watch dog timer and pic18f452

[delene]

I am using the PIC18f452 with WDT to reset.
The WDT timer only has a reset time on 1:128 which is not sufficient time.
I would like the timer to reset after 2 seconds.
My crystal is a 4 MHz.
How do I go about this

Thanks
Delene

[Ttelmah]

The 128 prescaler gives, a nominal 2.3 seconds timeout.
Remember the watchdog is running of it's own internal 'clock', not your crrystal. The watchdog interval is nominally 18mSec (caveat though, this changes a _lot_ with wide temperature excursions...). Hence the 128 prescaler gives 18E-3 * 128 = 2.304 seconds.
If you want longer watchdog times than this, the alternative is to have a system 'tick', running at say 100Hz, then in this reset the watchdog, if a counter is not zero, and decrement the counter. Set the counter to any value you require to give longer watchdog timeouts.

Best Wishes