Path: utzoo!utgpu!attcan!uunet!munnari!otc!metro!pta!teti!nswitgould!ausonics!grahams From: grahams@ausonics.OZ (Greyham Stoney) Newsgroups: comp.arch Subject: Re: real time clock chips Message-ID: <18@ausonics.OZ> Date: 12 Aug 88 04:36:45 GMT References: <91@jetson.UPMA.MD.US> Organization: Ausonics Pty Ltd, Sydney, Australia Lines: 37 in article <91@jetson.UPMA.MD.US>, susan@jetson.UPMA.MD.US (Susan Prothro) says: > > Hi. I'm seeking a real time clock chip that as a minimum can provide > month/day/year/day-of-week information as well as leap year > compensation and a configurable daylight savings time compensation. > In particular, for the daylight savings time I would like to be able > to configure the start and end dates and the amount of time > added/negated for the transition. > > A Hitachi part has been suggested, but the one I was shown doesn't > have the daylight savings time compensation function. BCD output is > preferable and I really only need one interrupt on a once-per-second > basis. I think you'll find that the Hitach part (ie: 146818) IS a good suggestion - although it has got built in daylight savings correction, it almost certainally does it on the wrong dates. (Does in Australia, anyway!). However, its got 50bytes of built in NVram which you could use to store all your configuration stuff. If you read the thing when your machine powers on, and get whatever O/S to do the timekeeping from then on, you can get the software to check if daylight savings has come into effect since the last time the machine was turned on, and correct the time accordingly (invisible to the user). You can do leap years the same way - the 146818 in particular does nothing about the end of century (ie: it goes back to year 00), and so doesn't correct for the 400year leap business; but you can do that in software at powerup too, and store the century in the nvram. Not exactly what you want, but you mightn't get a whole lot closer, and there's certainally no shortage of the chips around. Given the right software, you'd never know the difference anyway. regs, Greyham -- * Greyham Stoney: grahams@ausonics.oz - Ausonics Pty Ltd, Lane Cove. * (Time to PARTY!!!) greyham@utscsd.oz - The Uni of Technology, Sydney. * The views expressed may or may not be the views of my Uni or Employer. * (I don't know... I didn't ask them...)