I don't think I, for one, can HEAR at 40kHz, Alice (An OScope would see
the signal, of course.)  Zeuss can hear that, probably, and he'd howl &
bark in pain <G>  I'd suggest starting with an 800Hz tone, that jumped
to 2kHz, that sounds a LOT more audible to me <G>

  Mark

Alice Campbell wrote:
>
> 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 ?
> >