
224
CHAPTER 11 WATCHDOG TIMER
11.4
Operation of the Watchdog Timer
The watchdog timer generates a watchdog reset by an overflow of the watchdog
counter.
■
Watchdog Timer Operation
Operation of the watchdog timer requires the setting in Figure 11.4-1.
Figure 11.4-1 Setting of the Watchdog Timer
●
Activating the watchdog timer
•
The watchdog timer is activated when the first 0 after reset is written to the WTE bit of the watchdog
timer control register (WDTC). Specify the interval by specifying the WT1 and WT0 bits of the
watchdog timer control register at the same time.
•
When watchdog timer activation starts, it can be stopped only by a power-on or its own reset.
●
Clearing the watchdog timer
•
When a second or subsequent "0" is written to the WTE bit, the 2-bit counter of the watchdog timer is
cleared. If the counter is not cleared within the time interval, it overflows and a watchdog reset occurs.
•
The watchdog counter is cleared by reset generation, sleep mode or stop mode, transition to clock mode.
●
Intervals for the watchdog timer
Figure 11.4-2 shows the relationship between the clear timing of the watchdog timer and intervals. The
interval changes according to the clear timing of the watchdog timer and requires 3.5 to 4.5 times longer
than the count clock cycle.
●
Checking a reset cause
A reset cause can be determined by checking the PONR, WRST, ERST and SRST bits of the watchdog
timer control register (WDTC) after a reset.
PONR
-
WRST ERST SRST WTE
WT1 WT0
TBTC
7
6
5
4
3
2
1
0
WDTC
15
8
: Used
0 : Set "0"
0
bit
Summary of Contents for MB90460 Series
Page 1: ...The following document contains information on Cypress products ...
Page 3: ......
Page 5: ......
Page 9: ...iv ...
Page 41: ...22 CHAPTER 1 OVERVIEW ...
Page 45: ...26 CHAPTER 2 NOTES ON HANDLING DEVICES ...
Page 83: ...64 CHAPTER 3 CPU ...
Page 95: ...76 CHAPTER 4 RESET ...
Page 107: ...88 CHAPTER 5 CLOCK ...
Page 131: ...112 CHAPTER 6 LOW POWER CONSUMPTION MODE ...
Page 175: ...156 CHAPTER 7 INTERRUPT ...
Page 181: ...162 CHAPTER 8 MODE SETTING ...
Page 223: ...204 CHAPTER 9 I O PORT ...
Page 237: ...218 CHAPTER 10 TIME BASE TIMER ...
Page 247: ...228 CHAPTER 11 WATCHDOG TIMER ...
Page 275: ...256 CHAPTER 12 16 BIT RELOAD TIMER ...
Page 373: ...354 CHAPTER 14 MULTI FUNCTIONAL TIMER ...
Page 485: ...466 CHAPTER 16 PWC Timer ...
Page 531: ...512 CHAPTER 17 UART ...
Page 559: ...540 CHAPTER 19 DELAYED INTERRUPT GENERATOR MODULE ...
Page 589: ...570 CHAPTER 20 8 10 BIT A D CONVERTER ...
Page 601: ...582 CHAPTER 21 ROM CORRECTION FUNCTION ...
Page 633: ...614 CHAPTER 23 512K 1024K BIT FLASH MEMORY ...
Page 645: ...626 CHAPTER 24 EXAMPLE OF F2 MC 16LX MB90F462 F462A F463A CONNECTION FOR SERIAL WRITING ...
Page 715: ...696 APPENDIX ...
Page 716: ...697 INDEX INDEX The index follows on the next page This is listed in alphabetic order ...
Page 739: ......