Path: utzoo!utgpu!watmath!clyde!att!osu-cis!tut.cis.ohio-state.edu!unmvax!ncar!stout!cook
From: cook@stout.ucar.edu (Forrest Cook)
Newsgroups: sci.electronics
Subject: Re: Real time clock chip needed
Message-ID: <1112@ncar.ucar.edu>
Date: 9 Dec 88 19:42:58 GMT
References: <8519@burdvax.PRC.Unisys.COM> <1395@cseg.uucp>
Sender: news@ncar.ucar.edu
Reply-To: cook@stout.UCAR.EDU (Forrest Cook)
Distribution: na
Organization: Field Observing Facility, NCAR, Boulder, CO
Lines: 21

In article <1395@cseg.uucp> gmg@hcx.uucp (Greg M. Garner) writes:
>In article <8519@burdvax.PRC.Unisys.COM>, coltoff@PRC.Unisys.COM (Joel Coltoff) writes:
>> Does anyone know of a real time clock chip that can interface directly
>> to an 8051. Everyone I've seen so far is to slow to interface at 16 MHz.

>How about using the mostek 48T02 real time battery backed static ram?

I have used one of these clock chip/rams for over a year now and am quite
happy with its performance (with a Z-80).  There is no crystal trimmer cap, so
the trimming is done with a special pulse adder/stealer circuit that can be
set to add or subtract pulses every N minutes where N is stored in a special
register.  I have heard that HP uses a similar technique in their HP41
calculator.  The expected lifetime of the lithium cell is about 10 years if
I remember correctly, longer if the chip is usually powered up.

Maybe Mostek could come out with a 32K X 8 Ram with the same clock...

 ^	Forrest Cook   (The preceding comments were my Opinions)	 ^
/|\									/|\
/|\	  {husc6 | rutgers | ames | gatech}!ncar!stout!cook		/|\
/|\	{uunet | ucbvax | allegra | cbosgd}!nbires!ncar!stout!cook	/|\