Newsgroups: comp.sys.ibm.pc
Path: utzoo!utgpu!jarvis.csri.toronto.edu!godzilla.eecg.toronto.edu!noworol
From: noworol@eecg.toronto.edu (Mark Noworolski)
Subject: ROMable code continued
Message-ID: <88Dec27.173804est.2417@godzilla.eecg.toronto.edu>
Summary: ROMing code, misc RS-232 oddities, DDJ Dec/87 code
Organization: EECG, University of Toronto
Distribution: na
Date: Tue, 27 Dec 88 17:37:54 EST

After just having spent an infuriating 2 or 3 hours playing with an RS-232
port I just thought I should share something with you. 

 Symptoms: RS-232 port does not echo characters when pins 2&3 are shorted on
it. I used kermit so pins 4,5 6,20,8 or whatever did not need to be
shorted.  This is in a 16Mhz 386 machine (8 bit peripheral). Although
receive works, send doesn't.

Repair: Move the card to a slow 4.77Mhz 8088 machine - now it works!!!

So does this mean that the peripherals slots out of the 386 are too fast (I
always thought that the clock on 8 bit peripherals was slowed down to
4.77Mhz)?

ROMing code:  I want to write some Turbo C (2.0) code which I can plug into
a standard PC motherboard ROM slot (next to the BIOS). I want it to control
RS-232 ports and do a minimal amount of computing (essentially it will be a
diskless, keyboardless, and screenless microcontroller). In the IBM
technical reference manual they say to put the bytes 55 AA ll (where ll is
the length of the EPROM program /512) ahead of your program. And also that
the checksum of the program should be 0 (mod 100hex). They only mention this
for the case of adapter card ROMs- is it the same for my case?  Is this
really all there is to it (for an assembly language program)?

Just today I managed to photocopy a DDJ article (Dec 1987- Jan 1988) which
describes (vaguely) how to ROM Turbo C programs. Unfortunately the amount of
code involved is horrendous (15 pages or so). Is there a source for DDJ
listings or if it's legal can someone who has got this code (or any other
ROM related loader programs) e-mail me a copy?

After this whole trauma is worked out I will summarize my findings on the
net.

Hoping for some help,
Happy new year,
mark  (if the following address doesn't do it try noworol@ecf.toronto.edu)

-- 
There's a really fine line between stupid and clever.

	Nigel - Lead Guitar, Spinal Tap

noworol@ecf.toronto.edu