susan@jetson.UPMA.MD.US (Susan Prothro) (08/11/88)
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. Does anyone have any chip suggestions? Thanks in advance - Susan M. Prothro
grahams@ausonics.OZ (Greyham Stoney) (08/12/88)
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...)
peter@ficc.UUCP (Peter da Silva) (08/16/88)
This is, of course, a time-of-day clock. A real-time clock is a circuit that provides precisely timed interrupts to the CPU. Wasn't it IBM that first came up with this particular misnomer? -- Peter da Silva, Ferranti International Controls Corporation, sugar!ficc!peter. "You made a TIME MACHINE out of a VOLKSWAGEN BEETLE?" "Well, I couldn't afford another deLorean." "But how do you ever get it up to 88 miles per hour????"
grahams@ausonics.OZ (Greyham Stoney) (08/17/88)
in article , peter@ficc.UUCP (Peter da Silva) says: > > This is, of course, a time-of-day clock. A real-time clock is a circuit > that provides precisely timed interrupts to the CPU. Wasn't it IBM that > first came up with this particular misnomer? Sorry. Have a look at, say, the 146818 RTC (yes, RTC) data sheets. 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...)
susan@jetson.UPMA.MD.US (Susan Prothro) (08/20/88)
In article <1263@ficc.UUCP>, peter@ficc.UUCP (Peter da Silva) writes: > This is, of course, a time-of-day clock. A real-time clock is a circuit > that provides precisely timed interrupts to the CPU. Wasn't it IBM that > first came up with this particular misnomer? Oh, of course....... Please refer to the Hitachi manual, "8/16-Bit Multi-Chip Microcomputer Data Book," pg.668. On this page is a chapter entitled, "HD146818 RTC (Real Time Clock Plus RAM)." ^^^^^^^^^^^^^^^ In addition to providing *some* of the time-of-day features that I am seeking, this part is described as providing three "precisely timed" interrupts which can be set to various intervals. (I am also seeking this feature, which is why I asked about real-time clocks.) Also, I would very much like to thank the three gentlemen who were not confused by my posting: Per Fogelstrom, Phil Kos and Greyham Stoney. The information you have provided has been very useful. To all others: I am still seeking chip information. Perhaps I shouldn't post to this newsgroup when I am seeking information; it seems to be reserved for "nit-picking" and philosophical discussions. - Susan Prothro