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From: henry@utzoo.UUCP (Henry Spencer)
Newsgroups: sci.electronics,comp.unix.wizards
Subject: Re: time of year clock chips
Message-ID: <8089@utzoo.UUCP>
Date: Thu, 28-May-87 13:41:47 EDT
Article-I.D.: utzoo.8089
Posted: Thu May 28 13:41:47 1987
Date-Received: Thu, 28-May-87 13:41:47 EDT
References: <16819@amdcad.AMD.COM>
Organization: U of Toronto Zoology
Lines: 18

> I'm designing a CPU board and wondered if anyone could recommend a
> time of year clock chip. Flames about particularly bad or hard to
> program time of year clock chips are welcome too. 

Of the ones I've seen specs for, the Intersil 7170 is the clear winner.
It does leap years, it does the battery-backup power switchover itself
(just the way it should -- it simply has two power pins, and if the main
pin voltage drops too far, it switches to the backup pin and shuts down
everything except basic timekeeping), it's latched against race conditions
(read the 100ths-seconds register and everything else is latched until
you read that one again), it gives you a settable alarm or a periodic
tick, and it talks to an 8-bit bus with a 300-ns access time.  One thing
I am not sure of is price/availability -- haven't yet used it myself.

The Sun-3 clock is a 7170.
-- 
"The average nutritional value    Henry Spencer @ U of Toronto Zoology
of promises is roughly zero."     {allegra,ihnp4,decvax,pyramid}!utzoo!henry