Path: utzoo!utgpu!watmath!att!rutgers!ucsd!usc!samsung!uunet!ast!smithr
From: smithr@ast.UUCP (Richard H. E. Smith II)
Newsgroups: comp.sys.ibm.pc
Subject: Re: Turning off NumLock through softwar
Message-ID: <538@ast.UUCP>
Date: 17 Nov 89 01:19:55 GMT
References: <3932@ur-cc.UUCP> <110200029@uxe.cso.uiuc.edu> <1758@tellab5.TELLABS.COM>
Reply-To: smithr@ast.UUCP (Richard H. E. Smith II)
Organization: Northrop Corp. DSD, Rolling Meadows, IL
Lines: 23

In article <1758@tellab5.TELLABS.COM> fayne@tellab5.UUCP (Jeffrey Fayne) writes:
>In article <110200029@uxe.cso.uiuc.edu> mcdonald@uxe.cso.uiuc.edu writes:
>>
>>The interesting question is, why does it work? How does the light
>>bulb know that I changed a single bit in memory?
>>Doug MCDonald
>
>	The BIOS updates the keyboard (at least the AT keyboards) based
                                       ^^^^^^^^^^^^^^^^^^^^^^^^^
>  on the 0040:0017 status byte contents.
>

If you've got an XT with a clone keyboard that has a NUMLOCK light,
there's no support in the BIOS or keyboard interface for getting the bit
in ram back to the keyboard controller, so it won't change.  In that
case, the light (which is toggled by the keyboard controller micro when
it thinks you pressed NUMLOCK) will now work in reverse state.  Ditto
for the CAPSLOCK lamp if you've got one of those.

Why no support?  Genuine IBM keyboards didn't have the lamp.

------------------------------
---Dick Smith