Path: utzoo!attcan!uunet!husc6!bloom-beacon!mit-eddie!ll-xn!ames!ucsd!ucsdhub!jack!elgar!ford
From: ford@elgar.UUCP (Ford Prefect )
Newsgroups: comp.sys.att
Subject: Re: UNIX PC Graphics Questions
Summary: Actually some random trivia about the UnixPC keyboard/mouse driver
Keywords: unixpc kernel
Message-ID: <152@elgar.UUCP>
Date: 22 May 88 07:32:43 GMT
References: <2271@inco.UUCP> <267@uncle.UUCP> <700@naucse.UUCP> <989@umbc3.UMD.EDU>
Reply-To: ford@kenobi.UUCP (Mike Ditto)
Organization: Omnicron Data Systems,  Bonita, CA
Lines: 28

In article <989@umbc3.UMD.EDU> alex@umbc3.UMD.EDU (Alex S. Crain) writes:
>	On this train of thought though, Does anyone know how works the 
>keyboard controller? and does the mouse do its work through the controller
>registers, or is that different? If one of the folks with a hardware manual
>could breifly explain it, I would be most appreciative.

The microprocessor in the keyboard does most of the mouse work.  Mouse
motions are sent to the main cpu in the same stream as keystroke
codes.  There is a code that means "here comes some mouse info", and
another code that means "Ok, back to keyboard mode".  Anything
in-between is to be interpreted as mouse motions (given in relative x
and y distances and button states.)

The keyboard data format is rather interesting.  After any key
transition (pressing or releasing any key) the keyboard sends an
entire list of every key which is currently held down.  The driver
compares the new state with the previous state to see which key
changed, and in which direction (pressed or released).

None of this is documented, of course, even in the tech manuals.  I'll
let everyone guess how I discovered how it works.  :-) :-)

					-=] Ford [=-

"Once there were parking lots,		(In Real Life:  Mike Ditto)
now it's a peaceful oasis.		ford%kenobi@crash.CTS.COM
This was a Pizza Hut,			...!sdcsvax!crash!kenobi!ford
now it's all covered with daisies." -- Talking Heads