Real Time Clock IC Replacement ?

[Hugo Holden]

The 5832 OKI real time clock IC was popular in vintage computers in the 1980's. It was also teamed up with an interface IC the 8255A-5. Some of these were sold as kits to build on an ISA card. I have one and the supplied software from JDR Microdevices (1986) and I'm going to attempt to build it and fit it to my IBM5155.

I was wondering though, since the 5832 only goes to 1999, whether there was a pin compatible replacement (or at least a very similar one that I could adapt) more modern RTC IC that goes to 2099 ? Or should I attempt a software patch ?

 

[James0555]

A quick scan of the datasheet shows it only uses the last two digits of the year - I don't know anything about the kit but if you need all 4 digits just need to run the output to add the first two .

Jim

 

[Chuck(G)]

Yes, but the day-of-the-week output will be incorrect. You could always roll back the calendar to, say, 1911 and simply add 2006 to the year, which should make things come out correctly.

 

[modem7]

Have you considered the DS1216E for your 5155 ?
See [here].
PM me if you are interested in purchasing one (with external battery) from me.

 

[Chuck(G)]

There's a wider variety of clock chips than most people realize.

Consider, for example, the DS1251. Not only do you get a "phantom" clock, but you also get 512KB of 70nsec static RAM, battery-backed.

 

[Hugo Holden]

Thanks for those great replies. I may want to use the DS1216E later on so I will PM modem7 later. That looks like a very neat solution. The external battery sounds like a good idea too. The Dallas internal batteries, despite the freshness seal, sometimes only go for 8 or 10 years, at least for their memory IC's.

I once fitted external batteries to the Dallas DS1225 in parallel with their internal battery (but later I simply went to Ramtron Fram):

http://worldphaco.com/uploads/TEKTRONIX_2465b_OSCILLOSCOPE_CALIBRATION___REPOWERING_THE_DS1225.pdf

Initially I will use Chuck(G)'s suggestion to fix the date because one reason I want to make the vintage RTC from JDR micro-devices is that they have provided the program written in BASIC (which I understand) but also written in assembly language which I am attempting to learn. So I think this will help me comparing the two programs. Also they have a very nice address decoder on the prototype card which I can use for another project. I think I can probably make a backup battery arrangement for the 5832 IC as it looks like it is low power and was designed for that.

 

[Hugo Holden]

There's a wider variety of clock chips than most people realize.

Consider, for example, the DS1251. Not only do you get a "phantom" clock, but you also get 512KB of 70nsec static RAM, battery-backed.

Wow, a non volatile Ram with a phantom clock !

 

[modem7]

I once fitted external batteries to the Dallas DS1225 in parallel with their internal battery (but later I simply went to Ramtron Fram):

There, you have the situation of the external battery trying to charge the depleted internal non-rechargeable battery. I see on the Internet, "In conversations on this topic with other Apple II Enthusiasts on Facebook, participants indicated that running current from the new CR2032 though the old embedded internal battery may be problematic and may eventually lead to membrane degradation of the old battery and a short."

 

[Hugo Holden]

There, you have the situation of the external battery trying to charge the depleted internal non-rechargeable battery. I see on the Internet, "In conversations on this topic with other Apple II Enthusiasts on Facebook, participants indicated that running current from the new CR2032 though the old embedded internal battery may be problematic and may eventually lead to membrane degradation of the old battery and a short."

Yes, I found that the current consumption (by the internal battery from the external added battery, the figures are in the article I mentioned) was much higher if the internal battery was severely degraded prior to paralleling the external battery. Of course the external battery idea was only applied when the internal battery had failed (and the IC useless anyway) or was expected to fail soon. In the DS1225 it is possible to disconnect the internal battery's negative terminal from the IC's ground pin, for the type that have the battery on the under surface (there are two types) if one was worried about degradation of the internal battery and leakage or shorts. It helps that its potted in resin. Also for adding a big external battery on flying leads I recommended a current limiting resistor.