counts from BOTTOM to TOP (defined as OCR1C) then restarts from BOTTOM. The OCR1C
defines the TOP value for the counter, hence also its resolution, and allows control of the Compare Match output frequency. In toggle Compare Output Mode the Waveform Output (OCW1x)
is toggled at Compare Match between TCNT1 and OCR1x. In non-inverting Compare Output
Mode the Waveform Output is cleared on the Compare Match. In inverting Compare Output
Mode the Waveform Output is set on Compare Match. The timing diagram for Normal mode is
shown in Figure 12-11.
Figure 12-11. Normal Mode, Timing Diagram
TOVn Interrupt Flag Set
OCnx Interrupt Flag Set
TCNTn
OCWnx
(COMnx=1)
Period
1
2
3
4
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The counter value (TCNT1) that is shown as a histogram in Figure 12-11 is incremented until the
counter value matches the TOP value. The counter is then cleared at the following clock cycle
The diagram includes the Waveform Output (OCW1x) in toggle Compare Mode. The small horizontal line marks on the TCNT1 slopes represent Compare Matches between OCR1x and
TCNT1.
The Timer/Counter Overflow Flag (TOV1) is set in the same clock cycle as the TCNT1 becomes
zero. The TOV1 Flag in this case behaves like a 11th bit, except that it is only set, not cleared.
However, combined with the timer overflow interrupt, that automatically clears the TOV1 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. For generating a waveform, the OCW1x output can be set to
toggle its logical level on each Compare Match by setting the Compare Output mode bits to toggle mode (COM1x1:0 = 1). The OC1x 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
fOC1x = fclkT1/4 when OCR1C is set to zero. The waveform frequency is defined by the following
equation:
f clkT1
f OC1x = ------------------------------------------2 ⋅ ( 1 + OCR1C )
Resolution, RPWM, shows how many bit is required to express the value in the OCR1C register
and it can be calculated using the following equation:
R PWM = log 2 ( OCR1C + 1 )
The Output Compare Pin configurations in Normal Mode are described in Table 12-2.
Table 12-2.
12.8.2
Output Compare Pin Configurations in Normal Mode
COM1x1
COM1x0
OC1x Pin
OC1x Pin
0
0
Disconnected
Disconnected
0
1
Disconnected
OC1x
1
0
Disconnected
OC1x
1
1
Disconnected
OC1x
Fast PWM Mode
The fast Pulse Width Modulation or fast PWM mode (PWM1A/PWM1B = 1 and WGM11:10 = 00)
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
(defined as OCR1C) then restarts from BOTTOM. In non-inverting Compare Output mode the
Waveform Output (OCW1x) is cleared on the Compare Match between TCNT1 and OCR1x and
set at BOTTOM. In inverting Compare Output mode, the Waveform Output is set on Compare
Match and cleared at BOTTOM. In complementary Compare Output mode the Waveform Output
is cleared on the Compare Match and set at BOTTOM.
Due to the single-slope operation, the operating frequency of the fast PWM mode can be twice
as high as the Phase and Frequency Correct PWM mode that use dual-slope operation. This
high frequency makes the fast PWM mode well suited for power regulation, rectification, and
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DAC applications. High frequency allows physically small sized external components (coils,
capacitors), and therefore reduces total system cost.
The timing diagram for the fast PWM mode is shown in Figure 12-12. The counter is incremented until the counter value matches the TOP value. The counter is then cleared at the
following timer clock cycle. The TCNT1 value is in the timing diagram shown as a histogram for
illustrating the single-slope operation. The diagram includes the Waveform Output in noninverted and inverted Compare Output modes. The small horizontal line marks on the TCNT1
slopes represent Compare Matches between OCR1x and TCNT1.
Figure 12-12. Fast PWM Mode, Timing Diagram
OCRnx Interrupt Flag Set
OCRnx Update and
TOVn Interrupt Flag Set
TCNTn
OCWnx
(COMnx1:0 = 2)
OCWnx
(COMnx1:0 = 3)
Period
1
2
3
4
5
6
7
The Timer/Counter Overflow Flag (TOV1) 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 OC1x pins.
Setting the COM1x1:0 bits to two will produce a non-inverted PWM and setting the COM1x1:0 to
three will produce an inverted PWM output. Setting the COM1x1:0 bits to one will enable complementary Compare Output mode and produce both the non-inverted (OC1x) and inverted
output (OC1x). The actual 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 Waveforn
Output (OCW1x) at the Compare Match between OCR1x and TCNT1, and clearing (or setting)
the Waveform Output 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 clkT1
f OCnxPWM = ------------N
The N variable represents the number of steps in single-slope operation. The value of N equals
either to the TOP value.
The extreme values for the OCR1C Register represents special cases when generating a PWM
waveform output in the fast PWM mode. If the OCR1C is set equal to BOTTOM, the output will
be a narrow spike for each MAX+1 timer clock cycle. Setting the OCR1C equal to MAX will result
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in a constantly high or low output (depending on the polarity of the output set by the COM1x1:0
bits.)
A frequency (with 50% duty cycle) waveform output in fast PWM mode can be achieved by setting the Waveform Output (OCW1x) to toggle its logical level on each Compare Match
(COM1x1:0 = 1). The waveform generated will have a maximum frequency of fOC1 = fclkT1/4 when
OCR1C is set to three.
The general I/O port function is overridden by the Output Compare value (OC1x / OC1x) from
the Dead Time Generator, if either of the COM1x1:0 bits are set and the Data Direction Register
bits for the OC1X and OC1X pins are set as an output. If the COM1x1:0 bits are cleared, the
actual value from the port register will be visible on the port pin. The Output Compare Pin configurations are described in Table 12-3.
Table 12-3.
12.8.3
Output Compare Pin Configurations in Fast PWM Mode
COM1x1
COM1x0
OC1x Pin
OC1x Pin
0
0
Disconnected
Disconnected
0
1
OC1x
OC1x
1
0
Disconnected
OC1x
1
1
Disconnected
OC1x
Phase and Frequency Correct PWM Mode
The Phase and Frequency Correct PWM Mode (PWM1A/PWM1B = 1 and WGM11:10 = 01) provides a high resolution Phase and Frequency Correct PWM waveform generation option. The
Phase and Frequency Correct PWM mode is based on a dual-slope operation. The counter
counts repeatedly from BOTTOM to TOP (defined as OCR1C) and then from TOP to BOTTOM.
In non-inverting Compare Output Mode the Waveform Output (OCW1x) is cleared on the Compare Match between TCNT1 and OCR1x while upcounting, and set on the Compare Match while
down-counting. In inverting Output Compare mode, the operation is inverted. In complementary
Compare Output Mode, the Waveform Ouput is cleared on the Compare Match and set at BOTTOM. 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 timing diagram for the Phase and Frequency Correct PWM mode is shown on Figure 12-13
in which the TCNT1 value is shown as a histogram for illustrating the dual-slope operation. The
counter is incremented until the counter value matches TOP. When the counter reaches TOP, it
changes the count direction. The TCNT1 value will be equal to TOP for one timer clock cycle.
The diagram includes the Waveform Output (OCW1x) in non-inverted and inverted Compare
Output Mode. The small horizontal line marks on the TCNT1 slopes represent Compare
Matches between OCR1x and TCNT1.
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Figure 12-13. Phase and Frequency Correct PWM Mode, Timing Diagram
OCnx Interrupt Flag Set
OCRnx Update
TOVn Interrupt Flag Set
TCNTn
OCWnx
(COMnx = 2)
OCWnx
(COMnx = 3)
Period
1
2
3
The Timer/Counter Overflow Flag (TOV1) 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 the Phase and Frequency Correct PWM mode, the compare unit allows generation of PWM
waveforms on the OC1x pins. Setting the COM1x1:0 bits to two will produce a non-inverted
PWM and setting the COM1x1:0 to three will produce an inverted PWM output. Setting the
COM1A1:0 bits to one will enable complementary Compare Output mode and produce both the
non-inverted (OC1x) and inverted output (OC1x). The actual values 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 Waveform Output (OCW1x) at the Compare Match between OCR1x and
TCNT1 when the counter increments, and setting (or clearing) the Waveform Output at Compare
Match when the counter decrements. The PWM frequency for the output when using the Phase
and Frequency Correct PWM can be calculated by the following equation:
f clkT1
f OCnxPCPWM = ------------N
The N variable represents the number of steps in dual-slope operation. The value of N equals to
the TOP value.
The extreme values for the OCR1C Register represent special cases when generating a PWM
waveform output in the Phase and Frequency Correct PWM mode. If the OCR1C 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.
The general I/O port function is overridden by the Output Compare value (OC1x / OC1x) from
the Dead Time Generator, if either of the COM1x1:0 bits are set and the Data Direction Register
bits for the OC1X and OC1X pins are set as an output. If the COM1x1:0 bits are cleared, the
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actual value from the port register will be visible on the port pin. The configurations of the Output
Compare Pins are described in Table 12-4.
Table 12-4.
12.8.4
Output Compare pin configurations in Phase and Frequency Correct PWM Mode
COM1x1
COM1x0
OC1x Pin
OC1x Pin
0
0
Disconnected
Disconnected
0
1
OC1x
OC1x
1
0
Disconnected
OC1x
1
1
Disconnected
OC1x
PWM6 Mode
The PWM6 Mode (PWM1A = 1, WGM11:10 = 1X) provide PWM waveform generation option
e.g. for controlling Brushless DC (BLDC) motors. In the PWM6 Mode the OCR1A Register controls all six Output Compare waveforms as the same Waveform Output (OCW1A) from the
Waform Generator is used for generating all waveforms. The PWM6 Mode also provides an Output Compare Override Enable Register (OC1OE) that can be used with an instant response for
disabling or enabling the Output Compare pins. If the Output Compare Override Enable bit is
cleared, the actual value from the port register will be visible on the port pin.
The PWM6 Mode provides two counter operation modes, a single-slope operation and a dualslope operation. If the single-slope operation is selected (the WGM10 bit is set to 0), the counter
counts from BOTTOM to TOP (defined as OCR1C) then restart from BOTTOM like in Fast PWM
Mode. The PWM waveform is generated by setting (or clearing) the Waveforn Output (OCW1A)
at the Compare Match between OCR1A and TCNT1, and clearing (or setting) the Waveform
Output at the timer clock cycle the counter is cleared (changes from TOP to BOTTOM). The
Timer/Counter Overflow Flag (TOV1) is set each time the counter reaches the TOP and, if the
interrupt is enabled, the interrupt handler routine can be used for updating the compare value.
Whereas, if the dual-slope operation is selected (the WGM10 bit is set to 1), the counter counts
repeatedly from BOTTOM to TOP (defined as OCR1C) and then from TOP to BOTTOM like in
Phase and Frequency Correct PWM Mode. The PWM waveform is generated by setting (or
clearing) the Waveforn Output (OCW1A) at the Compare Match between OCR1A and TCNT1
when the counter increments, and clearing (or setting) the Waveform Output at the he Compare
Match between OCR1A and TCNT1 when the counter decrements. The Timer/Counter Overflow
Flag (TOV1) is set each time the counter reaches the BOTTOM and, if the interrupt is enabled,
the interrupt handler routine can be used for updating the compare value.
The timing diagram for the PWM6 Mode in single-slope operation when the COM1A1:0 bits are
set to “10” is shown in Figure 12-14. The counter is incremented until the counter value matches
the TOP value. The counter is then cleared at the following timer clock cycle. The TCNT1 value
is in the timing diagram shown as a histogram for illustrating the single-slope operation. The timing diagram includes Output Compare pins OC1A and OC1A, and the corresponding Output
Compare Override Enable bits (OC1OE1:OC1OE0).
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Figure 12-14. PWM6 Mode, Single-slope Operation, Timing Diagram
TCNT1
OCW1A
OC1OE0
OC1A Pin
OC1OE1
OC1A Pin
OC1OE2
OC1B Pin
OC1OE3
OC1B Pin
OC1OE4
OC1D Pin
OC1OE5
OC1D Pin
The general I/O port function is overridden by the Output Compare value (OC1x / OC1x) from
the Dead Time Generator if either of the COM1x1:0 bits are set. The Output Compare pins can
also be overriden by the Output Compare Override Enable bits OC1OE5:OC1OE0. If an Override Enable bit is cleared, the actual value from the port register will be visible on the port pin
and, if the Override Enable bit is set, the Output Compare pin is allowed to be connected on the
port pin. The Output Compare Pin configurations are described in Table 12-5, Table 12-6 and
Table 12-7.
Table 12-5.
Configuration of Output Compare Pins OC1A and OC1A in PWM6 Mode
COM1A1
COM1A0
OC1A Pin (PB0)
OC1A Pin (PB1)
0
0
Disconnected
Disconnected
0
1
OC1A • OC1OE0
OC1A • OC1OE1
1
0
OC1A • OC1OE0
OC1A • OC1OE1
1
1
OC1A • OC1OE0
OC1A • OC1OE1
Table 12-6.
Configuration of Output Compare Pins OC1B and OC1B in PWM6 Mode
COM1B1
COM1B0
OC1B Pin (PB2)
OC1B Pin (PB3)
0
0
Disconnected
Disconnected
0
1
OC1A • OC1OE2
OC1A • OC1OE3
1
0
OC1A • OC1OE2
OC1A • OC1OE3
1
1
OC1A • OC1OE2
OC1A • OC1OE3
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Table 12-7.
12.9
Configuration of Output Compare Pins OC1D and OC1D in PWM6 Mode
COM1D1
COM1D0
OC1D Pin (PB4)
OC1D Pin (PB5)
0
0
Disconnected
Disconnected
0
1
OC1A • OC1OE4
OC1A • OC1OE5
1
0
OC1A • OC1OE4
OC1A • OC1OE5
1
1
OC1A • OC1OE4
OC1A • OC1OE5
Timer/Counter Timing Diagrams
The Timer/Counter is a synchronous design and the timer clock (clkT1) is therefore shown as a
clock enable signal in the following figures. The figures include information on when Interrupt
Flags are set.
Figure 12-15 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 and Frequency Correct PWM
Mode.
Figure 12-15. Timer/Counter Timing Diagram, no Prescaling
clkPCK
clkTn
(clkPCK /1)
TCNTn
TOP - 1
TOP
BOTTOM
BOTTOM + 1
TOVn
Figure 12-16 shows the same timing data, but with the prescaler enabled, in all modes other
than Phase and Frequency Correct PWM Mode.
Figure 12-16. Timer/Counter Timing Diagram, with Prescaler (fclkT1/8)
clkPCK
clkTn
(clkPCK /8)
TCNTn
TOP - 1
TOP
BOTTOM
BOTTOM + 1
TOVn
Figure 12-17 shows the setting of OCF1A, OCF1B and OCF1D in all modes.
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Figure 12-17. Timer/Counter Timing Diagram, Setting of OCF1x, with Prescaler (fclkT1/8)
clkPCK
clkTn
(clkPCK /8)
TCNTn
OCRnx - 1
OCRnx
OCRnx
OCRnx + 1
OCRnx + 2
OCRnx Value
OCFnx
Figure 12-18 shows the setting of TOV1 in Phase and Frequency Correct PWM Mode.
Figure 12-18. Timer/Counter Timing Diagram, with Prescaler (fclkT1/8)
clkPCK
clkTn
(clkPCK /8)
TCNTn
BOTTOM + 1
BOTTOM + 1
BOTTOM
BOTTOM + 1
TOVn
12.10 Fault Protection Unit
The Timer/Counter1 incorporates a Fault Protection unit, which can be set to disable the PWM
output pins when an external event is triggered. The external signal indicating an event can be
applied via the external interrupt INT0 pin or, alternatively, via the analog-comparator unit. The
Fault Protection unit is illustrated in Figure 12-19. The elements of the block diagram that are not
directly a part of the Fault Protection unit are gray shaded.
Figure 12-19. Fault Protection Unit Block Diagram
FAULT_PROTECTION (Int. Req.)
ACO*
Analog
Comparator
INT0
FPAC1
FPNC1
Noise
Canceler
FPES1 FPEN1
Edge
Detector
Timer/Counter1
Fault Protection mode is enabled by setting the Fault Protection Enable (FPEN1) bit and triggered by a change in logic level at external interrupt pin (INT0). Alternatively, fault protection
mode can be triggered by the Analog Comparator Output (ACO).
When Fault Protection is triggered, the COM1x bits are cleared, Output Comparators are disconnected from the PWM output pins and PORTB register bits are connected to the PWM output
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pins. The Fault Protection Enable (FPEN1) is automatically cleared at the same system clock as
the COM1nx bits are cleared.
If the Fault Protection Interrupt Enable bit (FPIE1) is set, a Fault Protection interrupt is generated
and the FPEN1 bit is cleared. Alternatively the FPEN1 bit can be polled by software to figure out
when the Timer/Counter has entered to Fault Protection mode.
12.10.1
Fault Protection Trigger Source
The main trigger source for the Fault Protection unit is the external interrupt pin (INT0). Alternatively the Analog Comparator output can be used as trigger source for the Fault Protection unit.
The Analog Comparator is selected as trigger source by setting the Fault Protection Analog
Comparator (FPAC1) bit in the Timer/Counter1 Control Register (TCCR1D). Be aware that
changing trigger source can trigger a Fault Protection mode. Therefore it is recommended to
clear the FPF1 flag after changing trigger source, setting edge detector or enabling the Fault
Protection.
Both the external interrupt pin (INT0) and the Analog Comparator output (ACO) inputs are sampled using the same technique as with the T0 pin (see Figure 11-3 on page 72). The edge
detectors are also identical but when the noise canceler is enabled additional logic is activated
before the edge detector, increasing the propagation delay with four system clock cycles.
An Input Capture can also be triggered by software by controlling the port of the INT0 pin.
12.10.2
Noise Canceler
The noise canceler uses a simple digital filtering technique to improve noise immunity. Consecutive samples are monitored in a pipeline four units deep. The signal going to the edge detecter is
allowed to change only when all four samples are equal.
The noise canceler is enabled by setting the Fault Protection Noise Canceler (FPNC1) bit in
Timer/Counter1 Control Register D (TCCR1D). When enabled, the noise canceler introduces an
additional delay of four system clock cycles to a change applied to the input.
The noise canceler uses the system clock directly and is therefore not affected by the prescaler.
12.11 Accessing 10-Bit Registers
If 10-bit values are written to the TCNT1 and OCR1A/B/C/D registers, the 10-bit registers can be
byte accessed by the AVR CPU via the 8-bit data bus using two read or write operations. The
10-bit registers have a common 2-bit Timer/Counter1 High Byte Register (TC1H) that is used for
temporary storing of the two MSBs of the 10-bit access. The same TC1H register is shared
between all 10-bit registers. Accessing the low byte triggers the 10-bit read or write operation.
When the low byte of a 10-bit register is written by the CPU, the high byte stored in the TC1H
register, and the low byte written are both copied into the 10-bit register in the same clock cycle.
When the low byte of a 10-bit register is read by the CPU, the high byte of the 10-bit register is
copied into the TC1H register in the same clock cycle as the low byte is read.
To do a 10-bit write, the high byte must be written to the TC1H register before the low byte is
written. For a 10-bit read, the low byte must be read before the high byte.
12.11.1
106
Reusing the temporary high byte register
If writing to more than one 10-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.
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12.11.2
Code Examples
The following code examples show how to access the 10-bit timer registers assuming that no
interrupts updates the TC1H register. The same principle can be used directly for accessing the
OCR1A/B/C/D registers.
Assembly Code Example
...
; Set TCNT1 to 0x01FF
ldi r17,0x01
ldi r16,0xFF
out TC1H,r17
out TCNT1,r16
; Read TCNT1 into r17:r16
in r16,TCNT1
in r17,TC1H
...
C Code Example
unsigned int i;
...
/* Set TCNT1 to 0x01FF */
TC1H = 0x01;
TCNT1 = 0xFF;
/* Read TCNT1 into i */
i = TCNT1;
i |= ((unsigned int)TC1H << 8);
...
Note:
See “Code Examples” on page 6.
The assembly code example returns the TCNT1 value in the r17:r16 register pair.
It is important to notice that accessing 10-bit registers are atomic operations. If an interrupt
occurs between the two instructions accessing the 10-bit register, and the interrupt code
updates the TC1H register by accessing the same or any other of the 10-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 TC1H register, the main code must disable the interrupts
during the 16-bit access.
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The following code examples show how to do an atomic read of the TCNT1 register contents.
Reading any of the OCR1A/B/C/D registers can be done by using the same principle.
Assembly Code Example
TIM1_ReadTCNT1:
; Save global interrupt flag
in r18,SREG
; Disable interrupts
cli
; Read TCNT1 into r17:r16
in r16,TCNT1
in r17,TC1H
; Restore global interrupt flag
out SREG,r18
ret
C Code Example
unsigned int TIM1_ReadTCNT1( void )
{
unsigned char sreg;
unsigned int i;
/* Save global interrupt flag */
sreg = SREG;
/* Disable interrupts */
_CLI();
/* Read TCNT1 into i */
i = TCNT1;
i |= ((unsigned int)TC1H << 8);
/* Restore global interrupt flag
SREG = sreg;
return i;
}
Note:
See “Code Examples” on page 6.
The assembly code example returns the TCNT1 value in the r17:r16 register pair.
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The following code examples show how to do an atomic write of the TCNT1 register contents.
Writing any of the OCR1A/B/C/D registers can be done by using the same principle.
Assembly Code Example
TIM1_WriteTCNT1:
; Save global interrupt flag
in r18,SREG
; Disable interrupts
cli
; Set TCNT1 to r17:r16
out TC1H,r17
out TCNT1,r16
; Restore global interrupt flag
out SREG,r18
ret
C Code Example
void TIM1_WriteTCNT1( unsigned int i )
{
unsigned char sreg;
unsigned int i;
/* Save global interrupt flag */
sreg = SREG;
/* Disable interrupts */
_CLI();
/* Set TCNT1 to i */
TC1H = (i >> 8);
TCNT1 = (unsigned char)i;
/* Restore global interrupt flag */
SREG = sreg;
}
Note:
See “Code Examples” on page 6.
The assembly code example requires that the r17:r16 register pair contains the value to be written to TCNT1.
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12.12 Register Description
12.12.1
TCCR1A – Timer/Counter1 Control Register A
Bit
7
6
5
4
3
2
1
0
0x30 (0x50)
COM1A1
COM1A0
COM1B1
COM1B0
FOC1A
FOC1B
PWM1A
PWM1B
Read/Write
R/W
R/W
R/W
R/W
W
W
R/W
R/W
Initial value
0
0
0
0
0
0
0
0
TCCR1A
• Bits 7,6 - COM1A1, COM1A0: Comparator A Output Mode, Bits 1 and 0
These bits control the behaviour of the Waveform Output (OCW1A) and the connection of the
Output Compare pin (OC1A). If one or both of the COM1A1:0 bits are set, the OC1A output
overrides the normal port functionality of the I/O pin it is connected to. The complementary
OC1B output is connected only in PWM modes when the COM1A1:0 bits are set to “01”. Note
that the Data Direction Register (DDR) bit corresponding to the OC1A and OC1A pins must be
set in order to enable the output driver.
The function of the COM1A1:0 bits depends on the PWM1A, WGM10 and WGM11 bit settings.
Table 12-8 shows the COM1A1:0 bit functionality when the PWM1A bit is set to Normal Mode
(non-PWM).
Table 12-8.
COM1A1:0
Compare Output Mode, Normal Mode (non-PWM)
OCW1A Behaviour
OC1A Pin
OC1A Pin
00
Normal port operation.
Disconnected
Disconnected
01
Toggle on Compare Match.
Connected
Disconnected
10
Clear on Compare Match.
Connected
Disconnected
11
Set on Compare Match.
Connected
Disconnected
Table 12-9 shows the COM1A1:0 bit functionality when the PWM1A, WGM10 and WGM11 bits
are set to fast PWM mode.
Table 12-9.
COM1A1:0
110
Compare Output Mode, Fast PWM Mode
OCW1A Behaviour
OC1A
OC1A
00
Normal port operation.
Disconnected
Disconnected
01
Cleared on Compare Match.
Set when TCNT1 = 0x000.
Connected
Connected
10
Cleared on Compare Match.
Set when TCNT1 = 0x000.
Connected
Disconnected
11
Set on Compare Match
Cleared when TCNT1 = 0x000.
Connected
Disconnected
ATtiny261A/461A/861A
8197A–AVR–10/09
ATtiny261A/461A/861A
Table 12-10 shows the COM1A1:0 bit functionality when the PWM1A, WGM10 and WGM11 bits
are set to Phase and Frequency Correct PWM Mode.
Table 12-10. Compare Output Mode, Phase and Frequency Correct PWM Mode
COM1A1:0
OCW1A Behaviour
OC1A Pin
OC1A Pin
00
Normal port operation.
Disconnected
Disconnected
01
Cleared on Compare Match when up-counting.
Set on Compare Match when down-counting.
Connected
Connected
10
Cleared on Compare Match when up-counting.
Set on Compare Match when down-counting.
Connected
Disconnected
11
Set on Compare Match when up-counting.
Cleared on Compare Match when down-counting.
Connected
Disconnected
Table 12-11 shows the COM1A1:0 bit functionality when the PWM1A, WGM10 and WGM11 bits
are set to single-slope PWM6 Mode. In the PWM6 Mode the same Waveform Output (OCW1A)
is used for generating all waveforms and the Output Compare values OC1A and OC1A are connected on thw all OC1x and OC1x pins as described below.
Table 12-11. Compare Output Mode, Single-Slope PWM6 Mode
COM1A1:0
OCW1A Behaviour
OC1x Pin
OC1x Pin
00
Normal port operation.
Disconnected
Disconnected
01
Cleared on Compare Match.
Set when TCNT1 = 0x000.
OC1A
OC1A
10
Cleared on Compare Match.
Set when TCNT1 = 0x000.
OC1A
OC1A
11
Set on Compare Match.
Cleared when TCNT1 = 0x000.
OC1A
OC1A
Table 12-12 shows the COM1A1:0 bit functionality when the PWM1A, WGM10 and WGM11 bits
are set to dual-slope PWM6 Mode.I
Table 12-12. Compare Output Mode, Dual-Slope PWM6 Mode
COM1A1:0
OCW1A Behaviour
OC1x Pin
OC1x Pin
00
Normal port operation.
Disconnected
Disconnected
01
Cleared on Compare Match when up-counting.
Set on Compare Match when down-counting.
OC1A
OC1A
10
Cleared on Compare Match when up-counting.
Set on Compare Match when down-counting.
OC1A
OC1A
11
Set on Compare Match when up-counting.
Cleared on Compare Match when down-counting.
OC1A
OC1A
Bits COM1A1 and COM1A0 are shadowed in TCCR1C. Writing to bits COM1A1 and COM1A0
will also change bits COM1A1S and COM1A0S in TCCR1C. Similary, changes written to bits
COM1A1S and COM1A0S in TCCR1C will show here. See “TCCR1C – Timer/Counter1 Control
Register C” on page 115.
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8197A–AVR–10/09
• Bits 5,4 - COM1B1, COM1B0: Comparator B Output Mode, Bits 1 and 0
These bits control the behaviour of the Waveform Output (OCW1B) and the connection of the
Output Compare pin (OC1B). If one or both of the COM1B1:0 bits are set, the OC1B output
overrides the normal port functionality of the I/O pin it is connected to. The complementary
OC1B output is connected only in PWM modes when the COM1B1:0 bits are set to “01”. Note
that the Data Direction Register (DDR) bit corresponding to the OC1B pin must be set in order to
enable the output driver.
The function of the COM1B1:0 bits depends on the PWM1B and WGM11:10 bit settings. Table
12-13 shows the COM1B1:0 bit functionality when the PWM1B bit is set to Normal Mode (nonPWM).
Table 12-13. Compare Output Mode, Normal Mode (non-PWM)
COM1B1:0
OCW1B Behaviour
OC1B Pin
OC1B Pin
00
Normal port operation.
Disconnected
Disconnected
01
Toggle on Compare Match.
Connected
Disconnected
10
Clear on Compare Match.
Connected
Disconnected
11
Set on Compare Match.
Connected
Disconnected
Table 12-14 shows the COM1B1:0 bit functionality when the PWM1B and WGM11:10 bits are
set to Fast PWM Mode.
Table 12-14. Compare Output Mode, Fast PWM Mode
COM1B1:0
OCW1B Behaviour
OC1B Pin
OC1B Pin
00
Normal port operation.
Disconnected
Disconnected
01
Cleared on Compare Match.
Set when TCNT1 = 0x000.
Connected
Connected
10
Cleared on Compare Match.
Set when TCNT1 = 0x000.
Connected
Disconnected
11
Set on Compare Match.
Cleared when TCNT1 = 0x000.
Connected
Disconnected
Table 12-15 shows the COM1B1:0 bit functionality when the PWM1B and WGM11:10 bits are
set to Phase and Frequency Correct PWM Mode.
Table 12-15. Compare Output Mode, Phase and Frequency Correct PWM Mode
COM1B1:0
OCW1B Behaviour
OC1B Pin
OC1B Pin
00
Normal port operation.
Disconnected
Disconnected
01
Cleared on Compare Match when up-counting.
Set on Compare Match when down-counting.
Connected
Connected
10
Cleared on Compare Match when up-counting.
Set on Compare Match when down-counting.
Connected
Disconnected
11
Set on Compare Match when up-counting.
Cleared on Compare Match when down-counting.
Connected
Disconnected
Bits COM1B1 and COM1B0 are shadowed in TCCR1C. Writing to bits COM1B1 and COM1B0
will also change bits COM1B1S and COM1B0S in TCCR1C. Similary, changes written to bits
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ATtiny261A/461A/861A
COM1B1S and COM1B0S in TCCR1C will show here. See “TCCR1C – Timer/Counter1 Control
Register C” on page 115.
• Bit 3 - FOC1A: Force Output Compare Match 1A
The FOC1A bit is only active when the PWM1A bit specify a non-PWM mode.
Writing a logical one to this bit forces a change in the Waveform Output (OCW1A) and the Output Compare pin (OC1A) according to the values already set in COM1A1 and COM1A0. If
COM1A1 and COM1A0 written in the same cycle as FOC1A, the new settings will be used. The
Force Output Compare bit can be used to change the output pin value regardless of the timer
value. The automatic action programmed in COM1A1 and COM1A0 takes place as if a compare
match had occurred, but no interrupt is generated.
The FOC1A bit always reads zero.
• Bit 2 - FOC1B: Force Output Compare Match 1B
The FOC1B bit is only active when the PWM1B bit specify a non-PWM mode.
Writing a logical one to this bit forces a change in the Waveform Output (OCW1B) and the Output Compare pin (OC1B) according to the values already set in COM1B1 and COM1B0. If
COM1B1 and COM1B0 written in the same cycle as FOC1B, the new settings will be used. The
Force Output Compare bit can be used to change the output pin value regardless of the timer
value. The automatic action programmed in COM1B1 and COM1B0 takes place as if a compare
match had occurred, but no interrupt is generated.
The FOC1B bit always reads zero.
• Bit 1 - PWM1A: Pulse Width Modulator A Enable
When set (one) this bit enables PWM mode based on comparator OCR1A
• Bit 0 - PWM1B: Pulse Width Modulator B Enable
When set (one) this bit enables PWM mode based on comparator OCR1B.
12.12.2
TCCR1B – Timer/Counter1 Control Register B
Bit
7
6
5
4
3
2
1
0
0x2F (0x4F)
PWM1X
PSR1
DTPS11
DTPS10
CS13
CS12
CS11
CS10
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
TCCR1B
• Bit 7 - PWM1X : PWM Inversion Mode
When this bit is set (one), the PWM Inversion Mode is selected and the Dead Time Generator
outputs, OC1x and OC1x are inverted.
• Bit 6 - PSR1 : Prescaler Reset Timer/Counter1
When this bit is set (one), the Timer/Counter1 prescaler (TCNT1 is unaffected) will be reset. The
bit will be cleared by hardware after the operation is performed. Writing a zero to this bit will have
no effect. This bit will always read as zero.
• Bits 5,4 - DTPS11, DTPS10: Dead Time Prescaler Bits
The Timer/Counter1 Control Register B is a 8-bit read/write register.
