188
CHAPTER 12 WATCHDOG TIMER
■
Activation
The watchdog timer is activated by writing "0" to the WTE bit of the WDTC register while the watchdog
timer is stopped. At the same time, the WT1 and WT0 bits are used to set the watchdog timer reset interval.
Only the interval setting specified during activation is valid.
■
Watchdog Counter
Once the watchdog timer is activated, the watchdog timer counter must be periodically cleared within the
program. Writing "0" to the WTE bit of the WDTC register clears the watchdog counter. The watchdog
counter consists of a two-bit counter which uses the carry signals of the time-base timer as a clock source.
Therefore, the watchdog reset time may become longer than the setting if the time-base counter is cleared.
Figure 12.2-2 is a diagram of the watchdog timer operation.
Figure 12.2-2 Watchdog Timer Operation
■
Watchdog Stop
The watchdog timer is stopped by transition to stop mode, time-base timer mode or sleep mode.
■
Watchdog Deactivation
The watchdog timer is deactivated by any kind of reset
■
Watchdog Timer Behavior in Stop Mode, Time-base Timer Mode, and Sleep Mode
When transition to stop mode, time-base timer, mode or sleep mode occurs, watchdog timer is cleared and
stops. When CPU is release from stop mode, time-base timer mode, or sleep mode, watchdog timer starts
counting again from cleared state (Table 12.2-1).
00
01
10
00
01
10
11
00
Time-base
Watch-dog
WTE
w
rite
Watchdog
clear
Watchdog reset
Watchdog
activation
Summary of Contents for MB90390 Series
Page 2: ......
Page 4: ......
Page 17: ...xiii APPENDIX D List of Interrupt Vectors 690 INDEX 695 ...
Page 18: ...xiv ...
Page 132: ...104 CHAPTER 5 CLOCKS ...
Page 152: ...124 CHAPTER 6 CLOCK MODULATOR ...
Page 210: ...182 CHAPTER 11 TIME BASE TIMER ...
Page 218: ...190 CHAPTER 12 WATCHDOG TIMER ...
Page 264: ...236 CHAPTER 14 16 BIT RELOAD TIMER WITH EVENT COUNT FUNCTION ...
Page 274: ...246 CHAPTER 15 WATCH TIMER ...
Page 306: ...278 CHAPTER 17 DTP EXTERNAL INTERRUPTS ...
Page 338: ...310 CHAPTER 18 8 10 BIT A D CONVERTER ...
Page 364: ...336 CHAPTER 19 UART0 UART1 ...
Page 398: ...370 CHAPTER 20 UART2 UART3 Figure 20 5 2 ORE Set Timing Receive data RDRF ORE ...
Page 432: ...404 CHAPTER 20 UART2 UART3 ...
Page 482: ...454 CHAPTER 22 SERIAL I O ...
Page 560: ...532 CHAPTER 24 STEPPING MOTOR CONTROLLER ...
Page 582: ...554 CHAPTER 27 ROM MIRRORING MODULE ...
Page 632: ...604 CHAPTER 29 EXAMPLES OF SERIAL PROGRAMMING CONNECTION ...
Page 722: ...694 APPENDIX ...
Page 723: ...695 INDEX The index follows on the next page This is listed in alphabetic order ...
Page 740: ......