test program and circuit:

just write a simple delay loop that reduces 4mhz (effective
instruction rate 1 mhz) to about 8khz.  put a piezo buzzer at port
b1.  toggle b1 at 8khz.  replace crystal with 20khz.  the low tone at
8 khz should jump to a high tone at 40 khz.  No sound will come out
if it doesnt work.

alice

,
> >Please do anyone have a test code with simple circuit
> >for pic16f84 20mhz ?
>