> > If pre-scaler is changed to 1:1 (ie
> > 32768Hz count rate), then you'd re-load TMR1H with 0xC0,
> > so that the count starts at 0xC000 ( = -16384)
> 
> It doesn't seem to be your day, Jinx

It must be Thursday......... (well, it was, 3 hours ago, yawn)

>  I think it's easier to think of timer 1 as an unsigned 16 bit number
> that counts from 0 to 65535 then wraps back to 0 for a total of
> 65536 counts per interrupt.  If you want 32768 counts/interrupt,
> then the timer must be pre-loaded to skip 65536 - 32768 =
> 32768 counts = 8000h.

Just to clarify, mostly for Ed's benefit -

I'd been suggesting that the LED could be made to flash at 1Hz,
0.5s on, 0.5s off, which meant a 2Hz update rate. A pretty good
rate to flash at, as it has a real-world application

So with a 32768Hz crystal, 16384 increments (1:1 p/s) of
TMR1 would take 0.5s, hence loading it with 0xC000

-- 
http://www.piclist.com PIC/SX FAQ & list archive
View/change your membership options at
http://mailman.mit.edu/mailman/listinfo/piclist