Article View: comp.os.msdos.programmer
Article #1888Re: Programming the keyboard port
From: Jim Alves-Foss
Date: Wed, 15 Aug 1990 20:25
Date: Wed, 15 Aug 1990 20:25
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In article <90226.104110TOMIII@MTUS5.BITNET> TOMIII@MTUS5.BITNET (Thomas Dwyer III) writes:
>...
>Ok people, how can the same port be both read-only and write-only? Am
>I missing something?
>...
>Thanks,
>Thomas Dwyer III TOMIII @ MTUS5.BITNET
>Network Programmer DWYERIII @ MTUS5.BITNET
>Computing Technology Services
>Michigan Technological University
Well, In the PC architecture we have 512 (not 256) ports. 256 are Input ports
and 256 are Output ports. Often a card will have a R/W register with a
single address. In your case you have TWO DISTINCT registers, one input
and one output but with the same address (064H(In) and 064H(Out)).
Hope this helps.
-Jim Alves-Foss (foss@iris.ucdavis.edu) /* Of course these are MY opinions */
(foss@[127.120.57.20]) /* and may change without warning. */
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Path: arc1-ca.pugleaf.net!utzoo!utgpu!news-server.csri.toronto.edu!cs.utexas.edu!usc!ucsd!ucbvax!ucdavis!iris!foss From: foss@iris.ucdavis.edu (Jim Alves-Foss) Newsgroups: comp.os.msdos.programmer,comp.sys.zenith,comp.sys.ibm.pc.misc Subject: Re: Programming the keyboard port Message-ID: <7576@ucdavis.ucdavis.edu> Date: 15 Aug 90 20:25:50 GMT References: <90226.104110TOMIII@MTUS5.BITNET> Sender: usenet@ucdavis.ucdavis.edu Reply-To: foss@iris.ucdavis.edu (Jim Alves-Foss) Followup-To: comp.sys.ibm.pc.programmer Organization: U.C. Davis - Department of Electrical Engineering and Computer Science Lines: 20