NSC CR16MNS5 Family of compactrisc 16-bit microcontroller Datasheet

CR16MES5/CR16MES9/CR16MFS5/CR16MFS9/
CR16MHS5/CR16MHS9/CR16MNS5/CR16MNS9/
CR16M9S5/CR16MUS5/CR16MUS9/
Family of CompactRISC 16-Bit Microcontrollers
1.0
General Description
The family of CompactRISC™ microcontrollers are general-purpose 16-bit microcontrollers based on a Reduced Instruction Set Computer (RISC) architecture. The device
operates as a complete microcomputer with all system timing, interrupt logic, flash program memory or ROM memory, RAM, EEPROM data memory, and I/O ports included
on-chip. It is ideally suited to a wide range of embedded
controller applications because of its high performance,
on-chip integrated features and low power consumption,
resulting in decreased system cost.
The family of CompactRISC 16-bit microcontrollers offer
the high performance of a RISC architecture while retaining the advantages of a traditional Complex Instruction Set
Computer (CISC): compact code, on-chip memory and I/O,
and reduced cost. The CPU uses a three-stage instruction
pipeline that allows execution of up to one instruction per
clock cycle, or up to 20 million instructions per second (MIPS) at a clock rate of 20 MHz.
Block Diagram
Fast Osc
CR16B
Core
Clock Generator
Power-on-Reset
Core Bus
Peripheral
Bus
Controller
Slow Osc
Processing
Unit
48k Flash
Program
Memory
640 Bytes
EEPROM
Data
Memory
2 kbyte
RAM
boot
ROM
Interrupt Power-Save
Control
Management
(ICU)
WATCHDOG
Peripheral Bus
I/O
µWire/SPI
Two
USARTs
Two
MFTs
A/D
MIWU
Two Analog
Comparators
Real-Time
Timer
Please note that not all family members contain same peripheral modules and features.
TRI-STATE® is a registered trademark of National Semiconductor Corporation.
©2001 National Semiconductor Corporation
www.national.com
CR16MES5/CR16MES9/CR16MFS5/CR16MFS9/ CR16MHS5/CR16MHS9/CR16MNS5/CR16MNS9/ CR16M9S5/CR16MUS5/
CR16MUS9/ Family of CompactRISC 16-Bit Microcontrollers
December 2001
Table of Contents
1.0
2.0
3.0
4.0
5.0
6.0
7.0
8.0
9.0
10.0
General Description. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
Features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
Device Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
3.1
CR16B CPU Core . . . . . . . . . . . . . . . . . . . . . . . . . . 5
3.2
Memory . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
3.3
Input/Output Ports . . . . . . . . . . . . . . . . . . . . . . . . . . 5
3.4
Bus Interface Unit . . . . . . . . . . . . . . . . . . . . . . . . . . 5
3.5
Interrupts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
3.6
Multi-Input Wake-up . . . . . . . . . . . . . . . . . . . . . . . . . 6
3.7
Dual Clock and Reset . . . . . . . . . . . . . . . . . . . . . . . 6
3.8
Power Management . . . . . . . . . . . . . . . . . . . . . . . . . 6
3.9
Multi-Function Timer . . . . . . . . . . . . . . . . . . . . . . . . 6
3.10 Real-Time TIMER and Watchdog . . . . . . . . . . . . . . 6
3.11 USART . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
3.12 MICROWIRE/SPI . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
3.13 A/D Converter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
3.14 Analog Comparators . . . . . . . . . . . . . . . . . . . . . . . . 7
3.15 Development Support . . . . . . . . . . . . . . . . . . . . . . . 7
3.16 Pin Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
System Configuration . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
4.1
ENV0 and ENV1 Pins . . . . . . . . . . . . . . . . . . . . . . 12
4.2
Module Configuration (MCFG) Register . . . . . . . . 12
4.3
Module Status (MSTAT) Register . . . . . . . . . . . . . 12
Input/Output Ports . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
5.1
Port Registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
5.2
Open-Drain Operation . . . . . . . . . . . . . . . . . . . . . . 14
CPU and Core Registers . . . . . . . . . . . . . . . . . . . . . . . . . 15
6.1
General-Purpose Registers . . . . . . . . . . . . . . . . . . 15
6.2
Dedicated Address Registers . . . . . . . . . . . . . . . . 15
6.3
Processor Status Register . . . . . . . . . . . . . . . . . . . 15
6.4
Configuration Register . . . . . . . . . . . . . . . . . . . . . . 16
6.5
Addressing Modes . . . . . . . . . . . . . . . . . . . . . . . . . 16
6.6
Stacks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
6.7
Instruction Set . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
Bus Interface Unit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18
7.1
Bus Cycles . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18
7.2
BIU Control Registers . . . . . . . . . . . . . . . . . . . . . . 18
7.3
Wait and Hold States Used . . . . . . . . . . . . . . . . . . 19
Memory . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21
8.1
Flash Program Memory . . . . . . . . . . . . . . . . . . . . . 21
8.2
RAM Memory. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24
8.3
EEPROM Data Memory. . . . . . . . . . . . . . . . . . . . . 24
8.4
ISP Memory . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24
Interrupts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27
9.1
Interrupt Operation . . . . . . . . . . . . . . . . . . . . . . . . . 27
9.2
Non-Maskable Interrupt . . . . . . . . . . . . . . . . . . . . . 28
9.3
Maskable Interrupts . . . . . . . . . . . . . . . . . . . . . . . . 29
9.4
Interrupt Registers . . . . . . . . . . . . . . . . . . . . . . . . . 29
9.5
Interrupt Programming Procedures . . . . . . . . . . . . 31
Power Management . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33
10.1 Active Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33
10.2 Power Save Mode . . . . . . . . . . . . . . . . . . . . . . . . . 33
10.3 Idle Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33
10.4 Halt Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33
10.5 Switching Between Power Modes . . . . . . . . . . . . . 33
11.0
12.0
13.0
14.0
15.0
16.0
17.0
18.0
19.0
20.0
21.0
22.0
23.0
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2
Dual Clock and Reset . . . . . . . . . . . . . . . . . . . . . . . . . . .36
11.1 External Crystal Network . . . . . . . . . . . . . . . . . . . .36
11.2 Main System Clock . . . . . . . . . . . . . . . . . . . . . . . . .37
11.3 Slow System Clock . . . . . . . . . . . . . . . . . . . . . . . . .37
11.4 Power-On Reset . . . . . . . . . . . . . . . . . . . . . . . . . . .38
11.5 External Reset . . . . . . . . . . . . . . . . . . . . . . . . . . . .38
11.6 Dual Clock and Reset Registers . . . . . . . . . . . . . .38
11.7 Slow Clock Prescaler Register (PRSSC) . . . . . . . .38
Multi-Input Wake-Up . . . . . . . . . . . . . . . . . . . . . . . . . . . .39
12.1 Wake-Up Edge Detection Register (WKEDG) . . . .39
12.2 Wake-Up Enable Register (WKENA) . . . . . . . . . . .39
12.3 Wake-Up Source Select Register (WKCTRL) . . . .40
12.4 Wake-Up Pending Register (WKPND) . . . . . . . . . .40
12.5 Wake-Up Pending Clear Register (WKPCL) . . . . .40
12.6 Programming Procedures . . . . . . . . . . . . . . . . . . .40
Real-Time Timer and WATCHDOG . . . . . . . . . . . . . . . . .41
13.1 TWM Structure . . . . . . . . . . . . . . . . . . . . . . . . . . . .41
13.2 Timer T0 Operation . . . . . . . . . . . . . . . . . . . . . . . .41
13.3 WATCHDOG Operation . . . . . . . . . . . . . . . . . . . . .42
13.4 TWM Registers . . . . . . . . . . . . . . . . . . . . . . . . . . . .42
13.5 WATCHDOG Programming Procedure . . . . . . . . .43
Multi-Function Timer . . . . . . . . . . . . . . . . . . . . . . . . . . . .45
14.1 Timer Structure. . . . . . . . . . . . . . . . . . . . . . . . . . . .45
14.2 Timer Operating Modes . . . . . . . . . . . . . . . . . . . . .47
14.3 Timer Interrupts . . . . . . . . . . . . . . . . . . . . . . . . . . .50
14.4 Timer I/O Functions . . . . . . . . . . . . . . . . . . . . . . . .50
14.5 Timer Registers . . . . . . . . . . . . . . . . . . . . . . . . . . .51
MICROWIRE/SPI . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .54
15.1 MICROWIRE Operation . . . . . . . . . . . . . . . . . . . . .54
15.2 Master Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . .55
15.3 Slave Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .56
15.4 Interrupt Generation . . . . . . . . . . . . . . . . . . . . . . . .57
15.5 MICROWIRE Interface Registers. . . . . . . . . . . . . .58
USART . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .61
16.1 Functional Overview . . . . . . . . . . . . . . . . . . . . . . . .61
16.2 USART Operation . . . . . . . . . . . . . . . . . . . . . . . . .61
16.3 USART Registers . . . . . . . . . . . . . . . . . . . . . . . . . .65
16.4 Baud Rate Calculations . . . . . . . . . . . . . . . . . . . . .67
Analog Comparators . . . . . . . . . . . . . . . . . . . . . . . . . . . .68
17.1 Analog Comparator Control/Status Register
(CMPCTRL)68
17.2 Analog Comparator Usage . . . . . . . . . . . . . . . . . . .68
A/D Converter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .69
18.1 Operating Modes . . . . . . . . . . . . . . . . . . . . . . . . . .69
18.2 A/D Converter Registers . . . . . . . . . . . . . . . . . . . .70
18.3 A/D Converter Programming . . . . . . . . . . . . . . . . .72
Memory Map . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .73
Register Layouts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .77
20.1 Register layout . . . . . . . . . . . . . . . . . . . . . . . . . . . .77
ELECTRICAL CHARACTERISTICS . . . . . . . . . . . . . . . . .81
Comparator AC and DC Characteristics . . . . . . . . . . . .83
Output Signal Levels . . . . . . . . . . . . . . . . . . . . . . . . . . . .85
Appendix . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .95
22.1 8-bit MICROWIRE/SPI (MWSPI) . . . . . . . . . . . . . .95
22.2 Timing and watchdog module . . . . . . . . . . . . . . . .95
Physical Dimension . . . . . . . . . . . . . . . . . . . . . . . . . . . . .97
1.0
General Description (Continued)
— Programmable I/O pin characteristics: TRI-STATE output, push-pull output, weak pull-up input, high-impedance input
— Software-configurable Schmitt triggers on inputs
• Power Supply
— 4.5V to 5.5V single-supply operation
• Temperature Range
— 0°C to +70°C
— –40°C to +85°C
— –40°C to +125°C
• Development Support
— Real-time emulation and full program debug capabilities available
— CompactRISC tools provide C programming and debugging support
In the following text, device is alsays refered to the family of
CompactRISC 16-bit microcontrollers. For the exact feature
set, check individual datasheets.
The device is available in a variety of package sizes and
types. All devices have 48 kbytes of reprogrammable flash
program memory, 1.5 kbytes of ISP memory, 2 kbytes of static RAM, and 640 bytes of non-volatile EEPROM data memory. The 80-pin device has two USARTs, two 16-bit multifunction timers, one SPI/MICROWIRE-PLUS™ serial interface, an 8-channel A/D converter, two analog comparators,
WATCHDOG™ protection mechanism, and up to 48 generalpurpose I/O pins. The 44-pin devices offer the same basic
features as the 80-pin device, but with fewer I/O ports and
peripheral modules due to the smaller number of available
pins.
All devices operate with a high-frequency crystal as the main
clock source. Some packages allow the device to operate
with either the main clock source or with a slow (32.768 KHz)
oscillator in Power Save mode. The device supports several
Power Save modes which are combined with multi-source interrupt and wake-up capabilities.
Powerful cross-development tools are available from National Semiconductor and third party suppliers to support the development and debugging of application software for the
device. These tools let you program the application software
in C and are designed to take full advantage of the CompactRISC architecture.
2.0
Features
• CPU Features
— Fully static core, capable of operating at any rate from
0 to 20 MHz (4 MHz minimum in active mode)
— 50 ns instruction cycle time with a 20 MHz external
clock frequency
— Multi-source vectored interrupts (internal, external,
and on-chip peripheral)
— On-chip power-on reset
• On-Chip Memory
— 48 kbytes of flash program memory or ROM memory
(100K cycle)
— 1.5 kbytes of ISP memory (100K cycle)
— 2 kbytes of static RAM data memory
— 640 bytes of non-volatile EEPROM data memory,
word-programmable (100K cycle)
• On-Chip Peripherals
— Up to two Universal Synchronous/Asynchronous Receiver/Transmitter (USART) devices
— Programmable Idle Timer and real-time clock (T0)
— Up to two dual 16-bit multi-function timers (MFT1 and
MFT2)
— SPI/MICROWIRE-PLUS serial interface
— 8-channel, 8-bit Analog-to-Digital (A/D) converter with
external voltage reference, programmable sampleand-hold delay, and programmable conversion frequency
— Up to two analog comparators
— Integrated WATCHDOG logic
• I/O Features
— Up to 48 general-purpose I/O pins (shared with on-chip
peripheral I/O pins)
3
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CR16 CompactRISC microcontroller Family Selection Guide
Programmable devices
NSID
Speed
(MHz)
Flash/
ROM
(kByte)
EEPROM
Data
Memory
(Bytes)
SRAM
(kBytes)
USART
Timer
I/Os
Temp.
Range
Peripherals
Package
Type
CR16MHS9VJEx
20
48
640
2
2
2
48
E, I
ADC,
Comparators
80PQFP
CR16MFS944Vx
20
48
640
2
2
1
33
E, I
ADC
44PLCC
CR16MES944Vx
20
48
640
2
1
2
33
E, I
ADC
44PLCC
CR16MNS944Vx
20
48
None
2
1
2
33
C, I
None
44PLCC
CR16MUS944Vx
8
48
None
2
1
2
33
C
None
44PLCC
Temp.
Range
Peripherals
Package
Type
ROM devices
EEPROM
Data
SRAM
Memory (kBytes)
(Bytes)
NSID
Speed
(MHz)
Flash/
ROM
(kByte)
CR16MHS5VJExy
20
48
640
2
2
2
48
E, I
ADC,
Comparators
80PQFP
CR16MFS544Vxy
20
48
640
2
2
1
33
E, I
ADC
44PLCC
CR16MES544Vxy
20
48
640
2
1
2
33
E, I
ADC
44PLCC
CR16MPS544Vxy
20
48
None
2
1
2
33
C, I
ADC
44PLCC
CR16MNS544Vxy
20
48
None
2
1
2
33
C, I
None
44PLCC
CR16MUS544Vxy
8
48
None
2
1
2
33
C
None
44PLCC
USART
Timer I/Os
Note:
•
Suffix x in the NSID is defined below:
Temperature Ranges:
E = Extended
I = Industrial
C = Commercial
•
-40 °C to +125°C is represented when x is 7
-40 °C to +85°C is represented when x is 8
0°C to +70 °C is represented when x is 9
Suffix y in the NSID defines the ROM code.
Note: All devices contains Clock and Reset, MICROWIRE/
API, Multi-Input Wake-Up (MIWU), Power Management
(PMM), and the Real-Time Timer and Watchdog (TWM) modules.
44-Pin PLCC versus 80-Pin PQFP
For 44PLCC packages, MICROWIRE/SPI slave mode, the
first 4 MIWU channels and the Vref pin are not available. 80pin PQFP packages provide the MICROWIRE/SPI master
and slave modes, 8 MIWU channels, Vref pin, and two USARTs and two MFTs.
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4
3.0
Device Overview
The family of CompactRISC 16-bit microcontrollers are complete microcomputers with all system timing, interrupt logic,
program memory, data memory, and I/O ports included onchip, making it well-suited to a wide range of embedded controller applications.
3.1
The 640 bytes of EEPROM data memory are used for nonvolatile storage of data, such as configuration settings entered by the end-user. The CPU reads or writes this memory
by using ordinary byte-wide or word-wide memory access
commands. After the CPU performs a write to this memory,
the on-chip hardware completes the EEPROM programming
in the background. A register status bit indicates the status of
the EEPROM programming operation.
CR16B CPU CORE
The device uses the CR16B CPU core module. This is the
same core used in other CompactRISC family members.
There is a factory programmed boot memory used to store
In-System-Programming (ISP) code. (this code allows programming of the program memory via one of the USART interfaces in the final application.)
The high performance of the CPU core results from the implementation of a pipelined architecture with a two-bytes-percycle pipelined system bus. As a result, the CPU can support
a peak execution rate of one instruction per clock cycle.
For the flash program memory, the device internally generates the necessary voltages for programming. No additional
power supply is required.
Compared with conventional RISC processors, the device
differs in the following ways:
• The CPU core uses on-chip rather than external memory.
This eliminates the need for large and complex bus interface units.
• Most instructions are 16 bits, so all basic instructions are
just two bytes long. (Additional bytes are sometimes required for immediate values, so instructions can be two or
four bytes long.)
• Non-aligned word access is allowed. Each instruction can
operate on 8-bit or 16-bit.
• The device is designed to operate with a clock rate in the
10 to 25 MHz range rather than 100 MHz or more. Most
embedded systems face EMI and noise constraints that
limit clock speed to these lower ranges. A lower clock
speed means a simpler, less costly silicon implementation.
• The instruction pipeline uses three stages. A smaller pipeline eliminates the need for costly branch prediction
mechanisms and bypass registers, while maintaining adequate performance for typical embedded controller applications.
3.2
3.3
INPUT/OUTPUT PORTS
Each device has 48 software-configurable I/O pins, organized into six 8-pin ports called Port B, Port C, Port F, Port G,
Port L, and Port I. Each pin can be configured to operate as
a general-purpose input or general-purpose output. In addition, many I/O pins can be configured to operate as a designated input or output for an on-chip peripheral module such
as the USART, timer, A/D converter, or MICROWIRE/SPI interface.
The I/O pin characteristics are fully programmable. Each pin
can be configured to operate as a TRI-STATE output, pushpull output, weak pull-up input, or high-impedance input. Input pins can be software-configured to use Schmitt triggers
for noise resistance.
Each 44-pin device has a subset of the pins available in the
80-pin device. This results in the loss of some features that
are available in the larger-package device:
• One of the two USARTs or one of the two multi-function
timers (depending on package selection)
• Synchronous mode in the remaining USART(s)
• Slave mode operation for the MICROWIRE/SPI interface
• Separate external VREF for the A/D converter
• Comparators
• Four of the eight Multi-Input Wakeup pins
• NMI interrupt input pin
MEMORY
The CompactRISC architecture supports a uniform linear address space of 2 megabytes. The device implementation of
this architecture uses only the lowest 64 kbytes of address
space. Four types of on-chip memory occupy specific intervals within this address space: 48 kbytes of flash program
memory, 1.5 kbytes of ISP memory, 2 kbytes of static RAM,
and 640 bytes of EEPROM data memory.
3.4
BUS INTERFACE UNIT
The Bus Interface Unit (BIU) controls the interface between
the on-chip modules to the internal core bus. It determines
the configured parameters for bus access (such as the number of wait states for memory access) and issues the appropriate bus signals for each requested access.
The 48 kbytes of flash program memory are used to store the
application program. It has security features to prevent unintentional programming and to prevent unauthorized access
to the program code. This memory can be programmed either with the device plugged into an EPROM programmer
unit (external programming) or with the device installed in the
application system (in-system programming).
The BIU uses a set of control registers to determine how
many wait states and hold states are to be used when accessing EEPROM memory. Upon start-up of the device,
these registers must be programmed with appropriate values
so that the minimum allowable number states is used. This
number varies with the clock frequency and the type of onchip device being accessed.
The 2 kbytes of static RAM are used for temporary storage of
data and for the program stack and interrupt stack. Read and
write operations can be byte-wide or word-wide, depending
on the instruction executed by the CPU. Each memory access requires one clock cycle; no wait cycles or hold cycles
are required.
5
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3.5
INTERRUPTS
3.9
The Interrupt Control Unit (ICU) receives interrupt requests
from internal and external sources and generates interrupts
to the CPU. An interrupt is an event that temporarily stops the
normal flow of program execution and causes a separate interrupt service routine to be executed. After the interrupt is
serviced, CPU execution continues with the next instruction
in the program following the point of interruption.
The Multi-Function Timer (MFT16) module contains two independent timer/counter units called MFT1 and MFT2, each
containing a pair of 16-bit timer/counter registers. Each timer/
counter unit can be configured to operate in any of the following modes:
• Processor-Independent Pulse Width Modulation (PWM)
mode, which generates pulses of a specified width and
duty cycle, and which also provides a general-purpose
timer/counter
• Dual Input Capture mode, which measures the elapsed
time between occurrences of external events, and which
also provides a general-purpose timer/counter
• Dual Independent Timer mode, which generates system
timing signals or counts occurrences of external events
• Single Input Capture and Single Timer mode, which provides one external event counter and one system timer
Interrupts from the timers, USARTs, MICROWIRE/SPI interface, multi-input wake-up, and A/D converter are all
maskable interrupts; they can be enabled or disabled by the
software. There are 16 of these maskable interrupts, organized into 16 predetermined levels of priority.
The highest-priority interrupt is the Non-Maskable Interrupt
(NMI), which is generated by a signal received on the NMI input pin. This interrupt is not available in the 44-pin packages.
3.6
MULTI-INPUT WAKE-UP
3.10
The Multi-Input Wake-up (MIWU) module can be used for either of two purposes: to provide inputs for waking up (exiting)
from the HALT, IDLE, or Power Save mode; or to provide
general-purpose edge-triggered maskable interrupts from
external sources. This eight-channel module generates one
combined interrupt to the CPU based on the signals received
on its eight input channels. Channels can be individually enabled or disabled, and programmed to respond to positive or
negative edges.
3.7
The real-time timer generates a periodic interrupt to the CPU
at a software-programmed interval. This can be used for realtime functions such as a time-of-day clock.
The Watchdog is designed to detect program execution errors such as an infinite loop or a “runaway” program. Once
Watchdog operation is initiated, the application program
must periodically write a specific value to a Watchdog register, within specific time intervals. If the software fails to do so,
a Watchdog error is triggered, which resets the device.
DUAL CLOCK AND RESET
In the 80-pin package, the module also generates a slow system clock (32.768 KHz) from another external crystal network. The slow clock is used for operating the device in
power-save mode. For the 44-pin devices and for devices not
using a secondary crystal network, the slow clock can be
generated by dividing the high-speed main clock by a prescaler factor.
3.11
USART
The USART is a Universal Synchronous/Asynchronous Receiver-Transmitter, a device used for serial communications.
It supports a wide range of programmable baud rates and
data formats, and handles parity generation and several error detection schemes. The baud rate is generated on-chip,
under software control.
POWER MANAGEMENT
The synchronous mode of operation is not available in the
44-pin devices.
The Power Management Module (PMM) improves the efficiency of the device by changing the operating mode (and
therefore the power consumption) according to the current
level of activity.
3.12
MICROWIRE/SPI
The MICROWIRE/SPI (MWSPI) interface module supports
asynchronous serial communications with other devices that
conform to MICROWIRE or Serial Peripheral Interface (SPI)
specifications.
The device can operate in any of four power modes:
• Active: The device operates at full speed using the highfrequency clock. All device functions are fully operational.
• Power Save: The device operates at reduced speed using
the slow clock. The CPU and some modules can continue
to operate at this low speed.
• IDLE: The device is inactive except for the Power Management Module and Timing and Watchdog Module,
which continue to operate using the slow clock.
• HALT: The device is inactive but still retains its internal
state (RAM and register contents).
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REAL-TIME TIMER AND WATCHDOG
The Timing and Watchdog Module (TWM) generates the
clocks and interrupts used for timing periodic functions in the
system. It also provides Watchdog protection against software errors. The module operates on the slow (32.768 KHz)
clock.
The Dual Clock and Reset (CLK2RES) module generates a
high-speed main system clock from an external crystal network. It also provides the main system reset signal and a
power-on reset function.
3.8
MULTI-FUNCTION TIMER
The MICROWIRE interface allows several devices to communicate over a single system consisting of three wires: serial in, serial out, and shift clock. At any given time, one
device on the MICROWIRE interface operates as the master,
while all other devices operate as slaves. An 80-pin device
supports the full set of slave select and Ready lines for multislave implementation, while a 44-pin device has only the basic Data-in/Data-out/Clock lines, limiting its implementation
to master mode.
6
3.13
A/D CONVERTER
3.15
The A/D Converter (ADC) module is an 8-channel multiplexed-input analog-to-digital converter. The A/D Converter
receives an analog voltage signal on an input pin and converts the analog signal into an 8-bit digital value using successive approximation. The CPU can then read the result
from a memory-mapped register. The module supports four
automated operating modes, providing single-channel or
scanned 4-channel operation in single or continuous mode.
A powerful cross-development tool set is available from National Semiconductor and third parties to support the development and debugging of application software for the device.
The tool set lets you program the application software in C
and is designed to take full advantage of the CompactRISC
architecture.
There are In-System Emulation (ISE) devices available for
the device from iSYSTEM™, as well as lower-cost evaluation
boards. See your National Semiconductor sales representative for current information on availability of various features
of emulation equipment and evaluation boards.
The 80-pin device has a separate pin, Vref, for the A/D reference voltage. The 44-pin devices use the AVCC (analog
VCC) power supply pin as the reference voltage.
3.14
DEVELOPMENT SUPPORT
ANALOG COMPARATORS
The Dual Analog Comparator (ACMP2) module contains two
independent analog comparators with all necessary control
logic. Each comparator unit compares the analog input voltages applied to two input pins and determines which voltage
is higher. The CPU uses a memory-mapped register to control the comparator and to obtain the comparison results. The
comparison result can also be applied to comparator output
pins.
7
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Table 1
Package Pin Assignments
44-pin PLCC
Package
Pin Number
80-pin PQFP
Package
Pin Number
Type
GND
44
13
PWR
Vcc
1
14
PWR
GND
N/A
15
PWR
ENV0-44/SLCLK a
2
N/A
I/O
PC0
3
17
I/O
PC1
4
18
I/O
PC2
5
19
I/O
PC3
6
20
I/O
PC4
7
21
I/O
PC5
8
22
I/O
PC6
9
23
I/O
PC7
10
24
I/O
Pin Name
Alternate Function(s)
ENV0-80/SLCLK a
N/A
26
I/O
b
11
27
I/O
ENV1/CLK a
11
28
I/O
CLKOUT2
PG7
CKX1
N/A
29
I/O
PG6
TDX1
12
30
I/O
PG5
RDX1
13
31
I/O
PG4
MRDY
N/A
32
I/O
PG3
MCS
N/A
33
I/O
PG2
MSK
14
34
I/O
PG1
MDODI
15
35
I/O
PG0
MDIDO
16
36
I/O
N/A
38
I/O
PF7
PF6
CKX2
N/A
39
I/O
PF5
T2B
17
40
I/O
PF4
T2A
18
41
I/O
PF3 c
TDX2
19 or N/A *
42
I/O
PF2
c
RDX2
20 or N/A *
43
I/O
PF1
c
T1B
N/A or 19 *
44
I/O
PF0 c
T1A
N/A or 20 *
45
I/O
NMI
N/A
46
I
X1CKO
21
48
O
X1CKI
22
49
I
GND
N/A
50
PWR
Vcc
23
51
PWR
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8
Table 1
Package Pin Assignments
44-pin PLCC
Package
Pin Number
80-pin PQFP
Package
Pin Number
Type
GND
24
52
PWR
X2CKO
N/A
53
O
Pin Name
Alternate Function(s)
X2CKI
N/A
54
I
e,f
25
57
I/O
e,f
26
58
I/O
PI2
e,f
ACH2
27
59
I/O
PI3
ACH3e,f
PI0
ACH0
PI1
ACH1
PI4
28
60
I/O
e,f
29
61
I/O
e,f
30
62
I/O
e,f
ACH4 , MIWU4
PI5
ACH5 , MIWU5
PI6
ACH6 , MIWU6
31
63
I/O
PI7
ACH7 e,f, MIWU7
32
64
I/O
Vref
N/A
66
PWR
AVcc
f
33
67
PWR
AGND
f
34
68
PWR
GND
N/A
69
PWR
Vcc
N/A
70
PWR
N/A
71
PWR
RESET
35
76
I
PB0
36
77
I/O
PB1
37
78
I/O
PB2
38
79
I/O
PB3
39
80
I/O
PB4
40
1
I/O
PB5
41
2
I/O
PB6
42
3
I/O
PB7
43
4
I/O
GND
d
PL0
COMP1Ne
N/A
73
I/O
PL1
COMP1P
e
N/A
74
I/O
PL2
COMP1O
N/A
5
I/O
N/A
6
I/O
PL3
PL4
COMP2Ne , MIWU0
N/A
8
I/O
PL5
e
N/A
9
I/O
COMP2P , MIWU1
9
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Table 1
Package Pin Assignments
Pin Name
Alternate Function(s)
44-pin PLCC
Package
Pin Number
80-pin PQFP
Package
Pin Number
Type
PL6
COMP2O, MIWU2
N/A
11
I/O
PL7
MIWU3
N/A
12
I/O
Notes:
a. The ENV0 and ENV1 pins each have a weak pullup to keep the input from floating.
b. The CLKOUT2 function is shared with the ENV1/CLK pin in the 44-pin device.
c. In the 44-pin CR16MES, CR16MNS, CR16MPS, and CR16MUS packages, PF1 and PF0 are available; PF3 and PF2 are
not available.
In the 44-pin CR16MFS, CR16MOS, CR16MQS, and CR16M VS packages, PF3 and PF2 are available; PF1 and PF0 are
not available.
d. The RESET input has a weak pulldown.
e. These functions are always enabled due to the direct low-impedance path to these pins.
f. These functions may not be available on some 44-pin devices.
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10
3.16
The following is a brief description of all CR16MHR6 pins.
PIN DESCRIPTION
Some pins have alternate functions which may be enabled.
These pins can be individually configured as general purpose pins, even when the module they belong to is enabled.
Table 2 Input Pins
Signal
Type
Pin (* for a
shared pin)
Active
Function
X1CKI
OSC
High
Main oscillator clock input.
X2CKI
OSC
High
32kHz oscillator clock input.
RESET
CMOS
Low
Chip general reset pin. Schmitt trigger input, asynchronous.
ISE
CMOS
Low
Interrupt input for development system.
T1B
CMOS
Prog.
*
Timer 1 input B. Shares pin with I/O port pin PF1.
T2B
CMOS
Prog.
*
Timer 2 input B. Shares pin with I/O port pin PF5.
RDX1
CMOS
High
*
USART 1 receive data input. Shares pin with I/O port pin PG5.
RDX2
CMOS
High
*
USART 2 receive data input. Shares pin with I/O port pin PF4.
ACH0
Analog
*
A2D converter channel 0. Shares pin with I/O port pin PI0
ACH1
Analog
*
A2D converter channel 1. Shares pin with I/O port pin PI1
ACH2
Analog
*
A2D converter channel 2. Shares pin with I/O port pin PI2
ACH3
Analog
*
A2D converter channel 3. Shares pin with I/O port pin PI3
ACH4
Analog
*
A2D converter channel 4. Shares pin with I/O port pin PI4
ACH5
Analog
*
A2D converter channel 5. Shares pin with I/O port pin PI5
ACH6
Analog
*
A2D converter channel 6. Shares pin with I/O port pin PI6
ACH7
Analog
*
A2D converter channel 7. Shares pin with I/O port pin PI7
MCS
CMOS
Low
*
SPI/MICROWIRE slave select. Shares pin with I/O port pin PG3.
NMI
CMOS
Low
ENV0-44
CMOS
Low
*
Strap pin on 44-pin package to select operating environment.
ENV0-80
CMOS
Low
*
Strap pin on 80-pin package to select operating environment.
ENV1
CMOS
Low
*
Strap pin to select operating environment.
ENV2
CMOS
Low
External non-maskable interrupt.
Strap pin to select operating environment.
Table 3 Output Pins
Signal
Type
Pin (* for a
shared pin)
Active
Function
X1CKO
OSC
High
Main oscillator clock output.
X2CKO
OSC
High
32 kHz oscillator clock output.
CLK
CMOS High
TDX1
CMOS High
*
USART 1 transmit data output. Shares pin with I/O port pin PG6.
TDX2
CMOS High
*
USART 2 transmit data output. Shares pin with I/O port pin PF5.
MRDY
CMOS Low
*
SPI/MICROWIRE slave ready output. Shares pin with I/O port pin PG4
CLKOUT2
OSC
High
External reference clock for development environment.
System clock divided-by-2 output (shared with the ENV1 pin in the 44-pin
device)
11
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Table 4 Input/Output Pins
Pin (* for a
shared pin)
Signal
Type
Active
Function
PF[0:7]
CMOS
High
*
Generic I/O port. Shared with T1A, T1B, T2A, T2B, RDX2, TDX2, CKX2.
PG[0:7]
CMOS
High
*
Generic I/O port. Shared with MDIDO, MDODI, MSK, MCS, MRDY, RDX1,
TDX1, CKX1.
PB[0:7]
CMOS
High
*
Generic I/O port.
PC[0:7]
CMOS
High
*
Generic I/O port.
PL[0:7]
CMOS
High
*
Generic I/O port. Shared with six comparator pins and four MIWU pins.
PI[0:7]
CMOS
High
*
Generic I/O port. Shared with ADC input channels 0-7 and four MIWU pins.
T1A
CMOS
Prog
*
Timer 1 input A. Shared with I/O port pin PF0.
T2A
CMOS
Prog
*
Timer 2 input A. Shared with I/O port pin PF4.
MDIDO
CMOS
High
*
Master In/Slave Out port: SPI/Microwire. Shared with I/O pin PG0.
MDODI
CMOS
High
*
Master Out/Slave In port: SPI/Microwire. Shared with I/O pin PG1.
MSK
CMOS
High
*
SPI/Microwire clock. Shared with I/O pin PG2.
CKX1
CMOS
High
*
USART 1 clock signal. Shared with I/O pin PG7.
CKK2
CMOS
High
*
USART 2 clock signal. Shared with I/O pin PF6.
Table 5
Power Supply
Signal
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Function
Vcc
Main digital power supply.
Vref
Voltage reference supply for analog to digital converter.
AVcc
Analog power supply for analog/digital converter.
AGND
Analog reference ground supply.
GND
Main digital reference ground.
12
4.0
System Configuration
The CR16MHS9 has two input pins, ENV0 and ENV1, which
are used to specify the operating environment of the device
upon reset. There are also two system configuration registers, called the Module Configuration (MCFG) register and
the Module Status (MSTAT) register.
4.1
SLCLKOE
ENV0 AND ENV1 PINS
Upon reset, the operating mode of the device is determined
by the state of the ENV0 and ENV1 input pins, as indicated
in Table6.
FEEDM
Table 6 Operating Environment Selection
ENV1
ENV0
Operating Environment
0
0
Test Mode
0
1
Test Mode
1
0
In-System Programming mode
1
1
Internal ROM enabled Mode (IRE), if
program memory is not empty; or ISPMode, if program memory is empty
SLCOE2
CLK2OE
In the case where the ENV1 and ENV0 pins are both high,
the reset algorithm looks at the FLCTRL2.EMPTY bit to determine whether the program memory is empty, and sets the
operating mode accordingly.
4.3
The ENV0 and ENV1 pins have on-chip pull-up devices that
are enabled during reset while the pins are being sampled.
Therefore, if they are left unconnected, the inputs are considered high and the normal operating mode (IRE-Mode) is selected and the CPU starts to execute code at address 0. To
enter any other operating mode, the external hardware must
drive the appropriate input low.
MODULE STATUS (MSTAT) REGISTER
The MSTAT register is a byte-wide, read-only register that indicates the general status of the device.
The MCFG register format is shown below.
