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 however 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 13-1. 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.
