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参数资料
| 型号： | M34570M8-XXXFP |
| 元件分类： | 微控制器/微处理器 |
| 英文描述： | 4-BIT, MROM, MICROCONTROLLER, PDSO36 |
| 封装： | 0.450 INCH, 0.80 MM PITCH, PLASTIC, SSOP-36 |
| 文件页数： | 18/32页 |
| 文件大小： | 319K |
| 代理商： | M34570M8-XXXFP |
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25
MITSUBISHI MICROCOMPUTERS
4570 Group
SINGLE-CHIP 4-BIT CMOS MICROCOMPUTER
WATCHDOG TIMER
Watchdog timer provides a method to reset the system when a
program runs wild. Watchdog timer consists of 16-bit timer (WDT),
watchdog timer enable flag (WEF), and watchdog timer flags
(WDF1, WDF2).
Timer WDT starts downcounting the instruction clocks as the
count source immediately after system is released from reset.
The underflow signal is generated when the count value reaches
“000016.” This underflow signal can be used as the timer 2 count
source.
When the WRST instruction is executed after system is released
from reset, the WEF flag is set to “1.” At this time, the watchdog
timer starts operating.
When the count value of timer WDT reaches “BFFF16” or
“3FFF16,” WDF1 flag is set to “1.” Then, if the WRST instruction
is not executed while the timer WDT counts 32767, the WDF2
______
flag is set to “1” and the RESET pin outputs “L” level to reset the
microcomputer. In software using the watchdog timer, make sure
that the WRST instruction is executed in 32766 machine cycles
or less in order to keep the microcomputer operating normally.
To prevent the watchdog timer from stopping in the event of
misoperation, the WEF flag is designed not to be initialized once
the WRST instruction has been executed. Note also that, if the
WRST instruction is never executed, the watchdog timer does
not start.
Fig. 20 Watchdog timer function
Fig. 21 Program example to enter the RAM back-up mode
when using the watchdog timer
Value of timer WDT
Flag WDF2
RESET pin output
System reset
WRST instruction
execution
Flag WEF
FFFF16
0000 16
Flag WDF1
3FFF16
BFFF16
WRST instruction
execution
The contents of the WEF flag, the WDF1 and WDF2 flags and
the timer WDT are initialized at the RAM back-up mode.
However, if the WDF2 flag is set to “1” at the same time that the
microcomputer enters the RAM back-up mode, system reset may
be performed.
When using the watchdog timer and the RAM back-up mode,
initialize the WDF1 flag with the WRST instruction just before
the microcomputer enters the RAM back-up mode (refer to Figure
21).
POF
EPOF
; POF instruction execution enabled
(RAM back-up mode)
Oscillation stop
WRST
; Clear WDF1 flag
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相关代理商/技术参数 |
参数描述 |
|---|---|
| M34570MD | 制造商:MITSUBISHI 制造商全称:Mitsubishi Electric Semiconductor 功能描述:SINGLE-CHIP 4-BIT CMOS MICROCOMPUTER |
| M34570MD-XXXFP | 制造商:RENESAS 制造商全称:Renesas Technology Corp 功能描述:SINGLE-CHIP 4-BIT CMOS MICROCOMPUTER |
| M34570N4232FP | 制造商:MITS 功能描述:New |
| M34571G4 | 制造商:RENESAS 制造商全称:Renesas Technology Corp 功能描述:SINGLE-CHIP 4-BIT CMOS MICROCOMPUTER |
| M34571G4FP | 制造商:RENESAS 制造商全称:Renesas Technology Corp 功能描述:SINGLE-CHIP 4-BIT CMOS MICROCOMPUTER |
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