7
4
Reserved
3
PGMBUSY
2
Reserved
1
OENV1
0
OENV0
OENV(1:0)
Operating Environment. These two bits contain
the values applied to the ENV1 and ENV0 pins
upon reset. These bit values are controlled by
the external hardware upon reset and are held
constant in the register until the next reset.
PGMBUSY Flash Programming Busy. This bit is automatically set to 1 when either the program memory
or the data memory is busy being programmed.
It is cleared to 0 when neither of the two flash
memories are busy being programmed. When
this bit is set, the software should not attempt
to access either of these two memories.
In the case where the ISP-Mode is selected, the chip starts
executing the ISP code residing in the on-chip boot ROM area.
The Test Modes are reserved for factory testing and for external programming of the flash program memory; they
should not be invoked otherwise.
4.2
operating mode, the CLK pin operates as a
CPU clock output.
Slow Clock Output Enable. When cleared (0),
the SLCLK pin of the 44-pin package (ENV0-44
pin) remains in the high-impedance state.
When set (1), this pin produces the slow clock
as an output.
Fast EEPROM Data Memory Access. This bit
is set (1) for zero-wait-state access to the EEPROM data memory, or cleared (0) for onewait-state access to the data ROM. For information on the required number of wait states,
see Table8.
Slow Clock Output Enable. When cleared (0),
the SLCLK pin of the 80-pin package (ENV0-80
pin) remains in the high-impedance state.
When set (1), this pin produces the slow clock
as an output.
CPU Clock Divide-by-2 Output Enable. When
this bit is cleared (0), the CLKOUT2 pin remains in the high-impedance state. When this
bit is set (1) and the CLKOE bit is cleared, the
CLKOUT2 pin operates as clock output, with a
frequency of one-half that of the CPU clock.
MODULE CONFIGURATION (MCFG)
REGISTER
The MCFG register is a byte-wide, read/write register that
sets the general programmable features of the device.
Upon reset, the non-reserved bits of this register are cleared
to zero. The start-up software must write a specific value to
this register in order to configure the CLK output pin function.
When the software writes to this register, it must write a zero
to each reserved bit for the device to operate properly. The
register should be written in active mode only, not in power
save, HALT, or IDLE mode. However, the register contents
are preserved during all power modes.
The MCFG register format is shown below.
7
6
Reserved
CLKOE
5
4
3
2
1
0
CLK2OE
SLCOE2
FEEDM
SLCLKOE
CLKOE
Reserved
CPU Clock Output Enable. When this bit is
cleared (0), the CLK pin remains in the high-impedance state. When this bit is set (1) in normal
13
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5.0
Input/Output Ports
Each device has up to 48 software-configurable I/O pins, organized into six ports of up to eight pins per port. The exact
number of port pins varies with the package type. The ports
are named Port B, Port C, Port F, Port G, Port L, and Port I.
The electrical characteristics and drive capabilities of the input and output buffers are described in Section21.0.
For some pins, a direct low-impedance path is provided between the pin and an internal analog function. These are the
input pins to the A/D converter and the analog comparators
Each pin can be configured to operate as a general-purpose
input or general-purpose output. In addition, many I/O pins
can be configured to operate as a designated input or output
for an on-chip peripheral module such as the USART. This is
called the pin's “alternate function.” The alternate functions of
all I/O pins are shown in the pinout diagrams in Table1.
5.1
Each port has an associated set of memory-mapped registers used for controlling the port and for holding the port data.
In general, there are six such registers:
The I/O pin characteristics are fully programmable. Each pin
can be configured to operate as a TRI-STATE output, pushpull output, weak pull-up input, or high-impedance input. Different pins within the same port can be individually configured to operate in different modes.
•
•
•
•
•
•
Figure1 is a diagram showing the functional features of an I/
O port pin. The register bits, multiplexers, and buffers allow
the port pin to be configured into the various operating
modes.The output buffer is a TRI-STATE buffer with weak
pull-up capability. The weak pull-up, if used, prevents the port
pin from going to an undefined state when it operates as an
input.
Weak pull-up
Register
{
PxALT: Port alternate function register
PxDIR: Port direction register
PxDIN: Port data input register
PxDOUT: Port data output register
PxWKPU: Port weak pull-up register
PxSCHEN: Port Schmitt trigger enable register
In the descriptions of the ports and port registers, the lowercase letter “x” represents the port designation, either B, C, F,
G, L, or I. For example, “PxDIR register” means any one of
the port direction registers: PBDIR, PCDIR, PFDIR, and so
on.
All of the port registers are byte-wide read/write registers, except for the port data input registers, which are read-only registers. Each register bit controls the function of the
corresponding port pin. For example, PFDIR.2 (bit 2 of the
PFDIR register) controls the operation of port pin PF2.
The input buffer is disabled when it is not needed to prevent
leakage current. When enabled, it buffers the input signal
and sends the pin's logic level to the appropriate on-chip
module where it is latched. A Schmitt trigger, when enabled,
minimizes the effects of electrical noise.
Alternate Func.
Register
PORT REGISTERS
Alt. Function
{
{
Weak pull-up
Direction
Register
MUX1
Alt Device Direction
Direction
Alt
Data Out
Register
{
PIN
MUX2
Alt Device Data Output
Data Out
Alt
*
Data Input
Alt
1
Data In Read Strobe
Schmitt Enable
MUX2
Alternate Data Input
Alt
Analog Input
* Schmitt trigger is used at input when enabled or when the pin’s alternate function is selected.
Figure 1. I/O Pin Functional Diagram
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14
5.1.1
Port Alternate Function Register
5.1.6
Each port that supports an alternate function (any port other
than Port B or Port C) has an alternate function register (PxALT). This register determines whether the port pins are used
for general-purpose I/O or for the predetermined alternate
function. Each port pin can be controlled independently.
PxSCHEN registers are byte-wide read/write registers. They
enable the Schmitt trigger characteristics on Px input buffers
when these pins are used as general purpose I/O ports.
When cleared (0) with the pins used as general purpose I/O
ports, each bit in PxSCHEN enables the corresponding input
buffer only when the port is read, and therefore the input buffer may not exhibit any Schmitt trigger behavior. When set (1),
the input buffer is enabled, and will exhibit Schmitt trigger behavior. PxSCHEN registers are cleared upon reset.
A bit cleared to 0 in the alternate function register causes the
corresponding pin to be used for general-purpose I/O. In this
configuration, the output buffer is controlled by the direction
register and the data output register. The input buffer is routed to the data input register. The input buffer is blocked except when the buffer is actually being read.
5.2
OPEN-DRAIN OPERATION
A port pin can be configured to operate as an inverting opendrain output buffer. To do this, the CPU should clear the bit in
the data output register (PxDOUT) and then use the port direction register (PxDIR) to set the value of the port pin. With
the direction register bit set to 1 (direction=out), the value
zero is forced on the pin. With the direction register bit
cleared to 0 (direction=in), the pin is placed in the TRI-STATE
mode. If desired, the internal weak pull-up can be enabled to
pull the signal high when the output buffer is in the TRISTATE mode.
A bit set to 1 in the alternate function register causes the corresponding pin to be used for its predetermined peripheral I/
O function. The output buffer data and TRI-STATE configuration are controlled by signals coming from the on-chip peripheral device. The input buffer is enabled continuously in this
case. To minimize power consumption, the input signal
should be held within 0.2 volts of the VCC or GND voltage.
A reset operation clears the port alternate function registers
to 0, which programs the pins to operate as general-purpose
I/O ports. This register must be enabled before the corresponding alternate function is enabled.
5.1.2
Port Schmitt Input Enable Register
Port Direction Register
The port direction register (PxDIR) determines whether each
port pin is used for input or for output. A bit cleared to 0 causes the pin to operate as an input, which puts the output buffer
in the high-impedance state. A bit set to 1 causes the pin to
operate as an output, which enables the output buffer.
A reset operation clears the port direction registers to 0,
which programs the pins to operate as inputs.
5.1.3
Port Data Input Register
The data input register (PxDIN) is a read-only register that returns the current state of each port pin. The CPU can read
this register at any time even when the pin is configured as
an output.
5.1.4
Port Data Output Register
The data output register (PxDOUT) holds the data to be driven onto each port pin configured to operate as a general-purpose output. In this configuration, writing to the register
changes the output value. Reading the register returns the
last value written to the register.
A reset operation leaves the register contents unchanged.
Upon power-up, the registers contain unknown values.
5.1.5
Port Weak Pull-Up Register
The weak pull-up register (PxWKPU) determines whether
each port pin uses a weak pull-up on the output buffer. A bit
set to 1 causes the weak pull-up to be used, while a bit
cleared to 0 causes the weak pull-up not to be used.
The pull-up device, if enabled by the register bit, operates in
the general-purpose I/O mode whenever the port output buffer is in the TRI-STATE mode. In the alternate function mode,
the pull-ups are always disabled.
A reset operation clears the port weak pull-up registers to 0,
which disables all pull-ups.
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6.0
CPU and Core Registers
The device uses the same CR16B CPU core as other CompactRISC family members. The core's Reduced Instruction
Set Computer (RISC) architecture allows a processing rate of
up to one instruction per clock cycle.
E000-E7FF hex, which is the range of the RAM memory in
which the stack resides.
The CPU core uses the following set of internal registers:
The INTBASE register holds the address of the Dispatch Table for interrupts and traps. The five most significant bits and
the least significant bit of this register are always zero.
•
•
•
•
6.2.3
General-purpose registers (R0-R13, RA, and SP)
Dedicated address registers (PC, ISP, and INTBASE)
Processor Status Register (PSR)
Configuration Register (CFG)
6.3
15 14 13 12 11 10 9 8
Reserved
I P E 0
Some register bits are designated as “reserved.” The CPU
must write a zero to each of these bit locations when it writes
to the register. Read operations from reserved bit locations
return undefined values.
C bit
GENERAL-PURPOSE REGISTERS
There are 16 general-purpose registers, designated R0
through R13, RA, and SP. Registers R0 through R13 can be
used for any purpose such as holding variables, addresses,
or index values. The RA register is usually used to store the
return address upon entry into a subroutine. The SP register
is usually used as the pointer to the program run-time stack.
T bit
L bit
If a general-purpose register is used for a byte-wide operation, only the low-order byte is referenced or modified. The
high-order byte is not used or affected by a byte-wide operation.
6.2
F bit
DEDICATED ADDRESS REGISTERS
There are three dedicated address registers: the Program
Counter (PC), the Interrupt Stack Pointer (ISP), and the Interrupt Base Register (INTBASE). Each of these registers is 21
bits wide.
6.2.1
Program Counter
Z bit
The PC register contains the address of the first byte of the
instruction currently being executed. It is automatically incremented or changed by the appropriate amount each time an
instruction is executed.
N bit
The five most significant and the least significant bit of this
register are always zero. The least significant bit of the PC is
always zero, thus instruction must always be aligned to even
addresses in the range of 0000 to FFFE hex.
E bit
Upon reset, the PC register is initialized to zero and program
execution starts at that address. When a reset signal is received, bits 1 through 16 of the PC register (prior to initialization) are stored in register R0. This allows the software to
determine the point in the program at which the reset occurred.
6.2.2
Interrupt Stack Pointer
The ISP register points to the lowest address of the last item
stored on the interrupt stack. This stack is used by the hardware when an interrupt or trap service procedure is invoked.
P bit
The five most significant bits and the least significant bit of
this register are always zero. The last item stored on the interrupt stack must be at an even address in the range of
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PROCESSOR STATUS REGISTER
The Processor Status Register (PSR) holds status information and selects the operating modes for the CPU core. The
format of the register is shown below.
All of these registers are 16 bits wide except for the three address registers, which are 21 bits wide.
6.1
Interrupt Base Register
16
7 6
N Z
5
F
4
0
3
0
2
L
1 0
T C
The Carry (C) bit indicates whether a carry or
borrow has occurred after addition or subtraction. It is set to 1 if a carry or borrow has occurred, or cleared to 0 otherwise.
The Trace (T) bit, when set, causes a Trace
(TRC) trap to be executed after every instruction. This bit is automatically cleared to 0 when
a trap or interrupt occurs.
The Low (L) bit is set by comparison operations. In a comparison of unsigned integers, the
bit is set to 1 if the second operand (Rdest) is
less than the first operand (Rsrc). Otherwise, it
is cleared to 0.
The Flag (F) bit is a general condition flag that
is set by various instructions. It may be used to
signal exception conditions or to distinguish the
results of an instruction. For example, integer
arithmetic instructions use this bit to indicate an
overflow condition after an addition or subtraction operation.
The Zero (Z) bit is set by comparison operations. In a comparison of integers, the bit is set
to 1 if the two operands are equal. Otherwise,
it is cleared to 0.
The Negative (N) bit is set by comparison operations. In a comparison of signed integers, the
bit is set to 1 if the second operand (Rdest) is
less than the first operand (Rsrc). Otherwise, it
is cleared to 0.
The Local Maskable Interrupt Enable (E) bit is
used to enable or disable maskable interrupts.
If this bit and the Global Maskable Interrupt Enable (I) bit are both set to 1, all maskable interrupts are accepted. Otherwise, only nonmaskable interrupts are accepted. The E bit is
set to 1 by the Enable Interrupts (EI) instruction
and cleared to 0 by the Disable Interrupts (DI)
instruction.
The Trace Trap Pending (P) bit is used together
with the Trace (T) bit to prevent a Trace (TRC)
trap from occurring more than once for any instruction. The P bit may be cleared to 0 (no
TRC trap pending) or set to 1 (TRC trap pending).
I bit
The Global Maskable Interrupt Enable (I) bit is
used to enable or disable maskable interrupts.
If this bit and the Local Maskable Interrupt Enable (E) bit are both set to 1, all maskable interrupts are accepted. Otherwise, only the nonmaskable interrupts are accepted. This bit is
automatically cleared to 0 when an interrupt occurs and automatically set to 1 upon completion of an interrupt service routine.
Far-Relative
Mode
The operand is located in memory. Its address is obtained by concatenating a pair
of adjacent general-purpose registers to
form a 21-bit value, and adding this value
to the constant value encoded into the displacement field of the instruction. The device implementation only uses the first 64K
of the address space, so the relative mode
is sufficient to access the entire usable address space; the far-relative mode is not
used.
Absolute Mode The operand is located in memory. Its address is specified within the instruction.
For example:
LOADB 4000, R6
Upon reset, all non-reserved bits of the register are cleared
to 0 except for the E bit (bit 9), which is set to 1. When a device reset occurs, the PSR contents prior to the reset are
stored into register R1, allowing the initialization software to
determine the state of the device prior to the reset operation.
6.4
CONFIGURATION REGISTER
The Configuration (CFG) register is a 16-bit core register that
determines the size of the INTBASE register. For the device,
the CFG register should always be left in its default state
(cleared to zero), resulting in a 16-bit INTBASE register.
For additional information on the instruction set and instruction encoding, see the CompactRISC CR16B Programmer's
Reference manual.
6.5
A stack is a one-dimensional data buffer in which values are
entered and removed one at a time. The last value entered is
the first one removed. A register called the stack pointer contains the current address of the last item entered on the
stack. In the device, when an item is entered or “pushed”
onto the stack, the stack expands downward in memory (the
stack pointer is decremented). When an item is removed or
“popped” from the stack, the stack shrinks upward in memory
(the stack pointer is incremented).
6.6
ADDRESSING MODES
Each instruction operates on one or more operands. An operand can be a register or a memory location.
Most instructions use one, two, or three device registers as
operands. The instruction opcode specifies the registers to
be operated on. Some instructions may use an immediate
value (a value provided in the instruction itself) instead of a
register.
Memory locations are accessed only by the Load and Store
commands. The memory location to use for a particular instruction can be specified as an absolute, relative, or far-relative address.
STACKS
The device uses two type of stacks: the program stack and
the interrupt stack.
The program stack is used by the software to save and restore register values upon entry into and exit from a subroutine. The software can also use the program stack to store
local and temporary variables. The stack pointer for this
stack is the SP register.
The instruction set supports the following addressing modes:
Register Mode The operand is a general-purpose register: R0 through R13, RA, or SP. For example:
ADDB R1, R2
Immediate
A constant operand value is specified withMode
in the instruction. In a branch instruction,
the immediate operand is a displacement
from the program counter (PC). In the assembly language syntax, a dollar sign indicates an immediate value. For example:
MULW $4, R4
Relative Mode The operand is located in memory. Its address is obtained by adding the contents of
a general purpose register to the constant
value encoded into the displacement field
of the instruction. For example:
LOADW 12(R5), R6
The interrupt stack is used to save and restore the program
state when an exception occurs (an interrupt or software
trap). The on-chip hardware automatically pushes the program state information onto the stack before the exception
service procedure is executed. Upon exit from the exception
service procedure, the hardware pops this information from
the stack and restores the program state. The stack pointer
for this stack is the ISP, or Interrupt Stack Pointer.
6.7
INSTRUCTION SET
Table7 is a summary list of all instructions in the device instruction set. For each instruction, the table shows the mnemonic with a brief description of the operation performed.
In the Mnemonic column, the lower-case letter “i” is used to
indicate the type of integer that the instruction operates on,
either “B” for byte or “W” for word. For example, the notation
ADDi for the “add” instruction means that there are two forms
of this instruction, ADDB and ADDW, which operate on bytes
and words, respectively.
Similarly, the lower-case string “cond” is used to indicate the
type of condition tested by the instruction. For example, the
notation Jcond represents a class of conditional jump instruc-
17
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tions: JEQ for Jump on Equal, JNE for Jump on Not Equal,
and so on.
Table 7
Mnemonic
For detailed information on all instructions, see the
CompactRISC CR16B Programmer's Reference manual.
Table 7 Device Instruction Set Summary
Mnemonic
Description
ADDi
Add Integer
ADDUi
Add Unsigned Integer
ADDCi
Add Integer with Carry
ANDi
Bitwise Logical AND
ASHUi
Arithmetic Shift Unsigned
Bcond
Conditional Branch
Bcond0i
Compare Register to 0 and Branch
Bcond1i
Compare Register to 1and Branch
BAL
Branch and Link
BR
Unconditional Branch
CBITi
Clear Bit in Integer
CMPi
Compare Integer
DI
Disable Maskable Interrupts
EI
Enable Maskable Interrupts
EIWAIT
Enable Interrupts and Wait for Interrupt
EXCP
Exception
Jcond
Conditional Jump
JAL
Jump and Link
JUMP
Jump
LOADi
Load Integer
LOADM
Load Multiple Registers
LPR
Load Processor Register
LSHi
Logical Shift Integer
MOVi
Move Integer
MOVXB
Move with Sign-Extension
MOVZB
Move with Zero-Extension
MULi
Multiply Integer
MULSi
Multiply Signed
MULUW
Multiply Unsigned
NOP
No Operation
ORi
Bitwise Logical OR
POPrt
Pop Registers from Stack
PUSH
Push Registers on Stack
RETX
Return from Exception
Scond
Save Condition as Boolean
MULi
Multiply Integer
SBITi
Set Bit in Integer
STORi
Store Integer
STORM
Store Registers to Memory
SUBi
Subtract Integer
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Device Instruction Set Summary
18
Description
SUBCi
Subtract Integer with Carry
TBIT
Test Bit
WAIT
Wait for Interrupt
XORi
Bitwise Logical Exclusive OR
7.0
Bus Interface Unit
The Bus Interface Unit (BIU) controls the interface between
the on-chip modules and the internal core bus. It determines
the configured parameters for bus access (such as the number of wait states for memory access) and issues the appropriate bus signals for the requested access.
7.1
7.2.1
The BIU Configuration (BCFG) Register is a byte-wide, read/
write register that selects either early write or late write bus
cycles. The register address is F900 hex. Upon reset, the
register is initialized to 07 hex. The register format is shown
below.
BUS CYCLES
7
There are four types of data transfer bus cycles:
• Normal read
• Fast read
• Early write
• Late write
Note: For write operations, this device utilizes the Late write
operation.
6 5 4
Reserved
EWR
3
2
Note 1
1
Note 1
0
EWR
Early Write. This bit is cleared to 0 for late write
operation (two clock cycles to write) or set to 1
for early write operation.
Note 1: This bit (bit 1 or bit 2) controls the configuration of the
224-pin device used in emulation equipment. The CPU
should set this bit to 1 when it writes to the register.
The type of data cycle used in a particular transaction depends on the type of CPU operation (a write or a read), the
type of memory or I/O being accessed, and the access type
programmed into the BIU control registers (early/late write or
normal/fast read).
Upon reset, the BCFG register is initialized to 07 hex, which
selects early write operation. However, late write operation is
required for normal device operation, so the software should
change the register value to 06 hex.
For read operations, a basic normal read takes two clock cycles, whereas a fast read bus cycle takes one clock cycle.
Upon reset of the device, normal read bus cycles are enabled by default.
7.2.2
I/O Zone Configuration (IOCFG) Register
The I/O Zone Configuration (IOCFG) register is a word-wide,
read/write register that sets the timing and bus characteristics of I/O Zone memory accesses. In the device implementation, the registers associated to Port B and Port C reside in
the I/O memory array. (These ports are used as a 16-bit data
port, if the device operates in development mode.)
For write operations, a basic late write bus cycle takes two
clock cycles, whereas a basic early write bus cycle takes
three clock cycles. Upon reset of the device, early write bus
cycles are enabled by default. However, late write bus cycles
are needed for ordinary write operations, so this configuration should be changed by the application software (see
Section7.2.1).
The IOCFG register address is F902 hex. Upon reset, the
register is initialized to 069F hex. The register format is
shown below.
In certain cases, one or more additional clock cycles are added to a bus access cycle. There are two types of additional
clock cycles for ordinary memory accesses, called internal
wait cycles (TIW) and hold (Thold) cycles.
15
14 13 12
Reserved
7
BW
A wait cycle is inserted in a bus cycle just after the memory
address has been placed on the address bus. This gives the
accessed memory more time to respond to the transaction
request. A hold cycle is inserted at the end of a bus cycle.
This holds the data on the data bus for an extended number
of clock cycles.
7.2
BIU Configuration (BCFG) Register
WAIT
BIU CONTROL REGISTERS
The BIU has a set of control registers that determine how
many wait cycles and hold cycles are to be used for accessing memory. Upon start-up of the device, these registers
should be programmed with appropriate values so that the
minimum allowable number of cycles is used. This number
varies with the clock frequency used.
HOLD
There are two applicable BIU registers: the BIU Configuration (BCFG) register and the Static Zone 0 Configuration
(SZCFG0) register. These registers control the bus cycle
configuration used for accessing the flash program memory.
BW
Note: A system configuration register called the Module
Configuration (MCFG) register controls the number of wait
cycles used for accessing the EEPROM data memory. This
register is described in Section4.2.
19
11
6
5
Reserved
10
1
9
IPST
4
3
HOLD
2
8
Reserved
1
WAIT
0
Memory Wait cycles
This field specifies the number of TIW (internal
wait state) clock cycles added for each memory
access, ranging from 000 binary for no additional TIW wait cycles to 111 binary for seven
additional TIW wait cycles. These bits are ignored if the SZCFG0.FRE bit is set to 1.
Memory Hold cycles
This field specifies the number of Thold clock
cycles used for each memory access, ranging
from 00 binary for no Thold cycles to 11 binary
for three T hold clock cycles. These bits are ignored if the SZCFG0.FRE bit is set to 1.
Bus Width
BW defines the external bus width for the I/O
zone. Bus width is initialized during reset to its
default value, which is 16 bits. If this bit is
cleared to 0 the external bus is 8 bits wide. To
set to external bus width to 16 bits, this bit has
to be set to 1. For the 80 pin package the Bus
width has to be set to 1. When using the device
in 224 pin package in emulator equipment the
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IPST
7.2.3
bus width may have to be set to 8 bits depending on the requirements of the external hardware.
Post Idle
An idle cycle follows the current bus cycle,
when the next bus cycle is in a different zone.
For the 80-pin package where all zones are onchip, this bit can be cleared to 0; as this additional idle-cycle is not required.
cycle. A normal read operation takes at least
two clock cycles.
Note 1: These bits (bit 5 and 6) control the configuration to
the 224-pin device used in emulation equipment. The CPU
should clear these bits to 0 when it writes to the register.
7.3
The number of wait cycles and hold cycles inserted into a bus
cycle depends on whether it is a read or write operation, the
type of memory or I/O being accessed, and the control register settings.
Static Zone 0 Configuration (SZCFG0) Register
The Static Zone 0 Configuration (SZCFG0) register is a
word-wide, read/write register that sets the timing and bus
characteristics of Zone 0 memory accesses. In the
CR16MHS9 implementation of the CompactRISC architecture, Zone 0 is occupied by the flash EEPROM program
memory.
7.3.1
14 13 12
Reserved
7
BW
WAIT
HOLD
BW
IPST
IPRE
FRE
11
FRE
6
5
Note 1
10
IPRE
9
IPST
4
3
HOLD
2
For a read operation in fast read mode (SZCFG0.FRE=1), no
wait cycles or hold cycles are used.
For a read operation in normal read mode (SZCFG0.FRE=0),
the number of inserted wait cycles is one plus the value written to the SZCFG0.WAIT field. The number in this field can
range from zero to seven, so the total number of wait cycles
can range from one to eight. The number of inserted hold cycles is equal to the value written to the SCCFG0.HOLD field,
which can range from zero to three.
8
Reserved
1
WAIT
0
Memory Wait cycles
This field specifies the number of TIW (internal
wait state) clock cycles added for each memory
access, ranging from 000 binary for no additional TIW wait cycles to 111 binary for seven
additional TIW wait cycles. These bits are ignored if the SZCFG0.FRE bit is set to 1.
Memory Hold cycles
This field specifies the number of Thold clock
cycles used for each memory access, ranging
from 00 binary for no T hold cycles to 11 binary
for three T hold clock cycles. These bits are ignored if the SZCFG0.FRE bit is set to 1.
BW defines the external bus width for the zone.
Bus width is initialized during reset to its default
value, which is 16 bits. If this bit is cleared to 0
the external bus is 8 bits wide. To set to external bus width to 16 bits, this bit has to be set to
1. For the 80 pin package the Bus width has to
be set to 1.
Post Idle
An idle cycle follows the current bus cycle,
when the next bus cycle is in a different zone.
For the 80-pin package where all zones are onchip, this bit can be cleared to 0 as this additional idle-cycle is not required.
Preliminary Idle
An idle cycle is inserted prior to the current bus
cycle, when this bus cycle is in a new zone. For
the 80-pin package where all zones are onchip, this bit can be cleared to 0 as this additional idle-cycle is not required.
Fast Read Enable
This bit enables (1) or disables (0) fast read bus
cycles. A fast read operation takes one clock
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Flash Program Memory
When the CPU accesses the flash program memory (address 0000-BFFF hex), the number of added wait and hold
cycles depends on type of accesses and the BIU register settings.
The SZCFG0 register address is F904 hex. Upon reset, the
register is initialized to 069F hex. The register format is
shown below.
15
WAIT AND HOLD STATES USED
For a write operation in fast read mode (SZCFG0.FRE=1),
the number of inserted wait cycles is one. No hold cycles are
used.
For a write operation normal read mode (SZCFG0.FRE=0),
the number of wait cycles is equal to the value written to the
SZCFG0. WAIT field plus one (in the late write mode) or two
(in the early write mode). The number of inserted hold cycles
is equal to the value written to the SCCFG0.HOLD field,
which can range from zero to three.
Writing to the flash program memory is a ROM programming
operation that requires some additional steps, as explained
in Section8.3.2.
7.3.2
RAM Memory
When the CPU accesses RAM memory (address E000E7FF hex), no wait cycles or hold cycles are used.
7.3.3
EEPROM Data Memory
There is either no wait state or one wait state used when the
CPU accesses the EEPROM data memory (address F000F27F hex). The number of required wait states (zero or one)
depends on the CPU clock frequency and operating mode,
and is controlled by programming of the FEEDM bit in the
MCFG register, as explained in Section8.3. No hold cycles
are used.
7.3.4
Core Register and Peripheral Accesses
When the CPU accesses core registers and on-chip peripherals in the range of F000-FFFF, one wait cycle is used. No
hold cycles are used.
For the FB00-FBFF (Ports B and C) the IOCFG register determines the timing.
20
7.3.5
Wait/Hold Summary Table
Table8 is a summary showing the number of wait cycles and
hold cycles used for various address ranges.
Table 8
Address
Range (hex)
0000-BFFF
E000-E7FF
F000-F27F
Memory or
I/O Type
Wait Cycles Added
Flash Program
Memory
For read operation: 0 if SZCFG0.FRE=1, or
1+SZCFG0.WAIT if SZCFG0.FRE=0; For
write operation: 1+BCFG.EWR if
SZCFG0.FRE=1, or
1+BCFG.EWR+SZCFG0.WAIT if
SZCFG0.FRE=0
Static RAM Memory 0
EEPROM Data
For read operation: 0 if MCFG.FEEDM=1,
Memory
or 1 if MCFG.FEEDM=0
Core Registers And 1
On-Chip Peripherals
F900-FFFF
F800-F9FF
FC00-FFFF
FB00-FBFF Ports B and C
7.3.6
Access Timing Table
For read operation: 1+IOCFG.WAIT
For write: 1+BCFG.EWR+IOCFG.WAIT
Hold Cycles Added
0 if SZCFG0.FRE=1, or SZCFG0.HOLD if
SZCFG0.FRE=0
0
0
0
IOCFG.HOLD
Recommended Register Settings
Table9 shows the recommended register settings for various
clock rates. Different clock rates require different register settings because the flash program memories have specific setup and hold requirements that can be met only by using
enough wait cycles and hold cycles.
Table 9
Recommended Register Settings
Clock Rate
SZCFG0
IOCFG
< 12.5 MHz,
0 wait state
0E80 hex
0288 hex
12.5 to 16 MHz, 0
wait state
0E80 hex
0288 hex
12.5 to 16 MHz, 1
wait state
0680 hex
0288 hex
> 16 MHz,
1 wait state
0680 hex
0288 hex
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8.0
Memory
The CompactRISC architecture supports a uniform linear address space of 2 megabytes, addressed by 21 bits. The device implementation of this architecture uses only the lowest
64 kbytes of address space, addressed by 16 bits. Each
memory location contains a byte consisting of eight bits.
To enter one of the programming modes, the device must be
reset with the ENV1 and ENV0 pins configured to select the
desired mode: Test Mode for external programming or InSystem Programming mode for in-system programming.
Once the device enters the programming mode, the programming software performs the task of downloading the
program code through a serial port and writing the code to
the EEPROM memory. The software used for programming
the EEPROM resides outside of the device for external programming or in the on-chip boot ROM for conventional insystem programming.
Four types of on-chip memory occupy specific intervals within the address space: 48 kbytes of flash program memory,
1.5 kbytes of ISP memory, 2 kbytes of static RAM, and 640
bytes of EEPROM data memory. All of these memories are
16 bits wide, but their contents can be accessed either as
bytes (eight bits wide) or words (16 bits wide).
8.1.3
The CPU core uses the Load and Store instructions to access memory. These instructions can operate on bytes or
words. For a byte access, the CPU operates on a single byte
occupying a specified memory address. For a word access,
the CPU operates on two consecutive bytes. In that case, the
specified address refers to the least significant byte of the
data value; the most significant byte is located at the next
higher address. Thus, the ordering of bytes in memory is
from least to most significant byte. For more efficient data access operations, 16-bit variables should be stored starting at
word boundaries (at even address).
8.1
Instead of using an EPROM programmer unit or the conventional in-system programming mode, you can write your own
processor code to program and erase the flash program
memory. Writing your own code is more flexible than using
the other programming methods. Like the conventional insystem programming mode, you can program the device
while it is installed in the system, but no PC is required to
download the program data. It is not necessary to reset the
device or use the ENV0/ENV1 pins to configure the device.
If you write your own flash EEPROM programming code, the
code must reside in the 2 kbytes of RAM memory, in the address range of E000-E7FF. This is because the entire flash
program memory becomes unavailable when you program or
erase any part of that memory.
FLASH PROGRAM MEMORY
The flash program memory is used to store the application
program. The 48 kbytes of this memory reside in the address
range of 0000-BFFF hex. A normal CPU write operation to
this memory has no effect.
Also, for programming the flash program memory, you need
to design a protocol for the device to obtain the programming
data. For example, you can use the on-chip USART to obtain
the programming data from an external device through a serial interface.
The program memory has the following features:
•
•
•
•
•
•
•
•
48 kbytes arranged as 24K by 16 bits
Page size of 64 words, divided into two rows of 32 words
30 µs programming pulse per word
Page mode erase with a 1 ms pulse
Programming high voltage and timing generated on-chip
Boot-ROM controlled in-system programming capability
User-coded programming capability
Security features to limit read/write access
8.1.1
The flash program memory is divided into 384 pages, each
page containing 64 words (each 16 bits wide). Each page is
further divided into two rows of 32 words. Erasure is carried
out one page at a time, whereas programming is carried out
one row (or one partial row) at a time.
Once an erase or programming operation is started, the
PGMBUSY bit in the MSTAT register is automatically set, and
then cleared when the operation is complete. All high-voltage
pulses and timing needed for programming and erasing are
provided internally. The program memory cannot be accessed while the PGMBUSY bit is set.
Reading
Program memory read accesses can operate without wait cycles with a CPU clock rate of up to 12.5 MHz in the normal
mode. At higher clock rates, memory read accesses can operate with one wait state.
The programmed number of wait cycles used (either zero or
one) is controlled by the BIU Configuration (BCFG) register
and the Static Zone 0 Configuration (SZCFG0) register.
These registers are described in Section7.2.1 and 7.2.3.
8.1.2
8.1.4
Flash EEPROM Programming and Verify
The flash EEPROM program memory programming and
erase can be performed using different methods. It can be
done through user code that is stored in system RAM, or
through In-System-Programming mode, but should not be
programmed through the flash EEPROM program memory itself as no instruction or data can be fetched from it while it is
being programmed. All program and erase operations must
be preceded immediately by writing the proper key to the program memory key register PGMKEY.
Conventional Programming Modes
The flash program memory can be programmed either with
device plugged into an EPROM programmer unit (external
programming) or with the device installed in the application
system (in-system programming). The device internally generates the necessary voltages for programming. No additional power supply is required.
The flash EEPROM program memory is divided into 384 pages, each page containing 64 words (each 16 bits wide). Each
page is further divided into two adjacent rows. A page erase
will erase one page. Programming is done by writing to all
the words within a row, one word following another sequen-
Programming the memory requires placing the device in a
special programming mode. Programming commands issued while the device is in its normal operating mode are ignored.
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User-Coded Programming Routines
22
tially within one single high voltage pulse. This is supported
through a double-buffered write-data buffer scheme. Byte
programming is not supported. Programming should be
done on erased rows.
start
A page erase requires the following code sequence (assuming that this sequence will not be interrupted to do another
flash erase or programming):
1.
2.
3.
4.
5.
6.
7.
Check for MSTAT.PGMBUSY not set.
Set FLCSR.ERASE = 1.
If interrupt was enabled, disable interrupt.
Write proper key value to PGMKEY.
Write to any valid location within the page to be erased.
If interrupt was disabled in step 3, re-enable interrupt.
Set FLCSR.ERASE = 0.
MSTAT.PGMBUSY
=1?