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8197A–AVR–10/09
The dedicated Dead Time prescaler in front of the Dead Time Generator can divide the
Timer/Counter1 clock (PCK or CK) by 1, 2, 4 or 8 providing a large range of dead times that can
be generated. The Dead Time prescaler is controlled by two bits DTPS11 and DTPS10 from the
Dead Time Prescaler register. These bits define the division factor of the Dead Time prescaler.
The division factors are given in Table 12-16.
Table 12-16. Division factors of the Dead Time prescaler
DTPS11
DTPS10
Prescaler divides the T/C1 clock by
0
0
1x (no division)
0
1
2x
1
0
4x
1
1
8x
• Bits 3 : 0 - CS13, CS12, CS11, CS10: Clock Select Bits 3, 2, 1, and 0
The Clock Select bits 3, 2, 1, and 0 define the prescaling source of Timer/Counter1.
Table 12-17. Timer/Counter1 Prescaler Select
CS13
CS12
CS11
CS10
Asynchronous Clocking Mode
Synchronous Clocking Mode
0
0
0
0
T/C1 stopped
T/C1 stopped
0
0
0
1
PCK
CK
0
0
1
0
PCK/2
CK/2
0
0
1
1
PCK/4
CK/4
0
1
0
0
PCK/8
CK/8
0
1
0
1
PCK/16
CK/16
0
1
1
0
PCK/32
CK/32
0
1
1
1
PCK/64
CK/64
1
0
0
0
PCK/128
CK/128
1
0
0
1
PCK/256
CK/256
1
0
1
0
PCK/512
CK/512
1
0
1
1
PCK/1024
CK/1024
1
1
0
0
PCK/2048
CK/2048
1
1
0
1
PCK/4096
CK/4096
1
1
1
0
PCK/8192
CK/8192
1
1
1
1
PCK/16384
CK/16384
The Stop condition provides a Timer Enable/Disable function.
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ATtiny261A/461A/861A
12.12.3
TCCR1C – Timer/Counter1 Control Register C
Bit
7
6
5
4
3
2
1
0
0x27 (0x47)
COM1A1S
COM1A0S
COM1B1S
COM1B0S
COM1D1
COM1D0
FOC1D
PWM1D
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
TCCR1C
• Bits 7,6 - COM1A1S, COM1A0S: Comparator A Output Mode, Shadow Bits 1 and 0
These are shadow bits of COM1A1 and COM1A0 in TCCR1A. Writing to bits COM1A1S and
COM1A0S will also change bits COM1A1 and COM1A0 in TCCR1A. Similary, changes written
to bits COM1A1 and COM1A0 in TCCR1A will show here.
See “TCCR1A – Timer/Counter1 Control Register A” on page 110 for information on bit usage.
• Bits 5,4 - COM1B1S, COM1B0S: Comparator B Output Mode, Shadow Bits 1 and 0
These are shadow bits of COM1B1 and COM1B0 in TCCR1A. Writing to bits COM1B1S and
COM1B0S will also change bits COM1B1 and COM1B0 in TCCR1A. Similary, changes written
to bits COM1B1 and COM1B0 in TCCR1A will show here.
See “TCCR1A – Timer/Counter1 Control Register A” on page 110 for information on bit usage.
• Bits 3,2 - COM1D1, COM1D0: Comparator D Output Mode, Bits 1 and 0
These bits control the behaviour of the Waveform Output (OCW1D) and the connection of the
Output Compare pin (OC1D). If one or both of the COM1D1:0 bits are set, the OC1D output
overrides the normal port functionality of the I/O pin it is connected to. The complementary
OC1D output is connected only in PWM modes when the COM1D1:0 bits are set to “01”. Note
that the Data Direction Register (DDR) bit corresponding to the OC1D pin must be set in order to
enable the output driver.
The function of the COM1D1:0 bits depends on the PWM1D and WGM11:10 bit settings. Table
12-18 shows the COM1D1:0 bit functionality when the PWM1D bit is set to a Normal Mode (nonPWM).
Table 12-18. Compare Output Mode, Normal Mode (non-PWM)
COM1D1:0
OCW1D Behaviour
OC1D Pin
OC1D Pin
00
Normal port operation.
Disconnected
Disconnected
01
Toggle on Compare Match.
Connected
Disconnected
10
Clear on Compare Match.
Connected
Disconnected
11
Set on Compare Match.
Connected
Disconnected
Table 12-19 shows the COM1D1:0 bit functionality when the PWM1D and WGM11:10 bits are
set to Fast PWM Mode.
Table 12-19. Compare Output Mode, Fast PWM Mode
COM1D1:0
OCW1D Behaviour
OC1D Pin
OC1D Pin
00
Normal port operation.
Disconnected
Disconnected
01
Cleared on Compare Match. Set when TCNT1=0x000.
Connected
Connected
10
Cleared on Compare Match. Set when TCNT1=0x000.
Connected
Disconnected
11
Set on Compare Match. Cleared when TCNT1=0x000.
Connected
Disconnected
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8197A–AVR–10/09
Table 12-20 shows the COM1D1:0 bit functionality when the PWM1D and WGM11:10 bits are
set to Phase and Frequency Correct PWM Mode.
Table 12-20. Compare Output Mode, Phase and Frequency Correct PWM Mode
COM1D1:0
OCW1D Behaviour
OC1D Pin
OC1D Pin
00
Normal port operation.
Disconnected
Disconnected
01
Cleared on Compare Match when up-counting.
Set on Compare Match when down-counting.
Connected
Connected
10
Cleared on Compare Match when up-counting.
Set on Compare Match when down-counting.
Connected
Disconnected
11
Set on Compare Match when up-counting.
Cleared on Compare Match when down-counting.
Connected
Disconnected
• Bit 1 - FOC1D: Force Output Compare Match 1D
The FOC1D bit is only active when the PWM1D bit specify a non-PWM mode.
Writing a logical one to this bit forces a change in the Waveform Output (OCW1D) and the Output Compare pin (OC1D) according to the values already set in COM1D1 and COM1D0. If
COM1D1 and COM1D0 written in the same cycle as FOC1D, the new settings will be used. The
Force Output Compare bit can be used to change the output pin value regardless of the timer
value. The automatic action programmed in COM1D1 and COM1D0 takes place as if a compare
match had occurred, but no interrupt is generated. The FOC1D bit is always read as zero.
• Bit 0 - PWM1D: Pulse Width Modulator D Enable
When set (one) this bit enables PWM mode based on comparator OCR1D.
12.12.4
TCCR1D – Timer/Counter1 Control Register D
Bit
7
6
5
4
3
2
1
0
0x26 (0x46)
FPIE1
FPEN1
FPNC1
FPES1
FPAC1
FPF1
WGM11
WGM10
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
TCCR1D
• Bit 7 - FPIE1: Fault Protection Interrupt Enable
Setting this bit (to one) enables the Fault Protection Interrupt.
• Bit 6– FPEN1: Fault Protection Mode Enable
Setting this bit (to one) activates the Fault Protection Mode.
• Bit 5 – FPNC1: Fault Protection Noise Canceler
Setting this bit activates the Fault Protection Noise Canceler. When the noise canceler is activated, the input from the Fault Protection Pin (INT0) is filtered. The filter function requires four
successive equal valued samples of the INT0 pin for changing its output. The Fault Protection is
therefore delayed by four Oscillator cycles when the noise canceler is enabled.
• Bit 4 – FPES1: Fault Protection Edge Select
This bit selects which edge on the Fault Protection pin (INT0) is used to trigger a fault event.
When the FPES1 bit is written to zero, a falling (negative) edge is used as trigger, and when the
FPES1 bit is written to one, a rising (positive) edge will trigger the fault.
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ATtiny261A/461A/861A
• Bit 3 - FPAC1: Fault Protection Analog Comparator Enable
When written logic one, this bit enables the Fault Protection function in Timer/Counter1 to be
triggered by the Analog Comparator. The comparator output is in this case directly connected to
the Fault Protection front-end logic, making the comparator utilize the noise canceler and edge
select features of the Timer/Counter1 Fault Protection interrupt. When written logic zero, no connection between the Analog Comparator and the Fault Protection function exists. To make the
comparator trigger the Timer/Counter1 Fault Protection interrupt, the FPIE1 bit in the
Timer/Counter1 Control Register D (TCCR1D) must be set.
• Bit 2- FPF1: Fault Protection Interrupt Flag
When the FPIE1 bit is set (one), the Fault Protection Interrupt is enabled. Activity on the pin will
cause an interrupt request even, if the Fault Protection pin is configured as an output. The corresponding interrupt of Fault Protection Interrupt Request is executed from the Fault Protection
Interrupt Vector. The bit FPF1 is cleared by hardware when executing the corresponding interrupt handling vector. Alternatively, FPF1 is cleared after a synchronization clock cycle by writing
a logical one to the flag. When the SREG I-bit, FPIE1 and FPF1 are set, the Fault Interrupt is
executed.
• Bits 1:0 - WGM11, WGM10: Waveform Generation Mode Bits
These bits together with the PWM1A/PWM1B bits control the counting sequence of the counter
and the type of waveform generation to be used, as shown in Table 12-21. Modes of operation
supported by the Timer/Counter1 are: Normal mode (counter), Fast PWM Mode, Phase and Frequency Correct PWM and PWM6 Modes.
Table 12-21. Waveform Generation Mode Bit Description
12.12.5
PWM1A/
PWM1B
WGM11:10
Timer/Counter
Mode of Operation
TOP
Update
OCR1x at
Set TOV1
Flag at
0
XX
Normal
OCR1C
Immediate
TOP
1
00
Fast PWM
OCR1C
TOP
TOP
1
01
Phase & Frequency Correct PWM
OCR1C
BOTTOM
BOTTOM
1
10
PWM6 / Single-slope
OCR1C
TOP
TOP
1
11
PWM6 / Dual-slope
OCR1C
BOTTOM
BOTTOM
TCCR1E – Timer/Counter1 Control Register E
Bit
7
6
5
4
3
2
1
0
0x00 (0x20)
-
-
OC1OE5
OC1OE4
OC1OE3
OC1OE2
OC1OE1
OC1OE0
Read/Write
R
R
R/W
R/W
R/W
R/W
R/W
R/W
Initial value
0
0
0
0
0
0
0
0
TCCR1E
• Bits 7:6 - Res: Reserved Bits
These bits are reserved and always read zero.
• Bits 5:0 – OC1OE5:OC1OE0: Output Compare Override Enable Bits
These bits are the Ouput Compare Override Enable bits that are used to connect or disconnect
the Output Compare Pins in PWM6 Modes with an instant response on the corresponding Output Compare Pins. The actual value from the port register will be visible on the port pin, when
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the Output Compare Override Enable Bit is cleared. Table 12-22 shows the Output Compare
Override Enable Bits and their corresponding Output Compare pins.
Table 12-22. Output Compare Override Enable Bits vs. Output Compare Pins
12.12.6
Output CompareOverride Enable Bit
Output Compare Output
Output Compare Pin
OC1OE0
OC1A
PB0
OC1OE1
OC1A
PB1
OC1OE2
OC1B
PB2
OC1OE3
OC1B
PB3
OC1OE4
OC1D
PB4
OC1OE5
OC1D
PB5
PLLCSR – PLL Control and Status Register
Bit
7
6
5
4
3
2
1
0x29 (0x49)
LSM
-
-
-
-
PCKE
PLLE
0
PLOCK
Read/Write
R/W
R
R
R
R
R/W
R/W
R
Initial value
0
0
0
0
0
0
0/1
0
PLLCSR
• Bit 7- LSM: Low Speed Mode
The Low Speed mode is set, if the LSM bit is written to one. Then the fast peripheral clock is
scaled down to 32 MHz. The Low Speed Mode must be set, if the supply voltage is below 2.7
volts, because the Timer/Counter1 is not running fast enough on low voltage levels. It is recommended that the Timer/Counter1 is stopped whenever the LSM bit is changed.
Note, that LSM can not be set if PLLCLK is used as a system clock.
• Bit 6:3- Res : Reserved Bits
These bits are reserved and always read zero.
• Bit 2- PCKE: PCK Enable
The PCKE bit change the Timer/Counter1 clock source. When it is set, the asynchronous clock
mode is enabled and fast 64 MHz (or 32 MHz in Low Speed Mode) PCK clock is used as a
Timer/Counter1 clock source. If this bit is cleared, the synchronous clock mode is enabled, and
system clock CK is used as Timer/Counter1 clock source. It is safe to set this bit only when the
PLL is locked i.e the PLOCK bit is 1. Note that the PCKE bit can be set only, if the PLL has been
enabled earlier. The PLL is enabled when the CKSEL fuse has been programmed to 0x0001
(the PLL clock mode is selected) or the PLLE bit has been set to one.
• Bit 1- PLLE: PLL Enable
When the PLLE is set, the PLL is started and if needed internal oscillator is started as a 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. The PLOCK bit should be
ignored during initial PLL lock-in sequence when PLL frequency overshoots and undershoots,
before reaching steady state. The steady state is obtained within 100 µs. After PLL lock-in it is
recommended to check the PLOCK bit before enabling PCK for Timer/Counter1.
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12.12.7
TCNT1 – Timer/Counter1
Bit
7
6
5
4
3
2
1
0
0x2E (0x4E)
MSB
LSB
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
TCNT1
This 8-bit register contains the value of Timer/Counter1.
The Timer/Counter1 is realized as a 10-bit up/down counter with read and write access. Due to
synchronization of the CPU, Timer/Counter1 data written into Timer/Counter1 is delayed by one
and half CPU clock cycles in synchronous mode and at most one CPU clock cycles for asynchronous mode. When a 10-bit accuracy is preferred, special procedures must be followed for
accessing the 10-bit TCNT1 register via the 8-bit AVR data bus. These procedures are
described in section “Accessing 10-Bit Registers” on page 106. Alternatively the Timer/Counter1
can be used as an 8-bit Timer/Counter. Note that the Timer/Counter1 always starts counting up
after writing the TCNT1 register.
12.12.8
TC1H – Timer/Counter1 High Byte
Bit
7
6
5
4
3
2
1
0
0x25 (0x45)
-
-
-
-
-
-
TC19
TC18
Read/Write
R
R
R
R
R
R
R/W
R/W
Initial value
0
0
0
0
0
0
0
0
TC1H
The temporary Timer/Counter1 register is an 2-bit read/write register.
• Bits 7:2 - Res: Reserved Bits
These bits are reserved and always reads zero.
• Bits 1:0 - TC19, TC18: Two MSB bits of the 10-bit accesses
If 10-bit accuracy is used, the Timer/Counter1 High Byte Register (TC1H) is used for temporary
storing the MSB bits (TC19, TC18) of the 10-bit acceses. The same TC1H register is shared
between all 10-bit registers within the Timer/Counter1. Note that special procedures must be followed when accessing the 10-bit TCNT1 register via the 8-bit AVR data bus. These procedures
are described in section “Accessing 10-Bit Registers” on page 106.
12.12.9
OCR1A – Timer/Counter1 Output Compare Register A
Bit
7
6
5
4
3
2
1
0
0x2D (0x4D)
MSB
LSB
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
OCR1A
The output compare register A is an 8-bit read/write register.
The Timer/Counter Output Compare Register A contains data to be continuously compared with
Timer/Counter1. Actions on compare matches are specified in TCCR1A. A compare match does
only occur if Timer/Counter1 counts to the OCR1A value. A software write that sets TCNT1 and
OCR1A to the same value does not generate a compare match.
A compare match will set the compare interrupt flag OCF1A after a synchronization delay following the compare event.
Note that, if 10-bit accuracy is used special procedures must be followed when accessing the
internal 10-bit Ouput Compare Registers via the 8-bit AVR data bus. These procedures are
described in section “Accessing 10-Bit Registers” on page 106.
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12.12.10 OCR1B – Timer/Counter1 Output Compare Register B
Bit
7
6
5
4
3
2
1
0
0x2C (0x4C)
MSB
LSB
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
OCR1B
The output compare register B is an 8-bit read/write register.
The Timer/Counter Output Compare Register B contains data to be continuously compared with
Timer/Counter1. Actions on compare matches are specified in TCCR1. A compare match does
only occur if Timer/Counter1 counts to the OCR1B value. A software write that sets TCNT1 and
OCR1B to the same value does not generate a compare match.
A compare match will set the compare interrupt flag OCF1B after a synchronization delay following the compare event.
Note that, if 10-bit accuracy is used special procedures must be followed when accessing the
internal 10-bit Output Compare Registers via the 8-bit AVR data bus. These procedures are
described in section “Accessing 10-Bit Registers” on page 106.
12.12.11 OCR1C – Timer/Counter1 Output Compare Register C
Bit
7
6
5
4
3
2
1
0
0x2B (0x4B)
MSB
LSB
Read/Write
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
Initial value
1
1
1
1
1
1
1
1
OCR1C
The output compare register C is an 8-bit read/write register.
The Timer/Counter Output Compare Register C contains data to be continuously compared with
Timer/Counter1, and a compare match will clear TCNT1. This register has the same function in
Normal mode and PWM modes.
Note that, if a smaller value than three is written to the Output Compare Register C, the value is
automatically replaced by three as it is a minumum value allowed to be written to this register.
Note that, if 10-bit accuracy is used special procedures must be followed when accessing the
internal 10-bit Output Compare Registers via the 8-bit AVR data bus. These procedures are
described in section “Accessing 10-Bit Registers” on page 106.
12.12.12 OCR1D – Timer/Counter1 Output Compare Register D
Bit
7
6
5
4
3
2
1
0
0x2A (0x4A)
MSB
LSB
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
OCR1D
The output compare register D is an 8-bit read/write register.
The Timer/Counter Output Compare Register D contains data to be continuously compared with
Timer/Counter1. Actions on compare matches are specified in TCCR1A. A compare match does
only occur if Timer/Counter1 counts to the OCR1D value. A software write that sets TCNT1 and
OCR1D to the same value does not generate a compare match.
A compare match will set the compare interrupt flag OCF1D after a synchronization delay following the compare event.
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Note that, if 10-bit accuracy is used special procedures must be followed when accessing the
internal 10-bit Output Compare Registers via the 8-bit AVR data bus. These procedures are
described in section “Accessing 10-Bit Registers” on page 106.
12.12.13 TIMSK – Timer/Counter1 Interrupt Mask Register
Bit
7
6
5
4
3
2
1
0
0x39 (0x59)
OCIE1D
OCIE1A
OCIE1B
OCIE0A
OCIE0B
TOIE1
TOIE0
TICIE0
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
TIMSK
• Bit 7- OCIE1D: Timer/Counter1 Output Compare Interrupt Enable
When the OCIE1D bit is set (one) and the I-bit in the Status Register is set (one), the
Timer/Counter1 Compare MatchD, interrupt is enabled. The corresponding interrupt at vector
$010 is executed if a compare matchD occurs. The Compare Flag in Timer/Counter1 is set (one)
in the Timer/Counter Interrupt Flag Register.
• Bit 6 - OCIE1A: Timer/Counter1 Output Compare Interrupt Enable
When the OCIE1A bit is set (one) and the I-bit in the Status Register is set (one), the
Timer/Counter1 Compare MatchA, interrupt is enabled. The corresponding interrupt at vector
$003 is executed if a compare matchA occurs. The Compare Flag in Timer/Counter1 is set (one)
in the Timer/Counter Interrupt Flag Register.
• Bit 5 - OCIE1B: Timer/Counter1 Output Compare Interrupt Enable
When the OCIE1B bit is set (one) and the I-bit in the Status Register is set (one), the
Timer/Counter1 Compare MatchB, interrupt is enabled. The corresponding interrupt at vector
$009 is executed if a compare matchB occurs. The Compare Flag in Timer/Counter1 is set (one)
in the Timer/Counter Interrupt Flag Register.
• Bit 2 - TOIE1: Timer/Counter1 Overflow Interrupt Enable
When the TOIE1 bit is set (one) and the I-bit in the Status Register is set (one), the
Timer/Counter1 Overflow interrupt is enabled. The corresponding interrupt (at vector $004) is
executed if an overflow in Timer/Counter1 occurs. The Overflow Flag (Timer1) is set (one) in the
Timer/Counter Interrupt Flag Register - TIFR.
12.12.14 TIFR – Timer/Counter1 Interrupt Flag Register
Bit
7
6
5
4
3
2
1
0
0x38 (0x58)
OCF1D
OCF1A
OCF1B
OCF0A
OCF0B
TOV1
TOV0
ICF0
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
TIFR
• Bit 7- OCF1D: Output Compare Flag 1D
The OCF1D bit is set (one) when compare match occurs between Timer/Counter1 and the data
value in OCR1D - Output Compare Register 1D. OCF1D is cleared by hardware when executing
the corresponding interrupt handling vector. Alternatively, OCF1D is cleared, after synchronization clock cycle, by writing a logic one to the flag. When the I-bit in SREG, OCIE1D, and OCF1D
are set (one), the Timer/Counter1 D compare match interrupt is executed.
• Bit 6 - OCF1A: Output Compare Flag 1A
The OCF1A bit is set (one) when compare match occurs between Timer/Counter1 and the data
value in OCR1A - Output Compare Register 1A. OCF1A is cleared by hardware when executing
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the corresponding interrupt handling vector. Alternatively, OCF1A is cleared, after synchronization clock cycle, by writing a logic one to the flag. When the I-bit in SREG, OCIE1A, and OCF1A
are set (one), the Timer/Counter1 A compare match interrupt is executed.
• Bit 5 - OCF1B: Output Compare Flag 1B
The OCF1B bit is set (one) when compare match occurs between Timer/Counter1 and the data
value in OCR1B - Output Compare Register 1A. OCF1B is cleared by hardware when executing
the corresponding interrupt handling vector. Alternatively, OCF1B is cleared, after synchronization clock cycle, by writing a logic one to the flag. When the I-bit in SREG, OCIE1B, and OCF1B
are set (one), the Timer/Counter1 B compare match interrupt is executed.
• Bit 2 - TOV1: Timer/Counter1 Overflow Flag
In Normal Mode and Fast PWM Mode the TOV1 bit is set (one) each time the counter reaches
TOP at the same clock cycle when the counter is reset to BOTTOM. In Phase and Frequency
Correct PWM Mode the TOV1 bit is set (one) each time the counter reaches BOTTOM at the
same clock cycle when zero is clocked to the counter.
The bit TOV1 is cleared by hardware when executing the corresponding interrupt handling vector. Alternatively, TOV1 is cleared, after synchronization clock cycle, by writing a logical one to
the flag. When the SREG I-bit, and TOIE1 (Timer/Counter1 Overflow Interrupt Enable), and
TOV1 are set (one), the Timer/Counter1 Overflow interrupt is executed.
12.12.15 DT1 – Timer/Counter1 Dead Time Value
Bit
7
6
5
4
3
2
1
0
0x24 (0x44)
DT1H3
DT1H2
DT1H1
DT1H0
DT1L3
DT1L2
DT1L1
DT1L0
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
DT1
The dead time value register is an 8-bit read/write register.
The dead time delay of all Timer/Counter1 channels are adjusted by the dead time value register, DT1. The register consists of two fields, DT1H3:0 and DT1L3:0, one for each
complementary output. Therefore a different dead time delay can be adjusted for the rising edge
of OC1x and the rising edge of OC1x.
• Bits 7:4- DT1H3:DT1H0: Dead Time Value for OC1x Output
The dead time value for the OC1x output. The dead time delay is set as a number of the prescaled timer/counter clocks. The minimum dead time is zero and the maximum dead time is the
prescaled time/counter clock period multiplied by 15.
• Bits 3:0- DT1L3:DT1L0: Dead Time Value for OC1x Output
The dead time value for the OC1x output. The dead time delay is set as a number of the prescaled timer/counter clocks. The minimum dead time is zero and the maximum dead time is the
prescaled time/counter clock period multiplied by 15.
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13. USI – Universal Serial Interface
13.1
Features
•
•
•
•
•
•
13.2
Two-wire Synchronous Data Transfer (Master or Slave)
Three-wire Synchronous Data Transfer (Master or Slave)
Data Received Interrupt
Wakeup from Idle Mode
In Two-wire Mode: Wake-up from All Sleep Modes, Including Power-down Mode
Two-wire Start Condition Detector with Interrupt Capability
Overview
The Universal Serial Interface, or USI, provides the basic hardware resources needed for serial
communication. Combined with a minimum of control software, the USI allows significantly
higher transfer rates and uses less code space than solutions based on software only. Interrupts
are included to minimize the processor load.
A simplified block diagram of the USI is shown in Figure 13-1 For actual placement of I/O pins
refer to “Pinout ATtiny261A/461A/861A” on page 2. Device-specific I/O Register and bit locations are listed in the “Register Descriptions” on page 130.
Figure 13-1. Universal Serial Interface, Block Diagram
Bit7
Bit0
D Q
LE
DO
(Output only)
DI/SDA
(Input/Open Drain)
USCK/SCL
(Input/Open Drain)
3
2
USIDR
1
0
TIM0 COMP
USIPF
4-bit Counter
USIDC
USISIF
USIOIF
DATA BUS
USIDB
3
2
0
1
1
0
CLOCK
HOLD
[1]
Two-wire Clock
Control Unit
USISR
USITC
USICLK
USICS0
USICS1
USIWM0
USIWM1
USISIE
USIOIE
2
USICR
The 8-bit USI Data Register (USIDR) is directly accessible via the data bus and contains the
incoming and outgoing data. The register has no buffering so the data must be read as quickly
as possible to ensure that no data is lost. The data register is a serial shift register where the
most significant bit is connected to one of two output pins depending of the wire mode configuration. A transparent latch between the output of the data register and the output pin delays the
change of data output to the opposite clock edge of the data input sampling. The serial input is
always sampled from the Data Input (DI) pin, regardless of the configuration.
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The 4-bit counter can be both read and written via the data bus, and it can generate an overflow
interrupt. The data register and the counter are clocked simultaneously by the same clock
source, allowing the counter to count the number of bits received or transmitted and generate an
interrupt when the transfer is complete. Note that when an external clock source is selected the
counter counts both clock edges. In this case the counter counts the number of edges, and not
the number of bits. The clock can be selected from three different sources: The USCK pin, the
Timer/Counter0 Compare Match or from software.
The Two-wire clock control unit can generate an interrupt when a start condition is detected on
the Two-wire bus. It can also generate wait states by holding the clock pin low after a start condition is detected, or after the counter overflows.
13.3
13.3.1
Functional Descriptions
Three-wire Mode
The USI Three-wire mode is compliant to the Serial Peripheral Interface (SPI) mode 0 and 1, but
does not have the slave select (SS) pin functionality. However, this feature can be implemented
in software if necessary. Pin names used by this mode are: DI, DO, and USCK.
Figure 13-2. Three-wire Mode Operation, Simplified Diagram
DO
Bit7
Bit6
Bit5
Bit4
Bit3
Bit2
Bit1
DI
Bit0
USCK
SLAVE
DO
Bit7
Bit6
Bit5
Bit4
Bit3
Bit2
Bit1
DI
Bit0
USCK
PORTxn
MASTER
Figure 13-2 shows two USI units operating in three-wire mode, one as Master and one as Slave.
The two USI Data Register are interconnected in such way that after eight USCK clocks, the
data in each register are interchanged. The same clock also increments the USI’s 4-bit counter.
The Counter Overflow (interrupt) Flag, or USIOIF, can therefore be used to determine when a
transfer is completed. The clock is generated by the Master device software by toggling the
USCK pin via the PORT Register or by writing a one to the USITC bit in USICR.
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Figure 13-3. Three-wire Mode, Timing Diagram
CYCLE
( Reference )
1
2
3
4
5
6
7
8
USCK
USCK
DO
MSB
DI
MSB
A
B
C
6
5
4
3
2
1
LSB
6
5
4
3
2
1
LSB
D
E
The Three-wire mode timing is shown in Figure 13-3. At the top of the figure is a USCK cycle reference. One bit is shifted into the USI Data Register (USIDR) for each of these cycles. The
USCK timing is shown for both external clock modes. In External Clock mode 0 (USICS0 = 0), DI
is sampled at positive edges, and DO is changed (Data Register is shifted by one) at negative
edges. In external clock mode 1 (USICS0 = 1) the opposite edges with respect to mode 0 are
used. In other words, data is sampled at negative and output is changed at positive edges. The
USI clock modes corresponds to the SPI data mode 0 and 1.
Referring to the timing diagram (Figure 13-3), a bus transfer involves the following steps:
1. The slave and master devices set up their data outputs and, depending on the protocol
used, enable their output drivers (mark A and B). The output is set up by writing the
data to be transmitted to the USI Data Register. The output is enabled by setting the
corresponding bit in the Data Direction Register of Port A. Note that there is not a preferred order of points A and B in the figure, but both must be at least one half USCK
cycle before point C, where the data is sampled. This is in order to ensure that the data
setup requirement is satisfied. The 4-bit counter is reset to zero.
2. The master software generates a clock pulse by toggling the USCK line twice (C and
D). The bit values on the data input (DI) pins are sampled by the USI on the first edge
(C), and the data output is changed on the opposite edge (D). The 4-bit counter will
count both edges.
3. Step 2. is repeated eight times for a complete register (byte) transfer.
4. After eight clock pulses (i.e., 16 clock edges) the counter will overflow and indicate that
the transfer has been completed. The data bytes transferred must now be processed
before a new transfer can be initiated. The overflow interrupt will wake up the processor
if it is set to Idle mode. Depending on the protocol used the slave device can now set its
output to high impedance.
13.3.2
SPI Master Operation Example
The following code demonstrates how to use the USI module as a SPI Master:
SPITransfer:
sts
USIDR,r16
ldi
r16,(1<<USIOIF)
sts
USISR,r16
ldi
r16,(1<<USIWM0)|(1<<USICS1)|(1<<USICLK)|(1<<USITC)
SPITransfer_loop:
sts
USICR,r16
lds
r16, USISR
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sbrs
r16, USIOIF
rjmp
SPITransfer_loop
lds
r16,USIDR
ret
The code is size optimized using only eight instructions (plus return). The code example
assumes that the DO and USCK pins have been enabled as outputs in DDRA. The value stored
in register r16 prior to the function is called is transferred to the slave device, and when the
transfer is completed the data received from the slave is stored back into the register r16.
The second and third instructions clear the USI Counter Overflow Flag and the USI counter
value. The fourth and fifth instructions set three-wire mode, positive edge clock, count at USITC
strobe, and toggle USCK. The loop is repeated 16 times.
The following code demonstrates how to use the USI as an SPI master with maximum speed
(fSCK = fCK/2):
SPITransfer_Fast:
out
USIDR,r16
ldi
r16,(1<<USIWM0)|(0<<USICS0)|(1<<USITC)
ldi
r17,(1<<USIWM0)|(0<<USICS0)|(1<<USITC)|(1<<USICLK)
out
USICR,r16 ; MSB
out
USICR,r17
out
USICR,r16
out
USICR,r17
out
USICR,r16
out
USICR,r17
out
USICR,r16
out
USICR,r17
out
USICR,r16
out
USICR,r17
out
USICR,r16
out
USICR,r17
out
USICR,r16
out
USICR,r17
out
USICR,r16 ; LSB
out
USICR,r17
in
r16,USIDR
ret
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13.3.3
SPI Slave Operation Example
The following code demonstrates how to use the USI module as a SPI Slave:
init:
ldi
r16,(1<<USIWM0)|(1<<USICS1)
sts
USICR,r16
...
SlaveSPITransfer:
sts
USIDR,r16
ldi
r16,(1<<USIOIF)
sts
USISR,r16
SlaveSPITransfer_loop:
lds
r16, USISR
sbrs
r16, USIOIF
rjmp
SlaveSPITransfer_loop
lds
r16,USIDR
ret
The code is size optimized using only eight instructions (+ ret). The code example assumes that
the DO is configured as output and USCK pin is configured as input in the DDR Register. The
value stored in register r16 prior to the function is called is transferred to the master device, and
when the transfer is completed the data received from the Master is stored back into the r16
Register.
Note that the first two instructions are for initialization, only, and need only be executed once.
These instructions set three-wire mode and positive edge clock. The loop is repeated until the
USI Counter Overflow Flag is set.
