> cycles.  To achieve a 38KHz flash rate I need an interrupt every
> 26.3 us.  This calculates to loading the TMR0 with something like
> decimal 242 +/- 4 cycles for a half cycle at 38KHz.  This does not
> leave me very many cycles left for the ISR

Hi Tom, I imagine something like this for a simple LED flash and
1 sec counter

wait  goto wait   ;wait for TMR0 IRQ

isr  clear TMR0 IF flag
      reload TMR0 with half-cycle time
      toggle LED pin
      increment 76000 half cycles count
      skip if 76000 reached
      retfie        ;back to wait
      recognise and reset 76000 count
      retfie

You could bump Fosc up to 20MHz if you do need more ICs for
processing other tasks, but for this the 4MHz IntRC would be OK
To get as close to 38kHz as possible you'd need to work out a
pattern of reloads with 242 and 243 that will average out to 38kHz,
although most receivers have a fairly tolerant bandwidth (at the
expense of reducing range)

Have a look here for some other notes about timers

http://www.piclist.com/techref/microchip/timer.htm

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