Greetings, I tend to lurk on this list, as generally I have little of
value to contribute. However I do have some electronics experience, and
have been researching the DS1287 RTC for you.
The DS1287 is no longer available, but the DS12887 is a pin compatible RTC
with a bit more RAM. I understand that it may not be a drop in replacement
for all applications, but that is anecdotal.
According to the chip spec, and given that the DS1287 and DS12887 would
work in a very similar fashion, it is *possible* that you can get a
battery reading by placing the positive lead of a VOM on pin 24, and the
ground on pin 12. I am not certain that this will work; here is why.

The chip has the integrated Lithium battery as previously noted. The
operating voltage on pin 24 (VCC+) is +5v (> +4.25v). If VCC drops below
+4.25 volts the RTC functions are no longer accessible. If VCC drops to
>+3v then "the external VCC switched off " (their words) and the lithium
battery is used to power the RTC and RAM.

I am unable to locate anything which would tell me how the switching
mechanism works, and as a result I am not certain that it is possible to
directly measure the voltage on the battery.  Therefore with out a second
system with the same RTC to test the suspected faulty unit, is not
possible to measure the battery voltage, and have full confidence that you
are performing an accurate test.

Additionally it should be noted that the DS12887 (and I suspect) the
DS1287 have a shelf life of 5 years.

The data sheet is avalible here:

http://pdfserv.maxim-ic.com/en/ds/DS12887.pdf


I hope this helps,

Keith Blankenship


On Thu, 20 Nov 2003, BUEHL,REINER \(HP-Germany,ex1\) wrote:

> Since I have no access to the console or the system at all, I was thinking
> more of tests like "measure voltage at pin x of the chip". If I can not find
> a way to get to the prom prompt, I might have to replace the chip and hope.
>
> Best regards,
> Reiner.
>
<snip>