I'm using PBP244 and have not ever played with timers or interupts yet.

My project is a simple watchdog timer for an external device. The external device sends serial commands to the 877A to reset the count down timer. If for some reason, this command is not seen in xxx seconds, then the pic resets the external device.

All my serial code is working well and it's time for me to install the timer functions.

I assume, that the best way to acheive this would be to have a Word var that would be incremented by 1 each time a preset timer fires an interrupt. A predetermined serial command would Zero the word var and the process would repeat. If no command was received, the word var would increment to a point that causes my pic to perform the external device reset.

How would one have an interrupt fire approx once per second on a 877A @ 8 mhz? Any help would be much appreciated.