Path: utzoo!utgpu!jarvis.csri.toronto.edu!mailrus!cs.utexas.edu!usc!apple!dlyons
From: dlyons@Apple.COM (David A. Lyons)
Newsgroups: comp.sys.apple
Subject: Re: Serial port and Interrupts
Message-ID: <38343@apple.Apple.COM>
Date: 5 Feb 90 10:19:42 GMT
References: <9001250751.aa06917@SMOKE.BRL.MIL> <9001262305.AA18311@mwunix.mitre.org> <992@rbdc.UUCP>
Organization: Apple Computer Inc, Cupertino, CA
Lines: 24

In article <992@rbdc.UUCP> mitch@rbdc.UUCP (Mitch Berry) writes:
>well there's all this talk on serial ports .... uhh remember that the iigs
>has a "print buffer" that can be turned on for the serial modem port...
>which means whether or not the xon/xoff is sent if you have this "print
>bufer" on you wont loose data...correct?
>
>mitch@rbdc

The buffering features of the Printer and Modem ports are implemented in
firmware, using interrupts to catch incoming characters and store them
in RAM until the application is ready to fetch them.

Disk access, for many devices, disables interrupts for long enough that
you lose some incoming characters--the 8530 serial chip has only a
3-character buffer in the hardware, I believe.
-- 

 --David A. Lyons, Apple Computer, Inc.      |   DAL Systems
   Apple II Developer Technical Support      |   P.O. Box 875
   America Online: Dave Lyons                |   Cupertino, CA 95015-0875
   GEnie: D.LYONS2 or DAVE.LYONS         CompuServe: 72177,3233
   Internet/BITNET:  dlyons@apple.com    UUCP:  ...!ames!apple!dlyons
   
   My opinions are my own, not Apple's.