How to measure/recognize good RTC chips?

[PeteV]

Hi!

Is there someone who could explain and give some advice on how to
measure the voltages on a 24-pin RTC chip, or more generally said, to
recognize, if the RTC chip is good or somehow useable, or slightly
bad or finally dead?

This same question applies and do interest me also regarding the
32-pin BIOS chips, even the case is somehow different on these.

I do have the pin descriptions for both of these, but the voltage
measuring seems to be somehow complicated, e.g. I have not been
able to find any +3V level voltage on any of the RTC pins, not even on
a brand new one, when power is off, and when power is on the voltages
on some pins do not stay constant but are varying from time to time.

So, the Vcc and ground are easy to recognize, but which pin voltages
may tell you how good or bad the RTC chip is? I do have the types
DS12C887A, DS12C887, DS12B887, DS12887A, OEC12C887A and
OEC12B887A, some are brand new, some may be finally dead, and
some somewhere there between.


Best regards,

Pete V.

[Rainbow]

There is no voltage output from the RTC block. The internal battery is only used to power the chip inside. You have to insert it in a board and test it.
Some of them are rechargeable - they might look dead (losing settings after a short poweroff) but will charge and became alive when powered for longer time - for example ODIN OEC12C887A on my MS-5120 board.