HP98035 Real Time clock and AC5954N clock chip

[CuriousMarc]

Paul,
It will accept the set time command, but this has no effect. An error read shows code 16, "real time lost". The clock chip seems dead, nothing happening when looking at the test output after sending the test mode request.
Marc

-----Original Message-----
From: cctalk [mailto:cctalk-bounces at classiccmp.org] On Behalf Of Paul Berger via cctalk
Sent: Thursday, June 06, 2019 1:28 PM
To: CuriousMarc via cctalk
Subject: Re: HP98035 Real Time clock and AC5954N clock chip

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
>
>   
>