Yes
No
disable interrupt
if necessary
When programming, the data to be written into the flash EEPROM program memory is first written into a double-buffered
write-data buffer. When a piece of data is written to the page
while the flash EEPROM program memory is idle, the write
cycle will start. Due to the double-buffered nature of the
write-data buffer, a second word can be written to the flash
EEPROM program memory. This will then set FLCSR.PMLFULL flag indicating the buffer is now full. When the first
write is done, the memory address would be incremented,
and the second word would be written to that address while
keeping the high voltage pulse active; the FLCSR.PMLFULL
flag is cleared. Another word can then be written to the buffer, and this programming will repeat until there are no more
words to be programmed. This allows pipelined writes to different words on the same row within the same high voltage
pulse. If the programming sequence exceeds a row, the
flash programming interface will automatically initiate a programming pulse for the next row. The FLCSR.PMLFULL bit
is also cleared. when programming of the last word of the
current row is completed, e.g. programming of the entire row
is completed and MSTAT.PGMBUSY is cleared. This means,
the separation of the program memory into rows is transparent to the user, as the transition is handled by the flash program memory interface. Figure2 shows a flowchart for a
programming sequence.
write PGMKEY
write memory
re-enable interrupt
if necessary
last word?
Yes
done
No
Yes
FLCSR.PMLFULL
=0?
No
Figure 2. Programming Sequence for
the Program Memory
Erase Procedure
Erasing a page requires the following code sequence:
1.
2.
3.
4.
5.
6.
7.
Verify that the MSTAT.PGMBUSY bit is cleared.
Disable any enabled interrupts.
Set the FLCSR.ERASE bit to 1.
Write the proper key value to the PGMKEY register.
Write to any valid location in the page to be erased.
Clear the FLCSR.ERASE bit to 0.
Re-enable any interrupts disabled in Step 2.
Erased bits read back as 1.
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Programming Procedure
The register format is shown below.
Programming is done by writing to all the words within a row,
one word following another sequentially, within a single highvoltage pulse for the entire row. It is not possible to program
single bytes. Programming should be done only on erased
rows.
7
6
5
Reserved
ERASE
Programming a row requires the following code sequence:
1.
2.
3.
4.
5.
6.
7.
8.
9.
Verify that the MSTAT.PGMBUSY bit is cleared.
Disable any enabled interrupts.
Write the proper key value to the PGMKEY register.
Write the desired word to the lowest address of the row.
Wait until the FLCSR.PMLFULL bit is cleared to 0.
Write the proper key value to the PGMKEY register.
Write the desired word to the next address of the row.
Repeat Steps 5, 6, and 7 until the whole row is written.
Re-enable any interrupts disabled in Step 2.
PMBUSY
The programmed values can be verified by normal read operations from the applicable memory locations.
PMLFULL
Each time you write a word to the flash program memory using the procedure just described, the data word is stored in a
two-level write-data buffer. The first word written while the
program memory is idle starts the write cycle. Due to doublebuffering of the write path, a second word can be written to
the program memory while the first word is still being programmed. Writing the second word sets the FLCSR.PMLFULL flag, thus indicating that the write-data buffer is full.
IENPROG
When programming of the first word is done, the memory address is incremented, programming of the second word
starts, and the PLCSR.PMFULL flag is cleared. The next
word can then be written to the write-data buffer. This process is repeated until there are no more words in the buffer
or the entire row has been programmed. All of this happens
within the same high-voltage programming pulse.
8.1.7
Erase and Programming Timing
The internal hardware of the device handles the timing of
erase and programming operations. To drive the timing control circuits, the device divides the system clock by a programmable prescaler factor. You should select a prescaler
value to produce a program/erase clock of 200 kHz (or as
close as possible to 200 kHz without exceeding 200 kHz).
For the timing control circuit to operate correctly, you must
program the prescaler value in advance and leave it unchanged while a program or erase operation is in progress.
A similar (but separate) prescaler factor is applied to the EEPROM data memory. See Section8.1.7 and Section8.3.4 for
details.
8.1.6
2
1
0
PMBUSY
ERASE
Reserved
Erase Flash Program Memory Page. When set
(1), a write to the program memory erases the
whole page containing the addressed memory
location. When cleared (0), a write to the program memory either has no effect on programming the memory word (if properly set up for
programming). This bit should be changed only
when the flash memory is not busy being programmed or erased.
Program Memory Busy. This bit is automatically set to 1 when the flash program memory is
busy being programmed, and cleared to 0 at all
other times. (The MSTAT.PGMBUSY is also set
to 1 whenever the PMBUSY bit is set to 1.)
Program Memory Write-Latch Buffer Full.
When set (1), the double-buffered data register
for program memory write operations is full.
When cleared (0), the double-buffered data
register is not full.
Interrupt Enable for Program Memory Write.
When set (1), the flash program memory write
mechanism generates an interrupt whenever
the PMLFULL bit changes from 1 to 0. This is a
signal to the CPU to write the next word for programming. When IENPROG is cleared, no
such interrupt is generated.
Program Memory Timing Prescaler Register
(FLPSLR)
You should choose a value of FTDIV to produce a clock of the
highest possible frequency that is equal to or just less than
200 kHz. For example, if the system clock frequency is 12.5
MHz, use the value 3E hex (62 decimal) for FTDIV, because
12.5 MHz / (62+1) = 198.4 kHz. Do not modify this register
while a flash program or erase operation is in progress.
Upon reset, this register is programmed by default with the
value 33 hex (51 decimal), which is an appropriate setting for
a 10.4 MHz system clock.
8.1.8
Program Memory Write Key Register (PGMKEY)
The PGMKEY register is a byte-wide, write-only register that
must be written with a key value (A3 hex) immediately prior
to each write to the flash program memory. Otherwise, the
write operation to the program memory will fail. This feature
is intended to prevent unintentional programming of the program memory.
Flash Program Memory Control and Status
Register (FLCSR)
The Flash Program Memory Control and Status (FLCSR)
register is a byte-wide, read/write register that contains several status and control bits related to the program memory.
Upon reset, this register is cleared to zero when the flash
memory on the chip is in the idle state.
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3
PMLFULL
The FLPSLR register is a byte-wide, read/write register that
selects the prescaler divider ratio for the flash program memory programming clock. Before you program or erase the program memory for the first time, you should program the
FLPSLR register with the proper prescaler value, an 8-bit value called FTDIV. The device divides the system clock by (FTDIV+1) to produce the program memory programming clock.
If a reset occurs in the middle of an erase or programming
operation, the operation is terminated. The reset is extended
until the flash memory returns to the idle state.
8.1.5
4
IENPROG
Reading this register always returns FF hex.
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8.2
8.3.3
RAM MEMORY
The static RAM memory is used for temporary storage of
data and for the program and interrupt stacks. The 2 kbytes
of this memory reside in the address range of E000-E7FF
hex. Each memory access requires one clock cycle, for a
byte or word access. For non-aligned word access, each
memory access requires multiple clock cycles. No wait cycles or hold cycles are required.
8.3
Data Memory Control and Status Register
(DMCSR)
The DMCSR register is a byte-wide, read/write register used
with the EEPROM data memory. There are two status/control
bits, as shown in the register format below.
7
6 5 4
Reserved
ERASE
EEPROM DATA MEMORY
The EEPROM data memory is used for non-volatile storage
of data. The 640 bytes of this memory reside in the address
range of F000-F27F hex. The CPU reads or writes this memory by using ordinary byte-wide or word-wide memory access commands.
8.3.1
Reading
DMBUSY
EEPROM data memory read accesses can operate without
wait cycles with a CPU clock rate of up to 12.5 MHz in the
normal mode. At higher clock rates, read accesses can operate with one wait state.
The programmed number of wait cycles used (either zero or
one) is controlled by a bit in the Module Configuration register (MCFG.FEEDM). This register is described in
Section4.2.
8.3.2
3
2
DMBUSY
1
ERASE
0
Reserved
Erase ISP Flash Program Memory Page.
When set (1) a valid write to the ISP flash EEPROM program memory will erase the entire
ISP flash EEPROM program memory page
pointed to by the write address rather than performing a write to the addressed memory location. This bit should be cleared to 0 and remain
cleared after the write operation.
Data Memory Busy. This bit is automatically set
to 1 when the EEPROM data memory is busy
being programmed, and cleared to 0 at all other
times. (The MSTAT.PGMBUSY is also set to 1
whenever the DMBUSY bit is set to 1.)
Upon reset, the DMCSR register is cleared to zero when the
flash memory on the chip is in the idle state.
8.3.4
Data Memory Prescaler Register (DMPSLR)
The DMPSLR register is a byte-wide, read/write register that
selects the prescaler divider ratio for the EEPROM data
memory programming clock. Before you write to the data
memory for the first time, you should program the DMPSLR
register with the proper prescaler value, an 8-bit value called
FTDIV. The device divides the system clock by (FTDIV+1) to
produce the data memory programming clock.
Programming
Before you begin programming the EEPROM data memory,
you should set the value in the EEPROM Data Memory Prescaler register. This register sets the prescaler used to generate the data memory programming clock from the system
clock, as described in Section8.3.4.
After the CPU performs a write to the EEPROM data memory, the on-chip hardware completes the EEPROM programming in the background. When programming begins, the onchip hardware sets the DMCSR.DMBUSY bit to 1, and also
sets the MSTAT.PGMBUSY bit to 1. When programming is
completed, it resets these status bits back to 0. Once the
software writes to the EEPROM data memory, it should not
attempt to access the EEPROM data memory again until programming is completed and the status bit is reset to 0.
You should choose a value of FTDIV to produce a clock of the
highest possible frequency that is equal to or just less than
200 kHz. Upon reset, this register is programmed by default
with the value 33 hex (51 decimal), which is an appropriate
setting for a 10.4 MHz system clock.
8.3.5
Data Memory Write Key Register (DMKEY)
The DMKEY register is a byte-wide, read/write register that
provides a way to “lock” the data contained in the EEPROM
data memory. Upon reset, the register is automatically set to
C9 hex, which is the key value. Writing to the EEPROM data
memory is allowed as long as the DMKEY register contains
this value. When the register contains any value other than
C9 hex, writing the EEPROM data memory is disallowed.
The device hardware internally generates the voltages and
timing signals necessary for programming. No additional
power supply is required, nor any software required except to
check the status bit for completion of programming. The minimum time required to erase and reprogram a byte or word is
1.16 ms. The programmed values can be verified by using
normal memory read operations.
To “lock” the current data stored in the data memory, write another value (such as 00 hex) to the DMKEY register. To “unlock” the data memory, write the value C9 hex to the DMKEY
register.
If a reset occurs during a programming or erase operation,
the operation is terminated. The reset is extended until the
flash memory returns to the idle state.
Note: Operation of this register is different from the
PGMKEY register used with the program memory. It is not
necessary to write the key value to DMKEY every time you
write to the data memory.
The EEPROM data memory does not have permanent readprotection or write-protection features like those available for
the EEPROM program memory. However, the Data Memory
Write Key Register provides a way to “lock” the data written
to the data memory.
8.4
ISP MEMORY
The In-System Program memory is part of the flash memory
array that contains the flash EEPROM data memory. It is not
possible to access the ISP memory while programming the
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flash EEPROM data memory or access the flash EEPROM
data memory while programming the ISP memory. The 1.5
kbytes of ISP memory resides in the address range of DA00DFF7 and is used for storing a boot ROM. The ROM contains
the code that performs in-system programming, and is programmed at the factory. In ISP mode, code execution starts
at address DA00.
Once an erase or programming operation is started, the PGMBUSY bit in the MSTAT register is automatically set, and
then cleared when the operation is complete. All high-voltage
pulses and timing needed for programming and erasing are
provided internally. The program memory cannot be accessed while the PGMBUSY bit is set.
Erase Procedure
The ISP program memory and flash EEPROM data memory
share the same memory array, which makes it impossible to
access one type of memory while the other is being programmed.
Erasing a page requires the following code sequence:
1.
2.
3.
4.
5.
6.
7.
The ISP memory has the following features:
— 1.5 kbytes ISP flash EEPROM program memory
— Page size of 4 words, divided into two rows of 2 words
each
— Odd and even bytes within a page can be erased separately
— The lowest 384 rows are the ISP memory, the others
are data memory; A1 selects the columns and A[11:2]
select the rows
— 30µs programming pulse width per word
— Page mode erase with 1ms pulse
— All erased memory bits read 1
— Fast read access time
— Requires valid key for program and erase to proceed
— Provide memory protection and security features for
flash EEPROM program memory
— Security features may limit accesses to ISP memory
— Disable memory when address is out of range to prevent accessing data memory
— Provide busy status during programming and erase
— Read/write accesses disabled during programming/
erase
— Programming high voltage and timing generated onchip
— Support flash memory test mode with PADX for security overrides
8.4.1
8.4.3
Programming the ISP flash EEPROM program memory requires the following code sequence:
1.
2.
3.
4.
5.
Verify that the MSTAT.PGMBUSY bit is cleared.
Locally disable interrupts.
Write proper key value to the ISPKEY register.
Write a byte or word to the addressed location.
Re-enable interrupts disabled in Step 2.
Programmed values can be verified through normal read operations.
If a reset occurs in the middle of an erase or programming
operation, the operation is terminated. The rest is extended
until the flash EEPROM memory returns to the idle state.
8.4.4
Erase and Programming Timing
The program and erase timing are controlled by the flash EEPROM data memory logic.
8.4.5
Reading
Protection Features
The last byte of the ISP memory are reserved for special
functions and provide memory protection and security for the
flash EEPROM program memory. Read and write protection
is provided.
8.4.6
The programmed number of wait cycles used (either zero or
one) is controlled by BIU Configuration (BCFG) register and
the Static Zone 0 Configuration (SZOFG0) register. These
registers are described in Section7.2.1 and 7.2.3.
Program Memory Security Features
The program memory has security features to prevent unauthorized access to the program code and unintentional programming. These features are invoked by programming a
non-volatile control register, the Flash EEPROM Security
(FLSEC) register. This register contains a read-access control bit and a write-access control bit.
User-Coded Programming Routines
All program and erase operations must be preceded by writing the proper key to the program memory key register ISPKEY. The programming code can reside in the in-system
RAM, but cannot reside in the ISP flash EEPROM program
memory or flash EEPROM data memory as accesses within
these ranges are not permitted while ISP flash EEPROM program memory is being programmed.
Both control bits are initially set to 1. Programming the readaccess bit to 0 prevents outside access to the program code;
any attempt to access the code from outside returns all zeros. Programming the write-access bit to 0 prevents any further programming of the flash program memory, thus
protecting the program code from overwriting.
The ISP flash memory is divided into 192 pages, each page
containing 4 words (each 16 bits wide). Each page is further
divided into two rows. Erase is carried out one page at a time,
whereas programming is carried out one row (or one partial
row) at a time.
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Programming Procedure
Programming is done by writing one byte or word at a time
and should be done on already erased memory.
The ISP flash EEPROM program memory read accesses can
operate without wait cycles with a CPU clock rate of up to
20MHz in the normal mode. At higher clock rates, read accesses can operate with one wait state.
8.4.2
Verify that the MSTAT.PGMBUSY bit is cleared.
Set the DMCSR.ERASE bit to 1.
Locally disable interrupts.
Write proper key value to the ISPKEY register.
Write to any valid page to be erased.
Re-enable interrupts disabled in Step 3.
Set the DMCSR.ERASE bit to 0.
Programming either bit to 0 (or both bits to 0) also prevents
any further changes to the FLSEC register itself. Thus, invoking read protection and/or write protection is permanent.
26
The Flash Memory Security (FLSEC) register format is
shown below.
7 6 5 4 3
Reserved
FROMRD
FROMWR
2
FROMWR
1
Reserved
0
FROMRD
When this bit is set to 1, the flash program
memory can be read from outside the device.
When this bit is cleared to 0, the flash program
memory cannot be read from outside the device, and the FLSEC register itself is write-protected.
When this bit is set to 1, the flash program
memory can be erased and overwritten by subsequent programming operations. When this
bit is cleared to 0, the program memory and the
FLSEC register itself are both write-protected.
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9.0
Interrupts
The Interrupt Control Unit (ICU) receives interrupt requests
from internal and external sources and generates interrupts
to the CPU. Interrupts from the timers, USARTs, MICROWIRE/SPI interface, Multi-Input Wake-Up, and A/D converter
are all maskable interrupts. The highest-priority interrupt is
the Non-Maskable Interrupt (NMI), which is triggered by a
falling edge received on the NMI input pin. The NMI pin is not
available on the 44-pin packages.
9.1
Table 10 Dispatch Table Entries
0: Reserved
1: NMI
2: Reserved
3: Reserved
4: Reserved
5: SVC (Supervisor Call Trap)
INTERRUPT OPERATION
An exception is an event that temporarily stops the normal
flow of program execution and causes execution of a separate service routine. Upon completion of the service routine,
execution of the interrupted program continues from the point
at which it was stopped.
6: DVC (Divided by Zero Trap)
There are two kinds of exceptions, called traps and interrupts. A trap is the result of some action or condition in the
program itself, such as execution of an Exception (EXCP) instruction. An interrupt is a CPU-external event, such as a signal received on a Multi-Input Wake-Up input or a request
from an on-chip peripheral module for service.
10: UND (Undefined Instruction Trap)
7: FLG (Flag Trap)
8: BPT (Breakpoint Trap)
9: TRC (Trace Trap)
11: Reserved
12: Reserved
13: Reserved
14: Reserved
The operation of traps is beyond the scope of this data sheet.
For information on traps, and for additional detailed information on interrupts not provided in this data sheet, please refer
to the CompactRISC CR16B Programmer's Reference Manual.
9.1.1
15: Reserved
16: INT0 (Reserved)
17: INT1 (A/D Converter)
18: INT2 (Multi-Input Wake-Up)
Interrupt Operation Summary
19: INT3 (Reserved)
When an interrupt occurs, the on-chip hardware performs the
following steps:
20: INT4 (USART2 Tx)
21: INT5 (USART1 Tx)
1. Decrements the Interrupt Stack Point (ISP) by four.
2. Saves the contents of the Program Counter (PC) and
Processor Status Register (PSR) on the interrupt stack.
3. Clears the I, P, and T bits in the Processor Status Register (PSR). These are the Global Maskable Interrupt
Enable bit, Trace Trap Pending bit, and Trace bit, respectively.
4. Reads the interrupt vector from the Interrupt Vector Register (IVCT).
5. Combines the interrupt vector with the value in the Interrupt Base (INTBASE) register to obtain an address in the
Interrupt Dispatch Table, and loads the dispatch table
entry into the Program Counter (PC).
22: INT6 (MICROWIRE/SPI Rx/Tx)
23: INT7 (Reserved)
24: INT8 (USART2 Rx)
25: INT9 (USART1 Rx)
26: INT10 (Timer 2 Input B)
27: INT11 (Timer 2 Input A)
28: INT12 (Timer 1 Input B)
29: INT13 (Timer 1 Input A)
30: INT14 (Timer 0)
31: INT15 (Reserved)
From this point onward, the CPU executes the interrupt service routine. The service routine ends with a Return from Exception (RETX) instruction. This returns the CPU to the
interrupted program. The CPU restores the contents of the
PC and PSR registers from the stack and increments the Interrupt Stack Pointer by four.
9.1.2
Each entry in the Dispatch Table consists of two bytes that
provide bits 1 through 16 of the starting address of the corresponding service routine. The full 21-bit address of a service
routine is reconstructed by adding a leading 0 and a trailing
0 to the 16-bit table entry. Because the program memory of
the device only occupies the range of 0000-BFFF hex, entries in the table are restricted to this range.
Service Routine Addresses
When an interrupt or trap occurs, the CPU executes a service
routine. There are different service routines for different interrupts and traps. Each service routine may reside anywhere
in program memory. The starting addresses of the service
routines are contained in a table called the Dispatch Table.
Entries in the table are organized in the order shown in
Table10.
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The INTBASE register is a pointer to the Dispatch Table.
Upon reset, the initialization software must write the starting
address of the Dispatch Table to the INTBASE register, a 21bit register with the five most significant bits and the least significant bit always equal to 0. It is typically kept in the flash
EEPROM program memory. The Dispatch Table is 32 words
long.
28
Each interrupt or trap source has an associated vector number ranging from 0 to 31, as indicated in Table10. When an
interrupt occurs, the hardware multiplies the vector by 2,
adds the result to the contents of the INTBASE register, and
uses the resulting address to obtain the service routine starting address from the corresponding entry in the Dispatch Table. This address is placed in the Program Counter so that
the CPU begins executing the interrupt service routine.
memory (toward address zero) when an interrupt occurs and
items are pushed onto the stack. The stack shrinks upward
in memory when an interrupt service routine ends and items
are popped from the stack.
Many routines need to use the general-purpose registers R0
through R13. To preserve the existing register contents, a
routine can save register contents on the program stack
upon start of the routine and restore the register contents prior to completion of the routine. The software can also use the
program stack to transfer data parameters from one routine
to another when the parameters are too large to easily fit into
the scratch registers (large structures, large arrays, or a set
of more than four parameters in a single routine). A high-level
language typically allocates the local (non-static) variables
on the stack.
Figure3 summarizes the method used by the device to generate the starting address of a service routine.
9.1.3
Stack Usage
When an interrupt occurs, the CPU automatically preserves
the contents of the Program Counter (PC) and Processor
Status Register (PSR) by pushing them on the interrupt stack
and decrementing the Interrupt Stack Pointer by four. The
service routine ends with a Return from Exception (RETX) instruction, which returns control to the interrupted program by
restoring the PC and PSR values and incrementing the Interrupt Stack Pointer (ISP) by four.
The stack pointer for the program stack is the SP register,
which must be initialized prior to any register save/restore
operations or data transfer operations. Using the program
stack, an interrupt routine needs to initially save the contests
of all registers that it uses, and restore those register contents before returning to the interrupted program.
Prior to using any interrupts, the Interrupt Stack Pointer (ISP)
must be initialized so that it points to a space in RAM where
the interrupt stack will be kept. The stack grows downward in
~
~
31
INTBASE
0
Reserved
1
NMI
2
Reserved
3
Reserved
4
Reserved
5
SVC
Supervisor Call Trap
6
DVZ
Divide By Zero Trap
7
FLG
Flag Trap
8
BPT
Breakpoint Trap
9
TRC
Trace Trap
10
UND
Undefined Instruction Trap
11
Reserved
12
Reserved
13
Reserved
14
DBG
Debug Trap
15
ISE
In-System Emulator Interrupt
INTn
Maskable Interrupts
16 to 127
~
9.2
0
Figure 3.
Non-maskable Interrupt
~
and an internal synchronization circuit. Therefore, no external synchronizing is needed.
NON-MASKABLE INTERRUPT
A non-maskable interrupt is triggered by a falling edge on the
NMI input pin, which generates a software trap. The NMI pin
is an asynchronous input with Schmitt trigger characteristics
Upon reset, the non-maskable interrupt is disabled and
should remain disabled until the software initializes the interrupt table, interrupt base, and interrupt stack pointer. It can
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be enabled by setting either of two control bits in the External
NMI Control/Status (EXNMI) register. The two bits are called
the EN (Enable) bit and the ENLCK (Enable and Lock) bit.
to 1 in the PSR register. If either one of these bits is 0, then
all maskable interrupts are disabled.
Both the E bit and I bit can be controlled with the Load Processor Register (LPR) instruction. In addition, the E bit is
easily changed by executing the Enable Interrupts (EI) or
Disable Interrupts (DI) instruction. Using the EI and DI instructions avoids the possibility of an interrupt occurring within a read-modify-write operation on the PSR register.
The EN bit enables the NMI trap until an NMI trap event or a
reset occurs. An NMI trap automatically resets the EN bit. Using this bit to enable the NMI trap is intended for applications
where the NMI pin is toggled frequently but nested NMI traps
are not needed. The trap service routine should re-enable the
NMI trap by setting the EN bit before returning to the main
program.
For more information on the PSR bits, see Section6.3.
9.4
The ENLCK bit enables the NMI trap and locks it in the enabled state. In other words, it leaves the NMI trap enabled
even after the trap occurs. It can be cleared only by a reset
operation. After the bit is set, an NMI trap is triggered by each
falling edge on the NMI pin, allowing nested NMI traps.
The Interrupt Control Unit uses the following interrupt control
and status registers:
•
•
•
•
•
•
•
To use the EN bit, the ENLCK must remain cleared to 0. Otherwise, the EN bit is ignored.
9.3
MASKABLE INTERRUPTS
Maskable interrupts can be enabled or disabled under software control. There are 16 maskable interrupt sources (including some reserved for future expansion), organized into
levels of priority. If more than one interrupt event occurs at
any given time, the interrupt source with the highest priority
is serviced first. The others must wait until the highest-priority
interrupt is serviced and is no longer pending.
• Interrupt Stack Pointer (ISP)
• Interrupt Base Register (INTBASE)
• Processor Status Register (PSR)
Table 11 Maskable Interrupt Priority List
Source
IRQ15
Reserved (highest priority)
IRQ14
Timer 0
IRQ13
Timer 1 Input A
IRQ12
Timer 1 Input B
IRQ11
Timer 2 Input A
IRQ10
Timer 2 Input B
IRQ9
USART1 Rx
IRQ8
USART2 Rx
IRQ7
Reserved
IRQ6
MICROWIRE/SPI Rx/Tx
IRQ5
USART1 Tx
IRQ4
USART2 Tx
IRQ3
Reserved
IRQ2
Multi-Input Wake-Up
IRQ1
A/D Converter
IRQ0
Reserved (lowest priority)
To enable a maskable interrupt, the enable bit must be set in
the applicable peripheral module and also in the appropriate
Interrupt and Enable Mask register, IENAM0 or IENAM1. In
addition, both the Global Maskable Interrupt Enable bit (I)
and the Local Maskable Interrupt Enable bit (E) must be set
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Non-Maskable Interrupt Status Register (NMISTAT)
External NMI Control/Status Register (EXNMI)
Interrupt Enable and Mask Register 0 (IENAM0)
Interrupt Enable and Mask Register 1 (IENAM1)
Interrupt Vector Register (IVCT)
Interrupt Status Register 0 (ISTAT0)
Interrupt Status Register 1 (ISTAT1)
The following CPU core registers are also used in processing
interrupts:
Figure11 lists the maskable interrupt sources of the device
in order of priority, from the highest-priority interrupt (IRQ15)
to the lowest (IRQ0).
Interrupt Request
INTERRUPT REGISTERS
30
9.4.1
Non-Maskable Interrupt Status Register
(NMISTAT)
contents are guaranteed to be valid at that time. The register
is not guaranteed to contain valid data during a hardware update operation. The register format is shown below.
The NMISTAT register is a byte-wide, read-only register that
holds the current pending status of the Non-Maskable Interrupt (NMI). This register is cleared upon reset. It is also
cleared each time it is read. The register format is shown below.
7
6
EXT
9.4.2
5
4
3
Reserved
2
1
7
0
INTVECT
External Non-Maskable Interrupt Request.
When set to 1 by the hardware, it indicates an
external Non-Maskable Interrupt request has
occurred. See the description of the EXNMI
register below for more information.
9.4.4
EN
PIN
ENLCK
9.4.3
5
4
Reserved
3
2
ENLCK
1
PIN
4
3
2
1
INTVECT
0
Interrupt Enable and Mask Register 0 (IENAM0)
The IENAM0 register is a byte-wide, read/write register that
enables or disables the individual interrupts IRQ0 through
IRQ7. The register format is shown below.
External NMI Control/Status Register (EXNMI)
6
5
0
Interrupt Vector. This 5-bit field contains the encoded value of the enabled and pending
maskable interrupt with the highest priority. For
example, if interrupts IRQ1 and IRQ6 are both
enabled and pending, the higher-priority interrupt is IRQ6. As a result, the 5-bit interrupt vector is 10110.
0
EXT
The EXNMI register is a byte-wide, read/write register that
shows the current state of the NMI pin and also allows the
NMI trap to be enabled by setting either the EN bit or the ENLCK bit. Both of these bits are cleared upon reset. When the
software writes to this register, it must write 0 to all reserved
bit positions for the device to function properly. The register
format is shown below.
7
6
0
7
6
5
4
3
IENA(7:0)
2
1
0
A bit set to 1 enables the corresponding interrupt. A bit
cleared to 0 disables the corresponding interrupt. Upon reset, this register is initialized to FF hex.
0
EN
9.4.5
Interrupt Enable and Mask Register 1 (IENAM1)
The IENAM0 register is a byte-wide, read/write register that
enables or disables the individual interrupts IRQ8 through
IRQ15. The register format is shown below.
Enable NMI Trap. When set to 1, NMI traps are
enabled and falling edge on the NMI pin generates a NMI trap. Each occurrence of an NMI
trap automatically clears the EN bit. The trap
service routine should set the EN bit to 1 before
returning control to the interrupted program.
When EN is cleared to 0, NMI traps are disabled unless they are enabled with the ENLCK
bit. When the ENLCK bit is set to 1, the EN bit
is ignored.
NMI Pin. This bit shows the current state of the
NMI input pin (without logical inversion). A 1 indicates a high level and a 0 indicates a low level on the pin. This is a read-only bit. In a write
operation, the value written to this bit position is
ignored.
Enable and Lock NMI Trap. When set to 1, NMI
traps are enabled and locked in the enabled
state. Each falling edge on the NMI pin generates a NMI trap, even if a previous NMI trap
has occurred and is still being processed.
When ENLCK is cleared to 0, NMI traps are
disabled unless they are enabled with the EN
bit.
7
6
5
4
3
IENA(15:8)
2
1
0
A bit set to 1 enables the corresponding interrupt. A bit
cleared to 0 disables the corresponding interrupt. Upon reset, this register is initialized to FF hex.
9.4.6
Interrupt Status Register 0 (ISTAT0)
The ISTAT0 register is a byte-wide, read-only register that indicates which maskable interrupt inputs to the ICU (IRQ0
through IRQ7) are currently active. The register format is
shown below.
7
IST7
IST(0-7)
6
IST6
5
IST5
4
IST4
3
IST3
2
IST2
1
IST1
0
IST0
Interrupt Status bits. Each bit indicates the current status of an interrupt input to the ICU, corresponding to interrupts IRQ0 through IRQ7. A
bit set to 1 indicates an active interrupt input,
even when the interrupt is masked out by the
IENAM0 register. A bit cleared to 0 indicates an
inactive interrupt input.
Interrupt Vector Register (IVCT)
The IVCT register is a byte-wide, read-only register that contains the encoded value of the enabled and pending
maskable interrupt with the highest priority. The on-chip
hardware automatically updates this field whenever there is
a change in the highest-priority enabled and pending
maskable interrupt. The CPU reads this register during an interrupt acknowledge core bus cycle to determine where to
begin executing the interrupt service routine. The register
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9.4.7
Interrupt Status Register 1 (ISTAT1)
cant bit of this register are always zero. The Dispatch Table
is 32 words long, and limited to the flash program memory
space. Thus, the Dispatch Table must start at an even address in the range of 0004 to BFC0 hex.
The ISTAT1 register is a byte-wide, read-only register that indicates which maskable interrupt inputs to the ICU (IRQ8
through IRQ15) are currently active. The register format is
shown below.
7
6
5
4
3
2
1
IST15 IST14 IST13 IST12 IST11 IST10 IST9
IST(8-15)
9.4.8
ISP Register
0
IST8
The Interrupt Stack Pointer (ISP) is a 21-bit register that
points to the lowest address of the last item stored on the interrupt stack. The on-chip hardware modifies the stack contents and stack pointer when an interrupt or trap event occurs
and upon completion of an interrupt or trap service routine.
Interrupt Status bits. Each bit indicates the current status of an interrupt input to the ICU, corresponding to interrupts IRQ8 through IRQ15.
A bit set to 1 indicates an active interrupt input,
even when the interrupt is masked out by the
IENAM0 register. A bit cleared to 0 indicates an
inactive interrupt input.
The five most significant bits and the least significant bit of
this register are always zero. Because the stack must reside
in RAM and the device RAM occupies the address range of
E000-E7FF hex, the interrupt stack is restricted to this range.
9.5
Core Registers (PSR, INTBASE, and ISP)
INTERRUPT PROGRAMMING
PROCEDURES
Some of the CPU core registers are used for controlling interrupts: the Processor Status Register (PSR), the Interrupt
Base Register (INTBASE), and the Interrupt Stack Pointer
(ISP) register.
The following subsections provide information on initializing
the device for interrupts, clearing interrupts, and nesting interrupts.
PSR Register
9.5.1
The Processor Status Register (PSR) is a 16-bit register that
holds status information and selects the operating modes for
the CPU core. Bit 9 and Bit 11 are the Local Maskable Interrupt Enable (E) bit and the Global Maskable Interrupt Enable
(I) bit, respectively, as shown in Figure4. These bits are used
to enable or disable maskable interrupts.
Upon reset, all interrupts are disabled. To program the device
for interrupt operation and to enable interrupts, use the following procedure in the application software:
15 14 13 12 11 10 9
Reserved
I P E
8
0
7 6
N Z
5
F
4
0
3
0
2
L
Initialization
1. Set the interrupt stack pointer (ISP).
2. Load the INTBASE register so that it points to the base
of the interrupt Dispatch Table in ROM.
3. Perform any required preparation steps for the interrupt
service routines.
4. Initialize the peripheral devices that can generate interrupts and set their respective interrupt enable bits.
5. Use the Load Processor Register (LPR) instruction to
set I bit in the PSR register.
6. When the device is ready to execute interrupts, set the
E bit in the PSR register by executing the Enable Interrupts (EI) instruction.
1 0
T C
Figure 4. Processor Status Register (PSR) Format
Both the E bit and I bit can be controlled with the Load Processor Register (LPR) instruction. The E bit can also be controlled by the Enable Interrupts (EI) and Disable Interrupts
(DI) instructions. If the E and I bits are both set to 1, all
maskable interrupts are accepted. Otherwise, only the nonmaskable interrupt is accepted.
Once maskable interrupts are enabled by setting the E and I
bits, you can disable and re-enable all maskable interrupts by
using the Enable Interrupts (EI) and Disable Interrupts (DI)
instructions, which set and clear the E bit.
Upon reset, the E bit is set to 1 and the I bit is cleared to 0.
The processor uses the I bit to block maskable interrupts
while executing an interrupt handler. When an interrupt occurs, the processor saves the existing I bit (as part of the
PSR) on the interrupt stack and then clears the current I bit
to prevent further interrupts. When RETX is executed, the
former I bit it restored (with the rest of the PSR), again enabling masked interrupts.
9.5.2
Clearing Interrupts
Clearing an interrupt request before it is serviced may cause
a spurious interrupt because the CPU may detect an interrupt
not reflected in the Interrupt Vector (IVCT) register. To ensure
reliable operation, clear interrupt requests only while interrupts are disabled.
The E bit is intended to be used in a localized manner, allowing a process to operate without interruption for a short period while it accesses and modifies system variables and
semaphores. The E bit can be set to 1 by executing the Enable Interrupt (EI) or cleared to 0 by executing the Disable Interrupts (DI) instruction. Using these two instructions avoids
the possibility of an interrupt occurring within a read-modifywrite operation on the PSR register.
Changing the polarity of an interrupt input (for example, in the
Multi-Input Wake-Up module) can cause a spurious interrupt,
and therefore should be done only while interrupts are disabled.
For the same reason, clearing an enable bit in a peripheral
module should be carried out only while the interrupt is disabled.
INTBASE Register
9.5.3
The Interrupt Base Register (INTBASE) is a 21-bit register
that holds the address of the Dispatch Table for interrupts
and traps. The five most significant bits and the least signifi-
Interrupts may be nested, or in other words, an interrupt service routine can itself be interrupted by a different interrupt
source. There is no hardware limitation on the number of in-
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32
Nesting Interrupts
terrupt nesting levels. However, the interrupt stack must not
be allowed to overflow its allocated memory space.
Unless specifically enabled by the software, nested interrupts will not occur. When the CPU acknowledges an interrupt, the I bit in the PSR register is automatically cleared to 0
for the duration of the service routine, disabling any further
maskable interrupts.
To allow nested interrupts, an interrupt service routine should
first set or clear the respective interrupt enable bits to specify
which peripherals will be allowed to interrupt the current service routine. The present interrupt routine should be disabled
(or interrupt pending bit cleared). The service routine should
then set the PSR.I bit to 1, thus enabling maskable interrupts.
