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 /|\