From: Jason Green <news AT jgreen4 DOT fsnet DOT co DOT uk>
Newsgroups: comp.os.msdos.djgpp
Subject: Re: com1 programming .... a lot of question
Date: Thu, 18 May 2000 22:35:17 +0100
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Eli Zaretskii <eliz AT is DOT elta DOT co DOT il> wrote:

> On Thu, 18 May 2000, Alexei A. Frounze wrote:
> 
> > Btw, I usually connect 2nd and 3rd pins of the serial cable/connector in
> > order to test I/O on a single computer. Could this situation be problematic
> > for BIOS?
> 
> I don't think so, but I'm not really a hardware person.  Anybody?

I don't know about BIOS functions, but only looping pins 2&3 (Tx/Rx)
could definitely lead to different behaviours between programs.  

If some code is looking for a handshake line to be asserted then it
could appear to hang, if some other code ignores the handshake lines
then it will appear to work but could drop bytes.  

Loop-back the handshake lines, DTR-DSR and/or RTS-CTS.  And make sure
you also assert the outgoing handshake lines DTR & RTS.