HP98035 Real Time clock and AC5954N clock chip

[Paul Berger]

Are you able to set the date and time on your clock?  I had disconnected 
one end of the diode in the charge circuit and powered the clock from a 
lithium primary cell.  I got all 8s when the battery went dead but when 
it was in that state when I tried to set the date and time any commands 
after that to the clock hung, I suspect because the nano processor got 
hung up trying to set the time.  After changing the battery it 
functioned normally again.

Paul.

On 2019-06-06 4:57 p.m., CuriousMarc via cctalk wrote:
> All HP fans in general and Tony in particular,
> I have the exact same problem. HP98035 real time clock module
> (http://hpmuseum.net/display_item.php?hw=168), plugged into a HP9825T
> (http://hpmuseum.net/display_item.php?hw=171), accepts commands, reads back
> all 8's. Battery is new, is charging and at the correct voltage.
> Documentation says "never run the module without the battery or it would
> damage the AC5954N clock chip". When I got the module it had not battery in
> it, so this is what could have happened. Tony, did you eventually repair
> your module or find some data on the clock chip?
> Marc
>   
>   
> List:       classiccmp <https://marc.info/?l=classiccmp&r=1&w=2>
> Subject:    AC5954N clock chip (I think)
> From:       ard () p850ug1 ! demon ! co ! uk (Tony Duell)
> <https://marc.info/?a=104957097300008&r=1&w=2>
> Date:       2001-08-26 22:55:32
> <https://marc.info/?l=classiccmp&r=1&w=2&b=200108>
> [Download RAW message
> <https://marc.info/?l=classiccmp&m=104961357310567&q=mbox>  or body
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>   
> I've got a non-working HP98035 real time clock module (for HP9825, etc)
> on the bench.
>   
> It accepts commands, it sends something back, so I think the bus
> interface and microcontroller are all fine. The problems are :
>   
> The real time reads back as 88:88:88:88:88
>   
> There is no activity on the crystal connected to the AC5954N clock chip
> (or at least I think it's a clock chip). Enabling the oscillator
> testpoint doesn't do a darn thing (well, the control/setting latch U7
> changes state so again the microcontroller is doing something). There is
> no activity on any of the pins on the chip.
>   
> It is getting power (it's not a problem with the NiCd battery).
>   
> I suspect the chip. Has anyone come across it? It may be a common digital
> clock/calendar chip, or at least related to one (if it is HP-custom).
> It doesn't seem to be particularly designed for a microprocessor bus --
> the output may be for direct driving 7-segment displays or maybe a
> multiplexed BCD output to link to a display decoder/driver.
>   
> Thanks in advance for any help.
>   
> -tony
>
>   
>