Path: utzoo!utgpu!news-server.csri.toronto.edu!cs.utexas.edu!sdd.hp.com!elroy.jpl.nasa.gov!ncar!gatech!mcnc!ncsuvx!news
From: bank@lea.ncsu.edu (Dave The DM)
Newsgroups: comp.os.msdos.programmer
Subject: Re: Int 14h protocol
Message-ID: <1990Dec23.021020.12492@ncsuvx.ncsu.edu>
Date: 23 Dec 90 02:10:20 GMT
References: <CHAS.90Dec19185228@tira.uchicago.edu>
Distribution: comp.
Organization: /etc/organization
Lines: 45

In article <CHAS.90Dec19185228@tira.uchicago.edu> chas@tira.uchicago.edu (Charles Blair) writes:
>
>I would like a description of the Int 14h protocols so that I can
>adapt some asynchronous communications software written in 8086
>assembly language to run over Ethernet. Can anyone point me to the
>specs? (I already have the telnet driver I need which would grab the
>Int 14h I/O.) 
>
>Is it as simple as converting the program to using Int 14h BIOS calls
>instead of writing directly to the hardware, or is something else also
>involved?
>
>Thanks.
>--
>Bitnet:                 pmrcjdb@uchimvs1
>Internet:       cjdb@midway.uchicago.edu

    According to the book "System BIOS for the IBM PC/XT/AT" put out by
Phoenix Technologies (1989 printing, ISBN 0-201-51806-6, Chapter 12),
there are four INT 14h services offerred (Services 04h thru FFh are
listed as "Reserved"...the others are listed as being available on all
platforms).
    These are:
 
         00h - Initialize Serial Communications Port
         01h - Send character
         02h - Receive Character
         03h - Read Serial Port Status

    I won't go into detail of the I/O signals discussed, theory of
operation, baud rate, I/O ports used, and error conditions. Check the
book out at your local library or buy it from your local computer

store...it isn't worth the net bandwidth.
 
    I seem to recall the "C Programmer's Guide to Serial Communications"
...or perhaps it was "Microsoft C Run-Time Library Reference" saying
something about an effective data transmission rate limitation of 1200
baud due to interrupt overhead and that you'd do better to use your
own interrupt hander. I dunno for sure...all the stuff I've written
using this service has been polled operation rather than
interrupt-driven as I wasn't worried about speed.

Dave the DM
bank@lea.csc.ncsu.edu