Bruce - Thanks for your reply. What you said is starting to make sense... For a ST pin to recognize input, it has to reach ~4V. For a TTL pin to recognize input, it has to only reach ~2V. Is that correct? So what you are saying is that in order to use a ST pin for serial input, the "signal" needs to be ~4+ Volts. And I am assuming that in most cases this would require a MAX232 to achieve those levels. Correct?

OK, let's just forget about the input for the time being. Can I use a ST pin for TXmit without any problems? Right now, the program transmits (supposed to) the commands to start playing when it receives a trigger. Well, I don't seem to be able to do that either. Any thoughts?

Here's my code:
Code:
     INCLUDE "modedefs.bas" 'Needed for serial communication

@ DEVICE HS_OSC              ; Hi Speed Osc  

    ADCON1 = 7          ' Set PortA Pins as I/O pins
    CMCON = 7

    Trigger     var PORTC.6
    PlayLED     var PORTD.1

    TXPin       var PORTA.2 'E.1
    RXPin       var PORTA.3 'E.2
    
    B0          var byte
    CR          CON 13       ' constant value of a carriage return

'****************************************************************

    low playled
    
'****************************************************************    
    PAUSE 3000                               'allow VMusic2 to initialize
    SEROUT txpin, T9600,["VST",CR]           'stop anything that's playing
    
'****************************************************************
Loop0:
    if trigger = 0 then goto loop0 'button is pulled low via 10K resistor
    
    high playled
    SEROUT txpin, T9600,["VPF file000.mp3",CR] 'Play a file named "file000.mp3"
    PAUSE 2000
    
    SERIN rxpin, T9600, [">"],B0 'Waits for ">" to indicate playing done
    low playled
    PAUSE 2000
    goto loop0

end