13.3.4
Two-wire Mode
The USI Two-wire mode is compliant to the Inter IC (TWI) bus protocol, but without slew rate limiting on outputs and input noise filtering. Pin names used by this mode are SCL and SDA.
Figure 13-4 on page 128 shows two USI units operating in two-wire mode, one as master and
one as slave. It is only the physical layer that is shown since the system operation is highly
dependent of the communication scheme used. The main differences between the master and
slave operation at this level is the serial clock generation which is always done by the master.
Only the slave uses the clock control unit.
Clock generation must be implemented in software, but the shift operation is done automatically
in both devices. Note that clocking only on negative edges for shifting data is of practical use in
this mode. The slave can insert wait states at start or end of transfer by forcing the SCL clock
low. This means that the master must always check if the SCL line was actually released after it
has generated a positive edge.
Since the clock also increments the counter, a counter overflow can be used to indicate that the
transfer is completed. The clock is generated by the master by toggling the USCK pin via the
PORTA register.
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Figure 13-4. Two-wire Mode Operation, Simplified Diagram
VCC
Bit7
Bit6
Bit5
Bit4
Bit3
Bit2
Bit1
SDA
Bit0
SCL
HOLD
SCL
Two-wire Clock
Control Unit
SLAVE
Bit7
Bit6
Bit5
Bit4
Bit3
Bit2
Bit1
SDA
Bit0
SCL
PORTxn
MASTER
The data direction is not given by the physical layer. A protocol, like the one used by the TWIbus, must be implemented to control the data flow.
Figure 13-5. Two-wire Mode, Typical Timing Diagram
SDA
SCL
S
A
B
1-7
8
9
1-8
9
1-8
9
ADDRESS
R/W
ACK
DATA
ACK
DATA
ACK
C
D
E
P
F
Referring to the timing diagram (Figure 13-5), a bus transfer involves the following steps:
1. The start condition is generated by the master by forcing the SDA low line while keeping the SCL line high (A). SDA can be forced low either by writing a zero to bit 7 of the
USI Data Register, or by setting the corresponding bit in the PORTA register to zero.
Note that the Data Direction Register bit must be set to one for the output to be
enabled. The start detector logic of the slave device (see Figure 13-6 on page 129)
detects the start condition and sets the USISIF Flag. The flag can generate an interrupt
if necessary.
2. In addition, the start detector will hold the SCL line low after the master has forced a
negative edge on this line (B). This allows the slave to wake up from sleep or complete
other tasks before setting up the USI Data Register to receive the address. This is done
by clearing the start condition flag and resetting the counter.
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3. The master set the first bit to be transferred and releases the SCL line (C). The slave
samples the data and shifts it into the USI Data Register at the positive edge of the SCL
clock.
4. After eight bits containing slave address and data direction (read or write) have been
transferred, the slave counter overflows and the SCL line is forced low (D). If the slave
is not the one the master has addressed, it releases the SCL line and waits for a new
start condition.
5. When the slave is addressed, it holds the SDA line low during the acknowledgment
cycle before holding the SCL line low again (i.e., the USI Counter Register must be set
to 14 before releasing SCL at (D)). Depending on the R/W bit the master or slave
enables its output. If the bit is set, a master read operation is in progress (i.e., the slave
drives the SDA line) The slave can hold the SCL line low after the acknowledge (E).
6. Multiple bytes can now be transmitted, all in same direction, until a stop condition is
given by the master (F), or a new start condition is given.
If the slave is not able to receive more data it does not acknowledge the data byte it has last
received. When the master does a read operation it must terminate the operation by forcing the
acknowledge bit low after the last byte transmitted.
13.3.5
Start Condition Detector
The start condition detector is shown in Figure 13-6. The SDA line is delayed (in the range of 50
to 300 ns) to ensure valid sampling of the SCL line. The start condition detector is only enabled
in Two-wire mode.
Figure 13-6. Start Condition Detector, Logic Diagram
USISIF
D Q
D Q
CLR
CLR
SDA
CLOCK
HOLD
SCL
Write( USISIF)
The start condition detector works asynchronously and can therefore wake up the processor
from power-down sleep mode. However, the protocol used might have restrictions on the SCL
hold time. Therefore, when using this feature in this case the Oscillator start-up time set by the
CKSEL Fuses (see “Clock System” on page 24) must also be taken into the consideration. Refer
to the USISIF bit description on page 131 for further details.
13.3.6
13.4
Clock speed considerations
Maximum frequency for SCL and SCK is fCK / 2. This is also the maximum data transmit and
receive rate in both two- and three-wire mode. In two-wire slave mode the Two-wire Clock Control Unit will hold the SCL low until the slave is ready to receive more data. This may reduce the
actual data rate in two-wire mode.
Alternative USI Usage
The flexible design of the USI allows it to be used for other tasks when serial communication is
not needed. Below are some examples.
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13.4.1
Half-Duplex Asynchronous Data Transfer
Using the USI Data Register in three-wire mode it is possible to implement a more compact and
higher performance UART than by software, only.
13.4.2
4-Bit Counter
The 4-bit counter can be used as a stand-alone counter with overflow interrupt. Note that if the
counter is clocked externally, both clock edges will increment the counter value.
13.4.3
12-Bit Timer/Counter
Combining the 4-bit USI counter with one of the 8-bit timer/counters creates a 12-bit counter.
13.4.4
Edge Triggered External Interrupt
By setting the counter to maximum value (F) it can function as an additional external interrupt.
The Overflow Flag and Interrupt Enable bit are then used for the external interrupt. This feature
is selected by the USICS1 bit.
13.4.5
Software Interrupt
The counter overflow interrupt can be used as a software interrupt triggered by a clock strobe.
13.5
13.5.1
Register Descriptions
USIDR – USI Data Register
Bit
7
0x0F (0x2F)
MSB
6
5
4
3
2
1
0
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
LSB
USIDR
The USI Data Register can be accessed directly.
Depending on the USICS1:0 bits of the USI Control Register a (left) shift operation may be performed. The shift operation can be synchronised to an external clock edge, to a Timer/Counter0
Compare Match, or directly to software via the USICLK bit. If a serial clock occurs at the same
cycle the register is written, the register will contain the value written and no shift is performed.
Note that even when no wire mode is selected (USIWM1:0 = 0) both the external data input
(DI/SDA) and the external clock input (USCK/SCL) can still be used by the USI Data Register.
The output pin (DO or SDA, depending on the wire mode) is connected via the output latch to
the most significant bit (bit 7) of the USI Data Register. The output latch ensures that data input
is sampled and data output is changed on opposite clock edges. The latch is open (transparent)
during the first half of a serial clock cycle when an external clock source is selected (USICS1 =
1) and constantly open when an internal clock source is used (USICS1 = 0). The output will be
changed immediately when a new MSB is written as long as the latch is open.
Note that the Data Direction Register bit corresponding to the output pin must be set to one in
order to enable data output from the USI Data Register.
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ATtiny261A/461A/861A
13.5.2
USIBR – USI Buffer Register
Bit
7
0x10 (0x30)
MSB
6
5
4
3
2
1
0
Read/Write
R
R
R
R
R
R
R
R
Initial Value
0
0
0
0
0
0
0
0
LSB
USIBR
The content of the Serial Register is loaded to the USI Buffer Register when the trasfer is completed, and instead of accessing the USI Data Register (the Serial Register) the USI Data Buffer
can be accessed when the CPU reads the received data. This gives the CPU time to handle
other program tasks too as the controlling of the USI is not so timing critical. The USI flags as set
same as when reading the USIDR register.
13.5.3
USISR – USI Status Register
Bit
7
6
5
4
3
2
1
0x0E (0x2E)
USISIF
USIOIF
USIPF
USIDC
USICNT3
USICNT2
USICNT1
0
USICNT0
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
USISR
The Status Register contains Interrupt Flags, line Status Flags and the counter value.
• Bit 7 – USISIF: Start Condition Interrupt Flag
When Two-wire mode is selected, the USISIF Flag is set (to one) when a start condition is
detected. When output disable mode or Three-wire mode is selected and (USICSx = 0b11 &
USICLK = 0) or (USICS = 0b10 & USICLK = 0), any edge on the SCK pin sets the flag.
An interrupt will be generated when the flag is set while the USISIE bit in USICR and the Global
Interrupt Enable Flag are set. The flag will only be cleared by writing a logical one to the USISIF
bit. Clearing this bit will release the start detection hold of USCL in Two-wire mode.
A start condition interrupt will wakeup the processor from all sleep modes.
• Bit 6 – USIOIF: Counter Overflow Interrupt Flag
This flag is set (one) when the 4-bit counter overflows (i.e., at the transition from 15 to 0). An
interrupt will be generated when the flag is set while the USIOIE bit in USICR and the Global
Interrupt Enable Flag are set. The flag will only be cleared if a one is written to the USIOIF bit.
Clearing this bit will release the counter overflow hold of SCL in Two-wire mode.
A counter overflow interrupt will wakeup the processor from Idle sleep mode.
• Bit 5 – USIPF: Stop Condition Flag
When Two-wire mode is selected, the USIPF Flag is set (one) when a stop condition is detected.
The flag is cleared by writing a one to this bit. Note that this is not an Interrupt Flag. This signal is
useful when implementing Two-wire bus master arbitration.
• Bit 4 – USIDC: Data Output Collision
This bit is logical one when bit 7 in the USI Data Register differs from the physical pin value. The
flag is only valid when Two-wire mode is used. This signal is useful when implementing Twowire bus master arbitration.
• Bits 3:0 – USICNT3:0: Counter Value
These bits reflect the current 4-bit counter value. The 4-bit counter value can directly be read or
written by the CPU.
131
8197A–AVR–10/09
The 4-bit counter increments by one for each clock generated either by the external clock edge
detector, by a Timer/Counter0 Compare Match, or by software using USICLK or USITC strobe
bits. The clock source depends of the setting of the USICS1:0 bits. For external clock operation
a special feature is added that allows the clock to be generated by writing to the USITC strobe
bit. This feature is enabled by write a one to the USICLK bit while setting an external clock
source (USICS1 = 1).
Note that even when no wire mode is selected (USIWM1:0 = 0) the external clock input
(USCK/SCL) are can still be used by the counter.
13.5.4
USICR – USI Control Register
Bit
7
6
5
4
3
2
1
0
0x0D (0x2D)
USISIE
USIOIE
USIWM1
USIWM0
USICS1
USICS0
USICLK
USITC
Read/Write
R/W
R/W
R/W
R/W
R/W
R/W
W
W
Initial Value
0
0
0
0
0
0
0
0
USICR
The Control Register includes interrupt enable control, wire mode setting, Clock Select setting,
and clock strobe.
• Bit 7 – USISIE: Start Condition Interrupt Enable
Setting this bit to one enables the Start Condition detector interrupt. If there is a pending interrupt when the USISIE and the Global Interrupt Enable Flag is set to one, this will immediately be
executed. Refer to the USISIF bit description on page 131 for further details.
• Bit 6 – USIOIE: Counter Overflow Interrupt Enable
Setting this bit to one enables the Counter Overflow interrupt. If there is a pending interrupt when
the USIOIE and the Global Interrupt Enable Flag is set to one, this will immediately be executed.
Refer to the USIOIF bit description on page 131 for further details.
• Bit 5:4 – USIWM1:0: Wire Mode
These bits set the type of wire mode to be used, as shown in Table 13-1 on page 132.
Basically, only the function of the outputs are affected by these bits. Data and clock inputs are
not affected by the mode selected and will always have the same function. The counter and USI
Data Register can therefore be clocked externally, and data input sampled, even when outputs
are disabled.
Table 13-1.
USIWM1
USIWM0
0
0
Outputs, clock hold, and start detector disabled.
Port pins operate as normal.
1
Three-wire mode. Uses DO, DI, and USCK pins.
The Data Output (DO) pin overrides the corresponding bit in the PORTA
register. However, the corresponding DDRA bit still controls the data direction.
When the port pin is set as input the pin pull-up is controlled by the PORTA bit.
The Data Input (DI) and Serial Clock (USCK) pins do not affect the normal port
operation. When operating as master, clock pulses are software generated by
toggling the PORTA register, while the data direction is set to output. The
USITC bit in the USICR Register can be used for this purpose.
0
132
Relationship between USIWM1:0 and USI Operation
Description
ATtiny261A/461A/861A
8197A–AVR–10/09
ATtiny261A/461A/861A
Table 13-1.
USIWM1
1
1
Note:
Relationship between USIWM1:0 and USI Operation (Continued)
USIWM0
Description
0
Two-wire mode. Uses SDA (DI) and SCL (USCK) pins (1).
The Serial Data (SDA) and the Serial Clock (SCL) pins are bi-directional and
use open-collector output drives. The output drivers are enabled by setting the
corresponding bit for SDA and SCL in the DDRA register.
When the output driver is enabled for the SDA pin, the output driver will force
the line SDA low if the output of the USI Data Register or the corresponding
bit in the PORTA register is zero. Otherwise, the SDA line will not be driven (i.e.,
it is released). When the SCL pin output driver is enabled the SCL line will be
forced low if the corresponding bit in the PORTA register is zero, or by the start
detector. Otherwise the SCL line will not be driven.
The SCL line is held low when a start detector detects a start condition and the
output is enabled. Clearing the Start Condition Flag (USISIF) releases the line.
The SDA and SCL pin inputs is not affected by enabling this mode. Pull-ups on
the SDA and SCL port pin are disabled in Two-wire mode.
1
Two-wire mode. Uses SDA and SCL pins.
Same operation as in two-wire mode above, except that the SCL line is also
held low when a counter overflow occurs, and until the Counter Overflow Flag
(USIOIF) is cleared.
1. The DI and USCK pins are renamed to Serial Data (SDA) and Serial Clock (SCL) respectively
to avoid confusion between the modes of operation.
• Bit 3:2 – USICS1:0: Clock Source Select
These bits set the clock source for the USI Data Registerr and counter. The data output latch
ensures that the output is changed at the opposite edge of the sampling of the data input
(DI/SDA) when using external clock source (USCK/SCL). When software strobe or
Timer/Counter0 Compare Match clock option is selected, the output latch is transparent and
therefore the output is changed immediately. Clearing the USICS1:0 bits enables software
strobe option. When using this option, writing a one to the USICLK bit clocks both the USI Data
Register and the counter. For external clock source (USICS1 = 1), the USICLK bit is no longer
used as a strobe, but selects between external clocking and software clocking by the USITC
strobe bit.
Table 13-2 on page 133 shows the relationship between the USICS1:0 and USICLK setting and
clock source used for the USI Data Register and the 4-bit counter.
Table 13-2.
Relations between the USICS1:0 and USICLK Setting
USI Data Register Clock
Source
4-bit Counter Clock Source
0
No Clock
No Clock
0
1
Software clock strobe
(USICLK)
Software clock strobe
(USICLK)
0
1
X
Timer/Counter0 Compare
Match
Timer/Counter0 Compare
Match
1
0
0
External, positive edge
External, both edges
USICS1
USICS0
USICLK
0
0
0
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8197A–AVR–10/09
Table 13-2.
Relations between the USICS1:0 and USICLK Setting (Continued)
USI Data Register Clock
Source
4-bit Counter Clock Source
0
External, negative edge
External, both edges
0
1
External, positive edge
Software clock strobe (USITC)
1
1
External, negative edge
Software clock strobe (USITC)
USICS1
USICS0
USICLK
1
1
1
1
• Bit 1 – USICLK: Clock Strobe
Writing a one to this bit location strobes the USI Data Register to shift one step and the counter
to increment by one, provided that the USICS1:0 bits are set to zero and by doing so the software clock strobe option is selected. The output will change immediately when the clock strobe
is executed, i.e., in the same instruction cycle. The value shifted into the USI Data Register is
sampled the previous instruction cycle. The bit will be read as zero.
When an external clock source is selected (USICS1 = 1), the USICLK function is changed from
a clock strobe to a Clock Select Register. Setting the USICLK bit in this case will select the
USITC strobe bit as clock source for the 4-bit counter (see Table 13-2).
• Bit 0 – USITC: Toggle Clock Port Pin
Writing a one to this bit location toggles the USCK/SCL value either from 0 to 1, or from 1 to 0.
The toggling is independent of the setting in the Data Direction Register, but if the PORT value is
to be shown on the pin the DDB2 must be set as output (to one). This feature allows easy clock
generation when implementing master devices. The bit will be read as zero.
When an external clock source is selected (USICS1 = 1) and the USICLK bit is set to one, writing to the USITC strobe bit will directly clock the 4-bit counter. This allows an early detection of
when the transfer is done when operating as a master device.
13.5.5
USIPP – USI Pin Position
Bit
7
6
5
4
3
2
1
0
0x11 (0x31)
-
-
-
-
-
-
-
USIPOS
Read/Write
R
R
R
R
R
R
R
R/W
Initial Value
0
0
0
0
0
0
0
0
USIPP
• Bits 7:1 – Res: Reserved Bits
These bits are reserved and will always read as zero.
• Bit 0 – USIPOS: USI Pin Position
Setting this bit to one changes the USI pin position. As default pins PB2:PB0 are used for the
USI pin functions, but when writing this bit to one the USIPOS bit is set the USI pin functions are
on pins PA2:PA0.
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ATtiny261A/461A/861A
14. AC – Analog Comparator
The analog comparator compares the input values on the selectable positive pin (AIN0, AIN1 or
AIN2) and selectable negative pin (AIN0, AIN1 or AIN2). When the voltage on the positive pin is
higher than the voltage on the negative pin, the Analog Comparator Output, ACO, is set. The
comparator can trigger a separate interrupt, exclusive to the analog comparator. The user can
select Interrupt triggering on comparator output rise, fall or toggle. A block diagram of the comparator and its surrounding logic is shown in Figure 14-1.
Figure 14-1. Analog Comparator Block Diagram
BANDGAP
REFERENCE
ACBG
ACM2..1
AIN0
MUX
AIN1
HSEL
ACME
ADEN
HLEV
AIN2
ADC MULTIPLEXER
OUTPUT (1)
Notes:
1. See Table 14-1 on page 135.
See Figure 1-1 on page 2 and Table 10-3 on page 61 for Analog Comparator pin placement.
14.1
Analog Comparator Multiplexed Input
When the Analog to Digital Converter (ADC) is configurated as single ended input channel, it is
possible to select any of the ADC10:0 pins to replace the negative input to the analog comparator. The ADC multiplexer is used to select this input, and consequently, the ADC must be
switched off to utilize this feature. If the Analog Comparator Multiplexer Enable bit (ACME in
ADCSRB) is set and the ADC is switched off (ADEN in ADCSRA is zero), MUX5:0 in ADMUX
select the input pin to replace the negative input to the analog comparator, as shown in Table
14-1. If ACME is cleared or ADEN is set, either AIN0, AIN1 or AIN2 is applied to the negative
input to the analog comparator.
Table 14-1.
Analog Comparator Multiplexed Input
ACME
ADEN
MUX5:0
ACM2:0
Positive Input
Negative Input
0
x
xxxxxx
000
AIN0
AIN1
0
x
xxxxxx
001
AIN0
AIN2
0
x
xxxxxx
010
AIN1
AIN0
0
x
xxxxxx
011
AIN1
AIN2
135
8197A–AVR–10/09
Table 14-1.
136
Analog Comparator Multiplexed Input (Continued)
ACME
ADEN
MUX5:0
ACM2:0
Positive Input
Negative Input
0
x
xxxxxx
100
AIN2
AIN0
0
x
xxxxxx
101,110,111
AIN2
AIN1
1
1
xxxxxx
000
AIN0
AIN1
1
0
000000
000
AIN0
ADC0
1
0
000000
01x
AIN1
ADC0
1
0
000000
1xx
AIN2
ADC0
1
0
000001
000
AIN0
ADC1
1
0
000001
01x
AIN1
ADC1
1
0
000001
1xx
AIN2
ADC1
1
0
000010
000
AIN0
ADC2
1
0
000010
01x
AIN1
ADC2
1
0
000010
1xx
AIN2
ADC2
1
0
000011
000
AIN0
ADC3
1
0
000011
01x
AIN1
ADC3
1
0
000011
1xx
AIN2
ADC3
1
0
000100
000
AIN0
ADC4
1
0
000100
01x
AIN1
ADC4
1
0
000100
1xx
AIN2
ADC4
1
0
000101
000
AIN0
ADC5
1
0
000101
01x
AIN1
ADC5
1
0
000101
1xx
AIN2
ADC5
1
0
000110
000
AIN0
ADC6
1
0
000110
01x
AIN1
ADC6
1
0
000110
1xx
AIN2
ADC6
1
0
000111
000
AIN0
ADC7
1
0
000111
01x
AIN1
ADC7
1
0
000111
1xx
AIN2
ADC7
1
0
001000
000
AIN0
ADC8
1
0
001000
01x
AIN1
ADC8
1
0
001000
1xx
AIN2
ADC8
1
0
001001
000
AIN0
ADC9
1
0
001001
01x
AIN1
ADC9
1
0
001001
1xx
AIN2
ADC9
1
0
001010
000
AIN0
ADC10
1
0
001010
01x
AIN1
ADC10
1
0
001010
1xx
AIN2
ADC10
ATtiny261A/461A/861A
8197A–AVR–10/09
ATtiny261A/461A/861A
14.2
14.2.1
Register Description
ACSRA – Analog Comparator Control and Status Register A
Bit
7
6
5
4
3
2
1
0
0x08 (0x28)
ACD
ACBG
ACO
ACI
ACIE
ACME
ACIS1
ACIS0
Read/Write
R/W
R/W
R
R/W
R/W
R/W
R/W
R/W
Initial Value
0
0
N/A
0
0
0
0
0
ACSRA
• Bit 7 – ACD: Analog Comparator Disable
When this bit is written logic one, the power to the analog comparator is switched off. This bit
can be set at any time to turn off the analog comparator, thus reducing power consumption in
Active and Idle mode. When changing the ACD bit, the analog comparator Interrupt must be disabled by clearing the ACIE bit in ACSRA. Otherwise an interrupt can occur when the bit is
changed.
• Bit 6 – ACBG: Analog Comparator Bandgap Select
When this bit is set an internal 1.1V reference voltage replaces the positive input to the analog
comparator. The selection of the internal voltage reference is done by writing the REFS2:0 bits
in ADCSRB and ADMUX registers. When this bit is cleared, AIN0, AIN1 or AIN2 depending on
the ACM2:0 bits is applied to the positive input of the analog comparator.
• Bit 5 – ACO: Analog Comparator Output
Enables output of analog comparator. The output of the analog comparator is synchronized and
then directly connected to ACO. The synchronization introduces a delay of 1 - 2 clock cycles.
• Bit 4 – ACI: Analog Comparator Interrupt Flag
This bit is set by hardware when a comparator output event triggers the interrupt mode defined
by ACIS1 and ACIS0. The analog comparator interrupt routine is executed if the ACIE bit is set
and the I-bit in SREG is set. ACI is cleared by hardware when executing the corresponding interrupt handling vector. Alternatively, ACI is cleared by writing a logic one to the flag.
• Bit 3 – ACIE: Analog Comparator Interrupt Enable
When the ACIE bit is written logic one and the I-bit in the status register is set, the analog comparator interrupt is activated. When written logic zero, the interrupt is disabled.
• Bit 2 – ACME: Analog Comparator Multiplexer Enable
When this bit is written logic one and the ADC is switched off (ADEN in ADCSRA is zero), the
ADC multiplexer selects the negative input to the analog comparator. When this bit is written
logic zero, AIN1 is applied to the negative input of the analog comparator. For a detailed description of this bit, see Table 14-1 on page 135.
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8197A–AVR–10/09
• Bits 1, 0 – ACIS1, ACIS0: Analog Comparator Interrupt Mode Select
These bits determine which comparator events that trigger the Analog Comparator interrupt. The
different settings are shown in Table 14-2.
Table 14-2.
ACIS1/ACIS0 Settings
ACIS1
ACIS0
Interrupt Mode
0
0
Comparator Interrupt on Output Toggle.
0
1
Reserved
1
0
Comparator Interrupt on Falling Output Edge.
1
1
Comparator Interrupt on Rising Output Edge.
When changing the ACIS1/ACIS0 bits, the Analog Comparator Interrupt must be disabled by
clearing its Interrupt Enable bit in the ACSR Register. Otherwise an interrupt can occur when the
bits are changed.
14.2.2
ACSRB – Analog Comparator Control and Status Register B
Bit
7
6
5
4
3
2
1
0
0x09 (0x29)
HSEL
HLEV
-
-
-
ACM2
ACM1
ACM0
Read/Write
R/W
R/W
R
R
R
R/W
R/W
R/W
Initial Value
0
0
N/A
0
0
0
0
0
ACSRB
• Bit 7 – HSEL: Hysteresis Select
When this bit is written logic one, the hysteresis of the Analog Comparator is switched on. The
hysteresis level is selected by the HLEV bit.
• Bit 6 – HLEV: Hysteresis Level
When the hysteresis is enabled by the HSEL bit, the Hysteresis Level, HLEV, bit selects the hysteresis level that is either 20mV (HLEV=0) or 50mV (HLEV=1).
• Bit 2:0 – ACM2:ACM0: Analog Comparator Multiplexer
The Analog Comparator multiplexer bits select the positive and negative input pins of the Analog
Comparator. The different settings are shown in Table 14-1.
14.2.3
DIDR0 – Digital Input Disable Register 0
Bit
7
6
5
4
3
2
1
0
0x01 (0x21)
ADC6D
ADC5D
ADC4D
ADC3D
AREFD
ADC2D
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
• Bits 7:4,2:0 – ADC6D:ADC0D: ADC6:0 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.
• Bit 3 – AREFD: AREF Digital Input Disable
When this bit is written logic one, the digital input buffer on the AREF pin is disabled. The corresponding PIN register bit will always read as zero when this bit is set. When an analog signal is
138
ATtiny261A/461A/861A
8197A–AVR–10/09
ATtiny261A/461A/861A
applied to the AREF 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.
14.2.4
DIDR1 – Digital Input Disable Register 1
Bit
7
6
5
4
3
0x02 (0x22)
ADC10D
ADC9D
ADC8D
ADC7D
-
2
1
0
Read/Write
R/W
R/W
R/W
R/W
R
R
R
R
Initial Value
0
0
0
0
0
0
0
0
DIDR1
• Bits 7:4 – ADC10D:ADC7D: ADC10:7 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 ADC10:7 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.
139
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15. ADC – Analog to Digital Converter
15.1
Features
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
15.2
10-bit Resolution
1.0 LSB Integral Non-linearity
± 2 LSB Absolute Accuracy
13µs Conversion Time
15 kSPS at Maximum Resolution
11 Multiplexed Single Ended Input Channels
16 Differential input pairs
15 Differential input pairs with selectable gain
Temperature Sensor Input Channel
Optional Left Adjustment for ADC Result Readout
0 - VCC ADC Input Voltage Range
Selectable 1.1V / 2.56V ADC Voltage Reference
Free Running or Single Conversion Mode
ADC Start Conversion by Auto Triggering on Interrupt Sources
Interrupt on ADC Conversion Complete
Sleep Mode Noise Cancele
Unipolar / Bipolar Input Mode
Input Polarity Reversal Mode
Overview
A 10-bit, successive approximation, Analog to Digital Converter (ADC) is connected to a 11channel analog multiplexer, which allows 16 differential voltage input combinations and 11 single-ended voltage inputs constructed from the pins PA7:PA0 or PB7:PB4. The differential input
is equipped with a programmable gain stage, providing amplification steps of 1x, 8x, 20x or 32x
on the differential input voltage before the A/D conversion. The single-ended voltage inputs refer
to 0V (GND).
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 15-1
on page 141.
Internal reference voltages of nominally 1.1V or 2.56V are provided On-chip. The Internal referance voltage of 2.56V, can optionally be externally decoupled at the AREF (PA3) pin by a
capacitor, for better noise performance. Alternatively, VCC can be used as reference voltage for
single ended channels. There is also an option to use an external voltage reference and turn-off
the internal voltage reference. These options are selected using the REFS2:0 bits of the ADCSRB and ADMUX registers.
140
ATtiny261A/461A/861A
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ATtiny261A/461A/861A
Figure 15-1. Analog to Digital Converter Block Schematic
ADC CONVERSION
COMPLETE IRQ
15
ADC[9:0]
ADPS1
ADPS0
ADPS2
ADATE
ADIF
ADEN
ADSC
0
ADC DATA REGISTER
(ADCH/ADCL)
ADC CTRL. & STATUS
REGISTER A (ADCSRA)
ADLAR
MUX1
MUX0
MUX3
MUX2
MUX4
REFS1
REFS0
ADC MULTIPLEXER
SELECT (ADMUX)
MUX5
REFS2
GSEL
ADC CTRL. & STATUS
REGISTER B (ADCSRB)
ADIE
ADIF
8-BIT DATA BUS
PRESCALER
MUX DECODER
AREF
INTERNAL 2.56/1.1V
REFERENCE
GAIN SELECTION
CHANNEL SELECTION
CONVERSION LOGIC
VCC
SAMPLE & HOLD
COMPARATOR
10-BIT DAC
+
INTERNAL 1.18V
REFERENCE
AGND
TEMPERATURE
SENSOR
ADC10
SINGLE ENDED /
DIFFERENTIAL SELECTION
ADC9
ADC8
ADC7
ADC6
POS.
INPUT
MUX
ADC
MULTIPLEXER OUTPUT
ADC5
ADC4
ADC3
MUX
ADC2
+
ADC1
-
GAIN
AMPLIFIER
ADC0
NEG.
INPUT
MUX
15.3
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
VCC, the voltage on the AREF pin or an internal 1.1V / 2.56V voltage reference.
The voltage reference for the ADC may be selected by writing to the REFS2:0 bits in ADCSRB
and ADMUX registers. The VCC supply, the AREF pin or an internal 1.1V / 2.56V voltage reference may be selected as the ADC voltage reference. Optionally the internal 1.1V / 2.56V voltage
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reference may be decoupled by an external capacitor at the AREF pin to improve noise
immunity.
The analog input channel and differential gain are selected by writing to the MUX5:0 bits in
ADMUX. Any of the 11 ADC input pins ADC10:0 can be selected as single ended inputs to the
ADC. The positive and negative inputs to the differential gain amplifier are described in Table
15-5.
If differential channels are selected, the differential gain stage amplifies the voltage difference
between the selected input pair by the selected gain factor, 1x, 8x, 20x or 32x, according to the
setting of the MUX5:0 bits in ADMUX and the GSEL bit in ADCSRB. This amplified value then
becomes the analog input to the ADC. If single ended channels are used, the gain amplifier is
bypassed altogether.
If the same ADC input pin is selected as both the positive and negative input to the differential
gain amplifier, the remaining offset in the gain stage and conversion circuitry can be measured
directly as the result of the conversion. This figure can be subtracted from subsequent conversions with the same gain setting to reduce offset error to below 1 LSW.
The on-chip temperature sensor is selected by writing the code “111111” to the MUX5:0 bits in
ADMUX register when the ADC11 channel is used as an ADC input.
The ADC is enabled by setting the ADC Enable bit, ADEN in ADCSRA. Voltage reference and
input channel selections will not go into effect until ADEN is set. 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 completes 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. When ADC
access to the data registers is prohibited between reading of ADCH and ADCL, the interrupt will
trigger even if the result is lost.
15.4
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 still is set when the conversion completes, a new
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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.
Figure 15-2. ADC Auto Trigger Logic
ADTS[2:0]
PRESCALER
START
ADIF
CLKADC
ADATE
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.
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.
15.5
Prescaling and Conversion Timing
By default, the successive approximation circuitry requires an input clock frequency between 50
kHz and 200 kHz to get maximum resolution. If a lower resolution than 10 bits is needed, the
input clock frequency to the ADC can be higher than 200 kHz to get a higher sample rate.
Figure 15-3. 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
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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. See Figure 15-3.
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.
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,
as shown in Figure 15-4 below.
Figure 15-4. ADC Timing Diagram, First Conversion (Single Conversion Mode)
Next
Conversion
First Conversion
Cycle Number
1
2
12
13
14
15
16
17
18
19
20
21
22
23
24
25
1
2
3
ADC Clock
ADEN
ADSC
ADIF
Sign and MSB of Result
ADCH
LSB of Result
ADCL
MUX and REFS
Update
Conversion
Complete
Sample & Hold
MUX and REFS
Update
The actual sample-and-hold takes place 1.5 ADC clock cycles after the start of a normal conversion and 13.5 ADC clock cycles after the start of an first conversion. See Figure 15-5.
