Hanafi Tanudjaja wrote>

>> may I connect output from 16c54 (one pin of portb ) directly to mic
>> input of sound card ?  (just curious)

AndrŽ Malafaya Baptista wrote:

> not directly. you should put a capacitor in series (in case your sound
> card doesn't have one already) and a voltage divider. 5V is much too
> high for a MIC input which should be driven with just some millivolts.

  Five millivolts sounds quite generous.  Try a 0.047µF capacitor in
series with a 1 Mohm resistor, in series with the output of the PIC and
a 1k ohm resistor from that at the "Mic" input of the soundcard, in
parallel to ground.

          0.047µF   1M ohm
    PIC o----||----\/\/\/\----+------o Mic in
                              |
               *----\/\/\/\---*
               |    1k ohm
    Gnd o------+---------------------o Gnd
-- 
  Cheers,
        Paul B.