From:	"Richard Ellingworth" <ricell AT globalnet DOT co DOT uk>
Newsgroups:	comp.os.msdos.djgpp
Subject:	Serial communications
Date:	Fri, 15 Oct 1999 21:23:55 +0100
Organization:	GXSN
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To:	djgpp AT delorie DOT com
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Reply-To:	djgpp AT delorie DOT com

Hello there. I recently started messing about with DJGPP and Allegro and I
am attempting to use the serial port. I have played around with Bill
Currie's communications library and also with the DZComm library, but I have
come up against the same problem in both. Although the terminal programs
supplied with the libraries both work, after I have modified them slightly
the program crashes with a SIGSEGV error (segmentation violation). In the
case of DZComm, the program transmits on the serial port quite happily but
as soon as a character is received the program falls over. If you comment
out the line that reads from the serial port then the crash goes away. Why
is this? Am I missing something fairly fundamental? I have never used a DPMI
server before, and frankly don't fully understand what I have to do in my
code. Do I have to lock some of my code and data in place to stop it being
paged around and causing the RX interrupt to fail? Is there somewhere that
explains exactly how to use the functions specified in the DPMI.H header in
words of one syllable?

Any help would be greatly appreciated.

Richard Ellingworth

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