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.
Figure 15-5. ADC Timing Diagram, Single Conversion
One Conversion
Cycle Number
1
2
3
4
5
6
7
8
9
Next Conversion
10
11
12
13
1
2
3
ADC Clock
ADSC
ADIF
ADCH
Sign and MSB of Result
ADCL
LSB of Result
Sample & Hold
MUX and REFS
Update
144
Conversion
Complete
MUX and REFS
Update
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When Auto Triggering is used, the prescaler is reset when the trigger event occurs. See Figure
15-6. 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.
Figure 15-6. ADC Timing Diagram, Auto Triggered Conversion
One Conversion
Cycle Number
1
2
3
4
5
6
7
8
Next Conversion
10
9
11
12
13
1
2
ADC Clock
Trigger
Source
ADATE
ADIF
ADCH
Sign and MSB of Result
ADCL
LSB of Result
Prescaler
Reset
Sample &
Hold
Conversion
Complete
Prescaler
Reset
MUX and REFS
Update
In Free Running mode (see Figure 15-7), a new conversion will be started immediately after the
conversion completes, while ADSC remains high.
Figure 15-7. ADC Timing Diagram, Free Running Conversion
One Conversion
Cycle Number
11
12
Next Conversion
13
1
2
3
4
ADC Clock
ADSC
ADIF
ADCH
Sign and MSB of Result
ADCL
LSB of Result
Conversion
Complete
Sample & Hold
MUX and REFS
Update
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For a summary of conversion times, see Table 15-1.
Table 15-1.
ADC Conversion Time
Sample & Hold
(Cycles from Start of Conversion)
Total Conversion Time (Cycles)
First conversion
13.5
25
Normal conversions
1.5
13
2
13.5
Condition
Auto Triggered conversions
15.6
Changing Channel or Reference Selection
The MUX5:0 and REFS2:0 bits in the ADCSRB and ADMUX registers 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.
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:
• When ADATE or ADEN is cleared.
• During conversion, minimum one ADC clock cycle after the trigger event.
• 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.
15.6.1
ADC Input Channels
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
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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.
15.6.2
15.7
ADC Voltage Reference
The conversion range of the ADC is defined by the voltage reference (VREF). Single ended channels that exceed VREF will result in codes close to 0x3FF. VREF can be selected as either VCC, or
internal 1.1V / 2.56V voltage reference, or external AREF pin. The first conversion result after
switching voltage reference source may be inaccurate, and the user is advised to discard this
result.
ADC Noise Canceler
The ADC features a noise canceler that enables conversion during sleep mode. This reduces
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:
• 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.
• Enter ADC Noise Reduction mode (or Idle mode). The ADC will start a conversion once the
CPU has been halted.
• 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, it 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 automatically be 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.
15.8
Analog Input Circuitry
The analog input circuitry for single ended channels is illustrated in Figure 15-8 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).
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Figure 15-8. Analog Input Circuitry
IIH
ADCn
1..100 kΩ
CS/H= 14 pF
IIL
VCC/2
The capacitor in Figure 15-8 depicts the total capacitance, including the sample/hold capacitor
and any stray or parasitic capacitance inside the device. The value given is worst case.
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 the source needs to charge the S/H
capacitor, with can vary widely. The user is recommended to minmimize the charge transfer time
by using low impedant sources, only, with slowly varying signals.
Signal components higher than the Nyquist frequency (fADC/2) should not be present 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.
15.9
Noise Canceling Techniques
Digital circuitry inside and outside the device generates EMI which might affect the accuracy of
analog measurements. When conversion accuracy is critical, the noise level can be reduced by
applying the following techniques:
• Keep analog signal paths as short as possible.
• Make sure analog tracks run over the analog ground plane.
• Keep analog tracks well away from high-speed switching digital tracks.
• If any port pin is used as a digital output, it mustn’t switch while a conversion is in progress.
• Place bypass capacitors as close to VCC and GND pins as possible.
Where high ADC accuracy is required it is recommended to use ADC Noise Reduction Mode, as
described in Section 15.7 on page 147. This is especially the case when system clock frequency
is above 1 MHz, or when the ADC is used for reading the internal temperature sensor, as
described in Section 15.12 on page 152. A good system design with properly placed, external
bypass capacitors does reduce the need for using ADC Noise Reduction Mode
15.10 ADC Accuracy Definitions
An n-bit single-ended ADC converts a voltage linearly between GND and V REF in 2 n 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:
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• Offset: The deviation of the first transition (0x000 to 0x001) compared to the ideal transition
(at 0.5 LSB). Ideal value: 0 LSB.
Figure 15-9. 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 15-10. Gain Error
Output Code
Gain
Error
Ideal ADC
Actual ADC
VREF Input Voltage
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• 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 15-11. 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 15-12. Differential Non-linearity (DNL)
Output Code
0x3FF
1 LSB
DNL
0x000
0
150
VREF Input Voltage
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• 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.
15.11 ADC Conversion Result
After the conversion is complete (ADIF is high), the conversion result can be found in the ADC
Result Registers (ADCL, ADCH). The form of the conversion result depends on the type of the
conversio as there are three types of conversions: single ended conversion, unipolar differential
conversion and bipolar differential conversion.
15.11.1
Single Ended Conversion
For single ended conversion, the result is
V IN ⋅ 1024
ADC = -------------------------V REF
where VIN is the voltage on the selected input pin and VREF the selected voltage reference (see
Table 15-4 on page 155 and Table 15-5 on page 156). 0x000 represents analog ground, and
0x3FF represents the selected voltage reference minus one LSB. The result is presented in onesided form, from 0x3FF to 0x000.
15.11.2
Unipolar Differential Conversion
If differential channels and an unipolar input mode are used, the result is
( V POS – V NEG ) ⋅ 1024
ADC = -------------------------------------------------------- ⋅ GAIN
V REF
where VPOS is the voltage on the positive input pin, VNEG the voltage on the negative input pin,
and VREF the selected voltage reference (see Table 15-4 on page 155 and Table 15-5 on page
156). The voltage on the positive pin must always be larger than the voltage on the negative pin
or otherwise the voltage difference is saturated to zero. The result is presented in one-sided
form, from 0x000 (0d) to 0x3FF (+1023d). The GAIN is either 1x, 8x, 20x or 32x.
15.11.3
Bipolar Differential Conversion
As default the ADC converter operates in the unipolar input mode, but the bipolar input mode
can be selected by writting the BIN bit in the ADCSRB to one. In the bipolar input mode twosided voltage differences are allowed and thus the voltage on the negative input pin can also be
larger than the voltage on the positive input pin. If differential channels and a bipolar input mode
are used, the result is
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( V POS – V NEG ) ⋅ 512
ADC = ----------------------------------------------------- ⋅ GAIN
V REF
where VPOS is the voltage on the positive input pin, VNEG the voltage on the negative input pin,
and VREF the selected voltage reference. The result is presented in two’s complement form, from
0x200 (-512d) through 0x000 (+0d) to 0x1FF (+511d). The GAIN is either 1x, 8x, 20x or 32x.
However, if the signal is not bipolar by nature (9 bits + sign as the 10th bit), this scheme loses
one bit of the converter dynamic range. Then, if the user wants to perform the conversion with
the maximum dynamic range, the user can perform a quick polarity check of the result and use
the unipolar differential conversion with selectable differential input pair. When the polarity check
is performed, 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.
15.12 Temperature Measurement
The temperature measurement is based on an on-chip temperature sensor that is coupled to a
single ended ADC11 channel. Selecting the ADC11 channel by writing the MUX5:0 bits in
ADMUX register to “111111” enables the temperature sensor. The internal 1.1V voltage reference must also be selected for the ADC voltage reference source in the temperature sensor
measurement. When the temperature sensor is enabled, the ADC converter can be used in single conversion mode to measure the voltage over the temperature sensor.
The measured voltage has a linear relationship to the temperature as described in Table 15-2
The sensitivity is approximately 1 LSB / °C and the accuracy depends on the method of user calibration. Typically, the measurement accuracy after a single temperature calibration is ±10°C,
assuming calibration at room temperature. Better accuracies are achieved by using two
temperature points for calibration.
Table 15-2.
Temperature vs. Sensor Output Voltage (Typical Case)
Temperature
ADC
-40 °C
+25 °C
+85 °C
230 LSB
300 LSB
370 LSB
The values described in Table 15-2 are typical values. However, due to process variation the
temperature sensor output voltage varies from one chip to another. To be capable of achieving
more accurate results the temperature measurement can be calibrated in the application software. The sofware calibration can be done using the formula:
T = k * [(ADCH << 8) | ADCL] + TOS
where ADCH and ADCL are the ADC data registers, k is the fixed slope coefficient and TOS is
the temperature sensor offset. Typically, k is very close to 1.0 and in single-point calibration the
coefficient may be omitted. Where higher accuracy is required the slope coefficient should be
evaluated based on measurements at two temperatures.
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15.13 Register Description
15.13.1
ADCSRA – ADC Control and Status Register A
Bit
7
0x06 (0x26)
6
ADEN
5
ADSC
4
ADATE
3
ADIF
2
ADIE
ADPS2
1
0
ADPS1
ADPS0
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
ADCSRA
• Bit 7 – ADEN: ADC Enable
Writing this bit to one enables the ADC. By writing it to zero, the ADC is turned off. Turning the
ADC off while a conversion is in progress, will terminate this conversion.
• Bit 6 – ADSC: ADC Start Conversion
In Single Conversion mode, write this bit to one to start each conversion. In Free Running mode,
write this bit to one to start the first conversion. The first conversion after ADSC has been written
after the ADC has been enabled, or if ADSC is written at the same time as the ADC is enabled,
will take 25 ADC clock cycles instead of the normal 13. This first conversion performs initialization of the ADC.
ADSC will read as one as long as a conversion is in progress. When the conversion is complete,
it returns to zero. Writing zero to this bit has no effect.
• Bit 5 – ADATE: ADC Auto Trigger Enable
When this bit is written to one, Auto Triggering of the ADC is enabled. The ADC will start a conversion on a positive edge of the selected trigger signal. The trigger source is selected by setting
the ADC Trigger Select bits, ADTS in ADCSRB.
• Bit 4 – ADIF: ADC Interrupt Flag
This bit is set when an ADC conversion completes and the data registers are updated. The ADC
Conversion Complete Interrupt is executed if the ADIE bit and the I-bit in SREG are set. ADIF is
cleared by hardware when executing the corresponding interrupt handling vector. Alternatively,
ADIF is cleared by writing a logical one to the flag. Beware that if doing a Read-Modify-Write on
ADCSRA, a pending interrupt can be disabled. This also applies if the SBI and CBI instructions
are used.
• Bit 3 – ADIE: ADC Interrupt Enable
When this bit is written to one and the I-bit in SREG is set, the ADC Conversion Complete Interrupt is activated.
• Bits 2:0 – ADPS2:0: ADC Prescaler Select Bits
These bits determine the division factor between the system clock frequency and the input clock
to the ADC.
Table 15-3.
ADC Prescaler Selections
ADPS2
ADPS1
ADPS0
Division Factor
0
0
0
2
0
0
1
2
0
1
0
4
0
1
1
8
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Table 15-3.
15.13.2
15.13.2.1
ADPS2
ADPS1
ADPS0
Division Factor
1
0
0
16
1
0
1
32
1
1
0
64
1
1
1
128
ADCL and ADCH – The ADC Data Register
ADLAR = 0
Bit
15
14
13
12
11
10
9
8
0x05 (0x25)
–
–
–
–
–
–
ADC9
ADC8
ADCH
0x04 (0x24)
ADC7
ADC6
ADC5
ADC4
ADC3
ADC2
ADC1
ADC0
ADCL
7
6
5
4
3
2
1
0
Read/Write
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
Initial Value
15.13.2.2
ADC Prescaler Selections (Continued)
ADLAR = 1
Bit
15
14
13
12
11
10
9
8
0x05 (0x25)
ADC9
ADC8
ADC7
ADC6
ADC5
ADC4
ADC3
ADC2
ADCH
0x04 (0x24)
ADC1
ADC0
–
–
–
–
–
–
ADCL
7
6
5
4
3
2
1
0
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
Read/Write
Initial Value
When an ADC conversion is complete, the result is found in these two registers.
When ADCL is read, the ADC Data Register is not updated until ADCH is read. Consequently, 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.
The ADLAR bit in ADMUX, and the MUXn bits in ADMUX affect the way the result is read from
the registers. If ADLAR is set, the result is left adjusted. If ADLAR is cleared (default), the result
is right adjusted.
• ADC9:0: ADC Conversion Result
These bits represent the result from the conversion, as detailed in “ADC Conversion Result” on
page 151.
15.13.3
ADMUX – ADC Multiplexer Selection Register
Bit
154
7
6
5
4
3
2
1
0
0x07 (0x27)
REFS1
REFS0
ADLAR
MUX4
MUX3
MUX2
MUX1
MUX0
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
ADMUX
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ATtiny261A/461A/861A
• Bit 7:6 – REFS1:REFS0: Voltage Reference Selection Bits
These bits together with the REFS2 bit from the ADC Control and Status Register B (ADCSRB)
select the voltage reference for the ADC, as shown in Table 15-4.
Table 15-4.
Voltage Reference Selections for ADC
REFS2
REFS1
REFS0
Voltage Reference Selection
X
0
0
VCC used as voltage reference,
disconnected from AREF
X
0
1
External voltage reference at AREF pin,
internal voltage reference turned off
0
1
0
Internal 1.1V voltage reference
0
1
1
Reserved
1
1
0
Internal 2.56V voltage reference (VCC > 3.0V),
without external bypass capacitor,
disconnected from AREF
1
1
1
Internal 2.56V voltage reference (VCC > 3.0V),
with external bypass capacitor at AREF pin
If these bits are changed during a conversion, the change will not go in effect until this conversion is complete (ADIF in ADCSR is set). Also note, that when these bits are changed, the next
conversion will take 25 ADC clock cycles.
Special care should be taken when changing differential channels. Once a differential channel
has been selected the input stage may take a while to stabilize. It is therefore recommended to
force the ADC to perform a long conversion when changing multiplexer or voltage reference settings. This can be done by first turning off the ADC, then changing reference settings and then
turn on the ADC. Alternatively, the first conversion results after changing reference settings
should be discarded.
It is not recommended to use an external AREF higher than (VCC - 1V) for channels with differential gain, as this will affect ADC accuracy.
Internal voltage reference options may not be used if an external voltage is being applied to the
AREF pin.
• Bit 5 – ADLAR: ADC Left Adjust Result
The ADLAR bit affects the presentation of the ADC conversion result in the ADC Data Register.
Write one to ADLAR to left adjust the result. Otherwise, the result is right adjusted. Changing the
ADLAR bit will affect the ADC Data Register immediately, regardless of any ongoing conversions. For a comple te description of this bit, see “ADCL and ADCH – The ADC Data Register”
on page 154.
• Bits 4:0 – MUX4:0: Analog Channel and Gain Selection Bits
These bits and the MUX5 bit from the ADC Control and Status Register B (ADCSRB) select
which combination of analog inputs are connected to the ADC. In case of differential input, gain
selection is also made with these bits. Selecting the same pin as both inputs to the differential
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gain stage enables offset measurements. Selecting the single-ended channel ADC11 enables
the temperature sensor. Refer to Table 15-5 for details.
Table 15-5.
MUX5:0
Single-Ended
Input
000000
ADC0 (PA0)
000001
ADC1 (PA1)
000010
ADC2 (PA2)
000011
ADC3 (PA4)
000100
ADC4 (PA5)
000101
ADC5 (PA6)
000110
ADC6 (PA7)
000111
ADC7 (PB4)
001000
ADC8 (PB5)
001001
ADC9 (PB6)
001010
ADC10 (PB7)
Differential Input
Positive
Negative
Gain
NA
NA
NA
001011
ADC0 (PA0)
ADC1 (PA1)
20x
001100
ADC0 (PA0)
ADC1 (PA1)
1x
ADC1 (PA1)
ADC1 (PA1)
20x
001110
ADC2 (PA2)
ADC1 (PA1)
20x
001111
ADC2 (PA2)
ADC1 (PA1)
1x
010000
ADC2 (PA2)
ADC3 (PA4)
1x
ADC3 (PA4)
ADC3 (PA4)
20x
ADC4 (PA5)
ADC3 (PA4)
20x
010011
ADC4 (PA5)
ADC3 (PA4)
1x
010100
ADC4 (PA5)
ADC5 (PA6)
20x
010101
ADC4 (PA5)
ADC5 (PA6)
1x
ADC5 (PA6)
ADC5 (PA6)
20x
010111
ADC6 (PA7)
ADC5 (PA6)
20x
011000
ADC6 (PA7)
ADC5 (PA6)
1x
011001
ADC8 (PB5)
ADC9 (PB6)
20x
011010
ADC8 (PB5)
ADC9 (PB6)
1x
ADC9 (PB6)
ADC9 (PB6)
20x
011100
ADC10 (PB7)
ADC9 (PB6)
20x
011101
ADC10 (PB7)
ADC9 (PB6)
1x
N/A
N/A
N/A
001101
010001
010010
010110
011011
156
Input Channel Selections
NA
N/A
NA
NA
011110
1.1V
011111
0V
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Table 15-5.
MUX5:0
Input Channel Selections (Continued)
Single-Ended
Input
Differential Input
Positive
Negative
Gain
ADC0(PA0)
ADC1(PA1)
20x/32x
ADC0(PA0)
ADC1(PA1)
1x/8x
ADC1(PA1
ADC0(PA0)
20x/32x
100011
ADC1(PA1)
ADC0(PA0)
1x/8x
100100
ADC1(PA1)
ADC2(PA2)
20x/32x
ADC1(PA1)
ADC2(PA2)
1x/8x
ADC2(PA2
ADC1(PA1)
20x/32x
100111
ADC2(PA2)
ADC1(PA1)
1x/8x
101000
ADC2(PA2)
ADC0(PA0)
20x/32x
ADC2(PA2)
ADC0(PA0)
1x/8x
ADC0(PA0)
ADC2(PA2)
20x/32x
101011
ADC0(PA0)
ADC2(PA2)
1x/8x
101100
ADC4(PA5)
ADC5(PA6)
20x/32x
ADC4(PA5)
ADC5(PA6)
1x/8x
ADC5(PA6)
ADC4(PA5)
20x/32x
101111
ADC5(PA6)
ADC4(PA5)
1x/8x
110000
ADC5(PA6)
ADC6(PA7)
20x/32x
ADC5(PA6)
ADC6(PA7)
1x/8x
ADC6(PA7)
ADC5(PA6)
20x/32x
110011
ADC6(PA7)
ADC5(PA6)
1x/8x
110100
ADC6(PA7)
ADC4(PA5)
20x/32x
ADC6(PA7)
ADC4(PA5)
1x/8x
ADC4(PA5)
ADC6(PA7)
20x/32x
110111
ADC4(PA5)
ADC6(PA7)
1x/8x
111000
ADC0(PA0)
ADC0(PA0)
20x/32x
ADC0(PA0)
ADC0(PA0)
1x/8x
ADC1(PA1)
ADC1(PA1)
20x/32x
111011
ADC2(PA2)
ADC2(PA2)
20x/32x
111100
ADC4(PA5)
ADC4(PA5)
20x/32x
ADC5(PA6)
ADC5(PA6)
20x/32x
ADC6(PA7)
ADC6(PA7)
20x/32x
N/A
N/A
N/A
100000
100001
100010
100101
100110
101001
101010
101101
101110
110001
110010
110101
110110
111001
111010
111101
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
111110
111111
Note:
ADC11
(1)
1. Temperature sensor
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If these bits are changed during a conversion, the change will not go into effect until this conversion is complete (ADIF in ADCSRA is set).
15.13.4
ADCSRB – ADC Control and Status Register B
Bit
7
6
5
4
3
2
1
0
0x03 (0x23)
BIN
GSEL
-
REFS2
MUX5
ADTS2
ADTS1
ADTS0
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
ADCSRB
• Bit 7– BIN: Bipolar Input Mode
The gain stage is working in the unipolar mode as default, but the bipolar mode can be selected
by writing the BIN bit in the ADCSRB register. In the unipolar mode only one-sided conversions
are supported and the voltage on the positive input must always be larger than the voltage on
the negative input. Otherwise the result is saturated to the voltage reference. In the bipolar mode
two-sided conversions are supported and the result is represented in the two’s complement
form. In the unipolar mode the resolution is 10 bits and the bipolar mode the resolution is 9 bits +
1 sign bit.
• Bits 6 – GSEL: Gain Select
The Gain Select bit selects the 32x gain instead of the 20x gain and the 8x gain instead of the 1x
gain when the Gain Select bit is written to one.
• Bits 5 – Res: Reserved Bit
This bit is reserved and will always read zero.
• Bits 4 – REFS2: Reference Selection Bit
These bit selects either the voltage reference of 1.1 V or 2.56 V for the ADC, as shown in Table
15-4. If active channels are used, using AVCC or an external AREF higher than (AVCC - 1V) is
not recommended, as this will affect ADC accuracy. The internal voltage reference options may
not be used if an external voltage is being applied to the AREF pin.
• Bits 3 – MUX5: Analog Channel and Gain Selection Bit 5
The MUX5 bit is the MSB of the Analog Channel and Gain Selection bits. Refer to Table 15-5 for
details. If this bit is changed during a conversion, the change will not go into effect until this
conversion is complete (ADIF in ADCSRA is set).
• Bits 2:0 – ADTS2:0: ADC Auto Trigger Source
If ADATE in ADCSRA is written to one, the value of these bits selects which source will trigger
an ADC conversion. If ADATE is cleared, the ADTS2:0 settings will have no effect. A conversion
will be triggered by the rising edge of the selected Interrupt Flag. Note that switching from a trigger source that is cleared to a trigger source that is set, will generate a positive edge on the
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trigger signal. If ADEN in ADCSRA is set, this will start a conversion. Switching to Free Running
mode (ADTS[2:0]=0) will not cause a trigger event, even if the ADC Interrupt Flag is set.
Table 15-6.
15.13.5
ADC Auto Trigger Source Selections
ADTS2
ADTS1
ADTS0
Trigger Source
0
0
0
Free Running mode
0
0
1
Analog Comparator
0
1
0
External Interrupt Request 0
0
1
1
Timer/Counter0 Compare Match A
1
0
0
Timer/Counter0 Overflow
1
0
1
Timer/Counter0 Compare Match B
1
1
0
Timer/Counter1 Overflow
1
1
1
Watchdog Interrupt Request
DIDR0 – Digital Input Disable Register 0
Bit
7
6
5
4
3
2
1
0
0x01 (0x21)
ADC6D
ADC5D
ADC4D
ADC3D
AREFD
ADC2D
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
• Bits 7:4,2:0 – ADC6D:ADC0D: ADC6:0 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.
• Bit 3 – AREFD: AREF Digital Input Disable
When this bit is written logic one, the digital input buffer on the AREF 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 AREF 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.
15.13.6
DIDR1 – Digital Input Disable Register 1
Bit
7
6
5
4
3
0x02 (0x22)
ADC10D
ADC9D
ADC8D
ADC7D
-
2
1
0
Read/Write
R/W
R/W
R/W
R/W
R
R
R
R
Initial Value
0
0
0
0
0
0
0
0
DIDR1
• Bits 7:4 – ADC10D:ADC7D: ADC10:7 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 ADC10:7 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.
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16. debugWIRE On-chip Debug System
16.1
Features
•
•
•
•
•
•
•
•
•
•
16.2
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
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.
16.3
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.
Figure 16-1 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.
Figure 16-1. The debugWIRE Setup
1.8 - 5.5V
VCC
dW
dW(RESET)
GND
When designing a system where debugWIRE will be used, the following must be observed:
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• Pull-Up resistor on the dW/(RESET) line must be in the range of 10k to 20 kΩ. However, the
pull-up resistor is optional.
• Connecting the RESET pin directly to VCC will not work.
• Capacitors inserted on the RESET pin must be disconnected when using debugWire.
• All external reset sources must be disconnected.
16.4
Software Break Points
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 Falsh Data retention. Devices used for debugging purposes should not be shipped to
end customers.
16.5
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). See the debugWIRE documentation for detailed description of the limitations.
The debugWIRE interface is asynchronous, which means that the debugger needs to synchronize to the system clock. If the system clock is changed by software (e.g. by writing CLKPS bits)
communication via debugWIRE may fail. Also, clock frequencies below 100 kHz may cause
communication problems.
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.
16.6
Register Description
The following section describes the registers used with the debugWire.
16.6.1
DWDR – debugWire Data Register
Bit
7
6
5
4
0x20 (0x40)
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.
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17. Self-Programming the Flash
The device provides a Self-Programming mechanism for downloading and uploading program
code by the MCU itself. The Self-Programming can use any available data interface and associated protocol to read code and write (program) that code into the Program memory. The SPM
instruction is disabled by default but it can be enabled by programming the SELFPRGEN fuse
(to “0”).
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 re-written. 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.
17.1
Performing Page Erase by SPM
To execute Page Erase, set up the address in the Z-pointer, write “00000011” 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.
Note:
17.2
The CPU is halted during the Page Erase operation.
Filling the Temporary Buffer (Page Loading)
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 CTPB 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.
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If the EEPROM is written in the middle of an SPM Page Load operation, all data loaded will be
lost.
17.3
Performing a Page Write
To execute Page Write, set up the address in the Z-pointer, write “00000101” 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.
Note:
17.4
The CPU is halted during the Page Write operation.
Addressing the Flash During Self-Programming
The Z-pointer is used to address the SPM commands.
Bit
15
14
13
12
11
10
9
ZH (R31)
Z15
Z14
Z13
Z12
Z11
Z10
Z9
8
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 18-7 on page 170), 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 is shown in Figure 17-1. Note that the Page Erase and Page Write operations are
addressed independently. Therefore it is of major importance that the software addresses the
same page in both the Page Erase and Page Write operation.
The LPM instruction uses 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.
Figure 17-1. Addressing the Flash During SPM
BIT
15
ZPCMSB
ZPAGEMSB
Z - REGISTER
1 0
0
PCMSB
PROGRAM
COUNTER
PAGEMSB
PCPAGE
PAGE ADDRESS
WITHIN THE FLASH
PROGRAM MEMORY
PAGE
PCWORD
WORD ADDRESS
WITHIN A PAGE
PAGE
INSTRUCTION WORD
PCWORD[PAGEMSB:0]:
00
01
02
PAGEEND
Note:
The different variables used in Figure 17-1 are listed in Table 18-7 on page 170.
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17.5
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.
17.6
Reading Fuse and Lock Bits from Software
It is possible for firmware to read device fuse and lock bits.
Note:
17.6.1
Fuse and Lock bits that are programmed, will be read as zero. Fuse and Lock bits that are unprogrammed, will be read as one.
Reading Lock Bits from Firmware
Lock bit values are returned in the destination register after an LPM instruction has been issued
within three CPU cycles after RFLB and SELFPRGEN bits have been set in SPMCSR. The
RFLB and SELFPRGEN bits automatically clear upon completion of reading the lock bits, or if no
LPM instruction is executed within three CPU cycles, or if no SPM instruction is executed within
four CPU cycles. When RFLB and SELFPRGEN are cleared LPM functions normally.
To read the lock bits, follow the below procedure:
1. Load the Z-pointer with 0x0001.
2. Set RFLB and SELFPRGEN bits in SPMCSR.
3. Issue an LPM instruction within three clock cycles.
4. Read the lock bits from the LPM destination register.
If successful, the contents of the destination register are as follows.
Bit
7
6
5
4
3
2
1
0
Rd
–
–
–
–
–
–
LB2
LB1
See section “Program And Data Memory Lock Bits” on page 167 for more information.
17.6.2
Reading Fuse Bits from Firmware
The algorithm for reading fuse bytes is similar to the one described above for reading lock bits,
only the addresses are different. To read the Fuse Low Byte (FLB), follow the below procedure:
1. Load the Z-pointer with 0x0000.
2. Set RFLB and SELFPRGEN bits in SPMCSR.
3. Issue an LPM instruction within three clock cycles.
4. Read the FLB from the LPM destination register.
If successful, the contents of the destination register are as follows.
Bit
7
6
5
4
3
2
1
0
Rd
FLB7
FLB6
FLB5
FLB4
FLB3
FLB2
FLB1
FLB0
Refer to Table 18-5 on page 169 for a detailed description and mapping of the Fuse Low Byte.
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To read the Fuse High Byte (FHB), simply replace the address in the Z-pointer with 0x0003 and
repeat the procedure above. If successful, the contents of the destination register are as follows.
Bit
7
6
5
4
3
2
1
0
Rd
FHB7
FHB6
FHB5
FHB4
FHB3
FHB2
FHB1
FHB0
Refer to Table 18-4 on page 168 for detailed description and mapping of the Fuse High Byte.
To read the Fuse Extended Byte (FEB), replace the address in the Z-pointer with 0x0002 and
repeat the previous procedure. If successful, the contents of the destination register are as
follows.
Bit
7
6
5
4
3
2
1
0
Rd
FEB7
FEB6
FEB5
FEB4
FEB3
FEB2
FEB1
FEB0
Refer to Table 18-3 on page 168 for detailed description and mapping of the Fuse Extended
Byte.
17.7
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. 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.
2. 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.
17.8
Programming Time for Flash when Using SPM
The calibrated oscillator is used to time Flash accesses. Table 17-1 shows the typical programming time for Flash accesses from the CPU.
Table 17-1.
SPM Programming Time(1)
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
Note:
1. Minimum and maximum programming time is per individual operation.
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17.9
17.9.1
Register Description
SPMCSR – Store Program Memory Control and Status Register
The Store Program Memory Control and Status Register contains the control bits needed to control the Program memory operations.
Bit
7
6
5
4
3
2
1
0
0x37 (0x57)
–
–
–
CTPB
RFLB
PGWRT
PGERS
SPMEN
Read/Write
R
R
R
R/W
R/W
R/W
R/W
R/W
Initial Value
0
0
0
0
0
0
0
0
SPMCSR
• Bits 7:5 – Res: Reserved Bits
These bits are reserved and always read as zero.
• Bit 4 – CTPB: Clear Temporary Page Buffer
If the CTPB bit is written while filling the temporary page buffer, the temporary page buffer will be
cleared and the data will be lost.
• Bit 3 – RFLB: Read Fuse and Lock Bits
An LPM instruction within three cycles after RFLB and SPMEN 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 “EEPROM Write Prevents Writing to SPMCSR” on page 164 for details.
• Bit 2 – PGWRT: Page Write
If this bit is written to one at the same time as SPMEN, 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.
• Bit 1 – PGERS: Page Erase
If this bit is written to one at the same time as SPMEN, the next SPM instruction within four clock
cycles executes Page Erase. The page address is taken from the high 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.
• Bit 0 – SPMEN: Store Program Memory Enable
This bit enables the SPM instruction for the next four clock cycles. If written to one together with
either CTPB, RFLB, PGWRT, or PGERS, the following SPM instruction will have a special
meaning, see description above. If only SPMEN 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 SPMEN 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 SPMEN 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.
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18. Memory Programming
This section describes the different methods for programming ATtiny261A/461A/861A
memories.
18.1
Program And Data Memory Lock Bits
The device provides two lock bits which can be left unprogrammed (“1”) or can be programmed
(“0”) to obtain the additional security listed in Table 18-2. The lock bits can only be erased to “1”
with the Chip Erase command.
The device has no separate boot loader section. The SPM instruction is enabled for the whole
Flash, if the SELFPROGEN fuse is programmed (“0”), otherwise it is disabled.
Program memory can be read out via the debugWIRE interface when the DWEN fuse is programmed, even if lock bits are set. Thus, when lock bit security is required, debugWIRE should
always be disabled by clearing the DWEN fuse.
Table 18-1.