This bit can be controlled with the Store Processor Register
(SPR) and Load Processor Register (LPR) instructions.
Note: Clearing the pending bit of the current interrupt should
not be immediately followed by enabling further interrupts by
setting the I bit in the PSR register. Wait states must be inserted into the software after clearing the interrupt pending
bit and before another interrupt. Placing a NOP instruction
will perform this instruction. This is because the instruction
which resets the pending bit may not yet be finished when the
interrupts are already enabled again by setting the I bit in the
PSR register. To avoid this situation the user has to make
sure that prior to enabling the interrupt an additional instruction is inserted. This could look like the example below:
SBITi
NOP
MOVW
LPR
$0, T1ICRL
$0x0a00, r0
r0, psr
# clear pending bit
# NOP instruction
# enable further interrupts
A CBITi or SBITi instruction may be used to clear the interrupt
pending bit. In such cases, a spurious interrupt may occur.
33
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10.0 Power Management
The Power Management Module (PMM) improves the efficiency of the device by changing the operating mode (and
therefore the power consumption) according to the current
level of device activity.
terface, A/D Converter, and timers because they are driven
by the slow clock rather than the normal high-speed clock. In
order to work properly in Power Save mode, modules that
perform real-time operations (such as a USART baud rate
generator) must be reprogrammed to use the slower clock.
The device can operate in any of four power modes:
•
•
•
•
To reduce power consumption as much as possible, the program should execute a WAIT instruction during periods of
CPU inactivity.
Active
Power Save
Idle
Halt
10.3
Table12 summarizes the main properties of the four operating modes: the state of the high-frequency oscillator (on or
off), the type of clock used by most modules, and the clock
used by the Timing and Watchdog Module (TWM).
Table 12
IDLE MODE
In the Idle mode, the clock is stopped for most of the device.
Only the Power Management Module and Timing and Watchdog Module continue to operate. Both of these modules use
the slow clock in this mode.
Power Mode Operating Summary
10.4
Main Clock
Slow Clock
Power Save On or Off
Slow Clock
Slow Clock
In the Halt mode, all device clocks are disabled and the highfrequency oscillator is shut off. In this mode, the device consumes the least possible power while maintaining the device
memory and register contents. The low-frequency oscillator
continues to operate in this mode, but with very low power
consumption due to its power-optimized design.
Idle
On or Off
None
Slow Clock
10.5
Halt
Off
None
None
Switching from a higher to a lower power consumption mode
is accomplished by writing an appropriate value to the Power
Management Control/Status Register (PMCSR). Switching
from a lower power consumption mode to the Active mode is
usually triggered by a hardware interrupt. Figure5 shows the
four power consumption modes and the events that trigger a
transition from one mode to another.
Mode
Active
High-Frequency
Clock Used TWM Clock
Oscillator
HALT MODE
On
The low-frequency oscillator continues to operate in all four
modes and power must be provided continuously to the device power supply pins. In the Halt mode, however, the internal SLCLK does not toggle, and as a result, the TWM timer
and Watchdog Module do not operate. For the Power Save
and Idle modes, the high-frequency oscillator can be turned
on or off under software control, as long as the low-frequency
oscillator exists in the applicable device package.
10.1
Reset
ACTIVE MODE
Active
PSM =1
In the Active mode, all device modules are fully operational.
This is the operating mode upon reset. Most device modules
use the clock generated by the high-frequency clock oscillator. The clock rate is determined by the external crystal network.
Power Save
IDLE =1
HW event
or PSM =0
and WAIT
HALT =1
and WAIT
Power consumption in the Active mode can be reduced by
selectively disabling inactive modules and/or by executing
the WAIT instruction. When WAIT is executed, the core stops
executing new instructions and waits for an interrupt.
10.2
SWITCHING BETWEEN POWER MODES
Idle
HW event
Halt
POWER SAVE MODE
HW event
In the Power Save mode, all device modules operate off the
low-frequency clock. If the low-frequency clock is generated
from an external crystal network, the high-frequency clock
oscillator can be turned off to further reduce power consumption.
Figure 5. Power Modes and Transitions
All on-chip modules continue to operate in the Power Save
mode, with the SLCLK acting as their system clock. If this
mode is entered by using the WAIT command, the CPU is inactive and waits for an interrupt to wake up. Otherwise, CPU
continues to function normally at the lower frequency of the
slow clock.
Some of the power-up transitions are based on the occurrence of a wake-up event. An event of this type can be either
a maskable interrupt or a non-maskable interrupt (NMI). All of
the maskable hardware wake-up events are gathered and
processed by the Multi-Input Wake-Up Module, which is active in all modes. Once a wake-up event is detected, it is
latched until an interrupt acknowledge cycle occurs or a reset
is applied.
The low frequency of the clock in Power Save mode limits the
operation of modules such as the USARTs, MICROWIRE in-
A wake-up event causes a transition to the Active mode and
restores normal clock operation, but does not start execution
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34
of the program. It is the interrupt service routine associated
with the wake-up source (MIWU or NMI) that causes actual
program execution to resume.
10.5.1
Power Management Control/Status Register
(PMCSR)
OHFC
The Power Management Control/Status Register (PMCSR)
is a byte-wide, read/write register that controls the operating
power mode (Active, Power Save, Idle, or Halt) and enables
or disables the high-frequency oscillator in the Power Save
and Idle modes. The two most significant bits, OLFC and
OHFC, are read-only status bits controlled by the hardware.
Upon reset, the non-reserved bits of this register are cleared.
The format of the register is shown below.
OLFC
7
6
5
4
3
2
1
0
OLFC OHFC WBPSM Reserved HALT IDLE DHF PSM
PSM
DHF
IDLE
HALT
WBPSM
Power Save Mode. When this bit is 0, the device operates in the Active mode. Writing a 1 to
this bit position puts the device into the Power
Save mode, either immediately or upon execution of the next WAIT instruction, depending on
the WBPSM bit.
The PSM bit can be set and cleared by the software. It is also cleared by the hardware when a
hardware wake-up event is detected.
Disable High-Frequency Oscillator. This bit enables (0) or disables (1) the high-frequency oscillator in the Power Save or Idle mode. (The
high-frequency oscillator is always enabled in
Active mode and always disabled in Halt mode,
regardless of this bit settings.) The DHF bit is
cleared automatically when a hardware wakeup event is detected.
Idle Mode. When this bit is set, the device enters the Idle mode upon execution of a WAIT instruction. In order to enter the Idle mode from
the Active mode, the WBPSM bit must be set
before the WAIT instruction is executed.
The IDLE bit can be set and cleared by the software. When a hardware wake-up event is detected, this bit is cleared automatically and the
device returns to the Active mode.
Halt Mode. When this bit is set, the device enters the Halt mode upon execution of a WAIT
instruction. In order to enter the Halt mode from
the Active mode, the WBPSM bit must be set
before the WAIT instruction is executed.
The Halt bit can be set and cleared by the software. When a hardware wake-up event is detected, this bit is cleared automatically and the
device returns to the Active mode.
Wait Before Entering Power Save Mode. When
the CPU writes a 1 to the PSM bit, the WBPSM
determines when the transition from Active to
Power Save mode is done. If the WBPSM bit is
0, the switch to Power Save mode is initiated
immediately; the PSM bit in the register is set
to 1 upon completion of the switch to Power
Save mode. If the WBPSM bit is 1, the device
continues to operate in Active mode until the
next WAIT instruction, and then enters the
10.5.2
Power Save mode. In this case, the PSM bit is
set to 1 immediately, even if a WAIT instruction
has not yet been executed.
In the Active mode, the WBPSM bit must be set
in order to enter the Idle or Halt mode.
Oscillating High-Frequency Clock. This readonly bit indicates the status of the high-frequency clock. If this bit is 1, the high-frequency clock
is available and stable. If this bit is 0, the highfrequency clock is either disabled, not available
to the Power Management Module, or operating but not yet stable. The device can switch to
the Active mode only when this bit is 1.
Oscillating Low-Frequency Clock. This readonly bit indicates the status of the low-frequency (slow) clock. If this bit is 1, it indicates that
the slow clock is running and stable. The slow
clock can be either the prescaled fast clock (the
default) or the external oscillator (if selected).
The Dual Clock module will not allow a transition to the slow crystal mode unless the slow
crystal is operating, so this bit should be 1 under normal circumstances.
The OLFC bit is the multiplexed and sampled
output of the “Good Main Clk” and “Good Low
Speed Clk” indicator signals. These values are
determined at reset or power-up, and then selected according to the programmed slow clock
source.
The device can switch from the Active mode to
the Power Save or Idle mode only if the OLFC
bit is 1. (There is no such restriction on switching to the Halt mode.)
Active to Power Save Mode
A transition from the Active mode to the Power Save mode is
accomplished by writing a 1 to the PMCSR.PSM bit. The
transition to Power Save mode is either initiated immediately
or upon execution of the next WAIT instruction, depending on
the PMCSR.WBPSM bit.
For an immediate transition to Power Save mode (PMCSR.WBPSM=0), the CPU continues to operate using the lowfrequency clock. The PMCSR.PSM bit is set to 1 when the
transition to the Power Save mode is completed.
For a transition upon the next WAIT instruction (PMCSR.WBPSM=1), the CPU continues to operate in the Active
mode until it executes a WAIT instruction. Upon execution of
the WAIT instruction, the device enters the Power Save
mode and the CPU waits for the next interrupt event. In this
case, the PMCSR.PSM bit is set to 1 when it is written, even
before the WAIT instruction is executed.
10.5.3
Entering the Idle Mode
Entry into the Idle mode is accomplished by writing a 1 to the
PMCSR.IDLE bit and then executing a WAIT instruction.
The Idle mode can be entered only from the Active or Power
Save mode. For entry from the Active mode, the PMCSR.WBPSM bit must be set before the WAIT instruction is
executed.
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10.5.4
Disabling the High-Frequency Clock
The PMCSR.OHFC and PMCSR.OLFC bits indicate the current status of the high-frequency and low-frequency clock oscillators, respectively. The software can check the
appropriate bit before it changes to an operating mode that
requires the clock. A status bit set to 1 indicates an operating,
stable clock. A status bit cleared to 0 indicates a clock that is
disabled, not available, or not yet stable.
In systems where the low-frequency crystal is available and
is used to generate the Slow Clock (SLCLK), power consumption can be reduced further in the Power Save or Idle
mode by disabling the high-frequency clock. This is accomplished by writing a 1 to the PMCSR.DHF bit before executing the WAIT instruction that puts the device in the Power
Save or Idle mode. The high-frequency clock is turned off
only after the device enters the Power Save or Idle mode.
During a power mode transition, if there is a request to switch
to a mode that uses clock with the status bit cleared to 0, the
switch is delayed until that bit is set to 1 by the hardware.
The CPU operates on the low-frequency clock in Power Save
mode. It can turn off the high-frequency clock at any time by
writing a 1 to the PMCSR.DHF bit.
When the system is built without an external crystal network
for the low-frequency clock, the high-frequency clock is divided by a prescaler factor to produce the low-frequency clock.
In this situation, the high-frequency clock is disabled only in
the Halt mode, and cannot be disabled for the Power Save or
Idle mode, regardless of the software command issued.
The high-frequency oscillator is always enabled in Active
mode and always disabled in Halt mode, regardless of the
PMCSR.DHF bit setting.
Immediately following power-up and entry into the Active
mode, the software must wait for the low-frequency clock to
become stable before it can put the device in the Power Save
mode. It should monitor the PMCSR.OLFC bit for this purpose. Once this bit is set to 1, the slow clock is stable and the
Power Save mode can be entered.
10.5.5
Without an external crystal network for the low-frequency
clock, the device comes out of the Halt or Idle mode and enters the Active mode with the high-speed oscillator used as
the clock. The device can still enter the Power Save from the
Active mode by using the high-frequency-clock divider to
generate the slow clock (PMCSR.DHF=0).
Entering the Halt Mode
Note: For correct operation in the absence of a low-frequency crystal, the X2CKI pin must be tied low (not left floating) so
the hardware can detect the absence of the crystal.
Entry into the Halt mode is accomplished by writing a 1 to the
PMCSR.HALT bit and then executing a WAIT instruction.
The Halt mode can be entered only from the Active or Power
Save mode. For entry from the Active mode, the PMCSR.WBPSM bit must be set before the WAIT instruction is executed.
10.5.6
Software-Controlled Transition to Active Mode
A transition from the Power Save mode to the Active mode
can be accomplished by either a software command or a
hardware wake-up event. The software method is to write a
0 to the PMCSR.PSM bit. The value of the register bit changes only after the transition to the Active mode is completed.
If the high-frequency oscillator is disabled for Power Save operation, the oscillator must be enabled and allowed to stabilize before the transition to Active mode. To enable the highfrequency oscillator, the software writes a 0 to the PMCSR.DHF bit. Before writing a 0 to the PMCSR.PSM bit, the
software should first monitor the PMCSR.OHFC bit to determine whether the oscillator has stabilized.
10.5.7
Wake-Up Transition to Active Mode
A hardware wake-up event switches the device directly from
Power Save, Idle, or Halt mode to the Active mode. When a
wake-up event occurs, the on-chip hardware performs the
following steps:
1. Clears the PMCSR.DHF bit, thus enabling the high-frequency clock (if it was disabled).
2. Waits for the PMCSR.OHFC bit to be set, which indicates that the high-frequency clock is operating and is
stable.
3. Switches the device into the Active mode.
10.5.8
Power Mode Switching Protection
The Power Management Module has several mechanisms to
protect the device from malfunctions caused by missing or
unstable clock signals.
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11.0 Dual Clock and Reset
The Dual Clock and Reset module (CLK2RES) generates a
high-speed main system clock from an external crystal network and a slow clock (32.768 kHz or other rate) for operat-
ing the device in Power Save mode. It also provides the main
system reset signal and a power-on reset function.
Figure6 is block diagram of the Dual Clock and Reset module.
System
Reset
RESET
Power-On-Reset
Stop Main Osc.
Stop
Main Osc In
Preset
X1CKI
Start-Up-Delay
14-Bit Timer
Main Clk
Main Osc.
8-Bit
Prescaler
Div.
by-2
X2CKI
Mux
X1CKO
Time-out
Low Speed
Clk
Time-out
Good Low
Speed Clk
32kHz Osc.
Start-Up-Delay
6-Bit Timer
Preset
X2CKO
Stop 32kHz Osc.
Figure 6. Dual Clock and Reset Module Block Diagram
11.1
Good Main
Clk
Stop Low
Speed Clk
is not used for the slow clock, the clock is generated by dividing the fast main clock.
EXTERNAL CRYSTAL NETWORK
An external crystal network is required at pins X1CKI and
X1CKO for the main clock. A similar external crystal network
may be used at pins X2CKI and X2CKO for the slow clock in
packages that have these pins. If an external crystal network
Figure7 shows the required crystal network at X1CKI/
X1CKO and optional crystal network at X2CKI/X2CKO.
Table13 shows the component specifications for the main
crystal network and Table14 shows the component specifications for the 32.768 kHz crystal network.
X1CKI / X2CKI
XTAL
C1
R1
X1CKO / X2CKO
C2
R2
Figure 7. External Crystal Network
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Table 13
Component
Oscillator
Crystal
Component Values of the High Frequency Crystal Circuit
Parameters
Values
Values
Values
Values
Tolerance
Resonance Frequency
Type
Max. Serial Resistance
Max. Shunt Capacitance
Load Capacitance
4 MHz
AT-Cut
75 Ω
4 pF
12 pF
12 MHz
AT-Cut
35 Ω
4 pF
15 pF
16 MHz
AT-Cut
35 Ω
4 pF
15 pF
20 MHz
AT-Cut
35 Ω
4 pF
20 pF
N/A
Resistor R1
1 MΩ
1 MΩ
1 MΩ
1 MΩ
5%
Resistor R2
0Ω
0Ω
0Ω
0Ω
5%
22 pF
20 pF
20 pF
20 pF
20%
Capacitor C1, C2
Table 14 Component Values of the Low Frequency Crystal Circuit
Component
Oscillator
Parameters
Values
Tolerance
32.768kHz
Parallel
N-Cut or XY-bar
40 kΩ
2 pF
9-13 pF
N/A
Resistor R1
10-20 MΩ
5%
Resistor R2
4.7 kΩ
5%
Capacitor C1, C2
20 pF
20%
Resonance Frequency
Type
Maximum Serial Resistance
Maximum Shunt Capacitance
Load Capacitance
Crystal
The crystal oscillator you choose may require external components different from the ones specified above. In that case,
consult with National Semiconductor for the component
specifications.
is asserted, it presets the 14-bit timer to 3FFF hex and stops
the main oscillator. When the signal goes inactive, the main
oscillator starts and the 14-bit timer counts down from its preset value. When the timer reaches zero, it stops counting and
asserts the “Good Main Clk” signal.
The crystals and other oscillator components should be
placed close to the X1CKI/X1CKO and X2CKI/X2CKO device input pins to keep the printed trace lengths to an absolute minimum.
11.3
The slow (32.768 kHz) clock is necessary for operating the
device in Power Save modes and to provide a clock source
for modules such as the Timing and Watchdog Module.
Choose capacitor component values in the tables to obtain
the specified load capacitance for the crystal when combined
with the parasitic capacitance of the trace, socket, and package (which can vary from 0 to 8 pF). As a guideline, the load
capacitance is:
The slow clock operates in a manner similar to the main
clock. The “Stop Slow Osc” signal from the Power Management Module stops and starts the slow oscillator. When this
signal is asserted, it presets a 6-bit timer to 3F hex and disables the slow oscillator. When the signal goes inactive, the
slow oscillator starts and the 6-bit timer counts down from its
preset value. When the timer reaches zero, it stops counting
and asserts the “Good Low Speed Clk” signal, thus indicating
that the slow clock is stable.
CL = (C1 * C 2)/(C1+C2) + C parasitic
C 2 > C1
C1 can be trimmed to obtain the desired load capacitance.
The start-up time of the 32.768 kHz oscillator can vary from
one to six seconds. The long start-up time is due to the high
“Q” value and high serial resistance of the crystal necessary
to minimize power consumption in Power Save mode.
11.2
For systems that do not require a reduced power consumption mode, the external crystal network may be omitted for
the slow clock. In that case, the slow clock can be created by
dividing the main clock by a prescaler factor. The prescaler
circuit consists of a fixed divide-by-2 counter and a programmable 8-bit prescaler register. This allows a choice of clock
divisors ranging from 2 to 512. The resulting slow clock frequency must not exceed 100 KHz.
MAIN SYSTEM CLOCK
The main system clock is generated by the main oscillator. It
can be stopped by the Power Management Module to reduce
power consumption during periods of reduced activity. When
the main clock is restarted, a 14-bit timer generates a “Good
Main Clk” signal after a start-up delay of 32,768 clock cycles.
This signal is an indicator that the main clock oscillator is stable.
A software-programmable multiplexer selects either the
prescaled main clock or the 32.768 kHz oscillator as the slow
clock. Upon reset, the prescaled main clock is selected, ensuring that the slow clock is always present initially. Selection
of the 32.768 kHz oscillator as the slow clock disables the
clock prescaler, which allows the CLK1 oscillator to be turned
The “Stop Main Osc” signal from the Power Management
Module stops and starts the main oscillator. When this signal
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SLOW SYSTEM CLOCK
38
off during power-save operation, thus reducing power consumption and radiated emissions. This can be done only if
the module detects a toggling low-speed oscillator. If the lowspeed oscillator is not operating, the prescaler remains available as the slow clock source.
11.4
11.6
DUAL CLOCK AND RESET REGISTERS
The Dual Clock and Reset module (CLK2RES) contains two
registers: the Clock and Reset Control register (CRCTRL)
and the Slow Clock Prescaler register (PRSSC).
11.6.1
POWER-ON RESET
Clock and Reset Control Register (CRCTRL)
Clock and Reset Control Register (CRCTRL) is a byte-wide
read/write register that contains the power-on reset flag and
selects the type of slow clock. The register format is shown
below.
The Power-On Reset circuit generates a system reset signal
upon power-up and holds the signal active for a period of
time to allow the crystal oscillator to stabilize. The circuit detects a power turn-on condition, which presets the 14-bit timer to 3FFF hex. Once oscillation starts and the clock
becomes active, the timer starts counting down. When the
count reaches zero, the 14-bit timer stops counting and the
internal reset signal is deactivated (unless the RESET pin is
held low).
7
6
SCLK
The circuit sets a power-on reset flag bit upon detection of a
power-on condition. The CPU can read this flag to determine
whether a reset was caused by a power-up or by the RESET
input.
POR
EXTERNAL RESET
An active-low reset input pin called RESET allows the device
to be reset at any time. When the signal goes low, it generates an internal system reset signal that remains active until
the RESET signal goes high again.
11.7
3
2
1
POR
0
SCLK
Slow Clock Select. When this bit is set to 1, the
32.728 kHz oscillator is used for the slow clock.
When this bit is cleared to 0, the prescaled
main clock is used for the slow clock. Upon reset, this bit is cleared to 0.
Power-On Reset. This bit is set to 1 by the
hardware when a power-on condition is detected, allowing the CPU to determine whether a
power-up has occurred. The CPU can clear
this bit to 0 but cannot set it to 1. Any attempt
by the CPU to set this bit is ignored.
Note: Power-On Reset circuit cannot be used to detect a
drop in the supply voltage.
11.5
5
4
Reserved
SLOW CLOCK PRESCALER REGISTER
(PRSSC)
The Slow Clock Prescaler (PRSSC) register is a byte-wide
read/write register that holds the clock divisor used to generate the slow clock from the main clock. The format of the register is shown below.
7
SCDIV
39
6
5
4
3
SCDIV
2
1
0
Slow Clock Divisor. If the clock divider is enabled (CRCTRL.SCLK=0), the main clock is divided by (SCDIV+1)*2 to produce the slow
system clock. Upon reset, PRSSC register is
set to FF hex.
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12.0 Multi-Input Wake-Up
The Multi-Input Wake-Up (MIWU) module monitors its eight
input channels for a software-selectable trigger condition.
Upon detection of a trigger condition, the module generates
either a wake-up request or an interrupt request. A wake-up
request can be used by the power management unit to exit
the Halt, Idle, or Power Save mode and return to the active
mode. An interrupt request generates an interrupt to the CPU
(interrupt IRQ2), allowing interrupt processing in response to
external events.
The Multi-Input Wake-Up module is active at all times, including the Halt mode. All device clocks are stopped in this mode.
Therefore, detecting an external trigger condition and the
subsequent setting of the pending flag are not synchronous
to the system clock.
12.1
WAKE-UP EDGE DETECTION REGISTER
(WKEDG)
The Wake-Up Edge Detection (WKEDG) register is a bytewide read/write register that controls the edge sensitivity of
the Multi-Input Wake-Up pins. Register bits 0 through 7 control input pins WUI0 through WUI7, respectively. A bit cleared
to 0 configures the corresponding input to trigger on a rising
edge (a low-to-high transition). A bit set to 1 configures the
corresponding input to trigger on a falling edge (a high-to-low
transition).
The wake-up event only activates the clocks and CPU, but
does not by itself initiate execution of any code. It is the interrupt request associated with the MIWU that gets the CPU to
start executing code by jumping to the proper interrupt routine. Therefore, setting up the MIWU interrupt handler is essential for any wake-up operation.
Figure8 is a block diagram showing the internal operation of
the Multi-Input Wake-Up module.
This register is cleared upon reset, which configures all eight
inputs to be triggered on rising edges.
The input pins for the Multi-Input Wake-Up channels are
named WUI0 through WUI7. These pins are alternate functions of I/O pins in Port I and Port L. The first Multi-Input
Wake-Up channel is software-selectable between the WUI0
input pin and the T0OUT signal from the Timing and Watchdog (TWM) module, which can be used to wake up the device after a programmed time interval. The WKCTL register
controls this selection. The remaining seven channels always use input pins WUI1 through WUI7.
The register format is shown below.
7
6
5
4
3
2
1
0
WKED7 WKED6 WKED5 WKED4 WKED3 WKED2 WKED1 WKED0
12.2
WAKE-UP ENABLE REGISTER (WKENA)
The Wake-Up Enable (WKENA) register is a byte-wide read/
write register that enables or disables each of the Multi-Input
Wake-Up channels. Register bits 0 through 7 control channels WUI0 through WUI7, respectively. A bit cleared to 0 disables the wake-up/interrupt function and a bit set to 1
enables the function.
Each input can be configured to trigger on rising or falling
edges, as determined by the setting in the WKEDG register.
Each trigger event is latched into the WKPND register. If a
trigger event is enabled by its respective bit in the WNENA
register, an active wake-up/interrupt signal is generated. The
software can determine which channel has generated the active signal by reading the WKPND register.
This register is cleared upon reset, which disables all eight
wake-up/interrupt channels.
Peripheral Bus
WKCTRL
7
.......................... 0
7
.......................... 0
WKENA
WUI0
WUI0
0
T0OUT
WUI7
EXINT to ICU and
Wake-up Signal
To Power Mgt
7
WKEDG
WKPND
Figure 8. Multi-Input Wake-Up Module Block Diagram
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40
The register format is shown below.
7
6
5
4
3
12.6
2
1
0
To set up and use the Multi-Input Wake-Up function, use the
following procedure. Performing the steps in the order shown
will prevent false triggering of a wake-up condition. This
same procedure should be used following a reset because
the wake-up inputs are left floating, resulting in unknown data
on the input pins.
WKEN7 WKEN6 WKEN5 WKEN4 WKEN3 WKEN2 WKEN1 WKEN0
12.3
WAKE-UP SOURCE SELECT REGISTER
(WKCTRL)
The Wake-Up Source Select (WKCTRL) register is a bytewide read/write register that selects the trigger source for the
first of the eight channels. Register bit 0 controls this function; the seven higher-order bits are reserved. The register
format is shown below.
7
6
5
WKSEL0
12.4
4
3
Reserved
2
1
PROGRAMMING PROCEDURES
1. Clear the WKENA register to disable the wake-up channels.
2. If the input originates from an I/O port (the usual case),
set the corresponding bit in the port direction register to
configure the I/O pin to operate as an input.
3. Write the WKEDG register to select the desired type of
edge sensitivity (clear to 0 for rising edge, set to 1 for falling edge).
4. Set all bits in the WKPCL register to clear any pending
bits in the WKPND register.
5. Set the bits in the WKENA register corresponding to the
wake-up channels to be activated.
0
WKSEL0
Wake-Up Select 0. This bit cleared to 0 selects
the WUI0 pin as the trigger source. This bit set
to 1 selects the T0OUT signal from the Timing
and Watchdog (TWM) module as the trigger
source, which can be used to wake up the device after a programmed time interval. This bit
is cleared upon reset. All reserved bits must be
written with 0 for this module to function properly.
To change the edge sensitivity of a wake-up channel, use the
following procedure. Performing the steps in the order shown
will prevent false triggering of a wake-up/interrupt condition.
1. Clear the WKENA bit associated with the input to be reprogrammed.
2. Write the new value to the corresponding bit position in
the WKEDG register to reprogram the edge sensitivity of
the input.
3. Set the corresponding bit in the WKPCL register to clear
the pending bit in the WKPND register.
4. Set the same WKENA bit to re-enable the wake-up function.
WAKE-UP PENDING REGISTER (WKPND)
The Wake-Up Pending (WKPND) register is a byte-wide
read/write register in which the Multi-Input Wake-Up module
latches any detected trigger conditions. Register bits 0
through 7 serve as latches for channels WUI0 through WUI7,
respectively. A bit cleared to 0 indicates that no trigger condition has occurred. A bit set to 1 indicates that a trigger condition has occurred and is pending on the corresponding
channel. This register is cleared upon reset.
The CPU can only write a 1 to any bit position in this register.
If the CPU attempts to write a 0, it has no effect on that bit.
To clear a bit in this register, the CPU must use the WKPCL
register (described below). This implementation prevents a
potential hardware-software conflict during a read-modifywrite operation on the WKPND register.
The register format is shown below.
7
6
5
4
3
2
1
0
WKPD7 WKPD6 WKPD5 WKPD4 WKPD3 WKPD2 WKPD1 WKPD0
12.5
WAKE-UP PENDING CLEAR REGISTER
(WKPCL)
The Wake-Up Pending Clear (WKPCL) register is a bytewide write-only register that lets the CPU clear bits in the WKPND register. Writing a 1 to a bit position in the WKPCL register clears the corresponding bit in the WKPND register.
Writing a 0 leaves the corresponding bit in the WKPND register unchanged.
Reading this register location returns unknown data. Therefore, do not use a read-modify-write sequence to set the individual bits. In other words, do not attempt to read the
register and do a logical OR with the register value. Instead,
just write the mask directly to the register address.
The register format is shown below.
7
6
5
4
3
2
1
0
WKCL7 WKCL6 WKCL5 WKCL4 WKCL3 WKCL2 WKCL1 WKCL0
41
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13.0 Real-Time Timer and WATCHDOG
The Timing and WATCHDOG Module (TWM) generates the
clocks and interrupts used for timing periodic functions in the
system, and also provides Watchdog protection against software errors. The module operates off the slow clock either
generated by the external 32kHz oscillator or from the prescaled high speed system clock. The maximum operating
clock frequency is 100kHz.
All counting activities of the module are based on the slow
clock (SLCLK). A prescaler counter divides this clock to
make a slower clock. The prescaler factor is defined by a 3bit field in the Timer and WATCHDOG Prescaler register,
which selects either 1, 2, 4, 8, 16, or 32 and the divide-by factor. Thus, the prescaled clock period can be set to 1, 2, 4, 8,
16, or 32 times the slow clock period. The prescaled clock
signal is called T0IN.
The WATCHDOG is designed to detect program execution
errors. Once WATCHDOG operation is initiated, the software
must periodically write a specific value to a WATCHDOG register. If the software fails to do so, a WATCHDOG error is triggered, which resets the device.
13.2
Timer T0 is a programmable 16-bit down counter that can be
used as the time base for real-time operations such as a periodic audible tick. It can also be used to drive the WATCHDOG circuit.
The TWM is flexible in allowing selection of a variety of clock
ratios and clock sources for the WATCHDOG circuit. Once
the software configures the TWM, it can lock the configuration for a higher level of protection against erroneous software action. Once locked, the TWM can be released only by
a device reset.
13.1
TIMER T0 OPERATION
The timer starts counting from the value loaded into the
TWMT0 register and counts down on each rising edge of
T0IN. When the timer reaches zero, it is automatically reloaded from the TWMT0 register and continues counting down
from that value. Thus, the frequency of the timer is:
TWM STRUCTURE
f SLCLK / [ (TWMT0+1) * prescaler ]
Figure9 is a block diagram showing the internal structure of
the Timing and WATCHDOG module. There are two main
sections: the Real-Time Timer (T0) section at the top and the
WATCHDOG section on the bottom.
When an external crystal oscillator is used as the SLCLK
source or when the fast clock is divided accordingly, f SLCLK
is 32.768 kHz.
The value stored in TWMT0 can range from 0001 hex to
FFFF hex.
Peripheral Bus
REAL TIME TIMER (T0)
5-bit pre-scaler counter
(TWCP)
CLKIN1
slow clock from
dual clock and
reset module
T0IN
TWMT0 register
T0CSR Contrl. Reg.
T0LINT
(to ICU)
Restart
16-bit Timer (Timer0)
Underflow
T0OUT
(to Multi-InputWake-up)
WATCHDOG Timer
Underflow
Restart
WDSDM
WATCHDOG
Service
Logic
WDCNT
WATCHDOG ERROR
WATCHDOG
Figure 9. Timing and WATCHDOG Module Block Diagram
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42
WDERR
When the counter reaches zero, an internal timer signal
called T0OUT is set to 1 for one T0IN clock cycle. This signal
sets the TC bit in the TWMT0 Control and Status Register
(T0CSR). It also generates an interrupt called RTI (IRQ14) if
the interrupt is enabled by the T0CSR.T0INTE bit.
13.3.1
The Timer and WATCHDOG Configuration (TWCFG) register is used to set the WATCHDOG configuration. It controls
the WATCHDOG clock source (T0IN or T0OUT), the type of
WATCHDOG servicing (using WDCNT or WDSDM), and the
locking state of the TWCFG, TWCPR, TIMER0, T0CSR, and
WDCNT registers. A register that is locked cannot be read or
written. A write operation is ignored and a read operation returns unpredictable results.
If the software loads TWMT0 with a new value, the timer uses
that value the next time that it reloads the 16-bit timer register
(in other words, after reaching zero). The software can restart the timer at any time (on the very next edge of the T0IN
clock) by setting the Restart (RST) bit in the T0CSR register.
The T0CSR.RST bit is cleared automatically upon restart of
the 16-bit timer.
If the TWCFG register is itself locked, it remains locked until
the device is reset. Any other locked registers also remain
locked until the device is reset. This feature prevents a runaway program from tampering with the programmed
WATCHDOG function.
Note: If the user wishes to switch to power save or idle mode
after setting T0CSR.RST, the user must wait for reset operation to complete before doing the switch.
13.3
Register Locking
13.3.2
WATCHDOG OPERATION
Power Save Mode Operation
The Timer and WATCHDOG Module is active in both the
Power Save and Idle modes. The clocks and counters continue to operate normally in these modes. The WDSDM register is accessible in the Power Save and Idle modes, but the
other TWM registers are accessible only in the Active mode.
Therefore, WATCHDOG servicing must be carried out using
the WDSDM register in the Power Save or Idle mode.
The WATCHDOG is an 8-bit down counter that operates on
the rising edge of a specified clock source. Upon reset, the
WATCHDOG is disabled; it does not count and no WATCHDOG signal is generated. A write to either the WATCHDOG
Count (WDCNT) register or the WATCHDOG Service Data
Match (WDSDM) register starts the counter. The WATCHDOG counter counts down from the value programmed in to
the WDCNT register. Once started, only a reset can stop the
WATCHDOG from operating.
In the Halt mode, the entire device is frozen, including the
Timer and WATCHDOG Module. Upon return to the Active
mode, operation of the module resumes at the point at which
it was stopped.
The WATCHDOG can be programmed to use either T0OUT
or T0IN as its clock source (the output and input of Timer T0,
respectively). The TWCFG.WDCT0I bit controls this clock
selection.
Note: After a restart or WATCHDOG service through WDCNT, do not enter Power Save mode for a period equivalent
to 5 slow clock cycles.
The software must periodically “service” the WATCHDOG.
There are two ways to service the WATCHDOG, the choice
depending on the programmed value of the WDSDME bit in
the Timer and WATCHDOG Configuration (TWCFG) register.
13.4
TWM REGISTERS
The TWM registers controls the operation of the Timing and
WATCHDOG Module. There are six such registers:
• Timer and WATCHDOG Configuration Register (TWCFG)
• Timer and WATCHDOG Clock Prescaler Register
(TWCP)
• TWM Timer 0 Register (TWMT0)
• TWMT0 Control and Status Register (T0CSR)
• WATCHDOG Count Register (WDCNT)
• WATCHDOG Service Data Match Register (WDSDM)
If TWCFG.WDSDME bit is cleared to 0, the WATCHDOG is
serviced by writing a value to the WDCNT register. The value
written to the register is reloaded into the WATCHDOG
counter. The counter then continues counting down from that
value.
If TWCFG.WDSDME bit is set to 1, the WATCHDOG is serviced by writing the value 5C hex to the WATCHDOG Service
Data Match (WDSDM) register. This reloads the WATCHDOG counter with the value previously programmed into the
WDCNT register. The counter then continues counting down
from that value.
The WDSDM register is accessible in both Active and Power
Save mode. The other TWM registers are accessible only in
Active mode.
