Re: com port problem: it works on an Apple2, but not on a PC, why?

[grege@henson.cc.wwu.edu (Gregory M Ellis)]

kmccorm@access.digex.net (Kevin McCormick) writes:

>In article <1993Jun23.215637.11124@julian.uwo.ca> wlsmith@valve.heart.rri.uwo.ca (Wayne Smith) writes:
>>
>>We have an old Searle ISO-CAP Gamma counter that outputs data through
>>a serial line to an Apple ][.
>>A basic program does the data collection, and the Apple's serial port is
>>opened as 110 baud, 7 data bits, even parity, 1 stop (generic stuff).
>>
>>There are only 3 wires used: pins 1, 3 and 7.  Now, if this is standard
>>RS-232, then pins 1 and 7 are ground and 3 is the receive data line.

Try tying 6,8,20 together on the PC end - the serial port is waiting for 
handshaking signals from the peripheral (the Gama counter).  The Apple ][
used software handshaking (XON-XOFF) as I remember and PC's won't do that
unless the software controls it.  Someone else hinted at this as a possible
handshaking problem - and I think he's right.  We've frequently connected
XON-XOFF devices to PC's using the 6,8,20 to defeat the hardware handshaking
required by the PC.