Lock Bit Byte
Lock Bit Byte
Description
Default Value
7
–
1 (unprogrammed)
6
–
1 (unprogrammed)
5
–
1 (unprogrammed)
4
–
1 (unprogrammed)
3
–
1 (unprogrammed)
2
–
1 (unprogrammed)
LB2
1
Lock bit
1 (unprogrammed)
LB1
0
Lock bit
1 (unprogrammed)
Note:
Bit No
“1” means unprogrammed, “0” means programmed.
Table 18-2.
Lock Bit Protection Modes.
Memory Lock Bits (1)
(2)
Protection Type
LB Mode
LB2
LB1
1
1
1
No memory lock features enabled.
2
1
0
Further programming of the Flash and EEPROM is disabled in
High-voltage and Serial Programming mode. The Fuse bits are
locked in both Serial and High-voltage Programming mode.(1)
0
Further programming and verification of the Flash and EEPROM
is disabled in High-voltage and Serial Programming mode. The
Fuse bits are locked in both Serial and High-voltage
Programming mode.(1)
3
Notes:
0
1. Program fuse bits before programming LB1 and LB2.
2. “1” means unprogrammed, “0” means programmed.
Lock bits can also be read by device firmware. See section “Reading Fuse and Lock Bits from
Software” on page 164.
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18.2
Fuse Bytes
The device has three fuse bytes. Table 18-3, Table 18-4 and Table 18-5 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 18-3.
Fuse Extended Byte
Fuse High Byte
SELFPRGEN (1)
Notes:
Bit No
Description
Default Value
7
-
1 (unprogrammed)
6
-
1 (unprogrammed)
5
-
1 (unprogrammed)
4
-
1 (unprogrammed)
3
-
1 (unprogrammed)
2
-
1 (unprogrammed)
1
-
1 (unprogrammed)
0
Self-Programming Enable
1 (unprogrammed)
1. Enables SPM instruction. See “Self-Programming the Flash” on page 162.
Table 18-4.
Fuse High Byte
Fuse High Byte
Description
Default Value
7
External Reset disable
1 (unprogrammed)
DWEN (2)
6
DebugWIRE Enable
1 (unprogrammed)
SPIEN (3))
6
Enable Serial Program and Data
Downloading
0 (programmed, SPI prog.
enabled)
WDTON (4)
4
Watchdog Timer always on
1 (unprogrammed)
EESAVE
3
EEPROM memory is preserved
through the Chip Erase
1 (unprogrammed, EEPROM
not preserved)
BODLEVEL2 (5)
2
Brown-out Detector trigger level
1 (unprogrammed)
(5)
1
Brown-out Detector trigger level
1 (unprogrammed)
BODLEVEL0 (5)
0
Brown-out Detector trigger level
1 (unprogrammed)
RSTDISBL
(1)
BODLEVEL1
Notes:
Bit No
1. See “Alternate Functions of Port B” on page 64 for description of RSTDISBL and DWEN
Fuses. After programming the RSTDISBL fuse, parallel programming must be used to change
fuses and allow further programming.
2. DWEN must be unprogrammed when Lock Bit security is required. See “Program And Data
Memory Lock Bits” on page 167.
3. The SPIEN Fuse is not accessible in SPI programming mode.
4. Programming this fues will disable the Watchdog Timer Interrupt. See “WDTCR – Watchdog
Timer Control Register” on page 45 for details.
5. See Table 19-6 on page 187 for BODLEVEL Fuse decoding.
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Table 18-5.
Fuse Low Byte
Fuse Low Byte
Description
Default Value
7
Divide clock by 8
0 (programmed)
CKOUT (2)
6
Clock Output Enable
1 (unprogrammed)
SUT1
5
Select start-up time
1 (unprogrammed) (3)
SUT0
4
Select start-up time
0 (programmed) (3)
CKSEL3
3
Select Clock source
0 (programmed) (4)
CKSEL2
2
Select Clock source
0 (programmed) (4)
CKSEL1
1
Select Clock source
1 (unprogrammed) (4)
CKSEL0
0
Select Clock source
0 (programmed) (4)
CKDIV8
Notes:
(1)
Bit No
1. See “System Clock Prescaler” on page 31 for details.
2. Allows system clock to be output on pin. See “Clock Output Buffer” on page 32 for details.
3. The default value results in maximum start-up time for the default clock source. See Table 6-7
on page 28 for details.
4. The default setting results in internal oscillator @ 8.0 MHz. See Table 6-6 on page 28 for
details.
Note that fuse bits are locked if Lock Bit 1 (LB1) is programmed. Fuse bits should be programmed before lock bits. The status of fuse bits is not affected by chip erase.
Fuse bits can also be read by device firmware. See section “Reading Fuse and Lock Bits from
Software” on page 164.
18.2.1
18.3
Latching of Fuses
Fuse values are latched when the device enters programming mode and changes to fuse values
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. Fuses are also latched on power-up.
Signature Bytes
All Atmel microcontrollers have a three-byte signature code which identifies the device. This
code can be read in both serial and High-voltage Programming mode, also when the device is
locked. The three bytes reside in a separate address space. The signature bytes are given in
Table 18-6.
Table 18-6.
Device ID
Signature Bytes Address
18.4
Parts
0x000
0x001
0x002
ATtiny261A
0x1E
0x91
0x0C
ATtiny461A
0x1E
0x92
0x08
ATtiny861A
0x1E
0x93
0x0D
Calibration Byte
The signature area has one byte of calibration data for the internal oscillator. This byte resides in
the high byte of address 0x000. During reset, this byte is automatically written into the OSCCAL
Register to ensure correct frequency of the calibrated oscillator.
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18.5
Page Size
Table 18-7.
Device
Flash Size
Page Size
PCWORD
No. of Pages
PCPAGE
PCMSB
ATtiny261A
1K words (2K bytes)
16 words
PC[3:0]
64
PC[9:4]
9
ATtiny461A
2K words (4K bytes)
32 words
PC[4:0]
64
PC[10:5]
10
ATtiny861A
4K words (8K bytes)
32 words
PC[4:0]
128
PC[11:5]
11
Table 18-8.
18.6
No. of Words in a Page and No. of Pages in the Flash
No. of Words in a Page and No. of Pages in the EEPROM
Device
EEPROM
Size
Page Size
PCWORD
No. of Pages
PCPAGE
EEAMSB
ATtiny261A
128 bytes
4 bytes
EEA[1:0]
64
EEA[6:2]
6
ATtiny461A
256 bytes
4 bytes
EEA[1:0]
64
EEA[7:2]
7
ATtiny861A
512 bytes
4 bytes
EEA[1:0]
128
EEA[8:2]
8
Serial Programming
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). See Figure 18-1.
Figure 18-1. Serial Programming and Verify
+1.8 - 5.5V
VCC
MOSI
MISO
SCK
RESET
GND
Note:
170
If the device is clocked by the internal Oscillator, there is no need to connect a clock source to the
CLKI pin.
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ATtiny261A/461A/861A
After RESET is set low, the Programming Enable instruction needs to be executed first before
program/erase operations can be executed.
Table 18-9.
Note:
Pin Mapping Serial Programming
Symbol
Pins
I/O
Description
MOSI
PB0
I
Serial Data in
MISO
PB1
O
Serial Data out
SCK
PB2
I
Serial Clock
In Table 18-9, above, the pin mapping for SPI programming is listed. Not all parts use the SPI pins
dedicated for the internal SPI interface.
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
18.6.1
Serial Programming Algorithm
When writing serial data to the device, the data is clocked on the rising edge of SCK. When
reading, data is clocked on the falling edge of SCK. See Figure 19-3 and Figure 19-4 for timing
details.
To program and verify the device in Serial Programming mode, the following sequence is recommended (see four byte instruction formats in Table 18-11):
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 after SCK has been set to '0'. The duration
of the pulse must be at least tRST (the minimum pulse width on RESET pin, see Table
19-4 on page 187) plus two CPU clock cycles.
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 5 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 6 MSB
of the address. If polling (RDY/BSY) is not used, the user must wait at least tWD_FLASH
before issuing the next page. (See Table 18-10.) Accessing the serial programming
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interface before the Flash write operation completes can result in incorrect
programming.
5. A: 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 (RDY/BSY) is not used,
the user must wait at least tWD_EEPROM before issuing the next byte. (See Table 18-10.)
In a chip erased device, no 0xFFs in the data file(s) need to be programmed.
B: The EEPROM array is programmed one page at a time. The Memory page is loaded
one byte at a time by supplying the 2 LSB of the address and data together with the
Load EEPROM Memory Page instruction. The EEPROM Memory Page is stored by
loading the Write EEPROM Memory Page Instruction with the 6 MSB of the address.
When using EEPROM page access only byte locations loaded with the Load EEPROM
Memory Page instruction is altered. The remaining locations remain unchanged. If polling (RDY/BSY) is not used, the used must wait at least tWD_EEPROM before issuing the
next page (See Table 18-8). In a chip erased device, no 0xFF 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.
Table 18-10. Minimum Wait Delay Before Writing the Next Flash or EEPROM Location
18.6.2
Symbol
Minimum Wait Delay
tWD_FLASH
4.5 ms
tWD_EEPROM
4.0 ms
tWD_ERASE
4.0 ms
tWD_FUSE
4.5 ms
Serial Programming Instruction set
The instruction set is described in Table 18-11 and Figure 18-2 on page 174.
Table 18-11. Serial Programming Instruction Set
Instruction Format
Instruction/Operation
Byte 1
Byte 2
Byte 3
Byte4
Programming Enable
$AC
$53
$00
$00
Chip Erase (Program Memory/EEPROM)
$AC
$80
$00
$00
Poll RDY/BSY
$F0
$00
$00
data byte out
Load Extended Address byte(1)
$4D
$00
Extended adr
$00
Load Program Memory Page, High byte
$48
adr MSB
adr LSB
high data byte in
Load Instructions
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Table 18-11. Serial Programming Instruction Set (Continued)
Instruction Format
Instruction/Operation
Byte 1
Byte 2
Byte 3
Byte4
Load Program Memory Page, Low byte
$40
adr MSB
adr LSB
low data byte in
Load EEPROM Memory Page (page access)
$C1
$00
0000 000aa
data byte in
Read Program Memory, High byte
$28
adr MSB
adr LSB
high data byte out
Read Program Memory, Low byte
$20
adr MSB
adr LSB
low data byte out
Read EEPROM Memory
$A0
$00
00aa aaaa
data byte out
Read Lock bits
$58
$00
$00
data byte out
Read Signature Byte
$30
$00
0000 000aa
data byte out
Read Fuse bits
$50
$00
$00
data byte out
Read Fuse High bits
$58
$08
$00
data byte out
Read Extended Fuse Bits
$50
$08
$00
data byte out
Read Calibration Byte
$38
$00
$00
data byte out
Write Program Memory Page
$4C
adr MSB
adr LSB
$00
Write EEPROM Memory
$C0
$00
00aa aaaa
data byte in
Write EEPROM Memory Page (page access)
$C2
$00
00aa aa00
$00
Write Lock bits
$AC
$E0
$00
data byte in
Write Fuse bits
$AC
$A0
$00
data byte in
Write Fuse High bits
$AC
$A8
$00
data byte in
Write Extended Fuse Bits
$AC
$A4
$00
data byte in
Read Instructions
Write Instructions
Notes:
(6)
1. Not all instructions are applicable for all parts.
2. a = address
3. Bits are programmed ‘0’, unprogrammed ‘1’.
4. To ensure future compatibility, unused Fuses and Lock bits should be unprogrammed (‘1’) .
5. Refer to the correspondig section for Fuse and Lock bits, Calibration and Signature bytes and Page size.
6. Instructions accessing program memory use a word address. This address may be random within the page range.
7. See http://www.atmel.com/avr for Application Notes regarding programming and programmers.
If the LSB in RDY/BSY data byte out is ‘1’, a programming operation is still pending. Wait until
this bit returns ‘0’ before the next instruction is carried out.
Within the same page, the low data byte must be loaded prior to the high data byte.
After data is loaded to the page buffer, program the EEPROM page, see Figure 18-2 on page
174.
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Figure 18-2. Serial Programming Instruction example
Serial Programming Instruction
Load Program Memory Page (High/Low Byte)/
Load EEPROM Memory Page (page access)
Byte 1
Byte 2
Byte 3
Adr
A
drr MSB
M
MS
SB
Write Program Memory Page/
Write EEPROM Memory Page
Byte 1
Byte 4
Byte 2
Adr LSB
Bit 15 B
Adr MSB
Bit 15 B
0
Byte 3
Byte 4
Adr
A
dr LSB
LS
SB
0
Page Buffer
Page Offset
Page 0
Page 1
Page 2
Page Number
Page N-1
Program Memory/
EEPROM Memory
18.7
Parallel Programming
This section describes how to parallel program and verify Flash Program memory, EEPROM
Data memory, Memory Lock bits, and Fuse bits. Pulses are assumed to be at least 250 ns in
length, unless otherwise noted.
18.7.1
Signal Names
In this section, some pins are referenced by signal names describing their functionality during
parallel programming, see Figure 18-3 and Table 18-12. Pins not described in the following table
are referenced by pin names.
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Figure 18-3. Parallel Programming.
+5V
WR
PB0
XA0
PB1
XA1/BS2
PB2
PAGEL/BS1
PB3
VCC
+5V
AVCC
PA7 - PA0
DATA
XTAL1/PB4
OE
PB5
RDY/BSY
PB6
+12 V
RESET
GND
Table 18-12. Pin Name Mapping
Signal Name in
Programming Mode
Pin
Name
I/O
WR
PB0
I
Write Pulse (Active low).
XA0
PB1
I
XTAL Action Bit 0
XA1/BS2
PB2
I
XTAL Action Bit 1. Byte Select 2 (“0” selects low byte, “1”
selects 2’nd high byte).
PAGEL/BS1
PB3
I
Byte Select 1 (“0” selects low byte, “1” selects high byte).
Program Memory and EEPROM Data Page Load.
OE
PB5
I
Output Enable (Active low).
RDY/BSY
PB6
O
0: Device is busy programming, 1: Device is ready for new
command.
DATA I/O
PA7-PA0
I/O
Bi-directional Data bus (Output when OE is low).
Function
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Table 18-13. Pin Values Used to Enter Programming Mode
Pin
Symbol
Value
PAGEL/BS1
Prog_enable[3]
0
XA1/BS2
Prog_enable[2]
0
XA0
Prog_enable[1]
0
WR
Prog_enable[0]
0
The XA1/XA0 pins determine the action executed when the XTAL1 pin is given a positive pulse.
The bit coding is shown in Table 18-14.
Table 18-14. 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
When pulsing WR or OE, the command loaded determines the action executed. The different
Commands are shown in Table 18-15.
Table 18-15. Command Byte Bit Coding
Command Byte
176
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
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18.7.2
Entering Programming Mode
The following algorithm puts the device in parallel programming mode:
1. Apply 4.5 - 5.5V between VCC and GND.
2. Set RESET to “0” and toggle XTAL1 at least six times.
3. Set Prog_enable pins listed in Table 18-13 on page 176 to “0000” and wait at least 100
ns.
4. Apply 11.5 - 12.5V to RESET. Any activity on Prog_enable pins within 100 ns after
+12V has been applied to RESET, will cause the device to fail entering programming
mode.
5. Wait at least 50 µs before sending a new command.
18.7.3
Considerations for Efficient Programming
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.
18.7.4
Chip Erase
The Chip Erase will erase the Flash and EEPROM 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.
1. Load Command “Chip Erase”:
a. Set XA1, XA0 to “10”. This enables command loading.
b. Set BS1 to “0”.
c.
Set DATA to “1000 0000”. This is the command for Chip Erase.
d. Give XTAL1 a positive pulse. This loads the command.
e. Give WR a negative pulse. This starts the Chip Erase. RDY/BSY goes low.
f.
Note:
18.7.5
Wait until RDY/BSY goes high before loading a new command.
The EEPROM memory is preserved during Chip Erase if the EESAVE Fuse is programmed.
Programming the Flash
The Flash is organized in pages, see Table 18-7 on page 170. 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 (see Figure 18-5 for signal waveforms):
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1. Load Command “Write Flash”:
a. Set XA1, XA0 to “10”. This enables command loading.
b. Set BS1 to “0”.
c.
Set DATA to “0001 0000”. This is the command for Write Flash.
d. Give XTAL1 a positive pulse. This loads the command.
2. Load Address Low byte:
a. Set XA1, XA0 to “00”. This enables address loading.
b. Keep BS1 at “0”. This selects low address.
c.
Set DATA = Address low byte (0x00 - 0xFF).
d. Give XTAL1 a positive pulse. This loads the address low byte.
3. Load Data Low Byte:
a. Set XA1, XA0 to “01”. This enables data loading.
b. Set DATA = Data low byte (0x00 - 0xFF).
c.
Give XTAL1 a positive pulse. This loads the data byte.
4. Load Data High Byte:
a. Set BS1 to “1”. This selects high data byte.
b. Keep XA1, XA0 at “01”. This enables data loading.
c.
Set DATA = Data high byte (0x00 - 0xFF).
d. Give XTAL1 a positive pulse. This loads the data byte.
5. Repeat steps 2 to 4 until the entire buffer is filled or until all data within the page is
loaded.
6. Load Address High byte:
a. Set XA1, XA0 to “00”. This enables address loading.
b. Set BS1 to “1”. This selects high address.
c.
Set DATA = Address high byte (0x00 - 0xFF).
d. Give XTAL1 a positive pulse. This loads the address high byte.
7. Program Page:
a. Give WR a negative pulse. This starts programming of the entire page of data.
RDY/BSY goes low.
b. Wait until RDY/BSY goes high.
8. Repeat steps 2 to 7 until the entire Flash is programmed or until all data has been
programmed.
9. End Page Programming:
a. Set XA1, XA0 to “10”. This enables command loading.
b. Set DATA to “0000 0000”. This is the command for No Operation.
c.
Give XTAL1 a positive pulse. This loads the command, and the internal write signals are reset.
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 18-4. 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.
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Figure 18-4. Addressing the Flash Which is Organized in Pages
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:
PCPAGE and PCWORD are listed in Table 18-7 on page 170.
In the figure below, “XX” means don’t care. The numbers in the figure refer to the programming
description above.
WR
Figure 18-5. Flash Programming Waveforms
8
5
STEP
DATA
1
2
3
4
2
3
4
6
7
9
0x10
ADDR. LOW
DATA LOW
DATA HIGH
ADDR. LOW
DATA LOW
DATA HIGH
ADDR. HIGH
XXX
0x00
XA1 / BS2
XA0
PAGEL / BS1
XTAL1
WR
RDY / BSY
RESET +12V
OE
18.7.6
Programming the EEPROM
The EEPROM is organized in pages, see Table 18-8 on page 170. When programming the
EEPROM, the program data is latched into a page buffer. This allows one page of data to be
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8197A–AVR–10/09
programmed simultaneously. The programming algorithm for the EEPROM data memory is as
follows (refer to “Programming the Flash” on page 177 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).
6. K: Repeat 3 through 5 until the entire buffer is filled.
7. L: Program EEPROM page
a. Set BS to “0”.
b. Give WR a negative pulse. This starts programming of the EEPROM page.
RDY/BSY goes low.
c.
Wait until to RDY/BSY goes high before programming the next page (See Figure
18-6 for signal waveforms).
Figure 18-6. 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/BS2
XA0
PAGEL/BS1
XTAL1
WR
RDY/BSY
RESET +12V
OE
18.7.7
Reading the Flash
The algorithm for reading the Flash memory is as follows (refer to “Programming the Flash” on
page 177 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 BS to “1”. The Flash word high byte can now be read at DATA.
6. Set OE to “1”.
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18.7.8
Reading the EEPROM
The algorithm for reading the EEPROM memory is as follows (refer to “Programming the Flash”
on page 177 for details on Command and Address loading):
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”.
18.7.9
Programming the Fuse Low Bits
The algorithm for programming the Fuse Low bits is as follows (refer to “Programming the Flash”
on page 177 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.
18.7.10
Programming the Fuse High Bits
The algorithm for programming the Fuse High bits is as follows (refer to “Programming the
Flash” on page 177 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.
18.7.11
Programming the Extended Fuse Bits
The algorithm for programming the Extended Fuse bits is as follows (refer to “Programming the
Flash” on page 177 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.
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Figure 18-7. 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/BS2
XA0
PAGEL/BS1
XTAL1
WR
RDY/BSY
RESET +12V
OE
18.7.12
Programming the Lock Bits
The algorithm for programming the Lock bits is as follows (refer to “Programming the Flash” on
page 177 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.
18.7.13
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 177 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”.
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Figure 18-8. Mapping Between BS1, BS2 and the Fuse and Lock Bits During Read
0
Fuse Low Byte
0
Extended Fuse Byte
1
DATA
BS2
0
Lock Bits
1
Fuse High Byte
1
BS1
BS2
18.7.14
Reading the Signature Bytes
The algorithm for reading the Signature bytes is as follows (refer to “Programming the Flash” on
page 177 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 BS to “0”. The selected Signature byte can now be read at DATA.
4. Set OE to “1”.
18.7.15
Reading the Calibration Byte
The algorithm for reading the Calibration byte is as follows (refer to “Programming the Flash” on
page 177 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”.
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19. Electrical Characteristics
19.1
Absolute Maximum Ratings*
Operating Temperature.................................. -55°C to +125°C
*NOTICE:
Storage Temperature ..................................... -65°C to +150°C
Voltage on any Pin except RESET
with respect to Ground ................................-0.5V to VCC+0.5V
Voltage on RESET with respect to Ground......-0.5V to +13.0V
Maximum Operating Voltage ............................................ 6.0V
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.
DC Current per I/O Pin ............................................... 40.0 mA
DC Current VCC and GND Pins................................ 200.0 mA
19.2
DC Characteristics
Table 19-1.
Symbol
VIL
VIH
DC Characteristics. TA = -40°C to 85°C, VCC = 1.8V to 5.5V (unless otherwise noted).
Parameter
Condition
Input Low-voltage
Input High-voltage
(3)
Min (1)
Typ
Max (2)
Units
Except XTAL1 and
RESET pins
-0.5
0.2VCC
V
XTAL1 pin,
External Clock Selected
-0.5
0.1VCC
V
RESET pin
-0.5
0.2VCC
V
RESET pin as I/O
-0.5
0.2VCC
V
Except XTAL1 and
RESET pins
0.7VCC
VCC +0.5
V
XTAL1 pin,
External Clock Selected
0.8VCC
VCC +0.5
V
RESET pin
0.9VCC
VCC +0.5
V
RESET pin as I/O
0.7VCC
VCC +0.5
V
0.6
0.5
V
V
VOL
Output Low Voltage
(Except Reset pin) (5)
IOL = 10 mA, VCC = 5V
IOL = 5 mA, VCC = 3V
VOH
Output High-voltage (4)
(Except Reset pin) (5)
IOH = -10 mA, VCC = 5V
IOH = -5 mA, VCC = 3V
IIL
Input Leakage
Current I/O Pin
VCC = 5.5V, pin low
(absolute value)
<0.05
1
µA
IIH
Input Leakage
Current I/O Pin
VCC = 5.5V, pin high
(absolute value)
<0.05
1
µA
RRST
Reset Pull-up Resistor
30
60
kΩ
RPU
I/O Pin Pull-up Resistor
20
50
kΩ
184
4.3
2.5
V
V
ATtiny261A/461A/861A
8197A–AVR–10/09
ATtiny261A/461A/861A
Table 19-1.
Symbol
DC Characteristics. TA = -40°C to 85°C, VCC = 1.8V to 5.5V (unless otherwise noted).
Parameter
Min (1)
Typ
Max (2)
Units
(6)
0.2
0.5
mA
(6)
1.2
2
mA
(6)
Active 8MHz, VCC = 5V
3.6
7
mA
Idle 1MHz, VCC = 2V(6)
0.035
0.15
mA
Idle 4MHz, VCC = 3V(6)
0.25
0.4
mA
0.9
1.5
mA
4
10
µA
0.15
2
µA
Condition
Active 1MHz, VCC = 2V
Active 4MHz, VCC = 3V
Power Supply Current
ICC
(6)
Idle 8MHz, VCC = 5V
(7)
Power-down mode
Notes:
WDT enabled, VCC = 3V
WDT disabled, VCC = 3V(7)
1. “Min” means the lowest value where the pin is guaranteed to be read as high.
2. “Max” means the highest value where the pin is guaranteed to be read as low.
3. Although each I/O port can sink more than the test conditions (10 mA at VCC = 5V, 5 mA at VCC = 3V) under steady state
conditions (non-transient), the sum of all IOL (for all ports) should not exceed 60 mA. If IOL exceeds the test conditions, VOL
may exceed the related specification. Pins are not guaranteed to sink current greater than the listed test condition.
4. Although each I/O port can source more than the test conditions (10 mA at VCC = 5V, 5 mA at VCC = 3V) under steady state
conditions (non-transient), the sum of all IOH (for all ports) should not exceed 60 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. The RESET pin must tolerate high voltages when entering and operating in programming modes and, as a consequence,
has a weak drive strength as compared to regular I/O pins. See Figure 20-32, Figure 20-33, Figure 20-34, and Figure 20-35
(starting on page 210).
6. Values using methods described in “Minimizing Power Consumption” on page 36. Power Reduction is enabled (PRR =
0xFF) and there is no I/O drive.
7. BOD Disabled.
19.3
Speed Grades
The maximum operating frequency of the device depends on VCC . As shown in Figure 19-1 the
maximum frequency vs. VCC relationship is linear between 1.8V < VCC < 4.5V.
Figure 19-1. Maximum Frequency vs. VCC
20 MHz
4 MHz
1.8V
4.5V
5.5V
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19.4
Clock Characteristics
19.4.1
Accuracy of Calibrated Internal Oscillator
It is possible to manually calibrate the internal oscillator to be more accurate than default factory
calibration. Note that the oscillator frequency depends on temperature and voltage. Voltage and
temperature characteristics can be found in Figure 20-49 on page 219 and Figure 20-50 on
page 219.
Table 19-2.
Calibration Accuracy of Internal Oscillator
Calibration
Method
Target Frequency
VCC
Temperature
Accuracy at given
voltage & temperature (1)
8.0 MHz
3V
25°C
±10%
Fixed frequency
within:
7.3 - 8.1 MHz
Fixed voltage within:
1.8V - 5.5V
Fixed temperature
within:
-40°C - 85°C
±1%
Factory
Calibration
User
Calibration
Notes:
1. Accuracy of oscillator frequency at calibration point (fixed temperature and fixed voltage).
19.4.2
External Clock Drive
Figure 19-2. External Clock Drive Waveforms
V IH1
V IL1
Table 19-3.
External Clock Drive Characteristics
VCC = 1.8 - 5.5V
VCC = 2.7 - 5.5V
VCC = 4.5 - 5.5V
Symbol
Parameter
1/tCLCL
Clock Frequency
tCLCL
Clock Period
250
100
50
ns
tCHCX
High Time
100
40
20
ns
tCLCX
Low Time
100
40
20
ns
tCLCH
Rise Time
2.0
1.6
0.5
μs
tCHCL
Fall Time
2.0
1.6
0.5
μs
ΔtCLCL
Change in period from one clock cycle to the next
2
2
2
%
186
Min.
Max.
Min.
Max.
Min.
Max.
Units
0
4
0
10
0
20
MHz
ATtiny261A/461A/861A
8197A–AVR–10/09
ATtiny261A/461A/861A
19.5
System and Reset Characteristics
Table 19-4.
Symbol
Parameter
Condition
VRST
RESET Pin Threshold Voltage (1)
tRST
Min pulse width on RESET Pin
(1)
Brown-out Detector Hysteresis
(1)
VHYST
Min
Typ
0.2 VCC
VCC = 3V
tBOD
Min Pulse Width on
Brown-out Reset (1)
VBG
Internal bandgap voltage
VCC = 2.7V
TA = 25°C
tBG
Internal bandgap start-up time (1)
IBG
Internal bandgap reference
current consumption (1)
Notes:
19.5.1
Reset, Brown-out, and Internal Voltage Characteristics
1.0
Max
Units
0.9 VCC
V
2.5
µs
50
mV
2
µs
1.1
1.2
V
VCC = 5V
TA = 25°C
40
70
µs
VCC = 5V
TA = 25°C
15
µA
1. Not tested. Values are guidelines, only.
Enhanced Power-On Reset
Table 19-5.
Symbol
Characteristics of Enhanced Power-On Reset. TA = -40 – 85°C
Parameter
Min(1)
Typ(1)
Max(1)
Units
1.1
1.4
1.6
V
1.3
1.6
V
(2)
VPOR
Release threshold of power-on reset
VPOA
Activation threshold of power-on reset (3)
0.6
SRON
Power-On Slope Rate
0.01
Note:
V/ms
1. Values are guidelines, only.
2. Threshold where device is released from reset when voltage is rising.
3. The Power-on Reset will not work unless the supply voltage has been below VPOA.
19.5.2
Brown-Out Detection
Table 19-6.
BODLEVEL Fuse Coding(1)
BODLEVEL [2:0] Fuses
Min VBOT
111
Max VBOT
Units
BOD Disabled
110
1.7
1.8
2.0
101
2.5
2.7
2.9
100
4.1
4.3
4.5
0XX
Note:
Typ VBOT
V
Reserved
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.
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8197A–AVR–10/09
19.6
ADC Characteristics
Table 19-7.
Symbol
ADC Characteristics, Single Ended Channels. T = -40°C - 85°C
Parameter
Condition
Min
Typ
Resolution
Absolute accuracy
(Including INL, DNL, and
Quantization, Gain and Offset
Errors)
Units
10
Bits
VREF = 4V, VCC = 4V,
ADC clock = 200 kHz
2
LSB
VREF = 4V, VCC = 4V,
ADC clock = 1 MHz
3
LSB
VREF = 4V, VCC = 4V,
ADC clock = 200 kHz
Noise Reduction Mode
1.5
LSB
VREF = 4V, VCC = 4V,
ADC clock = 1 MHz
Noise Reduction Mode
2.5
LSB
Integral Non-Linearity (INL)
(Accuracy after Offset and
Gain Calibration)
VREF = 4V, VCC = 4V,
ADC clock = 200 kHz
1
LSB
Differential Non-linearity (DNL)
VREF = 4V, VCC = 4V,
ADC clock = 200 kHz
0.5
LSB
Gain Error
VREF = 4V, VCC = 4V,
ADC clock = 200 kHz
2.5
LSB
Offset Error
VREF = 4V, VCC = 4V,
ADC clock = 200 kHz
1.5
LSB
Conversion Time
Free Running Conversion
13
260
µs
50
1000
kHz
VCC - 0.3
VCC + 0.3
V
Single Ended Conversions
2.0
AVCC
V
Differential Conversions
2.0
AVCC - 1.0
V
GND
VREF
0
AVCC (1)
Clock Frequency
AVCC
Analog Supply Voltage
AREF
External Voltage Reference
VIN
Input Voltage
Single Ended Conversions
Differential Conversions
Single Ended Conversions
Input Bandwidth
VINT
Max
Differential Conversions
Internal 1.1V Reference
Internal 2.56V Reference
38.5
(1)
VCC > 3.0V
V
kHz
4
1.0
1.1
1.2
V
2.3
2.56
2.8
V
RREF
Reference Input Resistance
35
kΩ
RAIN
Analog Input Resistance
100
MΩ
ADC Conversion Output
Note:
0
1023
LSB
1. VDIFF must be below VREF.
2. Not tested in production.
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19.7
Serial Programming Characteristics
Figure 19-3. Serial Programming Waveforms
SERIAL DATA INPUT
(MOSI)
MSB
LSB
SERIAL DATA OUTPUT
(MISO)
MSB
LSB
SERIAL CLOCK INPUT
(SCK)
SAMPLE
Figure 19-4. Serial Programming Timing
MOSI
SCK
tSLSH
tSHOX
tOVSH
tSHSL
MISO
tSLIV
Table 19-8.