13.4.1
A WATCHDOG error signal is generated by any of the following events:
Timer and WATCHDOG Configuration Register
(TWCFG)
The TWCFG register is a byte-wide, read/write register that
selects the WATCHDOG clock input and service method,
and also allows the WATCHDOG registers to be selectively
locked. Once a bit is set, that bit cannot be cleared until the
device resets. Upon reset, the non-reserved bits of the register are all cleared to 0. The register format is shown below.
— The WATCHDOG serviced too late .
— The WATCHDOG serviced too often.
— The WDSDM register is written with a value other than
5C hex when WDSDM type servicing is enabled
(TWCFG.WDSDME=1).
A WATCHDOG error condition resets the device.
7
6
5
4
Reserve
WDSDME WDCT0I
d
LTWCFG
43
3
2
1
0
LWDCNT LTWMT0 LTWCP LTWCFG
Lock TWCFG Register. When cleared to 0, access to the TWCFG register is allowed. When
set to 1, the TWCFG register is locked. A
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locked register cannot be read or written; a
read operation returns unpredictable values
and a write operation is ignored. Locking the
TWCFG register remains in effect until the device is reset.
Lock TWCP Register. When cleared to 0, access to the TWCP register is allowed. When
set to 1, the TWCP register is locked.
Lock TWMT0 Register. When cleared to 0, access to the TWMT0 and T0CSR registers are
allowed. When set to 1, the TWMT0 and
T0CSR registers are locked.
Lock LDWCNT Register. When cleared to 0,
access to the LDWCNT register is allowed.
When set to 1, the LDWCNT register is locked.
WATCHDOG Clock from T0IN. When cleared
to 0, the T0OUT signal (the output of Timer T0)
is used as the WATCHDOG clock. When set to
1, the T0IN signal (the prescaled slow clock) is
used as the WATCHDOG clock.
WATCHDOG Service Data Match Enable.
When cleared to 0, WATCHDOG servicing is
accomplished by writing a count value to the
WDCNT register; write operations to the
WATCHDOG Service Data Match (WDSDM)
register are ignored. When set to 1, WATCHDOG servicing is accomplished by writing the
value 5C hex to the WDSDM register.
LTWCP
LTWMT0
LWDCNT
WDCT0I
WDSDME
13.4.2
ter is initialized to FFFF hex. The register format is shown below.
15 14 13 12 11 10 9
PRESET
13.4.4
7
RST
Timer and WATCHDOG Clock Prescaler
Register (TWCP)
MDIV
13.4.3
6
5
4
Reserved
3
2
1
MDIV
TC
T0INTE
0
Main Clock Divide. This 3-bit field defines the
prescaler factor used for dividing the low speed
device clock to create the T0IN clock. The allowed 3-bit values and the corresponding clock
divisors and clock rates are listed below.
MDIV
Clock Divisor TOIN Frequency
(fSCLK=32.768 kHz)
000
1
32.768 kHz
001
2
16.384 kHz
010
4
8.192 kHz
011
8
4.096 kHz
100
16
2.048 kHz
101
32
1.024 kHz
other
Reserved
N/A
13.4.5
4
3
2
1
0
Timer T0 Preset. Timer T0 is reloaded with this
value on each underflow. Thus, the frequency
of the Timer T0 interrupt is the frequency of
T0IN divided by (PRESET+1). The allowed values of PRESET are 0001 hex through FFFF
hex.
TWMT0 Control and Status Register (T0CSR)
6
5
4
Reserved
3
2
T0INTE
1
TC
0
RST
Restart. When this bit is set to 1, it forces the
timer to reload the value in the TWMT0 register
on the next rising edge of the selected input
clock. The RST bit is reset automatically by the
hardware on the same rising edge of the selected input clock. Writing a 0 to this bit position
has no effect. Upon reset, the non-reserved
bits of the register are cleared to 0.
Terminal Count. This bit is set to 1 by the hardware when the Timer T0 count reaches zero
and is cleared to 0 when the software reads the
T0CSR register. It is a read-only bit. Any data
written to this bit position is ignored.
Timer T0 Interrupt Enable. When this bit is set
to 1, it enables an interrupt to the CPU each
time the Timer T0 count reaches zero. When
this bit is cleared to 0, Timer T0 interrupts are
disabled.
WATCHDOG Count Register (WDCNT)
The WDCNT register is a byte-wide, write-only register that
holds the value that is loaded into the WATCHDOG counter
each time the WATCHDOG is serviced. The WATCHDOG is
started by the first write to this register. Each successive write
to this register restarts the WATCHDOG count with the written value. Upon reset, this register is initialized to 0F hex.
13.4.6
WATCHDOG Service Data Match Register
(WDSDM)
The WSDSM register is a byte-wide, write-only register used
for servicing the WATCHDOG. When this type of servicing is
enabled (TWCFG.WDSDME=1), the WATCHDOG is serviced by writing the value 5C hex to the WSDSM register.
Each such servicing reloads the WATCHDOG counter with
the value previously written to the WDCNT register. Writing
any data other than 5C hex triggers a WATCHDOG error.
Writing to the register more than once in one WATCHDOG
clock cycle also triggers a WATCHDOG error signal. If this
type of servicing is disabled (TWCFG.WDSDME=0), any
write to the WSDSM register is ignored.
TWM Timer 0 Register (TWMT0)
The TWMT0 register is a word-wide, read/write register that
defines the T0OUT interrupt rate. Upon reset, TWMT0 regis-
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5
The T0CSR register is a byte-wide, read/write register that
controls Timer T0 and shows its current status. Upon reset,
the non-reserved bits of the register are cleared to 0. The
register format is shown below.
The TWCP register is a byte-wide, read/write register that defines the prescaler value used for dividing the low frequency
clock to generate the T0IN clock. Upon reset, the non-reserved bits of the register are cleared to 0. The register format is shown below.
7
8 7 6
PRESET
44
13.5
WATCHDOG PROGRAMMING
PROCEDURE
The highest level of protection against software errors is
achieved by programming and then locking the WATCHDOG
registers and using the WDSDM register for servicing. This is
the procedure:
1. Write the desired values into the TWM Clock Prescaler
register (TWCP) and the TWM Timer 0 register
(TWMT0) to control the T0IN and T0OUT clock rates.
The frequency of T0IN can be programmed to any of six
frequencies ranging from 1/32*fSLCLK to fSLCLK (1.024
kHz to 32.768 kHz if SLCLK is 32.768 kHz). The frequency of T0OUT is equal to the frequency of T0IN divided by (1+PRESET), where PRESET is the value
written to the TWMT0 register.
2. Configure the WATCHDOG clock to use either T0IN or
T0OUT by setting or clearing the TWCFG.WDCT0I bit.
3. Write the initial value into the WDCNT register. This
starts operation of the WATCHDOG and specifies the
maximum allowed number of WATCHDOG clock cycles
between service operations.
4. Lock the WATCHDOG registers and enable the
WATCHDOG Service Data Match Enable function by
setting bits 0, 1, 2, 3, and 5 in the TWCFG register.
5. Service the WATCHDOG by periodically writing the value 5C hex to the WDSDM register at an appropriate
rate. Servicing must occur at least once per period programmed into the WDCNT register, but no more than
once in a single WATCHDOG input clock cycle.
45
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14.0 Multi-Function Timer
The Multi-Function Timer (MFT16) module contains two independent timer/counter units called MFT1 and MFT2, each
containing a pair of 16-bit timer/counters. Each timer/counter
unit offers a choice of clock sources for operation and can be
configured to operate in any of the following modes:
14.1
TIMER STRUCTURE
Figure10 is a block diagram showing the internal structure of
each timer. There are two main functional blocks: a Timer/
Counter and Action block and a Clock Source block. The
Timer/Counter and Action block contains two separate timer/
counter units, called Timer/Counter I and Timer/Counter II (a
total of four timer/counter unit in both MFT1 and MFT2).
• Processor-Independent Pulse Width Modulation (PWM)
mode, which generates pulses of a specified width and
duty cycle, and which also provides a general-purpose
timer/counter
• Dual Input Capture mode, which measures the elapsed
time between occurrences of external events, and which
also provides a general-purpose timer/counter
• Dual Independent Timer mode, which generates system
timing signals or counts occurrences of external events
• Single Input Capture and Single Timer mode, which provides one external event counter and one system timer
14.1.1
Timer/Counter Block
The Timer/Counter block contains the following functional
blocks:
— two 16-bit counters, Timer/Counter I (TnCNT1) and
Timer/Counter II (TnCNT2)
— two 16-bit reload/capture registers, TnCRA and
TnCRB
— control logic necessary to configure the timer to operate in any of the four operating modes
— interrupt control and I/O control logic
The two timer units, MFT1 and MFT2, are identical in operation and separately programmable. Each timer unit uses two
I/O pins, called T1A and T1B (for Timer MFT1) or T2A and
T2B (for Timer MFT2). The timer I/O pins are alternate functions of the Port F I/O pins.
In a power-saving mode that uses the low-frequency (32.768
kHz) clock as the system clock, the synchronization circuit requires that the slow clock operate at no more than one-fourth
the speed of the 32.768 kHz system clock.
In the description of the timers, the lower-case letter “n” represents the timer number, either 1 or 2. For example, “TnA”
means I/O pin T1A or T2A.
14.1.2
Clock Source Block
The Clock Source block generates the signals used to clock
the two timer/counter registers. The internal structure of the
Clock Source block is shown in Figure11.
Clock Source
Timer/Counter
Action
External Event
Figure 10.
Timer/Counter
1
Reload/Capture
B
Timer/Counter
2
Interrupt A
Interrupt B
TnB
Multi-Function Timer Block Diagram
— slow clock (derived from the low-frequency oscillator or
divided from the high-speed oscillator)
There are two clock source selectors that allow the software
to independently select the clock source for each of the two
16-bit counters from any one of the following sources:
Prescaler
The 5-bit clock prescaler allows the software to run the timer
with a prescaled clock signal. The prescaler consists of a 5bit read/write prescaler register (TnPRSC) and a 5-bit down
counter. The system clock is divided by the value contained
in the prescaler register plus 1. Thus, the timer clock period
no clock (which stops the counter)
prescaled system clock
external event count based on TnB
pulse accumulate mode based on TnB
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TnA
PWM/Capture/Counter
Mode Select + Control
Counter Clock Source Select
—
—
—
—
Toggle/Capture/Interrupt
System
Clock
Clock Prescaler/Selector
Reload/Capture
A
46
Prescaler Register
TnPRSC
Reset
System
Clock
TnB
5-bit
Prescaler Counter
No Clock
Prescaled
Clock
Pulse
Accumulate
Counter I
Clock
Select
Counter II
Clock
Select
External
Event
Synchr.
Counter I
Clock
Counter II
Clock
Figure 11. Clock Source Block Diagram
can be set to any value from 1 to 32 divisions of the system
clock period. The prescaler register and down counter are
both cleared upon reset.
Pulse Accumulate Mode
The counter can also be configured to count prescaler output
clock pulses when the TnB is high and not count when TnB
is low, as illustrated in Figure12. The resulting count is an indicator of the cumulative time that TnB is high. This is called
the “pulse accumulate” mode. In this mode, an AND gate
generates a clock signal for the counter whenever a prescaler clock pulse is generated and TnB input is high. (The polarity of the TnB signal is programmable, so the counter can
count when TnB is low rather than high.) The pulse accumulate mode is not available in the capture modes (modes 2 and
4) because the TnB pin is used as one of the two capture inputs.
External Event Clock
The TnB I/O pin can be configured to operate as an external
event input clock for either of the two 16-bit counters. This input can be programmed to detect either rising or falling edges. The minimum pulse width of the external signal is one
system clock cycle. This means that the maximum frequency
at which the counter can run in this mode is one-half of the
system clock frequency. This clock source is not available in
the capture modes (modes 2 and 4) because the TnB pin is
used as one of the two capture inputs.
Prescaler Output
TnB
Counter Clock
Figure 12. Pulse Accumulate Mode Operation
Slow Clock
Limitations in Low-Power Modes
The slow clock is generated by the Dual Clock and Reset
(CLK2RES) module. The clock source is either the divided
fast clock or the external 32.768 kHz clock crystal (if available
and selected). The slow clock can be used as the clock
source for the two 16-bit counters. Because the slow clock
can be asynchronous to the system clock, a circuit is provided to synchronize the clock signal to the high-frequency system clock before it is used for clocking the counters. The
synchronization circuit requires that the slow clock operate at
no more than one-fourth the speed of the system clock.
The Power Save mode uses the low-frequency clock as the
system clock. In this mode, the slow clock cannot be used as
a clock source for the timers because both CLK and SLCLK
are driven then at the same frequency, and the 2:1 systemclock to input clock ratio needed for the synchronization cannot be maintained. However, the External Event Clock and
Pulse Accumulate Mode will still work, as long as the external
event pulses are at least the size of the whole slow-clock period. Using the prescaled system clock will also work, but at
a much slower rate than the original system clock.
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Some Power Save modes stops the system clock (the highfrequency and/or low-frequency clock) completely. If the system clock is stopped, the timer stops counting until the system clock resumes operation.
Upon reset, the timers are disabled. To configure and start
the timers, the software must write a set of values to the registers that control the timers. The registers are described in
Section14.5.
In the Idle or Halt mode, the system clock stops completely,
which stops the operation of the timers. In that case, the timers stop counting until the system clock resumes operation.
14.2.1
14.2
Mode 1 is the Processor-Independent Pulse Width Modulation (PWM) mode, which generates pulses of a specified
width and duty cycle, and which also provides a separate
general-purpose timer/counter.
TIMER OPERATING MODES
Each timer/counter unit can be configured to operate in any
of the following modes:
Figure13 is a block diagram of the Multi-Function Timer configured to operate in Mode 1. Timer/Counter I (TnCNT1)
functions as the time base for the PWM timer. It counts down
at the clock rate selected for the counter. When an underflow
occurs, the timer register is reloaded alternately from the
TnCRA and TnCRB register, and counting proceeds downward from the loaded value.
• Processor-Independent Pulse Width Modulation (PWM)
mode
• Dual Input Capture mode
• Dual Independent Timer mode
• Single Input Capture and Single Timer mode
Reload A = Time 1
TnCRA
TnAPND
Underflow
Timer I
Clock
Mode 1: Processor-Independent PWM
Timer/Counter I
TnCNT1
TnAIEN
TnA
TnAEN
Underflow
Reload B = Time 2
TnCRB
Timer II
Clock
Timer
Interrupt A
TnBIEN
Timer
Interrupt B
TnBPND
Timer/Counter II
TnCNT2
TnDIEN
Timer
Interrupt D
TnDPND
Clock
Selector
TnB
Figure 13. Mode 1: Processor-Independent PWM Block Diagram
On the first underflow, the timer is loaded from TnCRA, then
from TnCRB on the next underflow, then from TnCRA again
on the next underflow, and so on. Every time the counter is
stopped and restarted, it always obtains its first reload value
from TnCRA. This is true whether the timer is restarted upon
reset, after entering Mode 1 from another mode, or after stopping and restarting the clock with the Timer/Counter I clock
selector.
The timer can be configured to generate separate interrupts
upon reload from TnCRA and TnCRB. The interrupts can be
enabled or disabled under software control. The CPU can determine the cause of each interrupt by looking at the TnAPND
and TnBPND flags, which are set by the hardware upon each
occurrence of a timer reload.
In Mode 1, Timer/Counter II (TnCNT2) can be used either as
a simple system timer, an external event counter, or a pulse
accumulate counter. The clock counts down using the clock
selected with the Timer/Counter II clock selector. It generates
an interrupt upon each underflow if the interrupt is enabled
with the TnDIEN bit.
The timer can be configured to toggle the TnA output bit upon
each underflow. This generates a clock signal on TnA with
the width and duty cycle determined by the values stored in
the TnCRA and TnCRB registers. This is a “processor-independent” PWM clock because once the timer is set up, no
more action is required from the CPU to generate a continuous PWM signal.
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14.2.2
Mode 2: Dual Input Capture
the clock selected with the Timer/Counter I clock selector.
The TnA and TnB pins function as capture inputs. A transition received on the TnA pin transfers the timer contents to
the TnCRA register. Similarly, a transition received on the
TnB pin transfers the timer contents to the TnCRB register.
Each input pin can be configured to sense either rising or falling edges.
Mode 2 is the Dual Input Capture mode, which measures the
elapsed time between occurrences of external events, and
which also provides a separate general-purpose timer/
counter.
Figure14 is a block diagram of the Multi-Function Timer configured to operate in Mode 2. The time base of the capture
timer depends on Timer/Counter I, which counts down using
TnAIEN
Timer
Interrupt I
TnAPND
Capture A
TnCRA
TnA
Preset
TnAEN
Timer I
Clock
Timer/Counter I
TnCNT1
TnCPND
Underflow
TnCIEN
Preset
Timer
Interrupt I
TnBEN
Capture B
TnCRB
TnB
TnBPND
TnBIEN
Timer II
Clock
Timer/Counter II
TnCNT2
Timer
Interrupt I
TnDPND
Underflow
TnDIEN
Figure 14. Mode 2: Dual Input Capture Block Diagram
Timer
Interrupt II
The TnA and TnB inputs can be configured to preset the
counter to FFFF hex upon reception of a valid capture event.
In this case, the current value of the counter is transferred to
the corresponding capture register and then the counter is
preset to FFFF hex. Using this approach allows the software
to determine the on-time and off-time and period of an external signal with a minimum of CPU overhead.
counter. The enable bits for these events are TnAIEN, TnBIEN, and TnCIEN, respectively.
The values captured in the TnCRA register at different times
reflect the elapsed time between transitions on the TnA pin.
The same is true for the TnCRB register and the TnB pin. The
input signal on TnA or TnB must have a pulse width equal to
or greater than one system clock cycle.
Neither Timer/Counter I (TnCNT1) nor Timer/Counter II
(TnCNT2) can be configured to operate as an external event
counter or to operate in the pulse accumulate mode because
the TnB input is used as a capture input. Attempting to select
one of these configurations will cause one or both counters
to stop.
In Mode 2, Timer/Counter II (TnCNT2) can be used as a simple system timer. The clock counts down using the clock selected with the Timer/Counter II clock selector. It generates
an interrupt upon each underflow if the interrupt is enabled
with the TnDIEN bit.
There are three separate interrupts associated with the capture timer, each with its own enable bit and pending flag. The
three interrupt events are reception of a transition on TnA, reception of a transition on TnB, and underflow of the TnCNT1
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14.2.3
Mode 3: Dual Independent Timer/Counter
event counter. In addition, Timer/Counter I can generate a
50% duty cycle PWM signal on the TnA pin. The TnB pin can
be used as an external event input or pulse accumulate input
and can be used as the clock source for either Timer/Counter
I or Timer/Counter II. Both counters can also be clocked by
the prescaled system clock.
Mode 3 is the Dual Independent Timer mode, which generates system timing signals or counts occurrences of external
events.
Figure15 is a block diagram of the Multi-Function Timer configured to operate in Mode 3. The timer is configured to operate as a dual independent system timer or dual external
Reload A
TnCRA
TnAPND
Underflow
Timer I
Clock
Timer
Interrupt I
TnAIEN
Timer/Counter I
TnCNT1
TnA
TnAEN
Reload B
TnCRB
Underflow
Timer II
Clock
Timer/Counter II
TnCNT2
TnDIEN
Timer
Interrupt II
TnDPND
Clock
Selector
TnB
Figure 15.
Mode 3: Dual Independent Timer/Counter Block Diagram
Timer/Counter I (TnCNT1) counts down at the rate of the selected clock. Upon underflow, it is reloaded from the TnCRA
register and counting proceeds down from the reloaded value. In addition, the TnA pin is toggled on each underflow if
this function is enabled by the TnAEN bit. The initial state of
the TnA pin is software-programmable. When the TnA pin is
toggled from low to high, it sets the TnCPND interrupt pending flag and also generates an interrupt if the interrupt is enabled by the TnAIEN bit.
14.2.4
Mode 4 is the Single Input Capture and Single Timer mode,
which provides one external event counter and one system
timer.
Figure16 is a block diagram of the Multi-Function Timer configured to operate in Mode 4. This mode offers a combination
of Mode 3 and Mode 2 functions. Timer/Counter I is used as
a system timer as in Mode 3 and Timer/Counter II is used as
a capture timer as in Mode 2, but with a single input rather
than two inputs.
Because TnA toggles on every underflow, a 50% duty cycle
PWM signal can be generated on TnA without any further action from the CPU once the pulse train is initiated.
Timer/Counter I (TnCNT1) operates the same as in Mode 3.
It counts down at the rate of the selected clock. Upon underflow, it is reloaded from the TnCRA register and counting proceeds down from the reloaded value. The TnA pin is toggled
on each underflow if this function is enabled by the TnAEN
bit. When the TnA pin is toggled from low to high, it sets the
TnCPND interrupt pending flag and also generates an interrupt if the interrupt is enabled by the TnAIEN bit. A 50% duty
cycle PWM signal can be generated on TnA without any further action from the CPU once the pulse train is initiated.
Timer/Counter II (TnCNT2) counts down at the rate of the selected clock. Upon underflow, it is reloaded from the TnCRB
register and counting proceeds down from the reloaded value. In addition, each underflow sets the TnDPND interrupt
pending flag and generates an interrupt if the interrupt is enabled by the TnDIEN bit.
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Mode 4: Input Capture Plus Timer
50
Timer/Counter II (TnCNT1) counts down at the rate of the selected clock. The TnB pin functions as the capture input. A
transition received on TnB transfers the timer contents to the
TnCRB register. The input pin can be configured to sense either rising or falling edges.
The values captured in the TnCRB register at different times
reflect the elapsed time between transitions on the TnA pin.
The input signal on TnB must have a pulse width equal to or
greater than one system clock cycle.
There are two separate interrupts associated with the capture timer, each with its own enable bit and pending flag. The
two interrupt events are reception of a transition on TnB and
underflow of the TnCNT2 counter. The enable bits for these
events are TnBIEN and TnDIEN, respectively.
The TnB input can be configured to preset the counter to
FFFF hex upon reception of a valid capture event. In this
case, the current value of the counter is transferred to the
capture register and then the counter is preset to FFFF hex.
Reload A
TnCRA
TnAPND
Underflow
Timer I
Clock
TnAIEN
Timer/Counter I
TnCNT1
Timer
Interrupt I
TnA
TnATEN
TnBIEN
Timer
Interrupt I
TnBPND
Capture B
TnCRB
TnB
Preset
TnBEN
Timer II
Clock
TnDPND
Timer/Counter II
TnCNT2
TnDIEN
Timer
Interrupt II
Figure 16. Mode 4: Input Capture Plus Timer Block Diagram
Neither Timer/Counter I (TnCNT1) nor Timer/Counter II
(TnCNT2) can be configured to operate as an external event
counter or to operate in the pulse accumulate mode because
the TnB input is used as a capture input. Attempting to select
one of these configurations will cause one or both counters
to stop. In this mode, Timer/Counter II must be enabled at all
times.
14.3
rupts I and II are system interrupts T2A and T2B (IRQ11 and
IRQ10), respectively.
Table15 shows the events that trigger interrupts A, B, C, and
D in each of the four operating modes. Note that some interrupt sources are not used in some operating modes, as indicated by the notation “N/A” (Not Applicable) in the table.
TIMER INTERRUPTS
Each Multi-Function Timer unit has four interrupt sources,
designated A, B, C, and D. Interrupt sources A, B, and C are
mapped into a single system interrupt called Timer Interrupt
I, while interrupt source D is mapped into a system interrupt
called Timer Interrupt II. Each of the four interrupt sources
has its own enable bit and pending flag. The enable flags are
named TnAIEN, TnBIEN, TnCIEN, and TnDIEN. The pending flags are named TnAPND, TnBPND, TnCPND, and TnDPND.
14.4
TIMER I/O FUNCTIONS
Each Multi-Function Timer unit uses two I/O pins, called T1A
and T1B (for Timer MFT1) or T2A and T2B (for Timer MFT2).
The function of each pin depends on the timer operating
mode and the TnAEN and TnBEN enable bits. Table16
shows the functions of the pins in each operating mode, and
for each combination of enable bit settings.
For Multi-Function Timer unit MFT1, Timer Interrupts I and II
are system interrupts T1A and T1B (IRQ13 and IRQ12), respectively. For Multi-Function Timer unit MFT2, Timer Inter-
When pin TnA is configured to operate as a PWM output
(TnAEN = 1), the state of the pin is toggled on each under-
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flow of the TnCNT1 counter. In this case, the initial value on
the pin is determined by the TnAOUT bit. For example, to
start with TnA high, the software should set the TnAOUT bit
to 1 prior to enabling the timer clock. This option is available
only when the timer is configured to operate in Mode 1, 3, or
Table 15
Sys. Int.
Timer
Int. I
(TnA)
Timer
Int. II
(TnB)
Interrupt
pending
flag
Timer Interrupts Overview
Mode 1
Mode 2
Mode 3
Mode 4
PWM + Counter
Dual Input Capture +
counter
Dual Counter
Single Capture +
counter
TnAPND
TnCNT1 reload from
TnCRA
Input capture on TnA
transition
TnCNT1 reload from
TnCRA
TnCNT1 reload from
TnCRA
TnBPND
TnCNT1 reload from
TnCRB
Input Capture on TnB
transition
N/A
Input Capture on TnB
transition
TnCPND
N/A
TnCNT1 underflow
N/A
N/A
TnDPND
TnCNT2 underflow
TnCNT2 underflow
TnCNT2 reload from
TnCRB
TnCNT2 underflow
Table 16
TnAEN
TnBEN
I/O
TnA
TnB
14.5
4 (in other words, when TnCRA is not used in Capture
mode).
Timer I/O Functions
Mode 1
Mode 2
Mode 3
Mode 4
PWM + Counter
Dual Input Capture +
counter
Dual Counter
Single Capture +
counter
TnAEN=0
TnBEN=X
No Output
TnAEN=1
TnBEN=X
Capture TnCNT1 into
TnCRA
No Output toggle
No Output toggle
Toggle Output on
Capture TnCNT1 into
underflow of TnCNT1 TnCRA and preset
TnCNT1
Toggle Output on
underflow of TnCNT1
Toggle Output on
underflow of TnCNT1
TnAEN=X
TnBEN=0
Ext. Event or Pulse
Accumulate Input
Capture TnCNT1 into
TnCRB
Ext. Event or Pulse
Accumulate Input
Capture TnCNT2 into
TnCRB
TnAEN=X
TnBEN=1
Ext. Event or Pulse
Accumulate Input
Capture TnCNT1 into
TnCRB and preset
TnCNT1
Ext. Event or Pulse
Accumulate Input
Capture TnCNT2 into
TnCRB and preset
TnCNT2
CLKPS
TIMER REGISTERS
Clock Prescaler. When the timer is configured
to use the prescaled clock, the system clock is
divided by CLKPS+1 to produce the timer
clock. Thus, the system clock divide-by factor
can range from 1 to 32.
The following CPU-accessible registers are used to control
the Multi-Function Timers:
•
•
•
•
•
•
•
•
•
Clock Prescaler Register (TnPRSC)
Clock Unit Control Register (TnCKC)
Timer/Counter I Register (TnCNT1)
Timer/Counter II Register (TnCNT2)
Reload/Capture A Register (TnCRA)
Reload/Capture B Register (TnCRB)
Timer Mode Control Register (TnCTRL)
Timer Interrupt Control Register (TnICTL)
Timer Interrupt Clear Register (TnICLR)
14.5.1
14.5.2
The Clock Unit Control (TnCKC) register is a byte-wide, read/
write register that selects the clock source for each timer/
counter. This register is cleared upon reset, which disables
the timer/counters. The register format is shown below.
7
6
Reserved
5
4
C2CSEL
3
2
1
0
C1CSEL
Clock Prescaler Register (TnPRSC)
C1CSEL
The Clock Prescaler (TnPRSC) register is a byte-wide, read/
write register that holds the current value of the 5-bit clock
prescaler (CLKPS). This register is cleared upon reset. The
register format is shown below.
7
Clock Unit Control Register (TnCKC)
6
5
Reserved
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4
3
2
CLKPS
1
Counter I Clock Select. This 3-bit field defines
the clock mode for Timer/Counter I as follows:
000 = no clock (timer/counter I stopped)
001 = prescaled system clock
010 = external event on TnB (modes 1 and 3
only)
0
52
011 = pulse accumulate mode based on TnB
(modes 1 and 3 only)
100 = slow clock *
other values = undefined
Counter II Clock Select. This 3-bit field defines
the clock mode for Timer/Counter II as follows:
C2CSEL
transitions). When set (1), input pin TnA is sensitive to rising edges (low to high transitions).
TnB Edge Polarity. When cleared (0), input pin
TnB is sensitive to falling edges (high to low
transitions). When set (1), input pin TnB is sensitive to rising edges (low to high transitions). In
pulse accumulate mode, when this bit is set (1),
the counter is enabled only when TnB is high;
when this bit is cleared (0), the counter is enabled only when TnB is low.
TnA Enable. When set (1), the TnA pin is enabled to operate as a preset input or as a PWM
output, depending on the timer operating
mode. In Mode 2 (Dual Input Capture), a transition on the TnA pin presets the TnCNT1
counter to FFFF hex. In the other modes, TnA
functions as a PWM output. When this bit is
cleared (0), operation of the pin for the timer/
counter is disabled.
TnB Enable. When set (1), the TnB pin in enabled to operate in Mode 2 (Dual Input Capture) or Mode 4 (Single Input Capture and
Single Timer). A transition on the TnB pin presets the corresponding timer/counter to FFFF
hex (TnCNT1 in Mode 2 or TnCNT2 in Mode
4). When this bit is cleared (0), operation of the
pin for the timer/counter is disabled. This bit
setting has no effect in Mode 1 or Mode 3.
TnA Output Data. This is a status bit that indicates the current state of the TnA pin when the
pin is used as a PWM output. When set (1), the
TnA pin is high; when cleared (0), the TnA pin
is low. The hardware sets and clears this bit,
but the software can also read or write this bit
at any time and thus control the state of the output pin. In case of conflict, a software write has
precedence over a hardware update. This bit
setting has no effect when TnA is used as an
input.
TnBEDG
000 = no clock (Timer/Counter II stopped
modes 1, 2, and 3 only)
001 = prescaled system clock
010 = external event on TnB (modes 1 and 3
only)
011 = pulse accumulate mode based on TnB
(modes 1 and 3 only)
100 = slow clock *
other values = undefined
TnAEN
* Operation of the slow clock is determined by the CRCTRL.SCLK control bit, as described in Section11.6.1.
14.5.3
Timer/Counter I Register (TnCNT1)
TnBEN
The Timer/Counter I (TnCNT1) register is a word-wide, read/
write register that holds the current count value for Timer/
Counter I. The register contents are not affected by a reset
and are unknown upon power-up.
14.5.4
Timer/Counter II Register (TnCNT2)
The Timer/Counter II (TnCNT2) register is a word-wide, read/
write register that holds the current count value for Timer/
Counter II. The register contents are not affected by a reset
and are unknown upon power-up.
14.5.5
TnAOUT
Reload/Capture A Register (TnCRA)
The Reload/Capture A (TnCRA) register is a word-wide,
read/write register that holds the reload or capture value for
Timer/Counter I. The register contents are not affected by a
reset and are unknown upon power-up.
14.5.6
Reload/Capture B Register (TnCRB)
The Reload/Capture B (TnCRB) register is a word-wide,
read/write register that holds the reload or capture value for
Timer/Counter II. The register contents are not affected by a
reset and are unknown upon power-up.
14.5.7
14.5.8
The Timer Interrupt Control (TnICTL) register is a byte-wide,
read/write register that contains the interrupt enable bits and
interrupt pending bits for the four timer interrupt sources,
designated A, B, C, and D. The condition that causes each
type of interrupt depends on the operating mode, as shown
in Table15.
Timer Mode Control Register (TnCTRL)
The Timer Mode Control (TnCTRL) register is a byte-wide,
read/write register that sets the operating mode of the timer/
counter and the TnA and TnB pins. This register is cleared
upon reset. The register format is shown below.
7
6
Reserved TnAOUT
MDSEL
TnAEDG
5
4
TnBEN
TnAEN
3
2
TnBEDG TnAEDG
1
Timer Interrupt Control Register (TnICTL)
This register is cleared upon reset. The register format is
shown below.
0
MDSEL
Mode Select. This 2-bit field sets the operating
mode of the timer/counter as follows:
7
6
5
4
3
TnDIEN
TnCIEN
TnBIEN
TnAIEN
TnDPND
TnAPND
00 = Mode 1: PWM plus system timer
01 = Mode 2: Dual Input Capture plus system
timer
10 = Mode 3: Dual Timer/Counter
11 = Mode 4: Single Input Capture and Single
Timer
TnA Edge Polarity. When cleared (0), input pin
TnA is sensitive to falling edges (high to low
53
2
1
0
TnCPND TnBPND TnAPND
Timer Interrupt Source A Pending. When this
bit is set (1), it indicates that timer interrupt condition “A” has occurred. When this bit is cleared
(0), it indicates that the interrupt condition has
not occurred. For an explanation of interrupt
conditions A, B, C, and D, see Table15
This bit can be set by the hardware or by the
software. To clear this bit, the software must
use the Timer Interrupt Clear Register (TnI-
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CLR). Any attempt by the software to directly
write a 0 to this bit is ignored.
Timer Interrupt Source B Pending. See the description of TnAPND.
Timer Interrupt Source C Pending. See the description of TnAPND.
Timer Interrupt Source D Pending. See the description of TnAPND.
Timer Interrupt A Enable. When set (1), this bit
enables an interrupt on each occurrence of interrupt condition “A.” When cleared (0), an occurrence of interrupt condition “A” does not
generate an interrupt to the CPU, but still sets
the associated pending flag (TnAPND). For an
explanation of interrupt conditions A, B, C, and
D, see Table15.
Timer Interrupt B Enable. See the description
of TnAIEN.
Timer Interrupt C Enable. See the description
of TnAIEN.
Timer Interrupt D Enable. See the description
of TnAIEN.
TnBPND
TnCPND
TnDPND
TnAIEN
TnBIEN
TnCIEN
TnDIEN
14.5.9
Timer Interrupt Clear Register (TnICLR)
The Timer Interrupt Clear (TnICLR) register is a byte-wide,
write-only register that allows the software to clear the TnAPND, TnBPND, TnCPND, and TnDPND bits in the Timer Interrupt Control (TnICTRL) register. The register format is shown
below.
7 6 5 4
Reserved
TnACLR
TnBCLR
TnCCLR
TnDCLR
3
TnDCLR
2
TnCCLR
1
TnBCLR
0
TnACLR
Timer Pending A Clear. When written with a 1,
the Timer Interrupt Source A Pending bit
(TnAPND) is cleared in the Timer Interrupt
Control register (TnICTL). Writing a 0 to the
TnACLR bit has no effect.
Timer Pending B Clear. See the description of
TnACLR.
Timer Pending C Clear. See the description of
TnACLR.
Timer Pending D Clear. See the description of
TnACLR.
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54
15.0 MICROWIRE/SPI
MICROWIRE/PLUS is a synchronous serial communications
protocol, originally implemented in National Semiconductor's
COPS™ and HPC™ families of microcontrollers to minimize
the number of connections, and therefore the cost, of communicating with peripherals.
5
The device has an enhanced MICROWIRE interface module
(MWSPI) that can communicate with all peripherals that conform to MICROWIRE or Serial Peripheral Interface (SPI)
specifications. This enhanced MICROWIRE interface is capable of operating as either a master or slave. Figure17
shows a typical enhanced MICROWIRE interface application.
Chip Select Lines
MCS
MCS
CS
Master
8-Bit
A/D
CS
LCD
Display
driver
1K Bit
EEPROM
I/O
Lines
DO SK DI
CS
CS
VF
Display
Driver
S K DI
DO SK DI
Slave
I/O
Lines
SK DI
MDIDO
MDIDO
MDODI
MDODI
MSK
MSK
Figure 17. MICROWIRE Interface
The enhanced MICROWIRE interface module includes the
following features:
—
—
—
—
—
—
—
—
—
—
—
15.1
In slave mode, an optional fourth signal (MCS) may be used
to enable the slave transmit. At any given time, only one
slave can respond to the master. Each slave device has its
own chip select signal (MCS) for this purpose.
