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From: stew@harvard.ARPA
Newsgroups: net.micro.mac
Subject: Re: serial port I/O
Message-ID: <189@harvard.ARPA>
Date: Thu, 13-Jun-85 01:01:43 EDT
Article-I.D.: harvard.189
Posted: Thu Jun 13 01:01:43 1985
Date-Received: Sat, 15-Jun-85 06:42:55 EDT
References: <2238@mordor.UUCP>
Distribution: net
Organization: Aiken Computation Laboratory, Harvard
Lines: 29

> I've been trying to put together an application which will use the
> modem port to talk to a standard RS-232C device (modem or VAX).
> I was able to get it to work, but I've run across a couple of
> unexpected software problems.  I am using the Megamax C compiler.
> 
> My first problem is that a number of the routines (OpenDriver,
> SerSetBuf, SerReset) are returning a positive "error code".  I
> interpreted *IM* to say that a successful driver call will return
> 0 and an unsuccessful one will return a negative error code.  The
> functions I call appear to work, so I now ignore the error code
> unless it is negative.  (Before I had this code debugged I would
> occasionally see a negative error code, and they were always
> meaningful.)  Does the positive number have any meaning?
>
>   John Bruner (S-1 Project, Lawrence Livermore National Laboratory)
>   MILNET: jdb@mordor.ARPA [jdb@s1-c]	(415) 422-0758
>   UUCP: ...!ucbvax!dual!mordor!jdb 	...!decvax!decwrl!mordor!jdb

The MegaMax PBOpen routine returns the wrong value.  It throws away
the ROM trap's result and instead returns the value in the ioResult
field.  I have fixed, but I don't think I can post source code for
MegaMax's library.  I suggest you disassemble and look at file6.o,
and then recode it yourself (it's only a few lines of asm).  This
will hopefully be fixed in a new version of MegaMax C rumored to
be out this month.
-- 
-----------------------
Stew Rubenstein     UUCP: ihnp4!harvard!stew
Harvard Chemistry   ARPA: stew@harvard