When this bit is written to '1' and the I-bit in the Status register
is set, the Watchdog Interrupt is enabled. If WDE is cleared in combination with
this setting, the Watchdog Timer is in Interrupt mode, and the corresponding
interrupt is executed if timeout in the Watchdog Timer occurs. If WDE is set,
the Watchdog Timer is in Interrupt and System Reset mode. The first timeout in
the Watchdog Timer will set WDIF. Executing the corresponding interrupt vector
will clear WDIE and WDIF automatically by hardware (the Watchdog goes to System
Reset mode).
This is useful for keeping the Watchdog Timer security while using
the interrupt. To stay in Interrupt and System Reset mode, WDIE must be set
after each interrupt. This should not be done within the interrupt service
routine itself, as this might compromise the safety function of the Watchdog
System Reset mode. If the interrupt is not executed before the next timeout, a
System Reset will be applied.
Table 14-1. Watchdog Timer Configuration| WDTON(1) | WDE | WDIE | Mode | Action on Time-out |
|---|
| 1 | 0 | 0 | Stopped | None |
| 1 | 0 | 1 | Interrupt mode | Interrupt |
| 1 | 1 | 0 | System Reset mode | Reset |
| 1 | 1 | 1 | Interrupt and System Reset mode | Interrupt, then go to System Reset mode |
| 0 | x | x | System Reset mode | Reset |
Note: 1. WDTON Fuse set to '0' means
programmed and '1' means unprogrammed.