Serial Programming Characteristics, TA = -40°C to 85°C, VCC = 1.8 - 5.5V (Unless
Otherwise Noted)
Symbol
Parameter
1/tCLCL
Oscillator Frequency
tCLCL
Oscillator Period
1/tCLCL
tCLCL
tSHSL
Min
0
Max
Units
4
MHz
250
Oscillator Frequency (VCC = 4.5V - 5.5V)
0
Oscillator Period VCC = 4.5V - 5.5V
50
SCK Pulse Width High
Typ
ns
20
ns
(1)
ns
(1)
ns
2 tCLCL
tSLSH
SCK Pulse Width Low
tOVSH
MOSI Setup to SCK High
tCLCL
ns
tSHOX
MOSI Hold after SCK High
2 tCLCL
ns
tSLIV
SCK Low to MISO Valid
Note:
2 tCLCL
MHz
100
ns
1. 2 tCLCL for fck < 12 MHz, 3 tCLCL for fck >= 12 MHz
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19.8
Parallel Programming Characteristics
Figure 19-5. Parallel Programming Timing, Including some General Timing Requirements
tXLWL
tXHXL
XTAL1
tDVXH
tXLDX
tBVPH
tPLBX t BVWL
Data & Contol
(DATA, XA0, XA1/BS2, PAGEL/BS1)
tWLBX
tWLWH
WR
tPLWL
WLRL
RDY/BSY
tWLRH
Figure 19-6. Parallel Programming Timing, Loading Sequence with Timing Requirements
LOAD ADDRESS
(LOW BYTE)
LOAD DATA
(LOW BYTE)
LOAD DATA
(HIGH BYTE)
LOAD ADDRESS
(LOW BYTE)
t XLXH
XTAL1
PAGEL/BS1
DATA
ADDR0 (Low Byte)
DATA (Low Byte)
DATA (High Byte)
ADDR1 (Low Byte)
XA0
XA1/BS2
Note:
190
The timing requirements shown in Figure 19-5 (i.e., tDVXH, tXHXL, and tXLDX) also apply to loading operation.
ATtiny261A/461A/861A
8197A–AVR–10/09
ATtiny261A/461A/861A
Figure 19-7. Parallel Programming Timing, Reading Sequence (within the Same Page) with Timing Requirements
LOAD ADDRESS
(LOW BYTE)
READ DATA
(LOW BYTE)
READ DATA
(HIGH BYTE)
LOAD ADDRESS
(LOW BYTE)
tXLOL
XTAL1
tBVDV
PAGEL/BS1
tOLDV
OE
DATA
tOHDZ
ADDR0 (Low Byte)
ADDR1 (Low Byte)
DATA (High Byte)
DATA (Low Byte)
XA0
XA1/BS2
Note:
The timing requirements shown in Figure 19-5 (i.e., tDVXH, tXHXL, and tXLDX) also apply to reading operation.
Table 19-9.
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
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)
tWLRH_CE
WR Low to RDY/BSY High for Chip Erase
tXLOL
XTAL1 Low to OE Low
(2)
Typ
Max
Units
12.5
V
250
μA
0
1
μs
3.7
4.5
ms
7.5
9
ms
0
ns
191
8197A–AVR–10/09
Table 19-9.
Parallel Programming Characteristics, VCC = 5V ± 10% (Continued)
Symbol
Parameter
tBVDV
BS1 Valid to DATA valid
tOLDV
tOHDZ
Notes:
1.
Min
Max
Units
250
ns
OE Low to DATA Valid
250
ns
OE High to DATA Tri-stated
250
ns
0
Typ
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.
192
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ATtiny261A/461A/861A
20. Typical Characteristics
The data contained in this section is largely based on simulations and characterization of similar
devices in the same process and design methods. Thus, the data should be treated as indications of how the part will behave.
The following charts show typical behavior. These figures are not tested during manufacturing.
During characterisation devices are operated at frequencies higher than test limits but they are
not guaranteed to function properly at frequencies higher than the ordering code indicates.
All current consumption measurements are performed with all I/O pins configured as inputs and
with internal pull-ups enabled. 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.
A sine wave generator with rail-to-rail output is used as clock source but current consumption in
Power-Down mode is independent of clock selection. 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.
The current drawn from pins with a capacitive load may be estimated (for one pin) as follows:
I CP ≈ V CC × C L × f SW
where VCC = operating voltage, CL = load capacitance and fSW = average switching frequency of
I/O pin.
20.1
Supply Current of I/O modules
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 “PRR – Power Reduction Register” on
page 38 for details.
Table 20-1.
Additional Current Consumption for the different I/O modules (absolute values).
Typical numbers
PRR bit
VCC = 2V, f = 1MHz
VCC = 3V, f = 4MHz
VCC = 5V, f = 8MHz
PRTIM1
35 uA
200 uA
900 uA
PRTIM0
5 uA
25 uA
100 uA
PRUSI
5 uA
25 uA
450 uA
PRADC
200 uA
280 uA
550 uA
Table 20-2 below can be used for calculating typical current consumption for other supply voltages and frequencies than those mentioned in Table 20-1 above.
193
8197A–AVR–10/09
Table 20-2.
Additional Current Consumption (percentage) in Active and Idle mode.
PRR bit
Additional Current consumption
compared to Active with external
clock (see Figure 20-1 on page
195 and Figure 20-2 on page 195)
Additional Current consumption
compared to Idle with external
clock (see Figure 20-6 on page
197 and Figure 20-7 on page 198)
PRTIM1
20...25 %
100 %
PRTIM0
2...3 %
10...15 %
PRUSI
2...12 %
10...50%
PRADC
15...100 %
50...500 %
It is possible to calculate the typical current consumption based on the numbers from Table 20-1
for other VCC and frequency settings than listed in Table 20-2.
20.1.1
Example
Calculate the expected current consumption in idle mode with TIMER0, ADC, and USI enabled
at VCC = 2.0V and F = 1MHz. From Table 20-2, third column, we see that we need to add 10%
for the TIMER0, 27.3 % for the ADC, and 6.5 % for the USI module. Reading from Figure 20-6
on page 197, we find that the idle current consumption is ~0,085 mA at VCC = 2.0V and F=1MHz.
The total current consumption in idle mode with TIMER0, ADC, and USI enabled, gives:
I CC total ≈ 0,085mA • ( 1 + 0,10 + 0,273 + 0,065 ) ≈ 0,122mA
194
ATtiny261A/461A/861A
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ATtiny261A/461A/861A
20.2
20.2.1
ATtiny261A
Current Consumption in Active Mode
Figure 20-1. Active Supply Current vs. Low Frequency (0.1 - 1.0 MHz)
ACTIVE SUPPLY CURRENT vs. LOW FREQUENCY
1
5.5 V
0.8
5.0 V
4.5 V
0.4
3.3 V
ICC (mA)
0.6
2.7 V
0.2
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)
Figure 20-2. Active Supply Current vs. Frequency (1 - 20 MHz)
ACTIVE SUPPLY CURRENT vs. FREQUENCY
PRR = 0xFF
10
5.5 V
8
5.0 V
4.5 V
ICC (mA)
6
4
3.3 V
2
2.7 V
1.8 V
0
0
2
4
6
8
10
12
14
16
18
20
Frequency (MHz)
195
8197A–AVR–10/09
Figure 20-3. Active Supply Current vs. VCC (Internal Calibrated Oscillator, 8 MHz)
ACTIVE SUPPLY CURRENT vs. SUPPLY VOLTAGE
INTERNAL OSCILLATOR, 8 MHz
5
85 °C
25 °C
-40 °C
4
ICC (mA)
3
2
1
0
1.5
2
2.5
3
3.5
4
4.5
5
5.5
VCC (V)
Figure 20-4. Active Supply Current vs. VCC (Internal Calibrated Oscillator, 1 MHz)
ACTIVE SUPPLY CURRENT vs. SUPPLY VOLTAGE
INTERNAL OSCILLATOR, 1 MHz
1.2
85 °C
25 °C
-40 °C
1
ICC (mA)
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)
196
ATtiny261A/461A/861A
8197A–AVR–10/09
ATtiny261A/461A/861A
Figure 20-5. Active Supply Current vs. VCC (Internal Calibrated Oscillator, 128 kHz)
ACTIVE SUPPLY CURRENT vs. SUPPLY VOLTAGE
INTERNAL OSCILLATOR, 128 kHz
0.12
-40 °C
25 °C
85 °C
0.1
ICC (mA)
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)
20.2.2
Current Consumption in Idle Mode
Figure 20-6. Idle Supply Current vs. Low Frequency (0.1 - 1.0 MHz)
IDLE SUPPLY CURRENT vs. LOW FREQUENCY
0.14
5.5 V
0.12
5.0 V
0.1
ICC (mA)
4.5 V
0.08
4.0 V
0.06
3.3 V
2.7 V
0.04
1.8 V
0.02
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
Frequency (MHz)
197
8197A–AVR–10/09
Figure 20-7. Idle Supply Current vs. Frequency (1 - 20 MHz)
IDLE SUPPLY CURRENT vs. FREQUENCY
3
2.5
5.5 V
5.0 V
2
ICC (mA)
4.5 V
1.5
4.0 V
1
0.5
2.7 V
1.8 V
0
0
2
4
6
8
10
12
14
16
18
20
Frequency (MHz)
Figure 20-8. Idle Supply Current vs. VCC (Internal Calibrated Oscillator, 8 MHz)
IDLE SUPPLY CURRENT vs. VCC
INTERNAL OSCILLATOR, 8 MHz
1.4
85 °C
25 °C
-40 °C
1.2
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)
198
ATtiny261A/461A/861A
8197A–AVR–10/09
ATtiny261A/461A/861A
Figure 20-9. Idle Supply Current vs. VCC (Internal Calibrated Oscillator, 1 MHz)
IDLE SUPPLY CURRENT vs. VCC
INTERNAL OSCILLATOR, 1 MHz
0.35
85 °C
25 °C
-40 °C
0.3
ICC (mA)
0.25
0.2
0.15
0.1
0.05
0
1.5
2
2.5
3
3.5
4
4.5
5
5.5
VCC (V)
Figure 20-10. Idle Supply Current vs. VCC (Internal Calibrated Oscillator, 128 kHz)
IDLE SUPPLY CURRENT vs. VCC
INTERNAL OSCILLATOR, 128 kHz
0.025
-40 °C
25 °C
85 °C
0.02
ICC (mA)
0.015
0.01
0.005
0
1.5
2
2.5
3
3.5
4
4.5
5
5.5
VCC (V)
199
8197A–AVR–10/09
20.2.3
Current Consumption in Power-Down Mode
Figure 20-11. Power-down Supply Current vs. VCC (Watchdog Timer Disabled)
POWER-DOWN SUPPLY CURRENT vs. SUPPLY VOLTAGE
WATCHDOG TIMER DISABLED
0.7
85 °C
0.6
ICC (uA)
0.5
0.4
0.3
0.2
25 °C
0.1
-40 °C
0
1.5
2
2.5
3
3.5
4
4.5
5
5.5
VCC (V)
Figure 20-12. Power-down Supply Current vs. VCC (Watchdog Timer Enabled)
POWER-DOWN SUPPLY CURRENT vs. SUPPLY VOLTAGE
WATCHDOG TIMER ENABLED
10
8
-40 °C
25 °C
85 °C
ICC (uA)
6
4
2
0
1.5
2
2.5
3
3.5
4
4.5
5
5.5
VCC (V)
200
ATtiny261A/461A/861A
8197A–AVR–10/09
ATtiny261A/461A/861A
20.2.4
Current Consumption in Reset
Figure 20-13. Reset Supply Current vs. Low Frequency (0.1 - 1.0 MHz, Excluding Current
Through the Reset Pull-up)
RESET CURRENT vs. FREQUENCY
EXCLUDING CURRENT THROUGH RESET PULLUP
0.12
5.5 V
0.1
5.0 V
ICC (mA)
0.08
4.5 V
4.0 V
0.06
3.3 V
2.7 V
0.04
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)
Figure 20-14. Reset Supply Current vs. Frequency (1 - 20 MHz, Excluding Current Through the
Reset Pull-up)
RESET CURRENT vs. SUPPLY VOLTAGE
EXCLUDING CURRENT THROUGH RESET PULLUP
2
5.5 V
1.8
5.0 V
1.6
4.5 V
ICC (mA)
1.4
1.2
4.0 V
1
0.8
3.3 V
0.6
0.4
2.7 V
0.2
1.8 V
0
0
2
4
6
8
10
12
14
16
18
20
Frequency (MHz)
201
8197A–AVR–10/09
20.2.5
Current Consumption of Peripheral Units
Figure 20-15. Analog Comparator Current vs. VCC
ANALOG COMPARATOR CURRENT vs. VCC
80
70
60
ICC (uA)
50
40
30
20
10
0
1.5
2
2.5
3
3.5
4
4.5
5
5.5
4
4.5
5
5.5
VCC (V)
Figure 20-16. ADC Current vs. VCC (AREF = AVCC)
ADC CURRENT vs. VCC
f = 1.0 MHz
450
400
350
ICC (uA)
300
250
200
150
100
50
0
1.5
2
2.5
3
3.5
VCC (V)
202
ATtiny261A/461A/861A
8197A–AVR–10/09
ATtiny261A/461A/861A
Figure 20-17. Timer/Counter1 Current vs. VCC
TIMER/COUNTER1 CURRENT vs. VCC
8000
7000
64MHz
6000
ICC (uA)
5000
4000
32MHz
3000
2000
1000
1MHz
0
1.5
2
2.5
3
3.5
4
4.5
5
5.5
VCC (V)
Figure 20-18. Brownout Detector Current vs. VCC
BROWNOUT DETECTOR CURRENT vs. VCC
40
35
30
ICC (uA)
25
20
15
10
5
0
1.5
2
2.5
3
3.5
4
4.5
5
5.5
VCC (V)
203
8197A–AVR–10/09
Figure 20-19. Programming Current vs. VCC
PROGRAMMING CURRENT vs. VCC
8000
7000
6000
ICC (uA)
5000
4000
3000
2000
1000
0
1.5
2
2.5
3
3.5
4
4.5
5
5.5
VCC (V)
20.2.6
Pull-up Resistors
Figure 20-20. Pull-Up Resistor Current vs. Input Voltage (I/O Pin, VCC = 1.8V)
I/O PIN PULL-UP RESISTOR CURRENT vs. INPUT VOLTAGE
VCC = 1.8V
60
50
IOP (uA)
40
30
20
25 ˚C
10
85 ˚C
-40 ˚C
0
0
0,2
0,4
0,6
0,8
1
1,2
1,4
1,6
1,8
2
VOP (V)
204
ATtiny261A/461A/861A
8197A–AVR–10/09
ATtiny261A/461A/861A
Figure 20-21. Pull-Up Resistor Current vs. Input Voltage (I/O Pin, VCC = 3V)
I/O PIN PULL-UP RESISTOR CURRENT vs. INPUT VOLTAGE
VCC = 2.7V
90
80
70
IOP (uA)
60
50
40
30
25 ˚C
20
85 ˚C
10
-40 ˚C
0
0
0,5
1
1,5
2
2,5
3
VOP (V)
Figure 20-22. Pull-Up Resistor Current vs. Input Voltage (I/O Pin, VCC = 5V)
I/O PIN PULL-UP RESISTOR CURRENT vs. INPUT VOLTAGE
VCC = 5V
160
140
120
IOP (uA)
100
80
60
40
25 ˚C
85 ˚C
-40 ˚C
20
0
0
1
2
3
4
5
6
VOP (V)
205
8197A–AVR–10/09
Figure 20-23. Pull-Up Resistor Current vs. Input Voltage (Reset Pin, VCC = 1.8V)
RESET PULL-UP RESISTOR CURRENT vs. RESET PIN VOLTAGE
VCC = 1.8V
40
35
30
IRESET (uA)
25
20
15
10
5
85 °C
25 °C
-40 °C
0
0
0.2
0.4
0.6
0.8
1
1.2
1.4
1.6
1.8
2
VRESET (V)
Figure 20-24. Pull-Up Resistor Current vs. Input Voltage (Reset Pin, VCC = 3V)
RESET PULL-UP RESISTOR CURRENT vs. RESET PIN VOLTAGE
VCC = 3V
60
50
IRESET (uA)
40
30
20
10
85 °C
25 °C
-40 °C
0
0
0.5
1
1.5
2
2.5
3
VRESET (V)
206
ATtiny261A/461A/861A
8197A–AVR–10/09
ATtiny261A/461A/861A
Figure 20-25. Pull-Up Resistor Current vs. Input Voltage (Reset Pin, VCC = 5V)
RESET PULL-UP RESISTOR CURRENT vs. RESET PIN VOLTAGE
VCC = 5V
120
100
IRESET (uA)
80
60
40
20
85 °C
25 °C
-40 °C
0
0
0.5
1
1.5
2
2.5
3
3.5
4
4.5
5
VRESET (V)
20.2.7
Output Driver Strength
Figure 20-26. VOL: Output Voltage vs. Sink Current (I/O Pin, VCC = 1.8V)
I/O PIN OUTPUT VOLTAGE vs. SINK CURRENT
VCC = 1.8V
0.4
0.35
85 °C
0.3
25 °C
VOL (V)
0.25
-40 °C
0.2
0.15
0.1
0.05
0
0
1
2
3
4
5
IOL (mA)
207
8197A–AVR–10/09
Figure 20-27. VOL: Output Voltage vs. Sink Current (I/O Pin, VCC = 3V)
I/O PIN OUTPUT VOLTAGE vs. SINK CURRENT
VCC = 3V
0.5
0.4
85 °C
25 °C
VOL (V)
0.3
-40 °C
0.2
0.1
0
0
2
4
6
8
10
IOL (mA)
Figure 20-28. VOL: Output Voltage vs. Sink Current (I/O Pin, VCC = 5V)
I/O PIN OUTPUT VOLTAGE vs. SINK CURRENT
VCC = 5V
0.7
0.6
VOL (V)
85 °C
0.5
25 °C
0.4
-40 °C
0.3
0.2
0.1
0
0
2
4
6
8
10
12
14
16
18
20
IOL (mA)
208
ATtiny261A/461A/861A
8197A–AVR–10/09
ATtiny261A/461A/861A
Figure 20-29. VOH: Output Voltage vs. Source Current (I/O Pin, VCC = 1.8V)
I/O PIN OUTPUT VOLTAGE vs. SOURCE CURRENT
VCC = 1.8V
1.8
1.7
VOH (V)
1.6
1.5
-40 °C
25 °C
1.4
85 °C
1.3
0
1
2
3
4
5
IOH (mA)
Figure 20-30. VOH: Output Voltage vs. Source Current (I/O Pin, VCC = 3V)
I/O PIN OUTPUT VOLTAGE vs. SOURCE CURRENT
VCC = 3V
3
2.9
VOH (V)
2.8
2.7
-40 °C
25 °C
2.6
85 °C
2.5
0
2
4
6
8
10
IOH (mA)
209
8197A–AVR–10/09
Figure 20-31. VOH: Output Voltage vs. Source Current (I/O Pin, VCC = 5V)
I/O PIN OUTPUT VOLTAGE vs. SOURCE CURRENT
VCC = 5V
5
VOH (V)
4.8
4.6
-40 °C
25 °C
4.4
85 °C
4.2
0
5
10
15
20
IOH (mA)
Figure 20-32. VOL: Output Voltage vs. Sink Current (Reset Pin as I/O, VCC = 5V)
OUTPUT VOLTAGE vs. SINK CURRENT
RESET PIN AS I/O
0.8
85 °C
VOL (V)
0.6
0.4
25 °C
0.2
-40 °C
0
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
IOL (mA)
210
ATtiny261A/461A/861A
8197A–AVR–10/09
ATtiny261A/461A/861A
Figure 20-33. VOL: Output Voltage vs. Sink Current (Reset Pin as I/O, T = 25°C)
OUTPUT VOLTAGE vs. SINK CURRENT
RESET PIN AS I/O
0.8
1.8 V
VOL (V)
0.6
0.4
0.2
3.0 V
5.0 V
0
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
IOL (mA)
Figure 20-34. VOH: Output Voltage vs. Source Current (Reset Pin as I/O, VCC = 5V)
OUTPUT VOLTAGE vs. SOURCE CURRENT
RESET PIN AS I/O, VCC = 5V
5
4
85 °C
25 °C
-40 °C
VOH (V)
3
2
1
0
0
0.2
0.4
0.6
0.8
1
IOH (mA)
211
8197A–AVR–10/09
Figure 20-35. VOH: Output Voltage vs. Source Current (Reset Pin as I/O, T = 25°C)
OUTPUT VOLTAGE vs. SOURCE CURRENT
RESET PIN AS I/O
5
4
3
VOH (V)
5.0 V
2
3.0 V
1
1.8 V
0
0
0.2
0.4
0.6
0.8
1
IOH (mA)
20.2.8
Input Thresholds and Hysteresis
Figure 20-36. VIH: Input Threshold Voltage vs. VCC (I/O Pin, Read as ‘1’)
I/O PIN INPUT THRESHOLD vs. SUPPLY VOLTAGE
VIH, I/O PIN READ AS '1'
3.5
3
85 °C
25 °C
-40 °C
Threshold (V)
2.5
2
1.5
1
0.5
0
1.5
2
2.5
3
3.5
4
4.5
5
5.5
VCC (V)
212
ATtiny261A/461A/861A
8197A–AVR–10/09
ATtiny261A/461A/861A
Figure 20-37. VIL: Input Threshold Voltage vs. VCC (I/O Pin, Read as ‘0’)
I/O PIN INPUT THRESHOLD vs. SUPPLY VOLTAGE
VIL, I/O PIN READ AS '0'
3
85 °C
25 °C
-40 °C
2.5
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)
Figure 20-38. VIH-VIL: Input Hysteresis vs. VCC (I/O Pin)
I/O PIN INPUT HYSTERESIS vs. SUPPLY VOLTAGE
0.6
-40 °C
Input Hysteresis (V)
0.5
0.4
25 °C
85 °C
0.3
0.2
0.1
0
1.5
2
2.5
3
3.5
4
4.5
5
5.5
VCC (V)
213
8197A–AVR–10/09
Figure 20-39. VIH: Input Threshold Voltage vs. VCC (Reset Pin, Read as ‘1’)
RESET INPUT THRESHOLD VOLTAGE vs. VCC
VIH, PIN READ AS '1'
2.5
Threshold (V)
2
1.5
-40 °C
25 °C
85 °C
1
0.5
0
1.5
2
2.5
3
3.5
4
4.5
5
5.5
VCC (V)
Figure 20-40. VIL: Input Threshold Voltage vs. VCC (Reset Pin, Read as ‘0’)
RESET INPUT THRESHOLD VOLTAGE vs. VCC
VIL, PIN READ AS '0'
2.5
-40 °C
25 °C
85 °C
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)
214
ATtiny261A/461A/861A
8197A–AVR–10/09
ATtiny261A/461A/861A
Figure 20-41. VIH-VIL: Input Hysteresis vs. VCC (Reset Pin)
RESET PIN INPUT HYSTERESIS vs. VCC
1
0.9
0.8
Input Hysteresis (V)
0.7
-40 °C
0.6
0.5
25 °C
0.4
85 °C
0.3
0.2
0.1
0
1.5
2
2.5
3
3.5
4
4.5
5
5.5
VCC (V)
20.2.9
BOD, Bandgap and Reset
Figure 20-42. BOD Threshold vs. Temperature (BOD Level set to 4.3V)
BOD THRESHOLDS vs. TEMPERATURE
BODLEVEL = 4.3V
4.38
4.36
VCC RISING
Threshold (V)
4.34
4.32
4.3
4.28
VCC FALLING
4.26
4.24
-40
-20
0
20
40
60
80
100
Temperature (C)
215
8197A–AVR–10/09
Figure 20-43. BOD Threshold vs. Temperature (BOD Level set to 2.7V)
BOD THRESHOLDS vs. TEMPERATURE
BODLEVEL = 2.7V
2.78
2.76
VCC RISING
Threshold (V)
2.74
2.72
2.7
VCC FALLING
2.68
2.66
-40
-20
0
20
40
60
80
100
Temperature (C)
Figure 20-44. BOD Threshold vs. Temperature (BOD Level set to 1.8V)
BOD THRESHOLDS vs. TEMPERATURE
BODLEVEL = 1.8V
1.85
1.84
Threshold (V)
1.83
VCC RISING
1.82
1.81
1.8
VCC FALLING
1.79
1.78
-40
-20
0
20
40
60
80
100
Temperature (C)
216
ATtiny261A/461A/861A
8197A–AVR–10/09
ATtiny261A/461A/861A
Figure 20-45. Bandgap Voltage vs. Supply Voltage.