Programmable operation as a Master or Slave
Programmable shift-clock frequency (master only)
8-bit serial I/O data shift register
Two modes of clocking data
Serial clock can be low or high when idle
Double read buffer (master mode only)
Busy flag, Read Buffer Full flag, and Overrun flag for
polling and as interrupt sources
Supports multiple masters
Maximum bit rate of 4M bits/second (master and slave)
Supports very low-end slaves with the Slave Ready
output
Echo back enable/disable (Slave only)
The MICROWIRE interface allows the device to operate either as a master or slave. This is configured via the MMNS
bit.
Figure18 shows a block diagram of the enhanced MICROWIRE serial interface in the device.
15.1.1
Shifting
The MICROWIRE interface is a full duplex transmitter/receiver. An 8-bit shifter is used for both transmitting and receiving.
The transmitted data is shifted out through MDODI pin (master mode) or MDIDO pin (slave mode), starting with the most
significant bit. At the same time, the received data is shifted
in through MDIDO pin (master mode) or MDODI pin (slave
mode), also starting with the most significant bit first.
MICROWIRE OPERATION
The MICROWIRE interface allows several devices to be connected on one three-wire system. At any given time, one of
these devices operates as the master while all other devices
operate as slaves.
The shift in and shift out are controlled by the MSK clock. In
each clock cycle of MSK, one bit of data is transmitted/received. The 8-bit shifter is accessible via the MWDAT register. Reading the MWDAT register returns the value in the
read buffer. Writing to the MWDAT register updates the 8-bit
shifter.
The master device supplies the synchronous clock (MSK) for
the serial interface and initiates the data transfer. The slave
devices respond by sending (or receiving) the requested data. Each slave device uses the master’s clock for serially
shifting data out (or in), while the master shifts the data in (or
out).
15.1.2
Reading
The enhanced MICROWIRE interface implements a double
buffer on read. As illustrated in Figure18, the double read
buffer consists of the 8-bit shifter and a buffer, called the read
buffer.
The three-wire system includes: the serial data in signal
(MDIDO for master mode, MDODI for slave mode), the serial
data out signal (MDODI for master mode, MDIDO for slave
mode) and the serial clock (MSK).
The 8-bit shifter loads the read buffer with new data when the
data transfer sequence is completed and previous data in the
55
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Interrupt Request
MCS
Control + Status
MRDY
Read Data
Read Buffer
Write Data
8
MWDAT
Slave
8-bit Shift Register
Data Out
Master
MDODI
Slave
Data In
Master
MDIDO
MSK
MSK
Clock Prescaler + Select
Master
System Clock
Figure 18. MICROWIRE Block Diagram
read buffer has been read. In master mode, an Overrun error
occurs when the read buffer is full, the 8-bit shifter is full and
a new data transfer sequence starts.
The clocking modes are selected with the MSKM bit. The
MIDL bit allows selection of the value of MSK when it is idle
(when there is no data being transferred). Various MSK clock
frequencies can be programmed via the MCDV bits. Figures
19, 20, 21, and 22 show the data transfer timing for the normal and the alternate modes with the MIDL bit equal to 0 and
equal to 1.
The “Receive Buffer Full” (MRBF) bit indicates if the MWDAT
register holds valid data. The MOVR bit indicates that an
overrun condition has occurred.
15.1.3
Writing
The “MICROWIRE Busy” (MBSY) bit indicates whether the
MWDAT register can be written. All write operations to the
MWDAT register update the shifter while the data contained in
the read buffer is not affected. Undefined results will occur if
the MWDAT register is written while the MBSY bit is set to 1.
Note that when data is shifted out on MDODI (master mode)
or MDIDO (slave mode) on the leading edge of the MSK
clock, bit 6 is shifted out on the second leading edge of the
MSK clock. When data are shifted out on MDODI (master
mode) or MDIDO (slave mode) on the trailing edge of MSK,
bit 6 is shifted out on the first trailing edge of MSK.
15.1.4
15.2
Clocking Modes
Two clocking modes are supported: the normal mode and the
alternate mode.
In Master mode, the MSK pin is an output for the shift clock,
MSK. When data is written to the 8-bit shifter (MWDAT register), eight clocks are generated to shift the eight bits of data
and then MSK goes idle again. The MSK idle state can be either high or low, depending on the MIDL bit.
In the normal mode, the output data is shifted out on the rising edge of MSK on the MDODI pin (master mode) or MDIDO
(slave mode). The input data, which is received via MDIDO
pin (master mode) or the MDODI pin (slave mode), is sampled on the fallowing edge of MSK.
If MDIDO is sampled on the leading edge of MSK, a sequence of eight clock is generated after a delay that may
range from half a period of MSK to one and a half periods of
MSK. If MDIDO is sampled on the trailing edge of MSK, a se-
In the alternate mode, the output data is shifted out on the rising edge of MSK on the MDODI pin (master mode) or MDIDO
pin (slave mode). The input data, which is received via MDIDO pin (master mode) or MDODI pin (slave mode), is sampled on the falling edge of MSK.
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MASTER MODE
56
End of Transfer
MSK
Data Out
MSB
msb-1
msb-2 5
Bit 1
Bit 0
(lsb)
Data In
MSB
msb-1
msb-2
Bit 1
Bit 0
(lsb)
Shift Out
Figure 19.
Sample Point
Normal Mode, MIDL Bit = 0
End of Transfer
MSK
Data Out
msb
msb-1
msb-2
Bit 1
Bit 0 (lsb)
Data In
msb
msb-1
msb-2
Bit 1
Bit 0 (lsb)
Shift Out
Figure 20.
Sample Point
Normal Mode, MIDL Bit = 1
End of Transfer
MSKn
Data Out
msb
msb-1
msb-2
Bit 1
Bit 0 (lsb)
Data In
msb
msb-1
msb-2
Bit 1
Bit 0 (lsb)
Shift Out
Sample Point
Figure 21. Alternate Mode, MIDL Bit = 0
quence of eight clocks is generated after a delay that may
range from zero to one period of MSK.
abled when MCS is active. MWCTL3.MBFL must be cleared
to 0.
15.3
The slave starts driving MDIDO when MCS is activated. The
most significant bit (MSB) of the 8-bit shifter is output onto the
MDIDO pin first. After eight clocks, the data transfer is completed.
SLAVE MODE
In Slave mode, the MSK pin is an input for the shift clock
MSK. MDIDO and MRDY (an optional signal) are placed in
TRI-STATE mode when MCS is inactive. Data transfer is en-
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End of Transfer
MSKn
Data Out
msb
msb-1
msb-2
Bit 1
Bit 0 (lsb)
Data In
msb
msb-1
msb-2
Bit 1
Bit 0 (lsb)
Shift Out
Sample Point
Figure 22. Alternate Mode, MIDL Bit = 1
If a new shift process starts before MWDAT was written, i.e.,
while MWDAT does not contain any valid data, and the “Echo
Enable” (MECH) bit is set to 1, the data received from MDODI is transmitted on MDIDO in addition to being shifted to
MWDAT. If the MECH bit is cleared to 0, the data transmitted
on MDIDO is the data held in the MWDAT register, regardless of its validity. The master may negate the MCS signal to
synchronize the bit count between the master and the slave.
In the case that the slave is the only slave in the system, MCS
can be tied to VSS .
An additional output signal, MRDY, may be used. This signal
supports very low-end slaves by indicating to the master the
current status of the MICROWIRE channel.
Upon reset, MRDY is inactive. Before transfer starts, MRDY
should be asserted by setting the MWCTL3.MRDY bit.
MRDY is de-asserted when the data transfer of one data byte
has been completed.
MRDY is asserted again only by writing 1 to the MRDY bit.
This should be done after the MWDAT register is read.
End of Transfer
MSK
MDIDO
Bit 7 Out
(MSB)
Bit 6
Bit 5
MDODI
Bit 7 In
(MSB)
Bit 6
Bit 5
Bit 1
Bit 1
Bit 0
Bit 0
MCS
MRDY
Shift Out
Sample Point
READY Bit
Set to 1
Figure 23. Slave, Normal Mode, MIDL Bit = 0, MRBF Bit = 1
15.4
• When an overrun condition occurs (MOVR is set to 1) and
the “Enable Interrupt on Overrun” bit is set (MEIO=1). This
usage is restricted to master mode.
INTERRUPT GENERATION
An interrupt is generated in any of the following cases:
• When the read buffer is full (MRBF=1) and the “Enable Interrupt for Read” bit is set (MEIR=1).
• Whenever the shifter is not busy, i.e. the MBSY bit is
cleared (MBSY=0) and the “Enable Interrupt for Write” bit
is set (MEIW=1).
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Figure24 illustrates the various interrupt capabilities of this
module.
58
For normal operation, the CPU should first read the received
data, thus allowing pending received data to be transferred
from the shifter into the MWDAT register, before it writes the
next transmit data into the MWDAT address, which loads the
shifter directly. (MWSTAT.MBSY=0 is an indicator that the
shifter is empty and ready to receive the next transmit data.)
Otherwise, a second received data byte pending in the shifter
may get overwritten by the transmit byte.
MEIO
MOVR = 1
MWSPI
Interrupt
MRBF = 1
MEIR
The MWDAT register contains unknown data following a reset operation.
MBSY = 0
15.5.2
MEIW
The MWCTL1 register is a byte-wide, read/write register that
controls the operating mode of the MICROWIRE interface
module. Upon reset, all non-reserved bits are cleared to 0.
The register format is shown below.
Figure 24. MWSPI Interrupts
15.5
MICROWIRE INTERFACE REGISTERS
7
The software interacts with the MICROWIRE interface by accessing the MICROWIRE registers. There are five such registers:
•
•
•
•
•
6 5 4
Reserved
MMNS
MICROWIRE Data Register (MWDAT)
MICROWIRE Control 1 Register (MWCTL1)
MICROWIRE Control 2 Register (MWCTL2)
MICROWIRE Control 3 Register (MWCTL3)
MICROWIRE Status Register (MWSTAT)
15.5.1
MICROWIRE Control 1 Register (MWCTL1)
MSKM
MICROWIRE Data Register (MWDAT)
The MWDAT register is a byte-wide, read/write register used
to transmit and receive data through the MDODI and MDIDO
pins. Figure25 shows the hardware structure of the register.
Data In
SHIFTER
Write
MIDL
Data Out
8
Read
READ BUFFER
MEN
Figure 25. MWDAT Register Structure
Reading the MWDAT register returns the data received
through the MDIDO pin in master mode or the MDODI pin in
slave mode. This data is read from a buffer. After the CPU
reads the buffer, if new data is ready in the shifter, the hardware immediately transfers the new value from the shifter to
the buffer.
Table 17
Writing the MWDAT register loads the shifter directly without
buffering, thus overwriting any existing data in the shifter. The
data byte is shifted out through the MDODI pin in master
mode or through the MDIDO pin in slave mode, most significant bit first.
The MWDAT register should be accessed only after a MICROWIRE interrupt. Before the CPU reads the register, the
Read Buffer Full status bit should be set (MWSTAT.MRBF=1). Before the CPU writes the register, the MICROWIRE Busy status bit should be cleared
(MWSTAT.MBSY=0).
59
3
MEN
2
MIDL
1
MSKM
0
MMNS
MICROWIRE Master/Slave Select. When
cleared to 0, the device operates as a slave.
When set to 1, the device operates as the master.
MICROWIRE Clocking Mode. When cleared to
0, the device uses the normal clocking mode.
When set to 1, the device uses the alternate
clocking mode. In the normal mode, the output
data is clocked out on the falling edge of MSK
and the input data is sampled on the rising
edge of MSK. In the alternate mode, the output
data is clocked out on the rising edge of MSK
and the input data is sampled on the falling
edge of MSK.
MICROWIRE Idle. This bit sets the value of the
MSK output when the MICROWIRE interface is
idle: 0 for low or 1 for high. This bit should be
changed only when the MICROWIRE interface
module is disabled (MEN=0) or when no bus
transaction is in progress (MWSTAT.MBSY=0).
MICROWIRE Enable. This bit enables (1) or
disables (0) the MICROWIRE interface module. Clearing this bit disables the module,
clears the status bits in the MICROWIRE status
register (the MBSY, MRBF, and MOVR flags in
MWSTAT), and places the MICROWIRE interface pins in the states described in Table17.
Pin Values with MICROWIRE Disabled
MSK
Master: MnIDL Bit
Slave: input
MCS
Input
MDIDO
Master: input
Slave: TRI-STATE
MDODI
Master: known Value
Slave: input
MRDY
TRI-STATE
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15.5.3
MICROWIRE Control 2 Register (MWCTL2)
The MWCTL2 register is a byte-wide, read/write register that
controls the clock divider used to generate the MSK shift
clock from the system clock. The MICROWIRE interface
module generates the MSK clock only in master mode, so
this register is ignored in slave mode. Upon reset, all non-reserved bits are cleared to 0. The register format is shown below.
7
MDV1
MCDV
MDV1
15.5.4
6
5
4
3
2
MCDV
1
MECH
0
MICROWIRE Clock Divider Value. This 7-bit
field specifies the divide-by factor used for generating the MSK shift clock from the system
clock. The divide-by factor is 2*(MCDV+1).
This allows selection of a divide-by ratio from 2
to 256. This field is ignored in slave mode
(MWCTL1.MMNS=0) or if the MDV1 bit is set.
MICROWIRE Clock Divide-by-1. When cleared
to 0, the MSK shift clock rate is determined by
the MCDV field. When set to 1, the divide-by
factor is 1 and the MSK clock operates at the
same rate as the system clock. This bit is ignored in slave mode (MWCTL1.MMNS=0).
MEIO
MEIR
MICROWIRE Control 3 Register (MWCTL3)
The MWCTL3 register is a byte-wide, read/write register that
controls the MRDY pin and enables or disables the MICROWIRE interrupts and echo back function. Upon reset, all
non-reserved bits are cleared to 0. When the software writes
to this register, the reserved bits must be written with 0 for the
MICROWIRE interface to function properly. The register format is shown below.
MEIW
7
6
5
4
3
2
1
0
Reserved MEIW MEIR MEIO MECH MRDY MBFL
MBFL
MRDY
bit is ignored entirely in master mode
(MWCTL1.MMNS=1).
Reading this bit returns an unknown value.
MICROWIRE Echo Back. This bit enables (1)
or disables (0) the echo back function in slave
mode. This bit should be written only when the
MICROWIRE interface is idle (MWSTAT.MBSY=0). The MECH bit is ignored in master
mode.
In the echo back mode, MDODI is transmitted
(echoed back) on MDIDO if MWDAT does not
contain any valid data. With the echo back
function disabled, the data held in the MWDAT
register is transmitted on MDIDO, whether or
not the data is valid.
MICROWIRE Enable Interrupt on Overrun.
This bit enables or disables the overrun error
interrupt. When set to 1, an interrupt is generated when the Receive Overrun Error flag
(MWSTAT.MOVR) is set. Otherwise, no interrupt is generated when an overrun error occurs. This bit should only be enabled in master
mode.
MICROWIRE Enable Interrupt for Read. When
set to 1, an interrupt is generated when the
Read Buffer Full flag (MWSTAT.MRBF) is set.
Otherwise, no interrupt is generated when the
read buffer is full.
MICROWIRE Enable Interrupt for Write. When
set to 1, an interrupt is generated when the
Busy bit (MWSTAT.MBSY) is cleared, which indicates that a data transfer sequence has been
completed and the read buffer is ready to receive the new data. Otherwise, no interrupt is
generated when the Busy bit is cleared.
15.5.5
The MICROWIRE Status Register is a byte-wide, read-only
register that shows the current status of the MICROWIRE interface module. Upon reset, all non-reserved bits are cleared
to 0. The register format is shown below.
MICROWIRE Buffer Length. This bit sets the
data buffer length in slave mode to either one
or two bytes.
When MBFL is cleared to 0, the buffer length is
one byte. The MRDY pin goes high when transmission or reception of one data byte is completed. This is the proper setting for slave
mode.
When MBFL is set to 1, the buffer length is two
bytes. The MRDY pin goes high when the read
buffer is full and a subsequent transmission or
reception of a data byte is completed. This setting is only intended for master mode and
should not be used for slave mode.
MICROWIRE Ready. This write-only bit allows
the software to control the MRDY pin when the
device operates in slave mode. Writing a 1 to
this bit position asserts the MRDY pin (makes
it go low). This should be done only when the
MICROWIRE interface is idle (MWSTAT.MBSY=0).
The hardware changes the MRDY pin from low
to high at the end of a data transfer, as defined
by the MBFL bit.
Writing a 0 to MRDY has no effect. The MRDY
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MICROWIRE Status Register (MWSTAT)
7 6 5 4
Reserved
MBSY
60
3
MOVR
2
Reserved
1
MRBF
0
MBSY
MICROWIRE Busy. This bit, when set to 1, indicates that the MICROWIRE shifter is busy.
In master mode, MBSY is set to 1 when the
MWDAT register is written. In slave mode, this
bit is set to 1 on the first leading edge of MSK
when MCS is asserted or when the MWDAT
register is written, whatever occurs first.
In both master and slave modes, this bit is
cleared to 0 when the MICROWIRE data transfer sequence is completed and the read buffer
is ready to receive the new data; in other
words, when the previous data held in the read
buffer has already been read.
If the previous data in the read buffer has not
been read and a new data has been received
into the shift register, the MBSY will not be
cleared, as the transfer could not be completed. This is because the contents of the shift
MRBF
MOVR
register could not be copied into the read buffer.
MICROWIRE Read Buffer Full. This bit, when
set to 1, indicates that the MICROWIRE read
buffer is full and ready to be read by the software. It is set to 1 when the shifter loads the
read buffer, which occurs upon completion of a
transfer sequence if the read buffer is empty.
The MRBF bit is updated when the MWDAT
register is read. At that time, the MRBF bit is
cleared to 0 if the shifter does not contain any
new data (in other words, the shifter is not receiving data or has not yet received a full byte
of data). The MRBF bit remains set to 1 if the
shifter already holds new data at the time that
MWDAT is read. In that case, MWDAT is immediately reloaded with the new data and is ready
to be read by the software.
MICROWIRE Receive Overrun Error. This bit,
when set to 1 in master mode, indicates that a
receive overrun error has occurred. This error
occurs when the read buffer is full, the 8-bit
shifter is full, and a new data transfer sequence
starts. This bit is undefined in slave mode.
The MOVR bit, once set, remains set until
cleared by the software. The software clears
this bit by writing a 1 to its bit position. Writing
a 0 to this bit position has no effect. No other
bits in the MWSTAT register are affected by a
write operation to the register.
61
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16.0 USART
The USART module is a full-duplex Universal Synchronous/
Asynchronous Receiver/Transmitter that supports a wide
range of software-programmable baud rates and data formats. It handles automatic parity generation and several error detection schemes. There are one or two independent
USART modules in each device, depending on the package
type.
stage based on the programmed baud rate divisor to create
the baud rate clock.
The Control and Error Detection block contains the USART
control registers, control logic, error detection circuit, parity
generator/checker, and interrupt generation logic. The control registers and control logic determine the data format,
mode of operation, clock source, and type of parity used. The
error detection circuit generates parity bits and checks for
parity, framing, and overrun errors.
Each USART module offers the following features:
— Full-duplex double-buffered receiver/transmitter
— Synchronous or asynchronous operation
— Programmable
baud
rate
from
SYS_CLK/
[2*(1+2^11)*16] up to SYSCLK/2 for USART configured to run in synchronous mode
— Programmable
baud
rate
from
SYS_CLK/
[16*(1+2^11)*16] up to SYSCLK/16 for USART configured to run in asynchronous mode
— Programmable framing formats: seven, eight, or nine
data bits; one or two stop bits; and odd, even, mark,
space, or no parity
— Hardware parity generation for data transmission and
parity check for data reception
— Interrupts on “transmit ready” and “receive ready” conditions, separately enabled
— Software-controlled break transmission and detection
— Internal diagnostic capability
— Automatic detection of parity, framing, and overrun errors
16.1
16.2
16.2.1
Asynchronous Mode
The asynchronous mode of the USART enables the device
to communicate with other devices using just two communication signals: transmit and receive.
In the asynchronous mode, the transmit shift register (TSFT)
and the transmit buffer (UnTBUF) double-buffer the data for
transmission. To transmit a character, a data byte is loaded
in the UnTBUF register. The data is then transferred to the
TSFT register. While the TSFT is shifting out the current character (LSB first) on the TDXn pin, the UnTBUF register is
loaded by software with the next byte to be transmitted.
When TSFT finishes transmission of the last stop bit of the
current frame, the contents of UnTBUF are transferred to the
TSFT register and the Transmit Buffer Empty flag (UnTBE) is
set. The UnTBE flag is automatically reset by the USART
when the software loads a new character into the UnTBUF
register. During transmission, the UnXMIP bit is set high by
the USART. This bit is reset only after the USART has sent
the last stop bit of the current character and the UnTBUF register is empty. The UnTBUF register is a read/write register.
The TSFT register is not user accessible.
FUNCTIONAL OVERVIEW
Figure26 is a block diagram of the USART module showing
the basic functional units in the USART:
— Transmitter
— Receiver
— Baud Rate Generator
— Control and Error Detection
Note: In the description of the USART, the lower-case letter
“n” represents the USART number. For example, TDXn
means TDX1 or TDX2.
In asynchronous mode, the input frequency to the USART is
16 times the baud rate. In other words, there are 16 clock cycles per bit time. In asynchronous mode the baud rate generator is always the USART clock source.
The Transmitter block consists of an 8-bit transmit shift register and an 8-bit transmit buffer. Data bytes are loaded in
parallel from the buffer into the shift register and then shifted
out serially on the TDXn pin.
The receive shift register (RSFT) and the receive buffer (UnRBUF) double buffer the data being received. The USART
receiver continuously monitors the signal on the RDXn pin for
a low level to detect the beginning of a start bit. Upon sensing
this low level, the USART waits for seven input clock cycles
and samples again three times. If all three samples still indicate a valid low, then the receiver considers this to be a valid
start bit, and the remaining bits in the character frame are
each sampled three times, around the mid-bit position. For
any bit following the start bit, the logic value is found by majority voting, i.e. the two samples with the same value define
the value of the data bit. Figure27 illustrates the process of
start bit detection and bit sampling.
The Receiver block consists of an 8-bit receive shift register
and an 8-bit receive buffer. Data is received serially on the
RDXn pin and shifted into the shift register. Once eight bits
have been received, the contents of the shift register are
transferred in parallel to the receive buffer.
The Transmitter and Receiver blocks both contain extensions for 9-bit data transfers, as required by the 9-bit and
loopback operating modes.
The Baud Rate Generator generates the clock for the synchronous and asynchronous operating modes. It consists of
two registers and a two-stage counter. The registers are used
to specify a prescaler value and a baud rate divisor. The first
stage of the counter divides the USART clock based on the
value of the programmed prescaler to create a slower clock.
The second stage of the counter divides the output of the first
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USART OPERATION
The USART has two basic modes of operation: synchronous
and asynchronous. In addition, there are two specialpurpose synchronous and asynchronous modes, called attention and diagnostic. This section describes the operating
modes of the USART.
Serial data input on the RDXn pin is shifted into the RSFT
register. Upon receiving the complete character, the contents
of the RSFT register are copied into the UnRBUF register
and the Receive Buffer Full flag (UnRBF) is set. The UnRBF
62
Transmitter
TDXn
Baud clock
Sys_clk
Internal Bus
Control and
Error Detection
CKXn
Baud Rate Generator
Parity
Generator/Checker
Baud Clock
Receiver
RDXn
Figure 26. USART Block Diagram
flag is automatically reset when software reads the character
from the UnRBUF register. The RSFT register is not user accessible.
16
1
2
3
4
5
6
7
8
Sample
9
10
11
12
13
14
15
1
2
1
Sample
DATA (LSB)
STARTBIT
16
16
3
4
5
6
7
8
9
10
11
12
13
14
15
16
1
Sample
DATABIT
Figure 27. USART Asynchronous Communication
16.2.2
In the synchronous mode, the transmit shift register (TSFT)
and the transmit buffer (UnTBUF) double-buffer the data for
transmission. To transmit a character, a data byte is loaded
in the UnTBUF register. The data is then transferred to the
TSFT register. The TSFT register shifts out one bit of the current character, LSB first, on each rising edge of the clock.
While the TSFT is shifting out the current character on the
TDXn pin, the UnTBUF register may be loaded by the software with the next byte to be transmitted. When the TSFT finishes transmission of the last stop bit within the current
frame, the contents of UnTBUF are transferred to the TSFT
Synchronous Mode
The synchronous mode of the USART enables the device to
communicate with other devices using three communication
signals: transmit, receive, and clock. In this mode, data bits
are transferred synchronously with the USART clock signal.
Data bits are transmitted on the rising edges and received on
the falling edges of the clock signal, as shown in Figure28.
Data bytes are transmitted and received least significant bit
(LSB) first.
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The operation of the USART transmitter is not affected by the
selection of this mode. The value of the ninth bit to be transmitted is programmed by setting or clearing a bit called
UnXB9 in the USART Frame Select Register. The value of
the ninth bit received is read from another register bit called
UnRB9 in the USART Status Register.
CKX
TDX
16.2.4
The Diagnostic mode is available for testing of the USART. In
this mode, the TDXn and RDXn pins are internally connected
together, and data that is shifted out of the transmit shift register is immediately transferred to the receive shift register.
This mode supports only the 9-bit data format with no parity.
The number of start and stop bits is programmable.
RDX
Sample Input
Figure 28. USART Synchronous Communication
16.2.5
register and the Transmit Buffer Empty flag (UnTBE) is set.
The UnTBE flag is automatically reset by the USART when
the software loads a new character into the UnTBUF register.
During transmission, the UnXMIP bit is set high by the
USART. This bit is reset only after the USART has sent the
last frame bit of the current character and the UnTBUF register is empty.
1
1a
1b
1c
START
BIT
7 BIT DATA
S
START
BIT
7 BIT DATA
START
BIT
7 BIT DATA
PA
START
BIT
7 BIT DATA
PA
2S
S
2S
Figure 29. Seven Data Bit Frame Options
The format shown in Figure30 consists of one start bit, eight
data bits (excluding parity), and one or two stop bits. If parity
bit generation is enabled by setting the UnPEN bit, a parity
bit is generated and transmitted following the eight data bits.
The transmitter and receiver may be clocked from either an
external source provided to the CKXn pin or by the internal
baud rate generator. In the latter case, the clock signal is
placed on the CKXn pin as an output.
2
Attention Mode
2a
The Attention mode is available for networking this device
with other processors. This mode requires the 9-bit data format with no parity. The number of start bits and number of
stop bits are programmable. In this mode, two types of 9-bit
characters are sent on the network: address characters consisting of 8 address bits and a 1 in the ninth bit position and
data characters consisting of 8 data bits and a 0 in the ninth
bit position.
2b
2c
START
BIT
8 BIT DATA
START
BIT
8 BIT DATA
START
BIT
8 BIT DATA
PA
START
BIT
8 BIT DATA
PA
S
2S
S
2S
Figure 30. Eight Data Bit Frame Options
While in Attention mode, the USART receiver monitors the
communication flow but ignores all characters until an address character is received. Upon the receipt of an address
character, the contents of the receive shift register are copied
to the receive buffer. The UnRBF flag is set and an interrupt
(if enabled) is generated. The UnATN bit is automatically reset to zero, and the USART begins receiving all subsequent
characters. The software must examine the contents of the
UnRBUF register and respond by accepting the subsequent
characters (by leaving the UnATN bit reset) or waiting for the
next address character (by setting the UnATN bit again).
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Frame Format Selection
The format shown in Figure29 consists of a start bit, seven
data bits (excluding parity), and one or two stop bits. If parity
bit generation is enabled by setting the UnPEN bit, a parity
bit is generated and transmitted following the seven data bits.
The receive shift register (RSFT) and the receive buffer
(UnRBUF) double-buffer the data being received. Serial data
received on the RDXn pin is shifted into the RSFT register at
the first falling edge of the clock. Each subsequent falling
edge of the clock causes an additional bit to be shifted into
the RSFT register. The USART assumes a complete character has been received after the correct number of rising edges on CKXn (based on the selected frame format) have been
detected. Upon receiving a complete character, the contents
of the RSFT register are copied into the UnRBUF register
and the Receive Buffer Full flag (UnRBF) is set. The UnRBF
flag is automatically reset when the software reads the character from the UnRBUF register.
16.2.3
Diagnostic Mode
The format shown in Figure31 consists of one start bit, nine
data bits, and one or two stop bits. This format also supports
the USART attention feature. When operating in this format,
all eight bits of UnTBUF and UnRBUF are used for data. The
ninth data bit is transmitted and received using two bits in the
control registers, called UnXB9 and UnRB9. Parity is not
generated or verified in this mode.
16.2.6
Baud Rate Generator
The Baud Rate Generator creates the basic baud clock from
the system clock. The system clock is passed through a two-
64
3
3a
Table 18 Prescaler Factors
START
BIT
9 BIT DATA
START
BIT
S
9 BIT DATA
Figure 31.
2S
Nine Data Bit Frame Options
The relationship between the 5-bit prescaler select (UnPSC)
setting and the prescaler factors is shown in Table18.
Table 18 Prescaler Factors
Prescaler
Factor
Prescaler
Select
Prescaler
Factor
00000
1
10000
8.5
00001
1
10001
9
00010
1.5
10010
9.5
Prescaler
Factor
Prescaler
Select
Prescaler
Factor
01111
8
11111
16
A prescaler factor of zero corresponds to “no clock.” The “no
clock” condition is the USART power down mode, in which
the USART clock is turned off to reduce power consumption.
The application program should select the “no clock” condition before entering a new baud rate. Otherwise, it could
cause incorrect data to be received or transmitted. The
UnPSR register must contain a value other than zero when
an external clock is used at CKXn.
stage divider chain consisting of a 5-bit baud rate prescaler
(UnPSC) and an 11-bit baud rate divisor (UnDIV).
Prescaler
Select
Prescaler
Select
In asynchronous mode, the baud rate is calculated by:
SYS_CLK
BR = ------------------------------( 16 × N × P )
where BR is the baud rate, SYS_CLK is the system clock, N
is the value of the baud rate divisor + 1, and P is the prescaler
divide factor selected by the value in the UnPSR register.
00011
2
10011
10
00100
2.5
10100
10.5
00101
3
10101
11
00110
3.5
10110
11.5
00111
4
10111
12
01000
4.5
11000
12.5
01001
5
11001
13
01010
5.5
11010
13.5
01011
6
11011
14
01100
6.5
11100
14.5
01101
7
11101
15
01110
7.5
11110
15.5
The divide by 16 is performed because in the asynchronous
mode, the input frequency to the USART is 16 times the baud
rate. In synchronous mode, the input clock to the USART is
equal to the baud rate.
16.2.7
Interrupts
The USART is capable of generating interrupts on:
• Receive Buffer Full
• Receive Error
• Transmit Buffer Empty
Figure32 shows a diagram of the interrupt sources and associated enable bits.
UnFE
UnEEI
UnDOE
UnPE
UnERR
RX
Interrupt
UnRBF
UnERI
TX
UnTBE
Interrupt
UnETI
Figure 32. USART Interrupts
The interrupts can be individually enabled or disabled using
the Enable Transmit Interrupt (UnETI), Enable Receive Inter-
rupt (UnERI) and Enable Receive Error Interrupt (UnEER)
bits in the UnICTRL register.
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A transmit interrupt is generated when both the UnTBE and
UnETI bits are set. To remove this interrupt, software must either disable the interrupt by clearing the UnETI bit or write to
the UnTBUF register (thus clearing the UnTBE bit).
For the prescaler factors corresponding to
each 5-bit value, see Table18.
UnDIV[10:8] Baud Rate Divisor (bits 10-8). This field contains the three highest-order bits (bits 10, 9,
and 8) of the USART baud rate divisor used in
the second stage of the two-stage divider
chain. The remaining bits of the baud rate divisor are contained in the UnBAUD register.
A receive interrupt is generated on two conditions:
1. Both the UnRBF and UnERI bits are set. To remove this
interrupt, software must either disable the interrupt by
clearing the UnERI bit or read from the UnRBUF register
(thus clearing the UnRBF bit).
2. Both the UnERR and the UnEEI bits are set. To remove
this interrupt the software must either disable it by clearing the UnEEI bit or read the UnSTAT register (thus
clearing the UnERR bit).
16.2.8
16.3.4
Break Generation and Detection
7
A line break is generated when the BRK bit is set in the UnMDSL register. The TDXn line remains low until the program
resets the BRK bit.
UnDIV[7:0]
Parity Generation and Detection
Parity is only generated or checked with the 7-bit and 8-bit
data formats. It is not generated or checked in the diagnostic
loopback mode, the attention mode, or in the normal mode
with the 9-bit data format. Parity generation and checking are
enabled and disabled via the PEN bit in the UnFRS register.
The UnPSEL bits in the UnFRS register are used to select
odd, even, mark, or space parity.
16.3
16.3.5
USART REGISTERS
UnCHAR
USART Receive Data Buffer (UnRBUF)
UnSTP
USART Transmit Data Buffer (UnTBUF)
UnXB9
The USART Transmit Data Buffer is a byte-wide, read/write
register used to transmit each data byte.
16.3.3
USART Baud Rate Prescaler (UnPSR)
The USART Baud Rate Prescaler Register is a byte-wide,
read/write register that contains the 5-bit clock prescaler and
the upper three bits of the baud rate divisor. This register is
cleared upon reset. The register format is shown below.
7
6 5 4
UnPSC
UnPSC
3
2
UnDIV10
1
UnDIV9
UnPSEL
0
UnDIV8
2
1
0
Baud Rate Divisor (bits 7-0). This field contains
the eight lowest-order bits of the USART baud
rate divisor used in the second stage of the
two-stage divider chain. The three highest-order bits are contained in the UnPSR register.
The divisor value used is the 11-bit UnDIV value plus 1.
USART Frame Select Register (UnFRS)
Character Frame Format. This 2-bit field selects the number of data bits per frame, not including the parity bit, as follows:
Number of Stop Bits. This bit sets the number
of stop bits transmitted in each frame. If this bit
is 0, one stop bit is transmitted. If this bit is 1,
two stop bits are transmitted.
Transmit 9th Data Bit. This bit is the value of the
ninth data bit, either 0 or 1, transmitted when
the USART is configured to transmit nine data
bits per frame. It has no effect when the USART is configured to transmit seven or eight
data bits per frame.
Parity Select. This 2-bit field selects parity type
as follows:
00 = odd parity
01 = even parity
10 = mark (0)
11 = space (1)
Prescaler. This 5-bit field specifies the prescaler value used for dividing the system clock in
the first stage of the two-stage divider chain.
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3
00 = eight data bits per frame
01 = seven data bits per frame
10 = nine data bits per frame
11 = loopback mode; nine data bits per frame
The USART Receive Data Buffer is a byte-wide, read/write
register used to receive each data byte.
16.3.2
4
7
6
5
4
3
2
1
0
Reserved UnPEN UnPSEL UnXB9 UnSTP UnCHAR
USART Receive Data Buffer (UnRBUF)
USART Transmit Data Buffer (UnTBUF)
USART Baud Rate Prescaler Register (UnPSR)
USART Baud Rate Divisor Register (UnBAUD)
USART Frame Select Register (UnFRS)
USART Mode Select Register (UnMDSL)
USART Status Register (UnSTAT)
USART Interrupt Control Register (UnICTRL)
16.3.1
5
The USART Frame Select Register is a byte-wide, read/write
register that controls the frame format, including the number
of data bits, number of stop bits, and parity type. This register
is cleared upon reset. The register format is shown below.
