phil@amdcad.AMD.COM (Phil Ngai) (05/26/87)
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.
--
Phil Ngai, {ucbvax,decwrl,allegra}!amdcad!phil or amdcad!phil@decwrl.dec.comapn@nonvon.UUCP (05/27/87)
in article <16819@amdcad.AMD.COM>, phil@amdcad.AMD.COM (Phil Ngai) says: > > > 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. > > -- > Phil Ngai, {ucbvax,decwrl,allegra}!amdcad!phil or amdcad!phil@decwrl.dec.com Most of the OKI chips are good. Small package, easy to program, and very low power. Price is competative. I have used them in about 3 of my designs so far. Alex P Novickis UUCP: {ihnp4,ames,qantel,sun,seismo,amdahl,lll-crg,pyramid}!ptsfa!nonvon!apn {* Only those who attempt the absurd ... will achieve the impossible *} {* I think... I think it's in my basement... Let me go upstairs and check. *} {* -escher *}
grr@cbmvax.UUCP (05/27/87)
In article <16819@amdcad.AMD.COM> phil@amdcad.AMD.COM (Phil Ngai) writes: > > 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. > > Phil Ngai, {ucbvax,decwrl,allegra}!amdcad!phil or amdcad!phil@decwrl.dec.com The OKI58321 is the low cost leader, but is super slow and needs to be accessed through some kind of parallel port. The OKI6242B can interface to a normal microcomputer bus running at normal, but not blazing speeds and is a good compromise. Ricoh makes a chip much like the 6242 that includes ~15 bytes of static RAM, useful for saving configuration or boot up data. These chips are also available as modules, with battery and/or crystal included, if the additional cost is a good trade off. There are lots of other chips available. Watch out for vapor chips and read the fine print on accessing, battery backup/voltage requirements and glitch/ latchup protection... -- George Robbins - now working for, uucp: {ihnp4|seismo|rutgers}!cbmvax!grr but no way officially representing arpa: cbmvax!grr@seismo.css.GOV Commodore, Engineering Department fone: 215-431-9255 (only by moonlite)
pozar@hoptoad.uucp (Tim Pozar) (05/27/87)
In article <16819@amdcad.AMD.COM> phil@amdcad.AMD.COM (Phil Ngai) writes: > >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. > >-- >Phil Ngai, {ucbvax,decwrl,allegra}!amdcad!phil or amdcad!phil@decwrl.dec.com I would watch out for chips that have the old daylight savings time programmed into them. I know of none that are on the current time standard. -- Tim Pozar UUCP pozar@hoptoad.UUCP Fido 125/406 USNail KLOK-FM 77 Maiden Lane San Francisco CA 94108
henry@utzoo.UUCP (Henry Spencer) (05/28/87)
> 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
henry@utzoo.UUCP (Henry Spencer) (05/31/87)
> I would watch out for chips that have the old daylight savings time > programmed into them. I know of none that are on the current time > standard. I recall none that are aware of daylight savings at all; that is usually left to the software, with good reason -- too much local variation. (My old home town, Saskatoon, ignores the whole stupid business and is on CST year round. Why did I come to Toronto... :-)) A subtle point that a number of the chips don't get quite right, by the way, is the possibility that leap years are not the ones with numbers divisible by 4. One chip -- I think it's the Oki one -- has a two-bit register that you set to indicate the leap-year phase; none of the others do. All users of the Gregorian calendar agree (I think) on which years are leap years, but they do not all agree on what numbers those years have. The obvious case in point is Japan, where traditional year numbering is referenced to the date the current Emperor took the throne. I'd guess that the Oki chip is the only one designed in Japan. (Of course, you can fudge around this in software by just using a different year as the origin year, since none of these chips have a full four-digit year register anyway...) -- "There is only one spacefaring Henry Spencer @ U of Toronto Zoology nation on Earth today, comrade." {allegra,ihnp4,decvax,pyramid}!utzoo!henry
jimc@iscuva.ISCS.COM (Jim Cathey) (06/01/87)
In article <8101@utzoo.UUCP> henry@utzoo.UUCP (Henry Spencer) writes: >> I would watch out for chips that have the old daylight savings time >> programmed into them. >I recall none that are aware of daylight savings at all; that is usually The Motorola 146818 _does_ have a daylight savings mode bit, but the notes with it state that it doesn't work quite right (especially not since they changed the DST week!) I think later versions of the documentation mark that bit as Reserved, Do Not Use!