Path: utzoo!utgpu!news-server.csri.toronto.edu!cs.utexas.edu!sdd.hp.com!hp-pcd!hpcvra!everett
From: everett@hpcvra.CV.HP.COM (Everett Kaser)
Newsgroups: comp.os.msdos.programmer
Subject: Re: Programming the keyboard port
Message-ID: <32430002@hpcvra.CV.HP.COM>
Date: 15 Aug 90 23:17:43 GMT
References: <90226.104110TOMIII@MTUS5.BITNET>
Organization: Hewlett-Packard Co., Corvallis, OR, USA
Lines: 23

/ TOMIII@MTUS5.BITNET (Thomas Dwyer III) /  8:41 am  Aug 14, 1990 / writes...
>According to my "Z-386/AT Series Workstation Technical Reference
>Manual, Volume II Programmable Registers" book, page 17-2 it says:
>  The Status Register (Port 064H)
>  The Status register is an 8-bit read-only register. [text ommited]
>Now on page 17-3 it says:
>  Command Register (Port 064H)
>  The command register is an 8-bit write-only register, addressed at I/O
>  port 064H. [text ommited]
>Ok people, how can the same port be both read-only and write-only?  Am
>I missing something?  
>
>Thomas Dwyer III                            TOMIII   @ MTUS5.BITNET

"Port" 64h is NOT read-only or write-only, it can be both read and written.
The "Status Register" (which is accessed by READing PORT 64h) is read-only.
The "Command Register" (which is accessed by Writing PORT 64h) is write-only.
Be careful not to confuse a CPU I/O port with the hardware to which it's
interfaced.

Everett Kaser                   Hewlett-Packard Company
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