Timer1 help - 500ms ISR for Timer1 on 16F688

[kd5uzz_]

Hello,
I've never used Timer1 before, I always use Timer2 for my LEDs, etc. This time I'm using a 16F688 and it doesn't support Timer2.

I'm using the internal clock @ 8mhz.

I need to check a pin every 500ms.

8,000,000/4 = 2,000,000 -> clock ticks
2,000,000/8 = 250,000 ticks per ISR

250,000 ticks = 5ms (1000/250,000) right?

So that means I've got to have a counter that counts 100 ISRs. Any better way to do it?

[kd5uzz_]

Oh yeah..

[PCM programmer]

It's a 16-bit counter. It can count from 0 to 65535. If you use a
pre-scaler of 8, the timer clock is 250,000 Hz. It takes that many clocks
to count up 1 second. To count for a 1/2 second, it takes half that many
clocks: 125,000. The timer can do that in two interrupts, at 62,500
clocks each.