BANDGAP VOLTAGE vs. VCC
1.11
Bandgap Voltage (V)
1.1
85 °C
25 °C
1.09
1.08
-40 °C
1.07
1.5
2.5
3.5
4.5
5.5
VCC (V)
Figure 20-46. Minimum Reset Pulse Width vs. VCC
MINIMUM RESET PULSE WIDTH vs. VCC
1800
1600
1400
Pulsewidth (ns)
1200
1000
800
600
400
85 °C
25 °C
-40 °C
200
0
1.5
2
2.5
3
3.5
4
4.5
5
5.5
VCC (V)
217
8197A–AVR–10/09
20.2.10
Internal Oscillators
Figure 20-47. Frequency of Watchdog Oscillator vs. VCC
WATCHDOG OSCILLATOR FREQUENCY vs. SUPPLY VOLTAGE
130000
Frequency (Hz)
125000
-40 °C
120000
25 °C
85 °C
115000
110000
1.5
2
2.5
3
3.5
4
4.5
5
5.5
VCC (V)
Figure 20-48. Frequency of Watchdog Oscillator vs. Temperature
WATCHDOG OSCILLATOR FREQUENCY vs. TEMPERATURE
130000
Frequency (kHz)
125000
120000
1.8 V
3.0 V
5.0 V
115000
110000
-40
-20
0
20
40
60
80
100
Temperature
218
ATtiny261A/461A/861A
8197A–AVR–10/09
ATtiny261A/461A/861A
Figure 20-49. Frequency of Calibrated 8.0 MHz Oscillator vs. VCC
CALIBRATED 8MHz OSCILLATOR FREQUENCY vs. SUPPLY VOLTAGE
8.4
85 °C
25 °C
8.2
Frequency (MHz)
-40 °C
8
7.8
7.6
1.5
2
2.5
3
3.5
4
4.5
5
5.5
VCC (V)
Figure 20-50. Frequency of Calibrated 8.0 MHz Oscillator vs. Temperature
CALIBRATED 8MHz OSCILLATOR FREQUENCY vs. TEMPERATURE
8.2
Frequency (MHz)
8.1
5.0 V
8
3.0 V
7.9
1.8 V
7.8
-40
-20
0
20
40
60
80
100
Temperature
219
8197A–AVR–10/09
Figure 20-51. Frequency of Calibrated 8.0 MHz Oscillator vs. OSCCAL Value
CALIBRATED 8MHz OSCILLATOR FREQUENCY vs. OSCCAL VALUE
16
-40 °C
25 °C
85 °C
14
12
FRC (MHz)
10
8
6
4
2
0
0
16
32
48
64
80
96
112 128 144 160 176 192 208 224 240
OSCCAL (X1)
220
ATtiny261A/461A/861A
8197A–AVR–10/09
ATtiny261A/461A/861A
20.3
20.3.1
ATtiny461A
Current Consumption in Active Mode
Figure 20-52. Active Supply Current vs. Low Frequency (0.1 - 1.0 MHz)
ACTIVE SUPPLY CURRENT vs. LOW FREQUENCY
1
5.5 V
0.8
5.0 V
4.5 V
ICC (mA)
0.6
4.0 V
0.4
3.3 V
2.7 V
0.2
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)
Figure 20-53. Active Supply Current vs. Frequency (1 - 20 MHz)
ACTIVE SUPPLY CURRENT vs. FREQUENCY
PRR = 0xFF
10
5.5 V
5.0 V
8
4.5 V
ICC (mA)
6
4.0 V
4
3.3 V
2.7 V
2
1.8 V
0
0
2
4
6
8
10
12
14
16
18
20
Frequency (MHz)
221
8197A–AVR–10/09
Figure 20-54. Active Supply Current vs. VCC (Internal Calibrated Oscillator, 8 MHz)
ACTIVE SUPPLY CURRENT vs. SUPPLY VOLTAGE
INTERNAL OSCILLATOR, 8 MHz
5
85 °C
25 °C
-40 °C
4
ICC (mA)
3
2
1
0
1.5
2
2.5
3
3.5
4
4.5
5
5.5
VCC (V)
Figure 20-55. Active Supply Current vs. VCC (Internal Calibrated Oscillator, 1 MHz)
ACTIVE SUPPLY CURRENT vs. SUPPLY VOLTAGE
INTERNAL OSCILLATOR, 1 MHz
1.2
85 °C
25 °C
-40 °C
1
ICC (mA)
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)
222
ATtiny261A/461A/861A
8197A–AVR–10/09
ATtiny261A/461A/861A
Figure 20-56. Active Supply Current vs. VCC (Internal Calibrated Oscillator, 128 kHz)
ACTIVE SUPPLY CURRENT vs. SUPPLY VOLTAGE
INTERNAL OSCILLATOR, 128 kHz
0.12
-40 °C
25 °C
85 °C
0.1
ICC (mA)
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)
20.3.2
Current Consumption in Idle Mode
Figure 20-57. Idle Supply Current vs. Low Frequency (0.1 - 1.0 MHz)
IDLE SUPPLY CURRENT vs. LOW FREQUENCY
0.14
5.5 V
0.12
5.0 V
4.5 V
0.1
ICC (mA)
4.0 V
0.08
3.3 V
0.06
2.7 V
0.04
1.8 V
0.02
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
Frequency (MHz)
223
8197A–AVR–10/09
Figure 20-58. Idle Supply Current vs. Frequency (1 - 20 MHz)
IDLE SUPPLY CURRENT vs. FREQUENCY
3
5.5 V
2.5
5.0 V
4.5 V
ICC (mA)
2
1.5
4.0 V
1
3.3 V
2.7 V
0.5
1.8 V
0
0
2
4
6
8
10
12
14
16
18
20
Frequency (MHz)
Figure 20-59. Idle Supply Current vs. VCC (Internal Calibrated Oscillator, 8 MHz)
IDLE SUPPLY CURRENT vs. VCC
INTERNAL OSCILLATOR, 8 MHz
1.4
85 °C
25 °C
-40 °C
1.2
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)
224
ATtiny261A/461A/861A
8197A–AVR–10/09
ATtiny261A/461A/861A
Figure 20-60. Idle Supply Current vs. VCC (Internal Calibrated Oscillator, 1 MHz)
IDLE SUPPLY CURRENT vs. VCC
INTERNAL OSCILLATOR, 1 MHz
0.35
85 °C
25 °C
-40 °C
0.3
ICC (mA)
0.25
0.2
0.15
0.1
0.05
0
1.5
2
2.5
3
3.5
4
4.5
5
5.5
VCC (V)
Figure 20-61. Idle Supply Current vs. VCC (Internal Calibrated Oscillator, 128 kHz)
IDLE SUPPLY CURRENT vs. VCC
INTERNAL OSCILLATOR, 128 kHz
0.025
-40 °C
85 °C
25 °C
0.02
ICC (mA)
0.015
0.01
0.005
0
1.5
2
2.5
3
3.5
4
4.5
5
5.5
VCC (V)
225
8197A–AVR–10/09
20.3.3
Current Consumption in Power-Down Mode
Figure 20-62. Power-down Supply Current vs. VCC (Watchdog Timer Disabled)
POWER-DOWN SUPPLY CURRENT vs. SUPPLY VOLTAGE
WATCHDOG TIMER DISABLED
1.2
1
85 °C
ICC (uA)
0.8
0.6
-40 °C
0.4
25 °C
0.2
0
1.5
2
2.5
3
3.5
4
4.5
5
5.5
VCC (V)
Figure 20-63. Power-down Supply Current vs. VCC (Watchdog Timer Enabled)
POWER-DOWN SUPPLY CURRENT vs. SUPPLY VOLTAGE
WATCHDOG TIMER ENABLED
10
-40 °C
85 °C
8
25 °C
ICC (uA)
6
4
2
0
1.5
2
2.5
3
3.5
4
4.5
5
5.5
VCC (V)
226
ATtiny261A/461A/861A
8197A–AVR–10/09
ATtiny261A/461A/861A
20.3.4
Current Consumption in Reset
Figure 20-64. Reset Supply Current vs. Low Frequency (0.1 - 1.0 MHz, Excluding Current
Through the Reset Pull-up)
RESET CURRENT vs. FREQUENCY
EXCLUDING CURRENT THROUGH RESET PULLUP
0.14
0.12
5.5 V
5.0 V
0.1
ICC (mA)
4.5 V
0.08
4.0 V
0.06
3.3 V
2.7 V
0.04
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)
Figure 20-65. Reset Supply Current vs. Frequency (1 - 20 MHz, Excluding Current Through the
Reset Pull-up)
RESET CURRENT vs. SUPPLY VOLTAGE
EXCLUDING CURRENT THROUGH RESET PULLUP
2.5
5.5 V
2
5.0 V
ICC (mA)
4.5 V
1.5
4.0 V
1
3.3 V
0.5
2.7 V
1.8 V
0
0
2
4
6
8
10
12
14
16
18
20
Frequency (MHz)
227
8197A–AVR–10/09
20.3.5
Current Consumption of Peripheral Units
Figure 20-66. Analog Comparator Current vs. VCC
ANALOG COMPARATOR CURRENT vs. VCC
70
60
ICC (uA)
50
40
30
20
10
0
1.5
2
2.5
3
3.5
4
4.5
5
5.5
VCC (V)
Figure 20-67. ADC Current vs. VCC (AREF = AVCC)
ADC CURRENT vs. VCC
f = 1.0 MHz
400
350
300
ICC (uA)
250
200
150
100
50
0
1.5
2
2.5
3
3.5
4
4.5
5
5.5
VCC (V)
228
ATtiny261A/461A/861A
8197A–AVR–10/09
ATtiny261A/461A/861A
Figure 20-68. Timer/Counter1 Current vs. VCC
TIMER/COUNTER1 CURRENT vs. VCC
7000
64MHz
6000
ICC (uA)
5000
4000
32MHz
3000
2000
1000
1MHz
0
1.5
2
2.5
3
3.5
4
4.5
5
5.5
VCC (V)
Figure 20-69. Brownout Detector Current vs. VCC
BROWNOUT DETECTOR CURRENT vs. VCC
40
35
30
ICC (uA)
25
20
15
10
5
0
1.5
2
2.5
3
3.5
4
4.5
5
5.5
VCC (V)
229
8197A–AVR–10/09
Figure 20-70. Programming Current vs. VCC
PROGRAMMING CURRENT vs. VCC
8000
7000
6000
ICC (uA)
5000
4000
3000
2000
1000
0
1.5
2
2.5
3
3.5
4
4.5
5
5.5
VCC (V)
20.3.6
Pull-up Resistors
Figure 20-71. Pull-Up Resistor Current vs. Input Voltage (I/O Pin, VCC = 1.8V)
I/O PIN PULL-UP RESISTOR CURRENT vs. INPUT VOLTAGE
VCC = 1.8V
60
50
IOP (uA)
40
30
20
25 ˚C
10
85 ˚C
-40 ˚C
0
0
0,2
0,4
0,6
0,8
1
1,2
1,4
1,6
1,8
2
VOP (V)
230
ATtiny261A/461A/861A
8197A–AVR–10/09
ATtiny261A/461A/861A
Figure 20-72. Pull-Up Resistor Current vs. Input Voltage (I/O Pin, VCC = 3V)
I/O PIN PULL-UP RESISTOR CURRENT vs. INPUT VOLTAGE
VCC = 2.7V
90
80
70
IOP (uA)
60
50
40
30
25 ˚C
20
85 ˚C
10
-40 ˚C
0
0
0,5
1
1,5
2
2,5
3
VOP (V)
Figure 20-73. Pull-Up Resistor Current vs. Input Voltage (I/O Pin, VCC = 5V)
I/O PIN PULL-UP RESISTOR CURRENT vs. INPUT VOLTAGE
VCC = 5V
160
140
120
IOP (uA)
100
80
60
40
25 ˚C
85 ˚C
-40 ˚C
20
0
0
1
2
3
4
5
6
VOP (V)
231
8197A–AVR–10/09
Figure 20-74. Pull-Up Resistor Current vs. Input Voltage (Reset Pin, VCC = 1.8V)
RESET PULL-UP RESISTOR CURRENT vs. RESET PIN VOLTAGE
VCC = 1.8V
40
35
30
IRESET (uA)
25
20
15
10
5
-40 °C
25 °C
85 °C
0
0
0.2
0.4
0.6
0.8
1
1.2
1.4
1.6
1.8
2
VRESET (V)
Figure 20-75. Pull-Up Resistor Current vs. Input Voltage (Reset Pin, VCC = 3V)
RESET PULL-UP RESISTOR CURRENT vs. RESET PIN VOLTAGE
VCC = 3V
60
50
IRESET (uA)
40
30
20
10
-40 °C
25 °C
85 °C
0
0
0.5
1
1.5
2
2.5
3
VRESET (V)
232
ATtiny261A/461A/861A
8197A–AVR–10/09
ATtiny261A/461A/861A
Figure 20-76. Pull-Up Resistor Current vs. Input Voltage (Reset Pin, VCC = 5V)
RESET PULL-UP RESISTOR CURRENT vs. RESET PIN VOLTAGE
VCC = 5V
120
100
IRESET (uA)
80
60
40
20
-40 °C
25 °C
85 °C
0
0
0.5
1
1.5
2
2.5
3
3.5
4
4.5
5
VRESET (V)
20.3.7
Output Driver Strength
Figure 20-77. VOL: Output Voltage vs. Sink Current (I/O Pin, VCC = 1.8V)
I/O PIN OUTPUT VOLTAGE vs. SINK CURRENT
VCC = 1.8V
0.4
85 °C
0.35
0.3
25 °C
VOL (V)
0.25
-40 °C
0.2
0.15
0.1
0.05
0
0
1
2
3
4
5
IOL (mA)
233
8197A–AVR–10/09
Figure 20-78. VOL: Output Voltage vs. Sink Current (I/O Pin, VCC = 3V)
I/O PIN OUTPUT VOLTAGE vs. SINK CURRENT
VCC = 3V
0.45
0.4
85 °C
0.35
25 °C
VOL (V)
0.3
-40 °C
0.25
0.2
0.15
0.1
0.05
0
0
2
4
6
8
10
IOL (mA)
Figure 20-79. VOL: Output Voltage vs. Sink Current (I/O Pin, VCC = 5V)
I/O PIN OUTPUT VOLTAGE vs. SINK CURRENT
VCC = 5V
0.7
0.6
VOL (V)
85 °C
0.5
25 °C
0.4
-40 °C
0.3
0.2
0.1
0
0
5
10
15
20
IOL (mA)
234
ATtiny261A/461A/861A
8197A–AVR–10/09
ATtiny261A/461A/861A
Figure 20-80. VOH: Output Voltage vs. Source Current (I/O Pin, VCC = 1.8V)
I/O PIN OUTPUT VOLTAGE vs. SOURCE CURRENT
VCC = 1.8V
1.8
VOL (V)
1.6
-40 °C
25 °C
1.4
85 °C
1.2
0
1
2
3
4
5
IOL (mA)
Figure 20-81. VOH: Output Voltage vs. Source Current (I/O Pin, VCC = 3V)
I/O PIN OUTPUT VOLTAGE vs. SOURCE CURRENT
VCC = 3V
3
VOL (V)
2.8
-40 °C
25 °C
2.6
85 °C
2.4
0
2
4
6
8
10
IOL (mA)
235
8197A–AVR–10/09
Figure 20-82. VOH: Output Voltage vs. Source Current (I/O Pin, VCC = 5V)
I/O PIN OUTPUT VOLTAGE vs. SOURCE CURRENT
VCC = 5V
5
VOL (V)
4.8
4.6
-40 °C
25 °C
4.4
85 °C
4.2
0
5
10
15
20
IOL (mA)
Figure 20-83. VOL: Output Voltage vs. Sink Current (Reset Pin as I/O, VCC = 5V)
OUTPUT VOLTAGE vs. SINK CURRENT
RESET PIN AS I/O, VCC = 5V
0.6
85 °C
0.5
25 °C
0.4
VOL (V)
-40 °C
0.3
0.2
0.1
0
0
0.5
1
1.5
2
2.5
3
IOL (mA)
236
ATtiny261A/461A/861A
8197A–AVR–10/09
ATtiny261A/461A/861A
Figure 20-84. VOL: Output Voltage vs. Sink Current (Reset Pin as I/O, T = 25°C)
OUTPUT VOLTAGE vs. SINK CURRENT
RESET PIN AS I/O
0.5
1.8 V
0.4
VOL (V)
0.3
0.2
3.0 V
5.0 V
0.1
0
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
IOL (mA)
Figure 20-85. VOH: Output Voltage vs. Source Current (Reset Pin as I/O, VCC = 5V)
OUTPUT VOLTAGE vs. SOURCE CURRENT
RESET PIN AS I/O, VCC = 5V
5
4
-40 °C
25 °C
85 °C
VOH (V)
3
2
1
0
0
0.2
0.4
0.6
0.8
1
IOH (mA)
237
8197A–AVR–10/09
Figure 20-86. VOH: Output Voltage vs. Source Current (Reset Pin as I/O, T = 25°C)
OUTPUT VOLTAGE vs. SOURCE CURRENT
RESET PIN AS I/O
5
4
3
VOH (V)
5.0 V
2
3.0 V
1
1.8 V
0
0
0.2
0.4
0.6
0.8
1
IOH (mA)
20.3.8
Input Thresholds and Hysteresis
Figure 20-87. VIH: Input Threshold Voltage vs. VCC (I/O Pin, Read as ‘1’)
I/O PIN INPUT THRESHOLD vs. SUPPLY VOLTAGE
VIH, I/O PIN READ AS '1'
3.5
85 °C
25 °C
-40 °C
3
Threshold (V)
2.5
2
1.5
1
0.5
0
1.5
2
2.5
3
3.5
4
4.5
5
5.5
VCC (V)
238
ATtiny261A/461A/861A
8197A–AVR–10/09
ATtiny261A/461A/861A
Figure 20-88. VIL: Input Threshold Voltage vs. VCC (I/O Pin, Read as ‘0’)
I/O PIN INPUT THRESHOLD vs. SUPPLY VOLTAGE
VIL, I/O PIN READ AS '0'
3
-40 °C
25 °C
85 °C
2.5
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)
Figure 20-89. VIH-VIL: Input Hysteresis vs. VCC (I/O Pin)
I/O PIN INPUT HYSTERESIS vs. SUPPLY VOLTAGE
0.6
0.5
85 °C
25 °C
Input Hysteresis (V)
-40 °C
0.4
0.3
0.2
0.1
0
1.5
2
2.5
3
3.5
4
4.5
5
5.5
VCC (V)
239
8197A–AVR–10/09
Figure 20-90. VIH: Input Threshold Voltage vs. VCC (Reset Pin, Read as ‘1’)
RESET INPUT THRESHOLD VOLTAGE vs. VCC
VIH, PIN READ AS '1'
2.5
Threshold (V)
2
1.5
-40 °C
25 °C
85 °C
1
0.5
0
1.5
2
2.5
3
3.5
4
4.5
5
5.5
VCC (V)
Figure 20-91. VIL: Input Threshold Voltage vs. VCC (Reset Pin, Read as ‘0’)
RESET INPUT THRESHOLD VOLTAGE vs. VCC
VIL, PIN READ AS '0'
2.5
85 °C
25 °C
-40 °C
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)
240
ATtiny261A/461A/861A
8197A–AVR–10/09
ATtiny261A/461A/861A
Figure 20-92. VIH-VIL: Input Hysteresis vs. VCC (Reset Pin)
RESET PIN INPUT HYSTERESIS vs. VCC
1
0.9
0.8
Input Hysteresis (V)
0.7
0.6
-40 °C
0.5
25 °C
0.4
0.3
85 °C
0.2
0.1
0
1.5
2
2.5
3
3.5
4
4.5
5
5.5
VCC (V)
20.3.9
BOD, Bandgap and Reset
Figure 20-93. BOD Threshold vs. Temperature (BOD Level set to 4.3V)
BOD THRESHOLDS vs. TEMPERATURE
BODLEVEL = 4.3V
4.4
4.38
VCC RISING
Threshold (V)
4.36
4.34
4.32
VCC FALLING
4.3
4.28
4.26
4.24
-40
-20
0
20
40
60
80
100
Temperature (C)
241
8197A–AVR–10/09
Figure 20-94. BOD Threshold vs. Temperature (BOD Level set to 2.7V)
BOD THRESHOLDS vs. TEMPERATURE
BODLEVEL = 2.7V
2.8
2.78
VCC RISING
Threshold (V)
2.76
2.74
2.72
VCC FALLING
2.7
2.68
2.66
-40
-20
0
20
40
60
80
100
Temperature (C)
Figure 20-95. BOD Threshold vs. Temperature (BOD Level set to 1.8V)
BOD THRESHOLDS vs. TEMPERATURE
BODLEVEL = 1.8V
1.86
1.85
Threshold (V)
1.84
VCC RISING
1.83
1.82
1.81
VCC FALLING
1.8
1.79
1.78
-40
-20
0
20
40
60
80
100
Temperature (C)
242
ATtiny261A/461A/861A
8197A–AVR–10/09
ATtiny261A/461A/861A
Figure 20-96. Bandgap Voltage vs. Supply Voltage.
BANDGAP VOLTAGE vs. VCC
1.12
Bandgap Voltage (V)
1.11
85 °C
25 °C
1.1
1.09
1.08
-40 °C
1.07
1.5
2.5
3.5
4.5
5.5
VCC (V)
Figure 20-97. Minimum Reset Pulse Width vs. VCC
MINIMUM RESET PULSE WIDTH vs. VCC
1800
1600
1400
Pulsewidth (ns)
1200
1000
800
600
400
85 °C
25 °C
-40 °C
200
0
1.5
2
2.5
3
3.5
4
4.5
5
5.5
VCC (V)
243
8197A–AVR–10/09
20.3.10
Internal Oscillators
Figure 20-98. Frequency of Watchdog Oscillator vs. VCC
WATCHDOG OSCILLATOR FREQUENCY vs. SUPPLY VOLTAGE
120000
115000
Frequency (Hz)
-40 °C
25 °C
110000
85 °C
105000
1.5
2
2.5
3
3.5
4
4.5
5
5.5
VCC (V)
Figure 20-99. Frequency of Watchdog Oscillator vs. Temperature
WATCHDOG OSCILLATOR FREQUENCY vs. TEMPERATURE
Frequency (kHz)
120000
115000
1.8 V
110000
3.0 V
5.0 V
105000
-40
-20
0
20
40
60
80
100
Temperature
244
ATtiny261A/461A/861A
8197A–AVR–10/09
ATtiny261A/461A/861A
Figure 20-100.Frequency of Calibrated 8.0 MHz Oscillator vs. VCC
CALIBRATED 8MHz OSCILLATOR FREQUENCY vs. SUPPLY VOLTAGE
8.4
25 °C
Frequency (MHz)
8.2
85 °C
-40 °C
8
7.8
7.6
1.5
2
2.5
3
3.5
4
4.5
5
5.5
VCC (V)
Figure 20-101.Frequency of Calibrated 8.0 MHz Oscillator vs. Temperature
CALIBRATED 8MHz OSCILLATOR FREQUENCY vs. SUPPLY VOLTAGE
8.4
Frequency (MHz)
8.2
5.0 V
8
3.0 V
1.8 V
7.8
7.6
-40
-20
0
20
40
60
80
100
VCC (V)
245
8197A–AVR–10/09
Figure 20-102.Frequency of Calibrated 8.0 MHz Oscillator vs. OSCCAL Value
CALIBRATED 8MHz OSCILLATOR FREQUENCY vs. OSCCAL VALUE
14
85 °C
25 °C
-40 °C
12
Frequency (MHz)
10
8
6
4
2
0
0
16
32
48
64
80
96
112 128 144 160 176 192 208 224 240
OSCCAL (X1)
246
ATtiny261A/461A/861A
8197A–AVR–10/09
ATtiny261A/461A/861A
20.4
20.4.1
ATtiny861A
Current Consumption in Active Mode
Figure 20-103.Active Supply Current vs. Low Frequency (0.1 - 1.0 MHz)
ACTIVE SUPPLY CURRENT vs. LOW FREQUENCY
1
5.5 V
0.8
5.0 V
4.5 V
ICC (mA)
0.6
4.0 V
0.4
3.3 V
2.7 V
0.2
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)
Figure 20-104.Active Supply Current vs. Frequency (1 - 20 MHz)
ACTIVE SUPPLY CURRENT vs. FREQUENCY
PRR = 0xFF
10
5.5 V
5.0 V
8
4.5 V
ICC (mA)
6
4.0 V
4
3.3 V
2.7 V
2
1.8 V
0
0
2
4
6
8
10
12
14
16
18
20
Frequency (MHz)
247
8197A–AVR–10/09
Figure 20-105.Active Supply Current vs. VCC (Internal Calibrated Oscillator, 8 MHz)
ACTIVE SUPPLY CURRENT vs. SUPPLY VOLTAGE
INTERNAL OSCILLATOR, 8 MHz
5
-40 °C
25 °C
85 °C
4
ICC (mA)
3
2
1
0
1.5
2
2.5
3
3.5
4
4.5
5
5.5
VCC (V)
Figure 20-106.Active Supply Current vs. VCC (Internal Calibrated Oscillator, 1 MHz)
ACTIVE SUPPLY CURRENT vs. SUPPLY VOLTAGE
INTERNAL OSCILLATOR, 1 MHz
1.2
-40 °C
25 °C
85 °C
1
ICC (mA)
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)
248
ATtiny261A/461A/861A
8197A–AVR–10/09
ATtiny261A/461A/861A
Figure 20-107.Active Supply Current vs. VCC (Internal Calibrated Oscillator, 128 kHz)
ACTIVE SUPPLY CURRENT vs. SUPPLY VOLTAGE
INTERNAL OSCILLATOR, 128 kHz
0.12
-40 °C
25 °C
85 °C
0.1
ICC (mA)
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)
20.4.2
Current Consumption in Idle Mode
Figure 20-108.Idle Supply Current vs. Low Frequency (0.1 - 1.0 MHz)
IDLE SUPPLY CURRENT vs. LOW FREQUENCY
0.14
0.12
5.5 V
5.0 V
0.1
ICC (mA)
4.5 V
0.08
4.0 V
0.06
3.3 V
2.7 V
0.04
1.8 V
0.02
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
Frequency (MHz)
249
8197A–AVR–10/09
Figure 20-109.Idle Supply Current vs. Frequency (1 - 20 MHz)
IDLE SUPPLY CURRENT vs. FREQUENCY
3
2.5
5.5 V
5.0 V
2
ICC (mA)
4.5 V
1.5
4.0 V
1
3.3 V
0.5
2.7 V
1.8 V
0
0
2
4
6
8
10
12
14
16
18
20
Frequency (MHz)
Figure 20-110.Idle Supply Current vs. VCC (Internal Calibrated Oscillator, 8 MHz)
IDLE SUPPLY CURRENT vs. VCC
INTERNAL OSCILLATOR, 8 MHz
1.4
-40 °C
85 °C
25 °C
1.2
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)
250
ATtiny261A/461A/861A
8197A–AVR–10/09
ATtiny261A/461A/861A
Figure 20-111.Idle Supply Current vs. VCC (Internal Calibrated Oscillator, 1 MHz)
IDLE SUPPLY CURRENT vs. VCC
INTERNAL OSCILLATOR, 1 MHz
0.35
-40 °C
85 °C
25 °C
0.3
ICC (mA)
0.25
0.2
0.15
0.1
0.05
0
1.5
2
2.5
3
3.5
4
4.5
5
5.5
VCC (V)
Figure 20-112.Idle Supply Current vs. VCC (Internal Calibrated Oscillator, 128 kHz)
IDLE SUPPLY CURRENT vs. VCC
INTERNAL OSCILLATOR, 128 kHz
0.025
-40 °C
85 °C
25 °C
0.02
ICC (mA)
0.015
0.01
0.005
0
1.5
2
2.5
3
3.5
4
4.5
5
5.5
VCC (V)
251
8197A–AVR–10/09
20.4.3
Current Consumption in Power-Down Mode
Figure 20-113.Power-down Supply Current vs. VCC (Watchdog Timer Disabled)
POWER-DOWN SUPPLY CURRENT vs. SUPPLY VOLTAGE
WATCHDOG TIMER DISABLED
0.8
85 °C
0.7
0.6
ICC (uA)
0.5
0.4
0.3
25 °C
0.2
-40 °C
0.1
0
1.5
2
2.5
3
3.5
4
4.5
5
5.5
VCC (V)
Figure 20-114.Power-down Supply Current vs. VCC (Watchdog Timer Enabled)
POWER-DOWN SUPPLY CURRENT vs. SUPPLY VOLTAGE
WATCHDOG TIMER ENABLED
10
8
-40 °C
85 °C
25 °C
ICC (uA)
6
4
2
0
1.5
2
2.5
3
3.5
4
4.5
5
5.5
VCC (V)
252
ATtiny261A/461A/861A
8197A–AVR–10/09
ATtiny261A/461A/861A
20.4.4
Current Consumption in Reset
Figure 20-115.Reset Supply Current vs. Low Frequency (0.1 - 1.0 MHz, Excluding Current
Through the Reset Pull-up)
RESET CURRENT vs. FREQUENCY
EXCLUDING CURRENT THROUGH RESET PULLUP
0.12
5.5 V
0.1
5.0 V
ICC (mA)
0.08
4.5 V
4.0 V
0.06
3.3 V
0.04
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)
Figure 20-116.Reset Supply Current vs. Frequency (1 - 20 MHz, Excluding Current Through the
Reset Pull-up)
RESET CURRENT vs. SUPPLY VOLTAGE
EXCLUDING CURRENT THROUGH RESET PULLUP
2.5
2
5.5 V
ICC (mA)
5.0 V
1.5
4.5 V
4.0 V
1
3.3 V
0.5
2.7 V
1.8 V
0
0
2
4
6
8
10
12
14
16
18
20
Frequency (MHz)
253
8197A–AVR–10/09
20.4.5
Current Consumption of Peripheral Units
Figure 20-117.Analog Comparator Current vs. VCC
ANALOG COMPARATOR CURRENT vs. VCC
80
70
60
ICC (uA)
50
40
30
20
10
0
1.5
2
2.5
3
3.5
4
4.5
5
5.5
VCC (V)
Figure 20-118.ADC Current vs. VCC (AREF = AVCC)
ADC CURRENT vs. VCC
f = 1.0 MHz
400
350
300
ICC (uA)
250
200
150
100
50
0
1.5
2
2.5
3
3.5
4
4.5
5
5.5
VCC (V)
254
ATtiny261A/461A/861A
8197A–AVR–10/09
ATtiny261A/461A/861A
Figure 20-119.Timer/Counter1 Current vs. VCC
TIMER/COUNTER1 CURRENT vs. VCC
6000
64MHz
5000
ICC (uA)
4000
32MHz
3000
2000
1000
1MHz
0
1.5
2
2.5
3
3.5
4
4.5
5
5.5
VCC (V)
Figure 20-120.Brownout Detector Current vs. VCC
BROWNOUT DETECTOR CURRENT vs. VCC
40
35
30
ICC (uA)
25
20
15
10
5
0
1.5
2
2.5
3
3.5
4
4.5
5
5.5
VCC (V)
255
8197A–AVR–10/09
Figure 20-121.Programming Current vs. VCC
PROGRAMMING CURRENT vs. VCC
16000
14000
12000
ICC (uA)
10000
8000
6000
4000
2000
0
1.5
2
2.5
3
3.5
4
4.5
5
5.5
VCC (V)
20.4.6
Pull-up Resistors
Figure 20-122.Pull-Up Resistor Current vs. Input Voltage (I/O Pin, VCC = 1.8V)
I/O PIN PULL-UP RESISTOR CURRENT vs. INPUT VOLTAGE
VCC = 1.8V
60
50
IOP (uA)
40
30
20
25 ˚C
10
85 ˚C
-40 ˚C
0
0
0,2
0,4
0,6
0,8
1
1,2
1,4
1,6
1,8
2
VOP (V)
256
ATtiny261A/461A/861A
8197A–AVR–10/09
ATtiny261A/461A/861A
Figure 20-123.Pull-Up Resistor Current vs. Input Voltage (I/O Pin, VCC = 3V)
I/O PIN PULL-UP RESISTOR CURRENT vs. INPUT VOLTAGE
VCC = 2.7V
90
80
70
IOP (uA)
60
50
40
30
25 ˚C
20
85 ˚C
10
-40 ˚C
0
0
0,5
1
1,5
2
2,5
3
VOP (V)
Figure 20-124.Pull-Up Resistor Current vs. Input Voltage (I/O Pin, VCC = 5V)
I/O PIN PULL-UP RESISTOR CURRENT vs. INPUT VOLTAGE
VCC = 5V
160
140
120
IOP (uA)
100
80
60
40
25 ˚C
85 ˚C
-40 ˚C
20
0
0
1
2
3
4
5
6
VOP (V)
257
8197A–AVR–10/09
Figure 20-125.Pull-Up Resistor Current vs. Input Voltage (Reset Pin, VCC = 1.8V)
RESET PULL-UP RESISTOR CURRENT vs. RESET PIN VOLTAGE
VCC = 1.8V
40
35
30
IRESET (uA)
25
20
15
10
5
-40 °C
25 °C
85 °C
0
0
0.2
0.4
0.6
0.8
1
1.2
1.4
1.6
1.8
2
VRESET (V)
Figure 20-126.Pull-Up Resistor Current vs. Input Voltage (Reset Pin, VCC = 3V)
RESET PULL-UP RESISTOR CURRENT vs. RESET PIN VOLTAGE
VCC = 3V
60
50
IRESET (uA)
40
30
20
10
-40 °C
25 °C
85 °C
0
0
0.5
1
1.5
2
2.5
3
VRESET (V)
258
ATtiny261A/461A/861A
8197A–AVR–10/09
ATtiny261A/461A/861A
Figure 20-127.Pull-Up Resistor Current vs. Input Voltage (Reset Pin, VCC = 5V)
RESET PULL-UP RESISTOR CURRENT vs. RESET PIN VOLTAGE
VCC = 5V
120
100
IRESET (uA)
80
60
40
20
-40 °C
25 °C
85 °C
0
0
0.5
1
1.5
2
2.5
3
3.5
4
4.5
5
VRESET (V)
20.4.7
Output Driver Strength
Figure 20-128.VOL: Output Voltage vs. Sink Current (I/O Pin, VCC = 1.8V)
I/O PIN OUTPUT VOLTAGE vs. SINK CURRENT
VCC = 1.8V
0.4
0.35
85 °C
0.3
25 °C
VOL (V)
0.25
-40 °C
0.2
0.15
0.1
0.05
0
0
1
2
3
4
5
IOL (mA)
259
8197A–AVR–10/09
Figure 20-129.VOL: Output Voltage vs. Sink Current (I/O Pin, VCC = 3V)
I/O PIN OUTPUT VOLTAGE vs. SINK CURRENT
VCC = 3V
0.4
85 °C
0.35
25 °C
0.3
-40 °C
VOL (V)
0.25
0.2
0.15
0.1
0.05
0
0
2
4
6
8
10
IOL (mA)
Figure 20-130.VOL: Output Voltage vs. Sink Current (I/O Pin, VCC = 5V)
I/O PIN OUTPUT VOLTAGE vs. SINK CURRENT
VCC = 5V
0.6
85 °C
0.5
25 °C
VOL (V)
0.4
-40 °C
0.3
0.2
0.1
0
0
5
10
15
20
IOL (mA)
260
ATtiny261A/461A/861A
8197A–AVR–10/09
ATtiny261A/461A/861A
Figure 20-131.VOH: Output Voltage vs. Source Current (I/O Pin, VCC = 1.8V)
I/O PIN OUTPUT VOLTAGE vs. SOURCE CURRENT
VCC = 1.8V
1.8
VOL (V)
1.6
-40 °C
25 °C
1.4
85 °C
1.2
0
1
2
3
4
5
IOL (mA)
Figure 20-132.VOH: Output Voltage vs. Source Current (I/O Pin, VCC = 3V)
I/O PIN OUTPUT VOLTAGE vs. SOURCE CURRENT
VCC = 3V
3
VOL (V)
2.8
-40 °C
25 °C
2.6
85 °C
2.4
0
2
4
6
8
10
IOL (mA)
261
8197A–AVR–10/09
Figure 20-133.VOH: Output Voltage vs. Source Current (I/O Pin, VCC = 5V)
I/O PIN OUTPUT VOLTAGE vs. SOURCE CURRENT
VCC = 5V
5
VOL (V)
4.8
4.6
-40 °C
25 °C
4.4
85 °C
4.2
0
5
10
15
20
IOL (mA)
Figure 20-134.VOL: Output Voltage vs. Sink Current (Reset Pin as I/O, VCC = 5V)
OUTPUT VOLTAGE vs. SINK CURRENT
RESET PIN AS I/O, VCC = 5V
0.6
85 °C
0.5
25 °C
VOL (V)
0.4
-40 °C
0.3
0.2
0.1
0
0
0.5
1
1.5
2
2.5
3
IOL (mA)
262
ATtiny261A/461A/861A
8197A–AVR–10/09
ATtiny261A/461A/861A
Figure 20-135.VOL: Output Voltage vs. Sink Current (Reset Pin as I/O, T = 25°C)
OUTPUT VOLTAGE vs. SINK CURRENT
RESET PIN AS I/O
0.5
1.8 V
0.4
VOL (V)
0.3
0.2
3.0 V
5.0 V
0.1
0
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
IOL (mA)
Figure 20-136.VOH: Output Voltage vs. Source Current (Reset Pin as I/O, VCC = 5V)
OUTPUT VOLTAGE vs. SOURCE CURRENT
RESET PIN AS I/O, VCC = 5V
5
4
3
VOH (V)
25 °C
85 °C
2
-40 °C
1
0
0
0.2
0.4
0.6
0.8
1
IOH (mA)
263
8197A–AVR–10/09
Figure 20-137.VOH: Output Voltage vs. Source Current (Reset Pin as I/O, T = 25°C)
OUTPUT VOLTAGE vs. SOURCE CURRENT
RESET PIN AS I/O
5
4
3
VOH (V)
5.0 V
2
3.0 V
1
1.8 V
0
0
0.2
0.4
0.6
0.8
1
IOH (mA)
20.4.8
Input Thresholds and Hysteresis
Figure 20-138.VIH: Input Threshold Voltage vs. VCC (I/O Pin, Read as ‘1’)
I/O PIN INPUT THRESHOLD vs. SUPPLY VOLTAGE
VIH, I/O PIN READ AS '1'
3.5
85 °C
25 °C
-40 °C
3
Threshold (V)
2.5
2
1.5
1
0.5
0
1.5
2
2.5
3
3.5
4
4.5
5
5.5
VCC (V)
264
ATtiny261A/461A/861A
8197A–AVR–10/09
ATtiny261A/461A/861A
Figure 20-139.VIL: Input Threshold Voltage vs. VCC (I/O Pin, Read as ‘0’)
I/O PIN INPUT THRESHOLD vs. SUPPLY VOLTAGE
VIL, I/O PIN READ AS '0'
3
-40 °C
25 °C
85 °C
2.5
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)
Figure 20-140.VIH-VIL: Input Hysteresis vs. VCC (I/O Pin)
I/O PIN INPUT HYSTERESIS vs. SUPPLY VOLTAGE
0.6
85 °C
25 °C
-40 °C
Input Hysteresis (V)
0.5
0.4
0.3
0.2
0.1
0
1.5
2
2.5
3
3.5
4
4.5
5
5.5
VCC (V)
265
8197A–AVR–10/09
Figure 20-141.VIH: Input Threshold Voltage vs. VCC (Reset Pin, Read as ‘1’)
RESET INPUT THRESHOLD VOLTAGE vs. VCC
VIH, PIN READ AS '1'
2.5
Threshold (V)
2
1.5
1
-40 °C
25 °C
85 °C
0.5
0
1.5
2
2.5
3
3.5
4
4.5
5
5.5
VCC (V)
Figure 20-142.VIL: Input Threshold Voltage vs. VCC (Reset Pin, Read as ‘0’)
RESET INPUT THRESHOLD VOLTAGE vs. VCC
VIL, PIN READ AS '0'
2.5
-40 °C
25 °C
85 °C
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)
266
ATtiny261A/461A/861A
8197A–AVR–10/09
ATtiny261A/461A/861A
Figure 20-143.VIH-VIL: Input Hysteresis vs. VCC (Reset Pin)
RESET PIN INPUT HYSTERESIS vs. VCC
1
0.9
0.8
Input Hysteresis (V)
0.7
-40 °C
0.6
0.5
25 °C
0.4
85 °C
0.3
0.2
0.1
0
1.5
2
2.5
3
3.5
4
4.5
5
5.5
VCC (V)
20.4.9
BOD, Bandgap and Reset
Figure 20-144.BOD Threshold vs. Temperature (BOD Level set to 4.3V)
BOD THRESHOLDS vs. TEMPERATURE
BODLEVEL = 4.3V
VCC RISING
4.36
4.34
Threshold (V)
4.32
4.3
4.28
VCC FALLING
4.26
4.24
4.22
-40
-20
0
20
40
60
80
100
Temperature (C)
267
8197A–AVR–10/09
Figure 20-145.BOD Threshold vs. Temperature (BOD Level set to 2.7V)
BOD THRESHOLDS vs. TEMPERATURE
BODLEVEL = 2.7V
2.78
2.76
VCC RISING
Threshold (V)
2.74
2.72
2.7
VCC FALLING
2.68
2.66
-40
-20
0
20
40
60
80
100
Temperature (C)
Figure 20-146.BOD Threshold vs. Temperature (BOD Level set to 1.8V)
BOD THRESHOLDS vs. TEMPERATURE
BODLEVEL = 1.8V
1.84
1.83
VCC RISING
Threshold (V)
1.82
1.81
1.8
VCC FALLING
1.79
1.78
-40
-20
0
20
40
60
80
100
Temperature (C)
268
ATtiny261A/461A/861A
8197A–AVR–10/09
ATtiny261A/461A/861A
Figure 20-147.Bandgap Voltage vs. Supply Voltage.
