djw@hpldsla.sid.hp.com (David Williams) (01/25/91)
Is there a definitive cheap, easy to get clock chip? ...the type which tells me the time, not the type that gives me a nice square wave! If not, what are people using to keep the time. Accuracy is not such a big deal, battery power use, cheapness, and availablity are. Also, I don't care if the output is in years/months/days/hours/etc or just seconds from some time, there will be a million layers of software above it. thanks, David Williams ___________________________________________________________________ Hewlett-Packard Scientific Instruments Division (SID) /\___________ 1601 California Ave, Palo Alto, CA, USA. /\______________/\________ phone: 415 857 6100. FAX: 415 852 8011 //\\____________|__________ HP-UX Mail: djw@hpldsla.hp.com / \____/\____/\___________ HPdesk: (djw)hpldsla/HP1900/00 /\____________/ \__________
lairdkb@mentor.cc.purdue.edu (Kyler Laird) (01/26/91)
Geez, there are so many! I have a Dallas Semiconductor data book that lists 16 different timekeeping devices. Some of the distinguishing features: serial output, built in battery, NV SRAM, watchdog circuits, alarms, EISA/ISA bus compat. The most basic chip (DS1202) is an 8-pin DIP, counts seconds-years (day of week) with leap year comp., 24x8 RAM, serial (3 wire) I/O, 2.0-5.5V operation, uses <300na@2V, single/multiple-byte data transfer, optional 16-pin SOIC package, TTL compat., temp -40 to +85 C. Needs 32.768 KHz crystal. Hope that helps! ------------------------------------------------------------------------------- Kyler Laird I'm the NRA lairdkb@mentor.cc.purdue.edu
terryb@cs.fau.edu (terry bohning) (01/27/91)
djw@hpldsla.sid.hp.com (David Williams) writes: > Is there a definitive cheap, easy to get clock chip? ...the > type which tells me the time, not the type that gives me a nice > square wave! > The Real Time Clock chip used in the PC/AT is an MC146818. Should be plentiful, but I don't know the cost. Hook up an xtal and it goes.
martin@adpplz.UUCP (Martin Golding) (01/30/91)
In <1990006@hpldsla.sid.hp.com> djw@hpldsla.sid.hp.com (David Williams) writes: >Is there a definitive cheap, easy to get clock chip? ...the >type which tells me the time, not the type that gives me a nice >square wave! >If not, what are people using to keep the time. Accuracy is not >such a big deal, battery power use, cheapness, and availablity >are. Aha, YES! The definitive clock chip is the Mostek: MK48T12B-15 Timekeeper (tm) ram Do Not Dispose of in Fire It's a regulation 8k by 8 SRAM, about half again as thick. In the top they've inserted a battery AND a crystal. The clock is sort of resident in part of the ram. Makes interfacing easy. And if you happen to need nearly 8k of free ram, there you are... We use the chip in a weird little computer we make, and I've never heard of a problem. Some drawbacks: I don't know what the current draw is compared to other SRAMs. If you're building a portable type circuit, this could be a problem. The increased thickness could be a problem (although we're using it on a Q-bus board just fine). You have to write some software, which presupposes a cpu. Although you could probably 'microcode' the thing with a prom and a sequencer. If you do end up using it, e-mail me. I'd like to hear. >David Williams >___________________________________________________________________ >Hewlett-Packard Scientific Instruments Division (SID) /\___________ And you didn't KNOW? tsk, tsk. Martin Golding
djw@hpldsla.sid.hp.com (David Williams) (02/01/91)
> >David Williams > >___________________________________________________________________ > >Hewlett-Packard Scientific Instruments Division (SID) /\___________ > > And you didn't KNOW? tsk, tsk. Hay, I'm a Unix software engineer. Some might say it's pretty good I even know what a real time clock chip is! :-) thanks for your input. djw@hpldsla.hp.com From now on I'll leave out the other stuff in sci.electronics!