NetNews Usenet Archive 1992 #30/NN_1992_30.iso/spool/sci/electron/20621

Text File | 1992-12-13 | 1.5 KB | 35 lines

Newsgroups: sci.electronics
Path: sparky!uunet!hobbes!deeptht!filbo
From: [e-mail] (Bela Lubkin)
Subject: WANTED: datasheet for Motorola MC146818 Real Time Clock chip
X-Claimer: I >am< R Pentomino!
Organization: R Pentomino
Date: Sat, 12 Dec 1992 05:31:22 GMT
Message-ID: <[e-mail]>
Sender: [e-mail] (News admin)
Lines: 23

Can anyone email me, or point me to a datasheet for the Motorola
MC146818 Real Time Clock chip used in IBM AT type computers?

What I'm most looking for is a table of the possible values for bits 3:0
of "status register A" -- the "rate selection bits".  The documentation
I have says that the IBM BIOS initializes these bits to 0110, thus
selecting a 1024 Hz square wave.  Unfortunately, it doesn't bother to
document what the other 15 combinations mean.  If you have only a
printed datasheet, let me know if you're willing to type in that table.

I suspect there's a lookup table in the chip, and that there might be
different versions of the chip with different lookup tables.  Any
further information or warnings about that would be appreciated.

If I receive an online datasheet I will make it available to others;
send me a request now (via email).  I do not intend to post it -- the
concept of a "summary" of a datasheet doesn't seem to make much sense...

Thanks in advance!

Bela Lubkin  * *  //  [e-mail]    ZURC ATNAS morf EVIL!
     @     * *   //  [e-mail]   uunet!sco!belal  uunet!sco!deeptht!filbo
R Pentomino  * \X/  Filbo @ Pyrzqxgl [phone] and XBBS [phone]