The software interacts with the USART by accessing the USART registers. There are eight such registers:
•
•
•
•
•
•
•
•
6
UnDIV7 UnDIV6 UnDIV5 UnDIV4 UnDIV3 UnDIV2 UnDIV1 UnDIV0
A line break is detected if RDXn remains low for 10 bit times
or longer after a missing stop bit is detected.
16.2.9
USART Baud Rate Divisor (UnBAUD)
The USART Baud Rate Divisor Register is a byte-wide, read/
write register that contains the lower eight bits of the baud
rate divisor. This register contents are unknown upon powerup and are left unchanged by a reset operation. The register
format is shown below.
When the USART is configured to transmit nine
66
data bits per frame, the parity bit is omitted and
the UnPSEL field is ignored.
Parity Enable. This bit enables (1) or disables
(0) parity bit generation and parity checking.
When the USART is configured to transmit nine
data bits per frame, there is no parity bit and
the UnPEN bit is ignored.
UnPEN
16.3.6
UnERR
USART Mode Select Register (UnMDSL)
UnBKD
The USART Mode Select Register is a byte-wide, read/write
register that selects the clock source, synchronization mode,
attention mode, and line break generation. This register is
cleared upon reset. When the software writes to this register,
the reserved bits must be cleared to 0 for proper operation.
The register format is shown below.
7
6 5 4
Reserved
UnMOD
2
UnBRK
1
UnATN
0
UnMOD
Mode of Operation. Set to 0 for asynchronous
operation or 1 for synchronous operation.
Attention Mode. When set to 1, this bit selects
the attention mode of operation for the USART.
When cleared to 0, the attention mode is disabled. The hardware clears this bit after an address frame is received. An address frame is a
9-bit character with a 1 in the ninth bit position.
Force Transmission Break. Setting this bit to 1
causes the TDXn pin to go low. TDXn remains
low until the UnBRK bit is cleared to 0 by the
software.
Synchronous Clock Source. This bit controls
the clock source when the USART operates in
the synchronous mode (UnMOD=1). If the
UnCKS bit is set to 1, the USART operates
from an external clock provided on the CKXn
pin. If the UnCKS bit is cleared to 0, the USART
operates from the baud rate clock produced by
the USART on the CKXn pin. This bit is ignored
when the USART operates in the asynchronous mode.
UnATN
UnBRK
UnCKS
16.3.7
3
UnCKS
UnRB9
UnXMIP
16.3.8
7
7
UnEEI
UnTBE
USART Status Register (UnSTAT)
6
5
UnPE
UnFE
UnDOE
UnRB9
4
3
UnBKD UnERR
2
1
USART Interrupt Control Register (UnICTRL)
The USART Interrupt Control Register is a byte-wide register
that contains the receive and transmit interrupt status flags
(read-only bits) and the interrupt enable bits (read/write bits).
The register is set to 01 hex upon reset. The register format
is shown below.
The USART Status Register is a byte-wide, read-only register that contains the receive and transmit status bits. This
register is cleared upon reset. Any attempt by the software to
write to this register is ignored. The register format is shown
below.
Reserved UnXMIP
read the previous character from UnBUF. This
bit is automatically cleared to 0 by the hardware when the UnSTAT register is read.
Error Status Flag. This bit is set when a parity,
framing, or overrun error occurs (any time that
the UnPE, UnFE, or UnDOE bit is set). It is automatically cleared to 0 by the hardware when
the UnPE, UnFE, and UnDOE bits are all 0.
Break Detect. This bit is set to 1 when a line
break condition occurs. This condition is detected if RDXn remains low for at least ten bit
times after a missing stop bit has been detected at the end of a frame.
The hardware automatically clears the UnBKD
bit upon read of the UnSTAT register, but only
if the break condition on RXDn no longer exists. If reading the UnSTAT register does not
clear the UnBKD bit because the break is still
actively driven on the line, the hardware clears
the bit as soon as the break condition no longer
exists (when RXDn returns to a high level).
Received 9th Data Bit. With the USART configured to operate in the 9-bit data format, this is
equal to the ninth data bit of the last frame received.
Transmit In Progress. The hardware sets this
bit to 1 when the USART is transmitting data
and clears it to 0 at the end of the last frame bit.
UnRBF
0
UnDOE UnFE UnPE
Parity Error. This bit is set to 1 when a parity error is detected within a received character. This
bit is automatically cleared to 0 by the hardware when the UnSTAT register is read.
Framing Error. This bit is set to 1 when the USART fails to receive a valid stop bit at the end
of a frame. This bit is automatically cleared to 0
by the hardware when the UnSTAT register is
read.
Data Overrun Error. This bit is set to 1 when a
new character is received and transferred to
the UnBUF register before the software has
UnETI
UnERI
UnEEI
67
6
UnERI
5
4 3 2
UnETI Reserved
1
UnRBF
0
UnTBE
Transmit Buffer Empty. This read-only bit is set
to 1 by the hardware when the USART transfers data from the UnTBUF register to the
transmit shift register for transmission. It is automatically cleared to 0 by the hardware on the
next write to the UnTBUF register.
Receive Buffer Full. This read-only bit is set by
the hardware when the USART has received a
complete data frame and has transferred the
data from the receive shift register to the UnRBUF register. It is automatically cleared to 0 by
the hardware when the UnRBUF register is
read.
Enable Transmitter Interrupt. This read/write
bit, when set to 1, enables generation of an interrupt when the hardware sets the UnTBE bit.
Enable Receiver Interrupt. This read/write bit,
when set to 1, enables generation of an interrupt when the hardware sets the UnRBF bit.
Enable Receive Error Interrupt. This read/write
bit, when set to 1, enables generation of an interrupt when the hardware sets the UnERR bit
in the UnSTAT register.
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16.4
Use the same procedure to determine the values of N and P
as in the asynchronous mode. In this case, however, only integer prescaler values are allowed.
BAUD RATE CALCULATIONS
The USART baud rate is determined by the system clock frequency and the values programmed into the UnPSR and UnBAUD registers. Unless the system clock frequency is an
exact multiple of the desired baud rate, there will be a small
amount of error in the resulting baud rate clock.
The method of baud rate calculation depends on whether the
USART is configured to operate in the asynchronous or synchronous mode.
16.4.1
Baud Rate in Asynchronous Mode
The equation for calculating the baud rate in asynchronous
mode is:
SYS _CLK
BR = ------------------------------( 16 × N × P)
where BR is the baud rate, SYS_CLK is the system clock, N
is the value of the baud rate divisor + 1, and P is the prescaler
divide factor selected by the value in the UnPSR register.
Assuming a system clock of 5 MHz and a desired baud rate
of 9600, the NxP term according to the equation above is:
6
( 5 ×10 )
N × P = ----------------------------- = 32.552
( 16 × 9600 )
The NxP term is then divided by each Prescaler Factor from
Table18 to obtain a value closest to an integer. The factor for
this example is 6.5.
32.552
N = ---------------- = 5.008 (N = 5)
6.5
The baud rate register is programmed with a baud rate divisor of 4 (N = baud rate divisor +1). This produces a baud
clock of:
6
( 5×10 )
BR = --------------------------------- = 9615.385
( 16 × 5 × 6.5 )
( 9615.385 – 9600)
%error = --------------------------------------------- = 0.16
9600
Note that the percent error is much lower than would be possible without the non-integer prescaler factor. Refer to the table below for more examples.
System
Clock
Desired
Baud Rate
4 MHz
9600
5 MHz
9600
10 MHz
20 MHz
16.4.2
Actual
Baud Rate
Percent
Error
2 13
9615.385
0.16
5 6.5
9615.385
0.16
19200
5 6.5
19230.769
0.16
19200
5 13
19230.769
0.16
N
P
Baud Rate in Synchronous Mode
The equation for calculating the baud rate in synchronous
mode is:
SYS_CLK
BR = ---------------------------(2 × N × P)
where BR is the baud rate, SYS_CLK is the system clock, N
is the value of the baud rate divisor + 1, and P is the prescaler
divide factor selected by the value in the UnPSR register.
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68
17.0 Analog Comparators
The Dual Analog Comparator (ACMP2) module contains two
independent analog comparators with all necessary control
logic. Each comparator unit compares the analog input voltages applied to two input pins and determines which voltage
is higher. The comparison results can be placed on two output pins and/or read by the software from a register.
when Comparator 2 is enabled (CMP2EN=1).
If Comparator 2 is disabled (CMP2EN=0), setting the CMP2OE bit results in a logic 0 on the
CMP2O output pin.
17.2
The comparator I/O pins are alternate functions of the Port L
pins. In order for a comparator to operate, its two input pins
must be configured to operate as inputs in the alternate function mode.
Figure33 is a block diagram of the Dual Analog Comparator
module.
The two comparators are designated Comparator 1 (CMP1)
and Comparator 2 (CMP2). Each comparator has a positive
and a negative input, called CMP1P and CMP1N for Comparator 1 and CMP2P and CMP2N for Comparator 2. An optional output, CMP1O for Comparator 1 or CMP2O for
Comparator 2, allows the external hardware to read the comparison results. If the positive input is greater than the negative input, the result is a logic 1. Otherwise, the result is a
logic 0. These same results are available to the software by
reading the CMPCTRL register. CMP1OP and CMP2OP are
the direct outputs of the analog comparator. These signals
are connected to the channels of the Multi-Wake-Up Module.
17.1
ANALOG COMPARATOR USAGE
Using a comparator's output pin is optional. If it is to be used,
it must be configured to operate as an output in the alternate
function mode. The comparison result bits in the CMPCTRL
register are available to the CPU whether or not the output
pin is enabled.
The comparators uses DC current whenever they are enabled. Therefore, in order to reduce power consumption, it is
recommended that the comparators be disabled when they
are not needed, especially before entering any of the Power
Save modes.
ANALOG COMPARATOR CONTROL/
STATUS REGISTER (CMPCTRL)
The CMPCTRL register is a byte-wide, read/write register
that controls the comparator module and contains the comparison results. The control bits are read/write bits and the
result bits are read-only bits. This register is cleared upon reset. The register format is shown below.
7
6
5
4
3
2
1
0
Reserved CMP2OE CMP1OE CMP2EN CMP1EN CMP2RD CMP1RD
CMP1RD
CMP2RD
CMP1EN
CMP2EN
CMP1OE
CMP2OE
Comparator 1 Read. This read-only bit contains the output of Comparator 1 when the
comparator
is
enabled
(CMP1EN=1).
CMP1RD is set to 1 when the voltage on
CMP1P is greater than the voltage on CMP1N.
This bit is always 0 when Comparator 1 is disabled.
Comparator 2 Read. This read-only bit contains the output of Comparator 2 when the
comparator
is
enabled
(CMP2EN=1).
CMP2RD is set to 1 when the voltage on
CMP2P is greater than the voltage on CMP2N.
This bit is always 0 when Comparator 2 is disabled.
Comparator 1 Enable. This read/write bit enables (1) or disables (0) Comparator 1.
Comparator 2 Enable. This read/write bit enables (1) or disables (0) Comparator 2.
Comparator 1 Output Enable. This read/write
bit, when set to 1, enables the use of the
CMP1O pin as the output of Comparator 1
when Comparator 1 is enabled (CMP1EN=1).
If Comparator 1 is disabled (CMP1EN=0), setting the CMP1OE bit results in a logic 0 on the
CMP1O output pin.
Comparator 2 Output Enable. This read/write
bit, when set to 1, enables the use of the
CMP2O pin as the output of Comparator 2
69
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CMP1P
CMP1N
+
CMP1
_
CMP1O
CMP1EN
CMP1OE
CONTROL + STATUS
CMP2EN
CMP2P
CMP2N
CMP2OE
+
CMP2
_
CMP2O
Figure 33. Dual Analog Comparator Block Diagram
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18.0 A/D Converter
The A/D Converter (ADC) module is an 8-channel, multiplexed-input, analog-to-digital converter. The A/D Converter
receives an analog voltage on an input pin and converts that
voltage into an 8-bit digital value using successive approximation. The CPU can then read the result from a memorymapped register. The module supports four automated operating modes, providing single-channel or 4-channel scanned
operation in single-conversion or continuous mode.
The conversion results are stored in a 4-level data buffer. Depending on the operating mode, the buffer can hold the results of four successive conversions from a single channel or
four conversions from adjacent channels scanned in sequence.
18.1
OPERATING MODES
The A/D Converter can be configured to operate in any one
of four modes:
Figure34 is a block diagram of the A/D Converter module.
•
•
•
•
The analog input signal is selected from eight analog inputs
using an 8-channel analog multiplexer. The input pins are alternate functions of Port I.
A sample-and-hold circuit samples the analog voltage prior
to conversion and holds it stable and throughout the conversion process. A programmable initial delay period allows the
sampled voltage to stabilize before the conversion process
begins.
Single channel, single conversion
Single channel, continuous conversion
4-channel scan, single conversion
4-channel scan, continuous conversion
The configuration is set by the SCAN and CONT fields in the
ADC Control 2 Register (ADCCNT2), as indicated in
Table19. The A/D converter must be disabled when switching to a different mode.
Table 19
A capacitor should be connected between the VREF and the
AVCC pin in order to minimize noise. The recommended value for this capacitor is about 0.47 µF
ADC Operation Modes
SCAN CONT
The input voltage range is from 0V to VREF (the A/D reference voltage). The 80-pin device have a separate pin, VREF,
for the reference voltage. The 44-pin devices use the AV CC
(analog VCC ) power supply pin as the reference voltage.
The internal analog-to-digital converter block is based on a
successive approximation algorithm, which compares the
sampled voltage against an internally generated sequence of
analog voltages. The result is a linear conversion of the analog voltage to an unsigned 8-bit value ranging from 00 hex for
0.0 volts to FF hex for VREF.
Mode
00
0
Single Channel, Single Conversion
00
1
Single Channel, Continuous Conversion
01
0
4 Channels Scan, Single Conversion
01
1
4 Channel Scan, Continuous Conversion
18.1.1
Single Channel, Single Conversion Mode
In the single channel, single conversion mode, the A/D Converter performs a single conversion using a specified channel.
The software starts a conversion by setting the START bit in
the ADCCNT2 register. Upon completion of the conversion,
the A/D Converter places the result in register ADDATA0,
clears the START bit, and sets the EOC (end of conversion)
bit in the ADCST register. If the A/D Converter interrupt is enabled, an interrupt to the CPU is generated at this time.
The clock used by the converter block is generated by a clock
divider that scales down the system clock by a programmable factor. The conversion algorithm requires ten A/D Converter clock cycles, or 10 microseconds at the maximum
allowed A/D Converter clock rate of 1 MHz.
Conversion can start after the power supply is stable and ADCEN set for 100 µs.
/
CH0
CH1
CH2
CH3
CH4
CH5
CH6
CH7
3
CONFIGURATION
STATUS
&
CONTROL
8:1
ANALOG
MUX
ANALOG
TO
DIGITAL
CONVERTER
SAMPLE
&
HOLD
VREF
5
DATA
BUFFER
CLK
CLOCK
DIVIDER
/
PERIPHERAL
BUS
CLK
Figure 34. A/D Converter Block Diagram
71
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18.1.2
Single Channel, Continuous Conversion Mode
software must read the results from the data registers before
the A/D Converter writes the next result into ADDATA0.
In the single channel, continuous conversion mode, the A/D
Converter performs conversions repeatedly using the same
specified channel.
When the software clears the START bit, the A/D Converter
first completes the 4-channel conversion sequence currently
in progress, then stops and sets the EOC bit.
The software starts a conversion sequence by setting the
START bit. The A/D Converter performs four A/D conversions in sequence using the same channel, pausing only for
the programmable sampling delay time used in all conversion operations. It loads the four results into the A/D data registers in sequence, starting with ADDATA0 and ending with
ADDATA3. After it loads all four registers, it sets the EOC
(end of conversion) bit. If the A/D Converter interrupt is enabled, an interrupt to the CPU is generated at this time.
18.2
The software controls the A/D Converter and reads the A/D
results by accessing the ADC registers. There are eight such
registers:
•
•
•
•
•
The START bit remains set until cleared by the software. If
the software does not clear the START bit, the A/D Converter
continues performing conversions using the same input
channel, storing the results in ADDATA0 following ADDATA3.
To prevent an overrun error, the software must read the results from the data registers before the A/D Converter writes
the next result into ADDATA0 following ADDATA3.
ADC Status Register (ADCST)
ADC Control 1 Register (ADCCNT1)
ADC Control 2 Register (ADCCNT2)
ADC Control 3 Register (ADCCNT3)
ADC Data Registers (ADDATA0 through ADDATA3)
18.2.1
7
6
Reserved
4-Channel Scan, Single Conversion Mode
EOC
In the 4-channel scan, single conversion mode, the A/D Converter performs four conversions using four adjacent input
channels.
The software starts the conversion sequence by setting the
START bit. The A/D Converter performs four A/D conversions in sequence using four adjacent channels, starting with
the specified channel and pausing only for the programmable
sampling delay time. It loads the four results into the A/D data
registers in sequence, starting with ADDATA0 and ending
with ADDATA3. After it loads all four registers, it clears the
START bit and sets the EOC (end of conversion) bit. If the A/
D Converter interrupt is enabled, an interrupt to the CPU is
generated at this time.
18.1.4
BUSY
OVF
Channel Scan, Continuous Conversion Mode
In the 4-channel scan, continuous conversion mode, the A/D
Converter performs conversions repeatedly using four adjacent input channels.
The software starts conversion operations by setting the
START bit. The A/D Converter performs four A/D conversions in sequence using four adjacent channels, starting with
the specified channel and pausing only for the programmable
sampling delay time. It loads the four results into the A/D data
registers in sequence, starting with ADDATA0 and ending
with ADDATA3. After it loads all four registers, it sets the EOC
(end of conversion) bit. If the A/D Converter interrupt is enabled, an interrupt to the CPU is generated at this time.
BUFPTR
The START bit remains set until cleared by the software. If
the software does not clear the START bit, the A/D Converter
continues performing conversions, repeating the same sequence using the same four input channels and the same sequence of data registers. To prevent an overrun error, the
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ADC Status Register (ADCST)
The ADCST register is a byte-wide register that indicates the
current status of the A/D Converter. One bit in this register,
the OVF flag bit, is cleared by writing a 1 to its bit position.
The other bits are read-only bits, so the values written to
them are ignored. Upon reset, the register is set to 30 hex.
The register format is shown below.
When the software clears the START bit, the A/D Converter
first completes the conversion currently in progress, then
stops and sets the EOC bit. A 2-bit buffer pointer in the
ADCST register points to the register containing the final result.
18.1.3
A/D CONVERTER REGISTERS
72
5
4
BUFPTR
3
Reserved
2
OVF
1
BUSY
0
EOC
End of Conversion. This read-only bit reports
the status of the most recent A/D Converter operation. When cleared to 0, it indicates that the
conversion is not complete. When set to 1, it indicates that the conversion is complete. The
hardware sets this bit when it places the conversion results in the buffer and clears it when
any of the data registers are read.
ADC Busy. This read-only bit is set to 1 when
the A/D Converter is busy converting data and
is cleared to 0 when the A/D Converter is idle
or disabled.
Overflow. The hardware sets this bit to 1 when
the A/D Converter finishes a conversion and attempts to store the results in one of the data
registers (ADDATA0-ADDATA3) while the register is full. When this happens, the A/D Converter overwrites the data in the data register,
sets the OVF flag, and continues operating.
The OVF flag remains set until cleared by the
software. The software clears the flag by writing a 1 to it. Writing a 0 to this bit has no effect.
Buffer Pointer. This 2-bit, read-only field identifies the data register that was most recently
written with new data:
00 = ADDATA0
01 = ADDATA1
10 = ADDATA2
11 = ADDATA3
This register is initialized to 11 when a new conversion is started (when ADCCNT2.START is
changed from 0 to 1) and is automatically incremented every time a result is written to buffers
ADDATA0-ADDATA3. The result is a four-entry
cyclic FIFO buffer, with BUFPTR pointing to the
last entry written by the A/D Converter.
18.2.2
SCAN
ADC Control 1 Register (ADCCNT1)
The ADCCNT1 register is a byte-wide, read/write register
used to enable the A/D Converter and its interrupts, and also
to control the reference voltage source. When writing to this
register, all reserved bits must be written with 0 for the A/D
Converter to function properly. Changing any bits other than
ADCEN (bit 0) is not allowed while the A/D Converter is active (ADCST.BUSY or ADCCNT2.START set). Upon reset,
all non-reserved bits are cleared to 0. The register format is
shown below.
7
6 5 4
Reserved
ADCEN
3
2
INTE
1
Reserved
START
0
ADCEN
A/D Converter Enable. Setting this bit enables
the A/D Converter and allows a conversion to
be started by setting the start bit
(ADCCNT2.START). Clearing the ADCEN bit
disables the A/D Converter, terminates any
conversion in progress, and clears the ADC
status flags (ADCST.EOC, ADCST.BUSY,
ADCST.OVF, and ADCCNT2.START).
Interrupt Enable. This bit enables (1) or disables (0) A/D Converter interrupts. If enabled,
and interrupt occurs at the end of a conversion
sequence or when the ADC data buffer is full,
depending on the operating mode.
INTE
18.2.4
ADC Control 3 Register (ADCCNT3)
The ADCCNT3 register is a byte-wide, read/write register
used to specify the analog sampling time delay and the divide-by factor for generating the ADC clock. This register
should be written only when the A/D Converter is disabled
(ADCCNT1.ADCEN=0). Upon reset, the non-reserved bits of
the ADCCNT3 register are cleared to 0. The register format
is shown below.
7
6
Reserved
CDIV
All reserved bits must be written with 0 for ADC to operate
properly.
18.2.3
ADC Control 2 Register (ADCCNT2)
The ADCCNT2 register is a byte-wide, read/write register
used to specify the A/D Converter operating mode and to
start conversion operations. All register fields other than the
START bit should be changed only while the A/D Converter
is inactive (START=0). Data written to the SCAN and CONT
fields is ignored if the START bit is already set. Upon reset,
the non-reserved bits of this register are cleared to 0. The
register format is shown below.
7
START
CHANNEL
CONT
6
5
SCAN
4
CONT
3
A/D Converter operates continuously by repeating the programmed conversion cycle.
Scan Mode. This 2-bit field selects the singleconversion mode or 4-channel scan mode as
follows:
00 = single-conversion mode
01 = 4-channel scan mode
1X = reserved
Start Conversion. The software sets this bit to
1 to start a conversion or a 4-channel conversion cycle. In the “continuous” mode, this bit remains set until cleared by the software. In the
“single” (non-continuous) mode, the hardware
clears this bit upon completion of the programmed conversion cycle. The software
should not attempt to set this bit while the A/D
Converter is busy (ADCST.BUSY=1).
2
1
0
CHANNEL
Channel Select. This 4-bit field selects one of
the eight analog input channels as follows:
0000 = ACH0
0001 = ACH1
0010 = ACH2
0011 = ACH3
0100 = ACH4
0101 = ACH5
0110 = ACH6
0111 = ACH7
1XXX = reserved
Continuous Conversion. When cleared to 0,
the A/D Converter stops operating upon completion of the programmed conversion cycle (a
single conversion or a sequence of four conversions on four channels). When set to 1, the
DELAY
5
4
DELAY
3
2
1
CDIV
0
Clock Divide. This 3-bit field sets the divide-by
factor for generating the A/D Converter clock
from the system clock. The frequency of the A/
D Converter clock is equal to the system clock
divided by the programmed factor. The resulting A/D Converter clock frequency must be
less than or equal to 1 MHz. The divide-by factor is defined as follows:
000 = divide by 1
001 = divide by 2
010 = divide by 4
011 = divide by 8
100 = divide by 16
101 = divide by 32
110 = reserved
111 = reserved
Sampling Time Delay. This 3-bit field defines
the number of A/D Converter clock cycles of
delay from the time that the input channel is selected until the analog voltage is sampled. The
programmed delay should be sufficient, dependent on the source impedance, to allow the
sampled signal to reach its final level before the
conversion begins. The delay is defined as follows:
000 = 1 A/D Converter clock cycle
001 = 2 A/D Converter clock cycles
010 = 4 A/D Converter clock cycles
011 = 8 A/D Converter clock cycles
100 = 16 A/D Converter clock cycles
101 = 32 A/D Converter clock cycles
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110 = 64 A/D Converter clock cycles
111 = reserved
18.2.5
the A/D Converter, together with the source resistance of the
device that drives the A/D input determine the charge-up time
required for the voltage to settle. Figure35 shows a schematic of the charge-up circuit. For the values of RAIN and C AIN ,
see Section21.0.
ADC Data Registers (ADDATA0-ADDATA3)
The four ADC Data Registers (ADDATA0 through ADDATA3)
are byte-wide, read/write registers that hold the conversion
results, which are stored sequentially starting with ADDATA0
and ending with ADDATA3. The results held in these registers are valid only after the ADCST.EOC flag is set. Upon reset, the contents of these registers are undefined.
Interrupts or polling can be used to read the A/D Converter
results. For interrupts, the A/D Converter interrupt must be
enabled by setting the ADCCNT1.INTE bit. The interrupt is
cleared automatically when any one of the data registers
(ADDATA0-ADDATA3) is read. For polling, the software
reads the ADCST.EOC bit to determine whether the conversion sequence is completed.
The value read from a data register is a linear mapping of the
analog input voltage to an 8-bit value. The value 00 hex represents 0.0 volts and the value FF hex represents the reference voltage, V REF.
18.3
Once the A/D Converter configuration has been set up, the
software can use the following procedure to perform an A/D
conversion sequence:
A/D CONVERTER PROGRAMMING
1. Enable the A/D Converter by setting the ADCCNT1.ADCEN bit and wait 100 µs before performing any conversion.
2. Select the operating mode and channel by writing to the
SCAN, CONT, and CHANNEL fields of the ADCCNT2
register. At the same time, start the conversion by setting
the START bit in the same register.
3. Wait until the conversion is finished, either by polling or
using the A/D Converter interrupt.
4. Read the conversion results from the data registers,
ADDATA0 through ADDATA3 (or just ADDATA0 in the
single-channel, single-conversion mode).
5. In the continuous conversion modes, repeat Step 3 and
Step 4 for as long as samples are needed. Then stop the
A/D Converter by clearing either the START bit
(ADCCNT2.START) or the A/D Converter enable bit
(ADCCNT1.ADCEN).
The software should set the A/D Converter configuration before it enables the A/D Converter module. The configuration
consists of the following settings:
• ADC clock rate: ADCCNT3.CDIV
• Sampling delay: ADCCNT3.DELAY
• Interrupt enable (if required): ADCCNT1.INTE
The ADC clock is created by scaling down the system clock.
The fastest allowable clock for the A/D Converter is 1 MHz.
Therefore, for the fastest possible operation of the A/D Converter, use the smallest available divide-by factor that results
in a clock frequency of 1 MHz or lower. The available divideby factors are 1, 2, 4, 8, 16, and 32.
For example, if the system clock is 10 MHz, use a divide-by
factor of 16. In that case, the A/D Converter clock frequency
is 625 kHz, the clock period is 1.6 microseconds, and the A/
D conversion time is 16 microseconds (ten clock A/D Converter clock cycles).
To minimize power consumption, the A/D Converter should
be disabled when it is not needed, especially before entering
a Power Save mode.
The programmable sampling time delay should be made
small for faster operation, but large enough to allow the input
voltage to settle. The internal resistance and capacitance of
RAIN
RSOURCE
Input
signal
CAIN
Analog
Multiplexer
Sample &
Hold
A/D Converter
Figure 35. Sample-and-Hold Charge-Up Schematic
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74
19.0 Memory Map
Please refer to individual datasheets for its own set of memory maps. The CompactRISC architecture supports a uniform linear address space of 2 megabytes. The device
implementation of this architecture uses only the lowest 64
kbytes of address space, ranging from 0000 to FFFF hex.
Table20 is a memory map showing the types of memory and
peripherals that occupy this memory space. Address ranges
not listed in the table are reserved and should not be read or
written.
Table 20
byte-wide and word-wide registers reside at word boundaries
(even address). Thus, each byte-wide register uses only the
lowest eight bits of the internal data bus.
Most device registers are read/write registers. However,
some registers are read-only or write-only, as indicated in the
table. An attempt to read a write-only register or to write a
read-only register will have unpredictable results.
When the software writes to a register in which one or more
bits are reserved, it must write a zero to each reserved bit unless indicated otherwise in the description of the register.
Reading a reserved bit returns an undefined value.
Device Memory Map
Address
Range (hex)
Description
0000-BFFF
Flash Program Memory (48 kbytes)
DA00-DFF7
ISP Memory (1.5 kbytes)
DFF8-DFFF
Program ROM control/status
E000-E7FF
Static RAM (2 kbytes)
F000-F27F
EEPROM Data Memory (640 bytes)
F900-F930
Device configuration registers
FB00-FB06
Port B registers
FB10-FB16
Port C registers
FC40-FC88
Clock, Power Management, and Wake-up
registers
FCA0-FCA8
Port G registers
FD20-FD28
Port F registers
FE00-FE0C
Interrupt registers
FE40-FE4E
USART 1 registers
FE60-FE68
MICROWIRE registers
FE80-FE8E
USART 2 registers
FEE0-FEE8
Port I registers
FF00-FF08
Port L registers
FF20-FF2A
Timer and WATCHDOG registers
FF40-FF50
MFT1 Timer registers
FF60-FF70
MFT2 Timer registers
FFC0-FFD0
A/D Converter registersa
FFE0-FFE0
Analog Comparator registera
a
. 44 pin devices may not include this module
Table21 is a detailed memory map showing the specific
memory address of the memory, I/O ports, and registers. The
table shows the starting address, the size, and a brief description of each memory block and register. For detailed information on using these memory locations, see the
applicable sections in the data sheet.
All addresses not listed in the table are reserved and should
not be read or written. An attempt to access an unlisted address will have unpredictable results.
Each byte-wide register occupies a single address and can
be accessed only in a byte-wide transaction. Each word-wide
register occupies two consecutive memory addresses and
can be accessed only in a word-wide transaction. Both the
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Table 21
Device Detailed Memory Map
Size
Register
Address
(hex)
Access
Type
48K
0000
Read/Write
Flash Program Memory
FLCTRL
byte
DFFE
Read/Write
Flash Program Memory Control Register (EMPTY bit)
FLSEC
byte
DFFF
Read/Write
Flash Program Memory Security Register
2K
E000
Read/Write
Static RAM
640
F000
Read/Write
EEPROM Data Memory
BCFG
byte
F900
Read/Write
BIU Configuration Register
SZCFG0
word
F904
Read/Write
Static Zone 0 Configuration Register
MCFG
byte
F910
Read/Write
Module Configuration Register
MSTAT
byte
F914
Read Only
Module Status Register
DMCSR
byte
F940
Read/Write
EEPROM Data Memory Control and Status Register
DMPSLR
byte
F942
Read/Write
EEPROM Data Memory Prescaler Register
DMKEY
byte
F954
Read/Write
EEPROM Data Memory Write Key Register
FLCSR
byte
F960
Read/Write
Flash Program Memory Control and Status Register
FLPSLR
byte
F962
Read/Write
Flash Program Memory Prescaler Register
PGMKEY
byte
F974
Read/Write
Flash Program Memory Write Key Register
PBDIR
byte
FB00
Read/Write
Port B Direction Register
PBDIN
byte
FB02
Read Only
Port B Data Input Register
PBDOUT
byte
FB04
Read/Write
Port B Data Output Register
PBWKPU
byte
FB06
Read/Write
Port B Weak Pull-Up Register
PCDIR
byte
FB10
Read/Write
Port C Direction Register
PCDIN
byte
FB12
Read/Write
Port C Data Input Register (read-only)
PCDOUT
byte
FB14
Read/Write
Port C Data Output Register
PCWKPU
byte
FB16
Read/Write
Port C Weak Pull-Up Register
CRCTRL
byte
FC40
Read/Write
Clock and Reset Control Register
PRSSC
byte
FC42
Read/Write
Slow Clock Prescaler Register
PMCSR
byte
FC60
Read/Write
Power Management Control/Status Register
WKEDG
byte
FC80
Read/Write
Wake-Up Edge Detection Register
WKENA
byte
FC82
Read/Write
Wake-Up Enable Register
WKCTRL
byte
FC84
Read/Write
Wake-Up Source Select Register
WKPND
byte
FC86
Read Set
Wake-Up Pending Register
WKPCL
byte
FC88
Write Only
Wake-Up Pending Clear Register
PGALT
byte
FCA0
Read/Write
Port G Alternate Function Register
PGDIR
byte
FCA2
Read/Write
Port G Direction Register
PGDIN
byte
FCA4
Read Only
Port G Data Input Register
Register Name
Contents
PGDOUT
byte
FCA6
Read/Write
Port G Data Output Register
PGWKPU
byte
FCA8
Read/Write
Port G Weak Pull-Up Register
PGSCHEN
byte
FCAA
Read/Write
Port G Schmitt Trigger Enable Register
PFALT
byte
FD20
Read/Write
Port F Alternate Function Register
PFDIR
byte
FD22
Read/Write
Port F Direction Register
PFDIN
byte
FD24
Read Only
Port F Data Input Register
PFDOUT
byte
FD26
Read/Write
Port F Data Output Register
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76
Table 21
Device Detailed Memory Map
Register Name
Size
Register
Address
(hex)
Access
Type
PFWKPU
byte
FD28
Read/Write
Port F Weak Pull-Up Register
PFSCHEN
byte
FD2A
Read/Write
Port F Schmitt Trigger Enable Register
Contents
IVCT
byte
FE00
Read Only
Interrupt Vector Register
NMISTAT
byte
FE02
Read Only
NMI Status Register
EXNMI
byte
FE04
Read/Write
External NMI Control/Status Register
ISTAT0
byte
FE0A
Read Only
Interrupt Status Register 0
ISTAT1
byte
FE0C
Read Only
Interrupt Status Register 1
IENAM
byte
FE0E
Read/Write
Interrupt and Enable Mask Register 0
IENAM1
byte
FE10
Read/Write
Interrupt and Enable Mask Register 1
U1TBUF
byte
FE40
Read/Write
USART 1 Transmit Data Buffer
U1RBUF
byte
FE42
Read Only
USART 1 Receive Data Buffer
U1ICTRL
byte
FE44
Read/Write
USART 1 Interrupt Control Register
U1STAT
byte
FE46
Read Only
USART 1 Status Register
U1FRS
byte
FE48
Read/Write
USART 1 Frame Select Register
U1MDSL
byte
FE4A
Read/Write
USART 1 Mode Select Register
U1BAUD
byte
FE4C
Read/Write
USART 1 Baud Rate Divisor Register
U1PSR
byte
FE4E
Read/Write
USART 1 Baud Rate Prescaler
MWDAT
byte
FE60
Read/Write
MICROWIRE Data Register
MWCTL1
byte
FE62
Read/Write
MICROWIRE Control 1 Register
MWCTL2
byte
FE64
Read/Write
MICROWIRE Control 2 Register
MWCTL3
byte
FE66
Read/Write
MICROWIRE Control 3 Register
MWSTAT
byte
FE68
Read Only
MICROWIRE Status Register
U2TBUF
byte
FE80
Read/Write
USART 2 Transmit Data Buffer
U2RBUF
byte
FE82
Read Only
USART 2 Receive Data Buffer
U2ICTRL
byte
FE84
Read/Write
USART 2 Interrupt Control Register
U2STAT
byte
FE86
Read Only
USART 2 Status Register
U2FRS
byte
FE88
Read/Write
USART 2 Frame Select Register
U2MDSL
byte
FE8A
Read/Write
USART 2 Mode Select Register
U2BAUD
byte
FE8C
Read/Write
USART 2 Baud Rate Divisor Register
U2PSR
byte
FE8E
Read/Write
USART 2 Baud Rate Prescaler
PIALT
byte
FEE0
Read/Write
Port I Alternate Function Register
PIDIR
byte
FEE2
Read/Write
Port I Direction Register
PIDIN
byte
FEE4
Read Only
Port I Data Input Register
PIDOUT
byte
FEE6
Read/Write
Port I Data Output Register
PIWKPU
byte
FEE8
Read/Write
Port I Weak Pull-Up Register
PISCHEN
byte
FEEA
Read/Write
Port I Schmitt Trigger Enable Register
PLALT
byte
FF00
Read/Write
Port L Alternate Function Register
PLDIR
byte
FF02
Read/Write
Port L Direction Register
PLDIN
byte
FF04
Read Only
Port L Data Input Register (read-only)
PLDOUT
byte
FF06
Read/Write
Port L Data Output Register
PLWKPU
byte
FF08
Read/Write
Port L Weak Pull-Up Register
PLSCHEN
byte
FF0A
Read/Write
Port L Schmitt Trigger Enable Register
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Table 21
Device Detailed Memory Map
Register Name
Size
Register
Address
(hex)
Access
Type
TWCFG
byte
FF20
Read/Write
Timer and WATCHDOG Configuration Register
TWCP
byte
FF22
Read/Write
Timer and WATCHDOG Clock Prescaler Register
TWMT0
word
FF24
Read/Write
TWM Timer 0 Register
Contents
T0CSR
byte
FF26
Read/Write
TWMT0 Control and Status Register
WDCNT
byte
FF28
Write Only
WATCHDOG Count Register
WDSDM
byte
FF2A
Write Only
WATCHDOG Service Data Match Register
T1CNT1
word
FF40
Read/Write
T1 Timer/Counter I Register
T1CRA
word
FF42
Read/Write
T1 Reload/Capture A Register
T1CRB
word
FF44
Read/Write
T1 Reload/Capture B Register
T1CNT2
word
FF46
Read/Write
T1 Timer/Counter II Register
T1PRSC
byte
FF48
Read/Write
T1 Clock Prescaler Register
T1CKC
byte
FF4A
Read/Write
T1 Clock Unit Control Register
T1CTRL
byte
FF4C
Read/Write
T1 Timer Mode Control Register
T1ICTL
byte
FF4E
Read/Write
T1 Timer Interrupt Control Register
T1ICLR
byte
FF50
Read/Write
T1 Timer Interrupt Clear Register
T2CNT2
word
FF60
Read/Write
T2 Timer/Counter I Register
T2CRA
word
FF62
Read/Write
T2 Reload/Capture A Register
T2CRB
word
FF64
Read/Write
T2 Reload/Capture B Register
T2CNT2
word
FF66
Read/Write
T2 Timer/Counter II Register
T2PRSC
byte
FF68
Read/Write
T2 Clock Prescaler Register
T2CKC
byte
FF6A
Read/Write
T2 Clock Unit Control Register
T2CTRL
byte
FF6C
Read/Write
T2 Timer Mode Control Register
T2ICTL
byte
FF6E
Read/Write
T2 Timer Interrupt Control Register
T2ICLR
byte
FF70
Read/Write
T2 Timer Interrupt Clear Register
ADCST
byte
FFC0
Read/Write
A/D Converter Status Register
ADCCNT1
byte
FFC2
Read/Write
A/D Converter Control 1 Register
ADCCNT2
byte
FFC4
Read/Write
A/D Converter Control 2 Register
ADCCNT3
byte
FFC6
Read/Write
A/D Converter Control 3 Register
ADDATA0
byte
FFCA
Read/Write
A/D Converter Data 0 Register
ADDATA1
byte
FFCC
Read Only
A/D Converter Data 1 Register
ADDATA2
byte
FFCE
Read Only
A/D Converter Data 2 Register
ADDATA3
byte
FFD0
Read Only
A/D Converter Data 3 Register
CMPCTRL
byte
FFE0
Read/Write
Analog Comparator Control/Status Register
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78
20.0 Register Layouts
The following tables show the functions of the bit fields of the device registers. For more information on using these registers,
see the detailed description of the applicable function elsewhere in the data sheet.
