dsPIC30F Family Reference Manual
DS70057C-page 10-8 © 2004 Microchip Technology Inc.
Table 10-2 shows time-out periods for various prescaler selections:
Table 10-2: WDT Time-out Period vs. Prescale A and Prescale B Settings
10.6.4 Resetting the Watchdog Timer
The WDT and all its prescalers are reset:
• On ANY device Reset
• When a PWRSAV instruction is executed (i.e., Sleep or Idle mode is entered)
•By a CLRWDT instruction during normal execution
10.6.5 Operation of WDT in Sleep and Idle Modes
If the WDT is enabled, it will continue to run during Sleep or Idle modes. When the WDT
time-out occurs, the device will wake the device and code execution will continue from where the
PWRSAV instruction was executed.
The WDT is useful for low power system designs, because it can be used to periodically wake
the device from Sleep mode to check system status and provide action if necessary. Note that
the SWDTEN bit is very useful in this respect. If the WDT is disabled during normal operation
(FWDTEN = 0), then the SWDTEN bit (RCON<5>) can be used to turn on the WDT just before
entering Sleep mode.
Prescaler B
Value
Prescaler A Value
1 8 64 512
1 2 16 128 1024
2 4 32 256 2048
3 6 48 384 3072
4 8 64 512 4096
5 10 80 640 5120
6 12 96 768 6144
7 14 112 896 7168
8 16 128 1024 8192
9 18 144 1152 9216
10 20 160 1280 10240
11 22 176 1408 11264
12 24 192 1536 12288
13 26 208 1664 13312
14 28 224 1792 14336
15 30 240 1920 15360
16 32 256 2048 16384
Note: All time values are in milliseconds.
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