BANDGAP VOLTAGE vs. VCC
1.11
85 °C
Bandgap Voltage (V)
1.1
25 °C
1.09
-40 °C
1.08
1.07
1.5
2.5
3.5
4.5
5.5
VCC (V)
Figure 20-148.Minimum Reset Pulse Width vs. VCC
MINIMUM RESET PULSE WIDTH vs. VCC
1800
1600
1400
Pulsewidth (ns)
1200
1000
800
600
400
85 °C
25 °C
-40 °C
200
0
1.5
2
2.5
3
3.5
4
4.5
5
5.5
VCC (V)
269
8197A–AVR–10/09
20.4.10
Internal Oscillators
Figure 20-149.Frequency of Watchdog Oscillator vs. VCC
WATCHDOG OSCILLATOR FREQUENCY vs. SUPPLY VOLTAGE
115000
-40 °C
Frequency (Hz)
110000
25 °C
105000
85 °C
100000
1.5
2
2.5
3
3.5
4
4.5
5
5.5
VCC (V)
Figure 20-150.Frequency of Watchdog Oscillator vs. Temperature
WATCHDOG OSCILLATOR FREQUENCY vs. TEMPERATURE
Frequency (kHz)
115000
110000
1.8 V
3.0 V
105000
5.0 V
100000
-40
-20
0
20
40
60
80
100
Temperature
270
ATtiny261A/461A/861A
8197A–AVR–10/09
ATtiny261A/461A/861A
Figure 20-151.Frequency of Calibrated 8.0 MHz Oscillator vs. VCC
CALIBRATED 8MHz OSCILLATOR FREQUENCY vs. SUPPLY VOLTAGE
8.4
-40 °C
25 °C
Frequency (MHz)
8.2
85 °C
8
7.8
7.6
1.5
2
2.5
3
3.5
4
4.5
5
5.5
VCC (V)
Figure 20-152.Frequency of Calibrated 8.0 MHz Oscillator vs. Temperature
CALIBRATED 8MHz OSCILLATOR FREQUENCY vs. SUPPLY VOLTAGE
8.4
Frequency (MHz)
8.2
8
5.0 V
3.0 V
7.8
1.8 V
7.6
-40
-20
0
20
40
60
80
100
VCC (V)
271
8197A–AVR–10/09
Figure 20-153.Frequency of Calibrated 8.0 MHz Oscillator vs. OSCCAL Value
CALIBRATED 8MHz OSCILLATOR FREQUENCY vs. OSCCAL VALUE
14
-40 °C
25 °C
85 °C
12
FRC (MHz)
10
8
6
4
2
0
0
16
32
48
64
80
96
112 128 144 160 176 192 208 224 240
OSCCAL (X1)
272
ATtiny261A/461A/861A
8197A–AVR–10/09
ATtiny261A/461A/861A
21. Register Summary
Address
Name
Bit 7
Bit 6
Bit 5
Bit 4
Bit 3
0x3F (0x5F)
0x3E (0x5E)
Bit 2
Bit 1
Bit 0
Page
SREG
I
T
H
S
V
N
Z
C
page 8
SPH
–
–
–
–
–
SP10
SP9
SP8
page 11
0x3D (0x5D)
SPL
SP7
SP6
SP5
SP4
SP3
SP2
SP1
SP0
page 11
0x3C (0x5C)
Reserved
0x3B (0x5B)
GIMSK
INT1
INT0
PCIE1
PCIE0
–
–
–
–
page 50
0x3A (0x5A)
GIFR
INTF1
INTF0
PCIF
–
–
–
–
–
page 51
0x39 (0x59)
TIMSK
OCIE1D
OCIE1A
OCIE1B
OCIE0A
OCIE0B
TOIE1
TOIE0
TICIE0
page 84, page 121
0x38 (0x58)
TIFR
OCF1D
OCF1A
OCF1B
OCF0A
OCF0B
TOV1
TOV0
ICF0
page 85, page 121
0x37 (0x57)
SPMCSR
–
–
–
CTPB
RFLB
PGWRT
PGERS
SPMEN
page 166
0x36 (0x56)
PRR
PRTIM1
PRTIM0
PRUSI
PRADC
page 35
0x35 (0x55)
MCUCR
BODS
PUD
SE
SM1
SM0
BODSE
ISC01
ISC00
page 37, page 67, page 50
0x34 (0x54)
MCUSR
–
–
–
–
WDRF
BORF
EXTRF
PORF
page 45,
0x33 (0x53)
TCCR0B
–
–
–
TSM
PSR0
CS02
CS01
CS00
page 83
0x32 (0x52)
TCNT0L
Timer/Counter0 Counter Register Low Byte
0x31 (0x51)
OSCCAL
Oscillator Calibration Register
0x30 (0x50)
TCCR1A
COM1A1
COM1A0
COM1B1
PWM1X
PSR1
DTPS11
–
page 83
page 32
COM1B0
FOC1A
FOC1B
PWM1A
PWM1B
page 110
DTPS10
CS13
CS12
CS11
CS10
page 166
0x2F (0x4F)
TCCR1B
0x2E (0x4E)
TCNT1
Timer/Counter1 Counter Register
page 119
0x2D (0x4D)
OCR1A
Timer/Counter1 Output Compare Register A
page 119
0x2C (0x4C)
OCR1B
Timer/Counter1 Output Compare Register B
page 120
0x2B (0x4B)
OCR1C
Timer/Counter1 Output Compare Register C
page 120
0x2A (0x4A)
OCR1D
Timer/Counter1 Output Compare Register D
0x29 (0x49)
PLLCSR
LSM
0x28 (0x48)
CLKPR
CLKPCE
0x27 (0x47)
TCCR1C
COM1A1S
COM1A0S
COM1B1S
0x26 (0x46)
TCCR1D
FPIE1
FPEN1
FPNC1
0x25 (0x45)
TC1H
0x24 (0x44)
DT1
0x23 (0x43)
PCMSK0
PCINT7
PCINT6
PCINT5
PCINT4
PCINT3
0x22 (0x42)
PCMSK1
PCINT15
PCINT14
PCINT13
PCINT12
PCINT11
0x21 (0x41)
WDTCR
WDIF
WDIE
WDP3
WDCE
WDE
WDP2
0x20 (0x40)
DWDR
0x1F (0x3F)
EEARH
0x1E (0x3E)
EEARL
0x1D (0x3D)
EEDR
0x1C (0x3C)
EECR
–
–
EEPM1
EEPM0
0x1B (0x3B)
PORTA
PORTA7
PORTA6
PORTA5
0x1A (0x3A)
DDRA
DDA7
DDA6
DDA5
0x19 (0x39)
PINA
PINA7
PINA6
0x18 (0x38)
PORTB
PORTB7
0x17 (0x37)
DDRB
0x16 (0x36)
DT1H3
DT1H2
DT1H1
page 120
PCKE
PLLE
PLOCK
CLKPS3
CLKPS2
CLKPS1
CLKPS0
page 32
COM1B0S
COM1D1
COM1D0
FOC1D
PWM1D
page 115
FPES1
FPAC1
FPF1
WGM11
WGM10
page 116
TC19
TC18
page 119
DT1L1
DT1L0
page 122
PCINT2
PCINT1
PCINT0
page 52
PCINT10
PCINT9
PCINT8
page 52
WDP1
WDP0
page 45
DT1H0
DT1L3
DT1L2
DWDR[7:0]
EEAR7
EEAR6
EEAR5
EEAR4
EEAR3
page 118
page 35
EEAR8
page 20
EEAR2
EEAR1
EEAR0
page 21
EERIE
EEMPE
EEPE
EERE
page 21
PORTA4
PORTA3
PORTA2
PORTA1
PORTA0
page 67
DDA4
DDA3
DDA2
DDA1
DDA0
page 67
PINA5
PINA4
PINA3
PINA2
PINA1
PINA0
page 68
PORTB6
PORTB5
PORTB4
PORTB3
PORTB2
PORTB1
PORTB0
page 68
DDB7
DDB6
DDB5
DDB4
DDB3
DDB2
DDB1
DDB0
page 68
PINB
PINB7
PINB6
PINB5
PINB4
PINB3
PINB2
PINB1
PINB0
page 68
0x15 (0x35)
TCCR0A
TCW0
ICEN0
ICNC0
ICES0
ACIC0
CTC0
page 82
0x14 (0x34)
TCNT0H
Timer/Counter0 Counter Register High Byte
page 84
0x13 (0x33)
OCR0A
Timer/Counter0 Output Compare Register A
page 84
0x12 (0x32)
OCR0B
Timer/Counter0 Output Compare Register B
0x11 (0x31)
USIPP
EEPROM Data Register
page 21
page 84
USIPOS
page 134
0x10 (0x30)
USIBR
USI Buffer Register
0x0F (0x2F)
USIDR
USI Data Register
0x0E (0x2E)
USISR
USISIF
USIOIF
USIPF
USIDC
USICNT3
USICNT2
USICNT1
USICNT0
page 131
0x0D (0x2D)
USICR
USISIE
USIOIE
USIWM1
USIWM0
USICS1
USICS0
USICLK
USITC
page 132
0x0C (0x2C)
GPIOR2
General Purpose I/O Register 2
page 22
0x0B (0x2B)
GPIOR1
General Purpose I/O Register 1
page 23
0x0A (0x2A)
GPIOR0
General Purpose I/O Register 0
0x09 (0x29)
ACSRB
HSEL
HLEV
page 131
page 130
page 23
ACM2
ACM1
ACM0
page 138
0x08 (0x28)
ACSRA
ACD
ACBG
ACO
ACI
ACIE
ACME
ACIS1
ACIS0
page 137
0x07 (0x27)
ADMUX
REFS1
REFS0
ADLAR
MUX4
MUX3
MUX2
MUX1
MUX0
page 154
0x06 (0x26)
ADCSRA
ADEN
ADSC
ADATE
ADIF
ADIE
ADPS2
ADPS1
ADPS0
page 153
0x05 (0x25)
ADCH
ADC Data Register High Byte
0x04 (0x24)
ADCL
ADC Data Register Low Byte
0x03 (0x23)
ADCSRB
BIN
GSEL
0x02 (0x22)
DIDR1
ADC10D
ADC9D
0x01 (0x21)
DIDR0
ADC6D
ADC5D
ADC4D
ADC3D
AREFD
ADC2D
ADC1D
ADC0D
page 159
0x00 (0x20)
TCCR1E
–
-
OC1OE5
OC1OE4
OC1OE3
OC1OE2
OC1OE1
OC1OE0
page 117
REFS2
ADC8D
MUX5
page 154
page 154
ADTS2
ADTS1
ADTS0
ADC7D
page 158
page 159
273
8197A–AVR–10/09
Note:
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 operation 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.
274
ATtiny261A/461A/861A
8197A–AVR–10/09
ATtiny261A/461A/861A
22. Instruction Set Summary
Mnemonics
Operands
Description
Operation
Flags
#Clocks
ARITHMETIC AND LOGIC INSTRUCTIONS
ADD
Rd, Rr
Add two Registers
Rd ← Rd + Rr
Z,C,N,V,H
ADC
Rd, Rr
Add with Carry two Registers
Rd ← Rd + Rr + C
Z,C,N,V,H
1
ADIW
Rdl,K
Add Immediate to Word
Rdh:Rdl ← Rdh:Rdl + K
Z,C,N,V,S
2
SUB
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
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
1
AND
Rd, Rr
Logical AND Registers
Rd ← Rd • Rr
Z,N,V
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
Relative Jump
PC ← PC + k + 1
None
2
Indirect Jump to (Z)
PC ← Z
None
2
BRANCH INSTRUCTIONS
RJMP
k
IJMP
Relative Subroutine Call
PC ← PC + k + 1
None
3
ICALL
Indirect Call to (Z)
PC ← Z
None
3
RET
Subroutine Return
PC ← STACK
None
4
RETI
Interrupt Return
PC ← STACK
I
if (Rd = Rr) PC ← PC + 2 or 3
None
RCALL
k
4
CPSE
Rd,Rr
Compare, Skip if Equal
1/2/3
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
SBRC
Rr, b
Skip if Bit in Register Cleared
if (Rr(b)=0) PC ← PC + 2 or 3
None
1
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
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
275
8197A–AVR–10/09
Mnemonics
Operands
Description
Operation
Flags
#Clocks
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
1
SEC
Set Carry
C←1
C
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
1
SES
Set Signed Test Flag
S←1
S
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
None
1
None
1
1
DATA TRANSFER INSTRUCTIONS
MOV
Rd, Rr
Move Between Registers
MOVW
Rd, Rr
Copy Register Word
Rd ← Rr
Rd+1:Rd ← Rr+1:Rr
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
2
LD
Rd, Y
Load Indirect
Rd ← (Y)
None
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
2
LDS
Rd, k
Load Direct from SRAM
Rd ← (k)
None
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
SPM
IN
Rd, P
In Port
Rd ← P
None
OUT
P, Rr
Out Port
P ← Rr
None
1
PUSH
Rr
Push Register on Stack
STACK ← Rr
None
2
POP
Rd
Pop Register from Stack
Rd ← STACK
None
2
1
MCU CONTROL INSTRUCTIONS
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
276
ATtiny261A/461A/861A
8197A–AVR–10/09
ATtiny261A/461A/861A
23. Ordering Information
23.1
ATtiny261A
Speed (MHz)
20(3)
Notes:
Power Supply
1.8 – 5.5V
Ordering Code(2)
Package(1)
ATtiny261A-MU
ATtiny261A-PU
ATtiny261A-SU
ATtiny261A-XU
32M1-A
20P3
20S2
20X
Operational Range
Industrial
(-40°C to 85°C)
1. This device can also be supplied in wafer form. Please contact your local Atmel sales office for detailed ordering information
and minimum quantities.
2. Pb-free packaging, complies to the European Directive for Restriction of Hazardous Substances (RoHS directive). Also
Halide free and fully Green.
3. For Speed vs. VCC, see Figure 19.3 on page 185.
Package Type
32M1-A
32-pad, 5 x 5 x 1.0 mm Body, Lead Pitch 0.50 mm, Micro Lead Frame Package (MLF)
20P3
20-lead, 0.300" Wide, Plastic Dual Inline Package (PDIP)
20S2
20-lead, 0.300" Wide, Plastic Gull Wing Small Outline Package (SOIC)
20X
20-lead, 4.4 mm Wide, Plastic Thin Shrink Small Outline Package (TSSOP)
277
8197A–AVR–10/09
23.2
ATtiny461A
Speed (MHz)
(3)
20
Notes:
Power Supply
1.8 – 5.5V
Ordering Code(2)
Package(1)
ATtiny461A-MU
ATtiny461A-PU
ATtiny461A-SU
ATtiny461A-XU
32M1-A
20P3
20S2
20X
Operational Range
Industrial
(-40°C to 85°C)
1. This device can also be supplied in wafer form. Please contact your local Atmel sales office for detailed ordering information
and minimum quantities.
2. Pb-free packaging, complies to the European Directive for Restriction of Hazardous Substances (RoHS directive). Also
Halide free and fully Green.
3. For Speed vs. VCC, see Figure 19.3 on page 185.
Package Type
32M1-A
32-pad, 5 x 5 x 1.0 mm Body, Lead Pitch 0.50 mm, Micro Lead Frame Package (MLF)
20P3
20-lead, 0.300" Wide, Plastic Dual Inline Package (PDIP)
20S2
20-lead, 0.300" Wide, Plastic Gull Wing Small Outline Package (SOIC)
20X
20-lead, 4.4 mm Wide, Plastic Thin Shrink Small Outline Package (TSSOP)
278
ATtiny261A/461A/861A
8197A–AVR–10/09
ATtiny261A/461A/861A
23.3
ATtiny861A
Speed (MHz)
(3)
20
Notes:
Power Supply
1.8 – 5.5V
Ordering Code(2)
Package(1)
ATtiny861A-MU
ATtiny861A-PU
ATtiny861A-SU
ATtiny861A-XU
32M1-A
20P3
20S2
20X
Operational Range
Industrial
(-40°C to 85°C)
1. This device can also be supplied in wafer form. Please contact your local Atmel sales office for detailed ordering information
and minimum quantities.
2. Pb-free packaging, complies to the European Directive for Restriction of Hazardous Substances (RoHS directive). Also
Halide free and fully Green.
3. For Speed vs. VCC, see Figure 19.3 on page 185.
Package Type
32M1-A
32-pad, 5 x 5 x 1.0 mm Body, Lead Pitch 0.50 mm, Micro Lead Frame Package (MLF)
20P3
20-lead, 0.300" Wide, Plastic Dual Inline Package (PDIP)
20S2
20-lead, 0.300" Wide, Plastic Gull Wing Small Outline Package (SOIC)
20X
20-lead, 4.4 mm Wide, Plastic Thin Shrink Small Outline Package (TSSOP)
279
8197A–AVR–10/09
24. Packaging Information
24.1
32M1-A
D
1
Pin 1 ID
2
SIDE VIEW
E
3
TOP VIEW
A2
D2
A1
A
0.08
1
2
Pin #1
Notch
(0.20 R)
3
COMMON DIMENSIONS
(Unit of Measure = mm)
E2
b
L
e
BOTTOM VIEW
SYMBOL
MIN
A
0.70
0.75
0.80
A1
–
0.01
0.05
A2
b
D
D2
E2
L
MAX
NOTE
0.23
0.30
4.00 BSC
2.45
2.60
2.75
4.00 BSC
2.45
e
Reference JEDEC Standard MO-220, Fig. 1 (SAW Singulation) WGGD-5.
NOM
0.20 REF
0.18
E
Note:
C
2.60
2.75
0.50 BSC
0.35
0.40
0.55
10/27/04
R
280
2325 Orchard Parkway
San Jose, CA 95131
TITLE
20M1, 20-pad, 4 x 4 x 0.8 mm Body, Lead Pitch 0.50 mm,
2.6 mm Exposed Pad, Micro Lead Frame Package (MLF)
DRAWING NO.
20M1
REV.
A
ATtiny261A/461A/861A
8197A–AVR–10/09
ATtiny261A/461A/861A
24.2
20P3
D
PIN
1
E1
A
SEATING PLANE
A1
L
B
B1
e
E
COMMON DIMENSIONS
(Unit of Measure = mm)
C
eC
eB
Notes:
1. This package conforms to JEDEC reference MS-001, Variation AD.
2. Dimensions D and E1 do not include mold Flash or Protrusion.
Mold Flash or Protrusion shall not exceed 0.25 mm (0.010").
SYMBOL
MIN
NOM
MAX
A
–
–
5.334
A1
0.381
–
–
D
25.493
–
25.984
E
7.620
–
8.255
E1
6.096
–
7.112
B
0.356
–
0.559
B1
1.270
–
1.551
L
2.921
–
3.810
C
0.203
–
0.356
eB
–
–
10.922
eC
0.000
–
1.524
e
NOTE
Note 2
Note 2
2.540 TYP
1/12/04
R
2325 Orchard Parkway
San Jose, CA 95131
TITLE
20P3, 20-lead (0.300"/7.62 mm Wide) Plastic Dual
Inline Package (PDIP)
DRAWING NO.
20P3
REV.
C
281
8197A–AVR–10/09
24.3
282
20S2
ATtiny261A/461A/861A
8197A–AVR–10/09
ATtiny261A/461A/861A
24.4
20X
Dimensions in Millimeters and (Inches).
Controlling dimension: Millimeters.
JEDEC Standard MO-153 AC
INDEX MARK
PIN
1
4.50 (0.177) 6.50 (0.256)
4.30 (0.169) 6.25 (0.246)
6.60 (.260)
6.40 (.252)
0.65 (.0256) BSC
0.30 (0.012)
0.19 (0.007)
1.20 (0.047) MAX
0.15 (0.006)
0.05 (0.002)
SEATING
PLANE
0.20 (0.008)
0.09 (0.004)
0º ~ 8º
0.75 (0.030)
0.45 (0.018)
10/23/03
R
2325 Orchard Parkway
San Jose, CA 95131
TITLE
20X, (Formerly 20T), 20-lead, 4.4 mm Body Width,
Plastic Thin Shrink Small Outline Package (TSSOP)
DRAWING NO.
REV.
20X
C
283
8197A–AVR–10/09
25. Errata
25.1
Errata ATtiny261A
The revision letter in this section refers to the revision of the ATtiny261A device.
25.1.1
Rev D
No known errata.
25.1.2
Rev C
Not sampled.
25.2
Errata ATtiny461A
The revision letter in this section refers to the revision of the ATtiny461A device.
25.2.1
Rev C
No known errata.
25.3
Errata ATtiny861A
The revision letter in this section refers to the revision of the ATtiny861A device.
25.3.1
Rev D
No known errata.
25.3.2
Rev C
Not sampled.
284
ATtiny261A/461A/861A
8197A–AVR–10/09
ATtiny261A/461A/861A
26. Datasheet Revision History
26.1
Rev. 8197A – 10/09
1. Initial revision created from document 2588C (ATtiny261/461/861)
2. Updated "Ordering Information" on page 277, page 278 and page 279. Pb-plated packages are no longer offered and there are no separate ordering codes for commercial
operation range, the only available option now is industrial. Also, added new package
options
3. Added sections:
– “Software BOD Disable” on page 35
– “ATtiny461A” on page 221
– “ATtiny861A” on page 247
4. Updated sections:
– “Stack Pointer” on page 11
– “OSCCAL – Oscillator Calibration Register” on page 32
– “MCUCR – MCU Control Register” on page 37
– “MCUCR – MCU Control Register” on page 50
– “MCUCR – MCU Control Register” on page 67
– “Speed Grades” on page 185
– “Enhanced Power-On Reset” on page 187
– “ATtiny261A” on page 195
– “Register Summary” on page 273
5. Updated tables:
– “DC Characteristics. TA = -40°C to 85°C, VCC = 1.8V to 5.5V (unless otherwise
noted).” on page 184
– “Additional Current Consumption for the different I/O modules (absolute values).” on
page 193
– “Additional Current Consumption (percentage) in Active and Idle mode.” on page
194
285
8197A–AVR–10/09
286
ATtiny261A/461A/861A
8197A–AVR–10/09
ATtiny261A/461A/861A
Table of Contents
Features ..................................................................................................... 1
1
Pin Configurations ................................................................................... 2
1.1
2
Overview ................................................................................................... 4
2.1
3
4
5
6
7
Pin Descriptions .................................................................................................3
Block Diagram ...................................................................................................4
General Information ................................................................................. 6
3.1
Resources .........................................................................................................6
3.2
Code Examples .................................................................................................6
3.3
Data Retention ...................................................................................................6
CPU Core .................................................................................................. 7
4.1
Architectural Overview .......................................................................................7
4.2
ALU – Arithmetic Logic Unit ...............................................................................8
4.3
Status Register ..................................................................................................8
4.4
General Purpose Register File ........................................................................10
4.5
Stack Pointer ...................................................................................................11
4.6
Instruction Execution Timing ...........................................................................12
4.7
Reset and Interrupt Handling ...........................................................................13
Memories ................................................................................................ 15
5.1
In-System Re-programmable Flash Program Memory ....................................15
5.2
SRAM Data Memory ........................................................................................15
5.3
EEPROM Data Memory ..................................................................................16
5.4
I/O Memory ......................................................................................................20
5.5
Register Description ........................................................................................20
Clock System ......................................................................................... 24
6.1
Clock Subsystems ...........................................................................................24
6.2
Clock Sources .................................................................................................25
6.3
System Clock Prescaler ..................................................................................31
6.4
Clock Output Buffer .........................................................................................32
6.5
Register Description ........................................................................................32
Power Management and Sleep Modes ................................................. 34
7.1
Sleep Modes ....................................................................................................34
7.2
Software BOD Disable .....................................................................................35
i
8197A–AVR–10/09
8
9
7.3
Power Reduction Register ...............................................................................36
7.4
Minimizing Power Consumption ......................................................................36
7.5
Register Description ........................................................................................37
System Control and Reset .................................................................... 39
8.1
Resetting the AVR ...........................................................................................39
8.2
Reset Sources .................................................................................................40
8.3
Internal Voltage Reference ..............................................................................42
8.4
Watchdog Timer ..............................................................................................42
8.5
Register Description ........................................................................................45
Interrupts ................................................................................................ 48
9.1
Interrupt Vectors ..............................................................................................48
9.2
External Interrupts ...........................................................................................49
9.3
Register Description ........................................................................................50
10 I/O Ports .................................................................................................. 53
10.1
Ports as General Digital I/O .............................................................................54
10.2
Alternate Port Functions ..................................................................................58
10.3
Register Description ........................................................................................67
11 Timer/Counter0 ...................................................................................... 69
11.1
Features ..........................................................................................................69
11.2
Overview ..........................................................................................................69
11.3
Clock Sources .................................................................................................70
11.4
Counter Unit ....................................................................................................72
11.5
Input Capture Unit ...........................................................................................73
11.6
Output Compare Unit .......................................................................................74
11.7
Modes of Operation .........................................................................................75
11.8
Timer/Counter Timing Diagrams .....................................................................77
11.9
Accessing Registers in 16-bit Mode ................................................................78
11.10
Register Description ........................................................................................82
12 Timer/Counter1 ...................................................................................... 87
ii
12.1
Features ..........................................................................................................87
12.2
Overview ..........................................................................................................87
12.3
Clock Sources .................................................................................................90
12.4
Counter Unit ....................................................................................................91
12.5
Output Compare Unit .......................................................................................92
ATtiny261A/461A/861A
8197A–AVR–10/09
ATtiny261A/461A/861A
12.6
Dead Time Generator ......................................................................................94
12.7
Compare Match Output Unit ............................................................................95
12.8
Modes of Operation .........................................................................................97
12.9
Timer/Counter Timing Diagrams ...................................................................104
12.10
Fault Protection Unit ......................................................................................105
12.11
Accessing 10-Bit Registers ............................................................................106
12.12
Register Description ......................................................................................110
13 USI – Universal Serial Interface .......................................................... 123
13.1
Features ........................................................................................................123
13.2
Overview ........................................................................................................123
13.3
Functional Descriptions .................................................................................124
13.4
Alternative USI Usage ...................................................................................129
13.5
Register Descriptions ....................................................................................130
14 AC – Analog Comparator .................................................................... 135
14.1
Analog Comparator Multiplexed Input ...........................................................135
14.2
Register Description ......................................................................................137
15 ADC – Analog to Digital Converter ..................................................... 140
15.1
Features ........................................................................................................140
15.2
Overview ........................................................................................................140
15.3
Operation .......................................................................................................141
15.4
Starting a Conversion ....................................................................................142
15.5
Prescaling and Conversion Timing ................................................................143
15.6
Changing Channel or Reference Selection ...................................................146
15.7
ADC Noise Canceler .....................................................................................147
15.8
Analog Input Circuitry ....................................................................................147
15.9
Noise Canceling Techniques .........................................................................148
15.10
ADC Accuracy Definitions .............................................................................148
15.11
ADC Conversion Result .................................................................................151
15.12
Temperature Measurement ...........................................................................152
15.13
Register Description ......................................................................................153
16 debugWIRE On-chip Debug System .................................................. 160
16.1
Features ........................................................................................................160
16.2
Overview ........................................................................................................160
16.3
Physical Interface ..........................................................................................160
16.4
Software Break Points ...................................................................................161
iii
8197A–AVR–10/09
16.5
Limitations of debugWIRE .............................................................................161
16.6
Register Description ......................................................................................161
17 Self-Programming the Flash ............................................................... 162
17.1
Performing Page Erase by SPM ....................................................................162
17.2
Filling the Temporary Buffer (Page Loading) .................................................162
17.3
Performing a Page Write ...............................................................................163
17.4
Addressing the Flash During Self-Programming ...........................................163
17.5
EEPROM Write Prevents Writing to SPMCSR ..............................................164
17.6
Reading Fuse and Lock Bits from Software ..................................................164
17.7
Preventing Flash Corruption ..........................................................................165
17.8
Programming Time for Flash when Using SPM ............................................165
17.9
Register Description ......................................................................................166
18 Memory Programming ......................................................................... 167
18.1
Program And Data Memory Lock Bits ...........................................................167
18.2
Fuse Bytes .....................................................................................................168
18.3
Signature Bytes .............................................................................................169
18.4
Calibration Byte .............................................................................................169
18.5
Page Size ......................................................................................................170
18.6
Serial Programming .......................................................................................170
18.7
Parallel Programming ....................................................................................174
19 Electrical Characteristics .................................................................... 184
19.1
Absolute Maximum Ratings* .........................................................................184
19.2
DC Characteristics .........................................................................................184
19.3
Speed Grades ...............................................................................................185
19.4
Clock Characteristics .....................................................................................186
19.5
System and Reset Characteristics ................................................................187
19.6
ADC Characteristics ......................................................................................188
19.7
Serial Programming Characteristics ..............................................................189
19.8
Parallel Programming Characteristics ...........................................................190
20 Typical Characteristics ........................................................................ 193
iv
20.1
Supply Current of I/O modules ......................................................................193
20.2
ATtiny261A ....................................................................................................195
20.3
ATtiny461A ....................................................................................................221
20.4
ATtiny861A ....................................................................................................247
ATtiny261A/461A/861A
8197A–AVR–10/09
ATtiny261A/461A/861A
21 Register Summary ............................................................................... 273
22 Instruction Set Summary .................................................................... 275
23 Ordering Information ........................................................................... 277
23.1
ATtiny261A ....................................................................................................277
23.2
ATtiny461A ....................................................................................................278
23.3
ATtiny861A ....................................................................................................279
24 Packaging Information ........................................................................ 280
24.1
32M1-A ..........................................................................................................280
24.2
20P3 ..............................................................................................................281
24.3
20S2 ..............................................................................................................282
24.4
20X ................................................................................................................283
25 Errata ..................................................................................................... 284
25.1
Errata ATtiny261A .........................................................................................284
25.2
Errata ATtiny461A .........................................................................................284
25.3
Errata ATtiny861A .........................................................................................284
26 Datasheet Revision History ................................................................ 285
26.1
Rev. 8197A – 10/09 .......................................................................................285
Table of Contents....................................................................................... i
v
8197A–AVR–10/09
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8197A–AVR–10/09