20.1
REGISTER LAYOUT
System
Configuration
Registers
7
MCFG
6
Reserved
MSTAT
5
4
3
2
1
0
CLK2OE
SLCOE2
FEEDM
SLCLKOE
CLKOE
Reserved
PGMBUSY
OENV2
OENV1
OENV0
Reserved
BIU Registers
15
12
11
10
9
8
7
6
5
BCFG
4
3
2
1
0
Reserved
IOCFG
1
Reserved
SZCFG0
Reserved
EEPROM Data
Memory Registers
7
IPST Res
BW
Reserved
HOLD
WAIT
FRE IPRE IPST Res
BW
Reserved
HOLD
WAIT
6
5
DMCSR
4
3
Reserved
DMPSLR
FTDIV
DMKEY
DMKEYVAL
Flash Program
Memory Registers
FLCSR
7
6
5
4
Reserved
PGMKEY
PMKEYVAL
Reserved
7
1
0
DMBUSY
ERASE
Reserved
2
1
0
ERASE
Reserved
FROMWR
ERASE
FROMRD
2
1
IENPROG PMLFULL PMBUSY
FTDIV
FLSEC
2
3
FLCSR
GPIO Registers
EWR
6
5
4
3
PxALT
Px Pins Alternate Function Enable
PxDIR
Px Port Direction
PxDIN
Px Port Output Data
PxDOUT
Px Port Input Data
PxWPU
Px Port Weak Pull-up Enable
PxSCHEN
Px Port Schmitt Trigger Enable
79
0
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ICU Registers
7
6
5
4
IVCT
0
0
0
1
NMISTAT
3
2
1
0
INTVECT
Reserved
NMIMNTR
EXT
Reserved
WD
ISTAT0
IST(7:0)
ISTAT1
IST(15:8)
IENAM0
IENA(7:0)
IENAM1
IENA(15:8)
EXNMI
Reserved
ERR
UND
EXT
ENCLK
PIN
EN
MIWU Registers
7
6
5
4
3
2
1
0
WKEDG
WKED7
WKED6
WKED5
WKED4
WKED3
WKED2
WKED1
WKED0
WKENA
WKEN7
WKEN6
WKEN5
WKEN4
WKEN3
WKEN2
WKEN1
WKEN0
WKCTRL
Reserved
WKSEL0
WKPND
WKPD7
WKPD6
WKPD5
WKPD4
WKPD3
WKPD2
WKPD1
WKPD0
WKPCL
WKCL7
WKCL6
WKCL5
WKCL4
WKCL3
WKCL2
WKCL1
WKCL0
Dual Clock + Reset Registers
7
6
5
CRCTRL
4
3
Reserved
PRSSC
PMCSR
SCLK
7
5
4
3
2
1
0
OLFC
OHFC
WBPSM
Reserved
HALT
IDLE
DHF
PSM
3
2
6
5
4
UnRBUF
UnRBUF
UnICTRL
UnEEI
UnERI
UnETI
UnSTAT
Reserved
UnXMIP
UnRB9
UnFRS
Reserved
UnPEN
Reserved
UnBKD
UnPSEL
Reserved
UnBAUD
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POR
6
UnTBUF
UnPSR
0
7
UnTBUF
UnMDSL
1
SCDIV
Power Management Register
USART Registers
2
UnERR
UnDOE
UnXB9
UnSTP
UnCKS
UnBRK
1
0
UnRBF
UnTBE
UnFE
UnPE
UnCHAR
UnATN
UnMOD
UnDIV[7]: UnDIV[0]
UnPSC
UnDIV[10]: UnDIV[8]
80
MWSPI Registers
7
6
5
4
MWDAT
1
0
MEN
MIDL
MCKM
MMNS
MEIO
MECH
MRDY
MBFL
MOVR
Reserved
MRBF
MBSY
Reserved
MWCTL2
MDV1
MWCTL3
MCDV
Reserved
MWSTAT
MEIW
MEIR
Reserved
15
8
7
6
5
4
3
TnCNT1
TnCNT1
TnCRA
TnCRA
TnCRB
TnCRB
TnCNT2
TnCNT2
TnPRSC
Reserved
TnCKC
Reserved
TnCTRL
Reserved TnAOUT
TnICTL
TnDIEN
8
TWCFG
7
6
Reserved
C1CSEL
TnAEN
TnBEDG
TnAEDG
TnBIEN
TnAIEN
TnDPND
TnCPND
TnBPND
TnAPND
TnDCLR
TnCCLR
TnBCLR
TnACLR
4
3
2
WDSDME
WDCT0I
LWDCNT
LTWMT0
Reserved
0
LTWCP LTWCFG
MDIV
Reserved
T0INTE
WDCNT
PRESET
WDSDM
RSTDATA
7
6
5
Reserved
ADCCNT1
ADCCNT3
1
PRESET
T0CSR
ADCCNT2
MDSEL
5
TWMTO
ADCST
0
TnBEN
TWCP
A/D Registers
1
CLKPS
Reserved
15
2
C2CSEL
TnCIEN
TnICLR
TWM Registers
2
MWnDAT
MWCTL1
TIMER Registers
3
4
BUFPTR
SCAN
2
1
0
Reserved
OVF
BUSY
EOC
INTE
Reserved
ADCEN
CONT
Reserved
DELAY
ADDATA0
RESULT 1 DATA
ADDATA1
RESULT 2 DATA
ADDATA2
RESULT 3 DATA
ADDATA3
RESULT 4 DATA
81
RST
3
Reserved
START
TC
CHANNEL
CDIV
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Analog Comp. Registers
CMPCTRL
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7
6
Reserved
5
4
3
2
1
0
CMP2OE
CMP1OE
CMP2EN
CMP1EN
CMP2RD
CMP1RD
82
21.0 ELECTRICAL CHARACTERISTICS
Absolute Maximum Ratings
If Military/Aerospace specified devices are required,
please contact the National Semiconductor Sales Office/
Distributors for availability and specifications.
Supply Voltage (VCC )
Voltage at Any Pin
ESD Protection Level
Total Current into VCC Pin (Source)
Total Current out of GND Pin (Sink)
Storage Temperature Range
7V
–0.6V to VCC +0.6V
6 kV
(Human Body Model)
80 mA
100 mA
–65°C to +140°C
Note: Absolute maximum ratings indicate limits beyond
which damage to the device may occur. DC and AC electrical
specifications are not ensured when operating the device at
absolute maximum ratings.
Thermal Characteristics
Characteristics
Symbol
Value
Unit
Average junction temperature
TJ
TA + (PD X ~JA)
°C
Ambient temperature
TA
User-determined
°C
Package thermal resistance (junction-to-ambient)
80-pin quad flat pack (QFP)
44-pin package (PLCC)
~JA
49.8
56
°C/W
Total power dissipation1
PD
PINT + PI/O
or
K
T J + 273°C
W
Device internal power
dissipation
PINT
IDD X VDD
W
I/O pin power dissipation2
PI/O
User-determined
W
K
PD x (TA + 273°C) +
~ JA x PD 2
W, °C
3
A constant
1. This is an approximate value, neglecting P I/O .
2. For most applications PI/O
<< PINT and can be neglected.
3. K is a constant pertaining to the device. Solve for K with a known TA and a measured P D (at equilibrium). Use this value of K to solve for
P D and T J iterntively for any value of TA .
DC Electrical Characteristics: –40°C ≤ TA ≤ +85°C (also supports -40°C to 125°C) depends on package type
Symbol
Parameter
Conditions
Operating Voltage
Min
Max
Units
4.5
5.5
V
0.8Vcc
Vcc + 0.5
V
-0.5
0.2Vcc
V
VIH
Logical 1 CMOS Hysteresis Input Voltage
VIL
Logical 0 CMOS Input Voltage
Vxl
Low Level Input Voltage OSC
External X1 clock
0 Vcc
0.2Vcc
V
Vxh
High Level Input Voltage OSC
External X1 clock
0.5Vcc
Vcc
V
Vxl2
X2CKI Logical 0 Input Voltage
External X2 clock
0.3
V
Vxh2
X2CKI Logical 1 Input Voltage
External X2clock
ab
1.2
V
0.1Vcc
V
Vhys
Hysteresis Loop Width
I OH
Logical 1 CMOS Output Current
VOH = 3.8V, Vcc=4.5V
-1.6
mA
IO L
Other Pins
Logical 0 CMOS Output Current
VOL = 0.45V, Vcc=4.5V
1.6
mA
I OHW
Weak Pull-up Current
VOH = 3.8V, Vcc=4.5V
-10
Input Leakage Current
0V ≤ Vin ≤ Vcc
Output Leakage Current (I/O pins in input mode)
0V ≤ Vout ≤ Vcc
IL
I O(Off)
83
- 2.0
- 2.0
µA
2.0
j
µA
2.0
j
µA
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Symbol
Parameter
Conditions
normal c
Min
Max
Units
Icca1
Digital Supply Current Active Mode,
TC = 20 MHz, Vcc= 5.5V
38
mA
Iccprog
Digital Supply Current Active Mode, flash mem.d TC = 20 MHz, Vcc = 5.5V
46
mA
23.2
mA
38
mA
TC = 8 MHz, Vcc = 5.5V
46
mA
TC = 8 MHz, Vcc = 5.5V
23.2
mA
Vcc= 5.5V
9
mA
Vcc = 5.5V
60
µA
Vcc = 5.5V
15k
µA
3
mA
Icca2
Icca1
Digital Supply Current Active Mode,
WAIT e
TC = 20 MHz, Vcc = 5.5V
Digital Supply Current Active Mode,
normal c
TC = 8 MHz, Vcc= 5.5V
mem.d
Iccprog
Digital Supply Current Active Mode, flash
Icca2
Digital Supply Current Active Mode, WAIT e
Iccps
Iccid
Iccq
Digital Supply Current Power Save
Digital Supply Current Idle Mode
g
Digital Supply Current Halt Mode
h
Mode f
Iacc
Analog Supply Current Active Mode i
Vcc = 5.5V
a. Guaranteed by design.
b. Hysteresis applies only when the Schmitt trigger is enabled or when alternate function is selected.
c. Running from internal memory, Iout = 0 mA, XCKI1 = 20 and 8 MHz, not programming flash memory.
d. Same conditions as c. (Icca1), but while programming or erasing one of the flash memory arrays.
e. CPU executing an WAIT instruction, Iout = 0 mA, XCKI1 = 20 and 8 MHz, peripherals not active.
f. Running from internal memory, Iout = 0mA, Iout = 0mA, XCKI1 = 20 MHz, XCKI2 = 32.768 kHz.
g. Iout = 0mA, XCKI1 = Vcc, X2CKI = 32.768 kHz
h. Same conditions as g. (Iccps), but in Halt mode instead of Idle mode
i. A/D converter and analog comparators enabled.
j. I L and I O are 2.0 µA at 85°C and 5.0 µA at 125°C
k. I acq is 20 µA at 85°C and 50 µA at 125°Ci.
i.
A/D Converter Characteristics
Symbol
NIL
Parameter
Integral Errorb
c
Conditionsa
Min
Max
Units
VREF = VCC
1
LSB
1
LSB
0
VREF
V
VDD
V
2.625
V
VREF = 5 V
1.0
mA
VREF = VCC
±1
µA
200
Ω
5
pF
1
µs
NDL
Differential Error
VREF = VCC
VIN
Input Voltage Range
VREF < VCC - 0.1
VREFEX
External Reference Voltage
3.0
VREFI
Internal Reference Voltage
2.375
I VREF
VREF input current
IA L
Analog input leakage current
RAIN
d
Analog input resistance
capacitancee
CAIN
Analog input
tADCCLK
Conversion Clock period
CREFEX
External Vref bypass capacitance
0.47
Typ
2.5
µF
t ACT
First A/D conversion after Vcc stable
100
µsec
a. All parameters specified for fOSC = 1 MHz,
VDD = 5.0V ± 10%, VDD = 5.0V ± 10% unless otherwise noted.
b. Integral (non-linearity) error; the maximum difference between the best-fit straight line reference and the actual
conversion curve.
c. Differential (non-linearity) error; the maximum difference between the best-fit stair-step reference with 1-LSB
resolution and the actual conversion curve.
d. The resistance between the device input and the internal analog input capacitance.
e. The input signal is measured across the internal capacitance.
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84
Comparator AC and DC Characteristics
Symbol
Parameter
Conditions
VO S
Input Offset Voltage
VCM
I CS
Input Common Mode Voltage Range
DC Supply Current per Comparator (When
Enabled)
Response Time
Min
Typ
Vcc = 5V,
0.4V ≤ VIN ≤ VCC – 1.5V
0.4
VCC =5.5V
1V Step / 100mV Overdrive
Max
Units
±25
mV
VCC -1.5
V
250
µA
1
µs
Flash EEPROM Program Memory Programming
Symbol
t PWP
t EWP
t SDP
Parameter
Conditions
Programming pulse width a
Erase pulse width
b
Min
Max
Units
30
40
µs
1
-
ms
c
10
-
µs
d
Charge pump power-up delay
t TTP
Program/erase transition time
5
-
µs
t PAH
Programming address hold, new address setup
time
2
-
clock
cycles
t PEP
Charge pump enable hold time
1
-
clock
cycles
t EDP
Charge pump power hold timee
5
t CHVP
Cumulative program high voltage period for each
row after erase.f
-
Data retention
µs
25
ms
100
-
years
-
100K
cycles
a. The programming pulse width is determined by the following equation:
tP W P = Tclk x (FTDIV+1) x (FTPROG+1), where Tclk is the system clock period, FTDIV is the contents of the
FLPSLR register and FTPROG is the contents of the FLPROG register.
b. The erase pulse width is determined by the following equation:
tE W P = Tclk x (FTDIV+1) x 4 x (FTER+1), where Tclk is the system clock period, FTDIV is the contents of the
FLPSLR register and FTER is the contents of the FLERASE register.
c. The program/erase start delay time is determined by the following equation:
tSDP = Tclk x (FTDIV+1) x (FTSTART+1), where Tclk is the system clock period, FTDIV is the contents of the
FLPSLR register and FTSTART is the contents of the FLSTART register.
d. The program/erase transition time is determined by the following equation:
tTTP = Tclk x (FTDIV+1) x (FTTRAN+1), where Tclk is the system clock period, FTDIV is the contents of the
FLPSLR register and FTTRAN is the contents of the FLTRAN register.
e. The program/erase end delay time is determined by the following equation:
tEDP = Tclk x (FTDIV+1) x (FTEND+1), where Tclk is the system clock period, FTDIV is the contents of the FLPSLR
register and FTEND is the contents of the FLEND register.
f. Cumulative program high voltage period for each row after erase t CHVP is the accumulated duration a flash cell is
exposed to the programming voltage after the last erase cycle. It is the sum of all tHV after the last erase.
85
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Flash EEPROM Data Programming
Symbol
Parameter
Conditions
re-programming timea
t PWD
Programming pulse width
t EWD
Erase pulse widthc
b
Min
Max
Units
1.32
-
ms
30
40
µs
1
-
ms
10
-
µs
t TTD
Program/erase transition time
e
5
-
µs
t PED
Charge pump enable hold time
1
-
clock
cycles
t EDD
Charge pump power hold timef
5
-
µs
100,000
-
cycles
-
years
t SDD
d
Charge pump power-up time
Write/erase endurance (high endurance)
Data retention
100
a. One re-programming cycle involves one erase pulse followed by programming of four bytes.
b. The programming pulse width is determined by the following equation:
tP W D = Tclk x (FTDIV+1) x (FTPROG+1), where Tclk is the system clock period, FTDIV is the contents of the
DMPSLR register and FTPROG is the contents of the DMPROG register.
c. The erase pulse width is determined by the following equation:
tE W D = Tclk x (FTDIV+1) x 4 x (FTER+1), where Tclk is the system clock period, FTDIV is the contents of the
DMPSLR register and FTER is the contents of the DMERASE register.
d. The program/erase start delay time is determined by the following equation:
tSDD = Tclk x (FTDIV+1) x (FTSTART+1), where Tclk is the system clock period, FTDIV is the contents of the
DMPSLR register and FTSTART is the contents of the DMSTART register.
e. The program/erase transition time is determined by the following equation:
tTTD = Tclk x (FTDIV+1) x (FTTRAN+1), where Tclk is the system clock period, FTDIV is the contents of the
DMPSLR register and FTTRAN is the contents of the DMTRAN register.
f. The program/erase end delay time is determined by the following equation:
tEDD = Tclk x (FTDIV+1) x (FTEND+1), where Tclk is the system clock period, FTDIV is the contents of the
DMPSLR register and FTEND is the contents of the DMEND register.
Flash EEPROM ISP-Memory Programming
Symbol
t PWI
t EWI
Parameter
Programming pulse with
Erase pulse width
Conditions
a
b
Data retention
a. Programming timing is controlled by the flash EEPROM data memory interface
b. Erase timing is controlled by the flash EEPROM data memory interface
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86
Min
Max
Units
30
40
µs
1
-
ms
100
-
years
Output Signal Levels
All output signals are powered by the digital supply (VCC).
The RESET and NMI input pins are active during the Power
Save mode. In order to guarantee that the Power Save current not exceed 1mA, these inputs must be driven to a voltage lower than 0.5V or higher than VCC-0.5V. An input
voltage between 0.5V and (VCC-0.5V) may result in power
consumption exceeding 1 mA.
Table22 summarizes the states of the output signals during
the reset state (when VCC power exists in the reset state)
and during the Power Save mode.
Table 22
Signals on a pin
Output Pins During Reset and Power-Save
Reset state
(with Vcc)
Power Save mode
PF[0:7]
TRI-STATE
Previous state
PG[0:7]
TRI-STATE
Previous state
PI[0:7]
TRI-STATE
Previous state
PL[0:7]
TRI-STATE
Previous state
PB[0:7]
TRI-STATE
Previous state
PC[0:7]
TRI-STATE
Previous state
87
Comments
I/O ports will maintain their values when
entering power-save mode
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21.0.1
Timing Waveforms
tXSp
X1 & X2
t XSh
tXSl
tCLKp
t CLKr
t CLKf
CLK
t CLKh
tCLKl
Output Valid
Output Hold
Output
Signal
Input Hold
Input Setup
Input
Signal
Output Active/Inactive time
Control
Signal 1
Output Active/Inactive time
Control
Signal 2
ac-1
Figure 36. Clock Waveforms
CLK
t Is
tIh
t Iw
ISE
t Is
NMI
tIh
t Iw
Figure 37. ISE & NMI Signal Timing
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88
CLK
t RST
RESET
Figure 38. Non-Power-On Reset
1
2
1
2
1
2
1
2
1
2
1
2
CLK
tCOv2
t COv2
TXD
tIS
RXD
tIH
Figure 39. USART Asynchronous Mode Timing
tCLKX
CKXn
t TXD
TXDn
tRXS
RXDn
tRXH
Figure 40. USART Synchronous Mode Timing
89
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2
1
1
2
1
2
2
1
1
2
2
1
CLK
t Is
PORTS B, C (input)
tIh
tO f
PORTS B, C (output)
tCOv1
t COv2
tCOv1
tCOv2
BUZCLK
Figure 41. Ports Signals Timing
tMSKp
MSK
t MSKs
tMSKl
Data In
t MSKh
tMSKh
D7
D6
D1
D0
tMDIs tMDIh
MDIDO
(slave)
D7
D6
D1
D0
tMDOv
t MDOf
tMDOf
tMDOh
MDODI
(master)
D7
D6
D1
D0
MCS
(Slave)
t MCSs
tMCSh
MRDY
(Slave)
tMRDYia
tMRDYa
CLK
Figure 42. MICROWIRE Transaction Timing, Normal Mode, MIDL Bit = 1
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90
tMSKp
MSK
tMSKs
tMSKh
D7
Data In
tMDIs
MDIDO
(Slave)
tMSKh
t MSKl
D7
D6
D1
D0
tMDIh
D6
D1
D0
tMDOv
t MDOf
t MDOf
tMDOh
MDODI
(Master)
D7
D6
D1
D0
MCS
(Slave)
tMCSh
t MCSs
MRDY
(Slave)
tMRDYia
CLK
tMRDYa
Figure 43.
MICROWIRE Transaction Timing, Alternate Mode, MIDL bit = 0
91
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t MSKp
MSK
t MSKs
tMSKh
Data In
D7
t MDIs
MDIDO
(slave)
t MSKh
tMSKl
D0
D6
t MDIh
D7
D0
D6
tMDOf
tMDOf
t MDOv
tMDOh
MDODI
(master)
D7
D0
D6
t MSKd
MCS
(Slave)
tMCSs
t MCSh
MRDY
(Slave)
t MRDYia
CLK
Figure 44. MICROWIRE Transaction Timing, Normal Mode, MIDL bit = 0
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92
tMRDYa
tMSKp
MSK
t MSKs
t MSKl
D7
Data In
D6
D0
D6
D0
t MDIh
t MDIs
MDIDO
(Slave)
t MSKh
t MSKh
D7
tMDOf
tMDOv
tMDOf
tMDOh
MDODI
(Master)
D7
D6
D0
tSKd
MCS
(Slave only)
tMCSs
t MCSh
MRDY
(Slave only)
tMRDYia
CLK
tMRDYa
Figure 45.
MICROWIRE Transaction Timing, Alternate Mode, MIDL bit = 1
93
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tMSKp
MSK
tMSKs
tMSKh
MDODI
(Slave)
DI7
t MDIs
MDIDO
(Slave)
t MSKh
t MSKl
DI6
DI0
t MDIh
tMITOp
DO7
tMITOp
DO0
DO6
tMDOnf
tMDOf
MCS
tMCSs
t MCSh
MRDY
t MRDYia
tMRDYa
CLK
Figure 46. MICROWIRE Transaction Timing, Data Echoed to Output, Normal Mode, MIDLBit= 0, MECHBit= 1, Slave
CLK
tTAL/ tTBL
tTAH/ t TBH
TnA/TnB
Figure 47. Multi-Function-Timer (MFT16) Input Timing
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94
21.0.2
Timing Tables
Table 23
Symbol Figure
a
36
tCLKh
36
tCLKl
36
tCLKr
t CLKf
Tclk
Output Signals
Description
Reference
Min (ns) Max (ns)
R.E. CLK to next R.E. CLK
CLK high time
At 2.0V
(Both Edges)
17.3
CLK low time
At 0.8V
(Both Edges)
17.3
36
CLK rise time on R.E. CLK
0.8V to 2.0V
3
36
CLK fall time on F.E. CLK
2.0V to 0.8V
3
CMOS output valid
All signals with prop. delay from CLK
R.E.
After R.E. CLK
tCOv1
50
64000a
CLK clock period
35
USART Output Signals
t TXD
45
TXDn output valid
After R.E. CLKXn
35
MICROWIRE / SPI Output Signals
tMSKh
42
MICROWIRE Clock High
At 2.0V (both edges)
80
tMSKl
42
MICROWIRE Clock Low
At 0.8V (both edges)
80
42
MICROWIRE Clock Period
MnIDL bit = 0: R.E. MSK to next R.E. MSKn
tMSKp
tMSKd
42
t MDOf
42
tMDOh
42
tMDOnf
42
200
MnIDL bit = 1: F.E. MSK to next F.E. MSKn
43
MSK Leading Edge Delayed (master
only)
Data Out Bit #7 Valid
MICROWIRE Data Float b
(slave only)
After R.E. MCSn
MICROWIRE Data Out Hold
Normal Mode: After F.E. MSK
0.5 t MSK 1.5 tMSK
56
0.0
Alternate Mode: After R.E. MSK
MICROWIRE Data No Float (slave only) After F.E. MWCS
MICROWIRE Data Out Valid
0
Normal Mode: After F.E. MSK
t MDOv
42
t MITOp
46
MDODI to MDIDO
(slave only)
Propagation Time
Value is the same in all clocking modes of the
MICROWIRE
tMRDYa
42
MRDY Active (slave only)
After R.E. of CLK
t MRDYia
MRDY Inactive (slave only)
MIDL bit = 0: After F.E. MSK
42
56
56
Alternate Mode: After R.E. MSK
56
MIDL bit = 1: After R.E. MSK
0
28
0
56
a. Tclk is the actual clock period of the CPU clock used in the system.
The value of Tclk is system dependent.
The maximum cycle time of 64000ns is for Power Save mode; in active mode, the maximum cycle time is limited to 250ns by the
high frequency oscillator.
b. Guaranteed by design, but not fully tested.
c. Hold time is 0 ns (min) for all outputs, unless specified otherwise.
Table 24 Input Signal Requirements
Symbol Figure
Description
Reference
Min (ns)
Max (ns)
250
tXSp
36
X1 period
R.E. X1 to next R.E. X1
50
tXSh
36
X1 high time, external clock
At 2V level (Both Edges)
0.5 Tclk - 4
tXSl
36
X1 low time, external clock
At 0.8V level (Both Edges)
0.5 Tclk - 4
a
t X2p
36
X2 period
t X2h
36
X2 high time, external clock
R.E. X2 to next R.E. X2
10,000
At 2V level (both edges)
0.5 Tclk - 500
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Table 24 Input Signal Requirements
Symbol Figure
Description
Reference
tX2l
36
X2 low time, external clock
At 0.8V level (both edges)
t Is
42
Input setup time
ISE
Before R.E. CLK
tIh
42
Input hold time
ISE, NMI, RXD1, RXD2
After R.E. CLK
t RST
43
Reset time
Reset active to reset end
Min (ns)
Max (ns)
0.5 Tclk - 500
12
0
4Tclk
Input Signals
Input Pulse Width
1*Tclk+13
USART Input Signals
t Is
39
Input setup time
RXDn (asynchronous mode)
Before R.E. CLK
tIh
39
Input hold time
RXDn (asynchronous mode)
After R.E. CLK
t CLKX
40
CKXn input period
(synchronous mode)
tRXS
40
RDXn setup time
(synchronous mode)
Before F.E. CKX in synchronous mode
tRXH
40
RDXn hold time
(synchronous mode)
After F.E. CKX in synchronous mode
12
0
200
4
2
MICROWIRE / SPI Input Signals
tMSKh
42
MICROWIRE Clock High
At 2.0V (both edges)
80
tMSKl
42
MICROWIRE Clock Low
At 0.8V (both edges)
80
42
MICROWIRE Clock Period
MnIDL bit = 0; R.E. MSK to next R.E. MSK
tMSKp
43
MIDL bit = 1; F.E. MSK to next F.E. MSK
200
tMSKh
42
MSK Hold (slave only)
After MCS becomes inactive
40
t MSKs
42
MSK Setup (slave only)
Before MCS becomes active
80
42
MCS Hold (slave only)
MIDL bit = 0: After F.E. MSK
tMCSh
tMCSs
tMDIh
43
42
MIDL bit = 1: After R.E. MSK
MCS Setup (slave only)
MIDL bit = 0: Before R.E. MSK
43
MIDL bit = 1: Before F.E. MSK
42
MICROWIRE Data In Hold (master) Normal Mode: After R.E. MSK
Alternate Mode: After F.E. MSK
44
42
MICROWIRE Data In Hold (slave)
Alternate Mode: After F.E. MSK
44
tMDIs
42
Normal Mode: After R.E. MSK
MICROWIRE Data In Setup
Normal Mode: Before R.E. MSK
Alternate Mode: Before F.E. MSK
44
40
80
0
40
80
Multi-Function Timer Input Signals
tTAH
47
TnA High Time
R.E. CLK
TCLK+5
tTAL
47
TnA Low Time
R.E. CLK
TCLK+5
tTBH
47
TnB High Time
R.E. CLK
TCLK+5
47
TnB Low Time
R.E. CLK
TCLK+5
a. Only when operating with an external square wave on X2CKI; otherwise a 32 kHz crystal network must be used
between X2CKI and X2CKO. If the slow clock is internally generated from the fast clock, it may not exceed this
given limit.
tTBL
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96
22.0 Appendix
22.1
8-BIT MICROWIRE/SPI (MWSPI)
22.1.1
MWSPI Problem Description
22.2.2
The timing and WATCHDOG module uses two different clock
signals for its operation, the slow system clock as well as the
fast system clock.
According to the specification, the MSKn clock output in master mode should have the value of the MnIDL bit of the
MUnCTL1 register, even when the module is disabled. However, the MSKn pin will always be at low level, when the alternate function of the MSKn pin is enabled and the module
is disabled. Thus, even if the MnIDL bit is set, the MSKn clock
will change to a low level as soon as the module is disabled.
If any slave is selected at this time, it will interpret this unwanted transition as a shift clock.
22.1.2
The slow system clock can either be generated by an external 32 kHz quartz or it can be derived from the fast system
clock by means of a prescaler counter in the CLK2RES modules. The TWM can operate off a maximum slow system
clock of 100 kHz. The WATCHDOG counter (down-counter)
is either clocked directly by the slow system (T0IN) or it is
decremented every time the counter T0 underflows
(T0OUT).
MWSPI Problem Cause
Even if the module is disabled and the alternate function of
the MSKn pin is enabled, the module can still influence the
MSKn pin and drives the default value ‘0’.
22.1.3
The fast system clock is used for accesses to TWM registers,
which build the user interface of the TWM. These user interface registers include all memory-mapped registers of the
TWM.
MWSPI Problem Solutions
Every time the user (CR16B core) writes to a TWM configuration register or to the WATCHDOG Service Data Match
register, this “high speed operation” must be synchronized to
the internal TWM logic running at the slow clock rate. This
synchronization process takes a variable number of low
speed clock cycles, depending on the ratio between the lowspeed and the high-speed system clock and the phase shift
between the two clock signals. The more the two frequencies
differ from each other, the longer it takes the synchronization
process.
When the MSKn idle level of ‘1’ is to be used, the following
procedure should be followed when the module is disabled:
1. Set the MSKn pin to high level in the corresponding port
data output register.
2. Configure the MSKn pin to an output in the corresponding port direction register.
3. Disable the alternate function of the MSKn pin in the corresponding port alternate function register.
4. Disable the MWSPI module.
22.2
TIMING AND WATCHDOG MODULE
22.2.1
Timing and WATCHDOG Module Problem
Description
Timing and WATCHDOG Module Problem
Cause
In other words, write operations to the TWM registers take a
certain number of low-speed clock cycles to show the desired effects to the TWM logic.
This fact is especially critical for the write operation for the
WATCHDOG service, as it affects the allowed window for a
valid WATCHDOG service.
The available window for a valid WATCHDOG service varies
with the TWM configuration and the operating mode of the
R16MHS9. Therefore it is not possible to generally provide
the limits for the maximum service window. However, the limits for the minimum service window is guaranteed and should
be used.
If the device runs in active mode, the synchronization process can take up to four WATCHDOG counter clock cycles.
This limits the available WATCHDOG service to the window
shown in Figure48:
Figure 48. WATCHDOG Services Windows in Active Mode
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If the device runs in power save mode, the synchronization
process can take up to eight WATCHDOG counter clock cy-
Figure 49.
22.2.3
cles. This limits the available WATCHDOG service to the window shown in Figure49:
WATCHDOG Services Windows in Power Save Mode
Timing and WATCHDOG Module Problem
Solutions
In order to guarantee a valid WATCHDOG service under all
circumstances, the WATCHDOG should only be serviced
within the guaranteed minimum valid window, as illustrated in
figure 48 and figure 49 in the previous section.
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CR16MES5/CR16MES9/CR16MFS5/CR16MFS9/ CR16MHS5/CR16MHS9/CR16MNS5/CR16MNS9/ CR16M9S5/
CR16MUS5/CR16MUS9/ Family of CompactRISC 16-Bit Microcontrollers
23.0 Physical Dimension
inches (millimeters) unless otherwise noted
80 Lead Molded Plastic Quad Flat Package
See NS Package Number VJE80A
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