NVRAM IC for Prema 6048 (or 6047) - DS1220AD doesn't work!

[perdrix]

For those of you who have a Prema 6047 or 6048, the original NVRAM that was fitted to my meter was a DS1220Y with a date code from 1987.  Clearly in need of replacement.

I ordered a DS1220AD-100 and found that it didn't work (Error 8 - checksum failure).  I could read the original DS1220Y, and could write the content into the DS1220AD with my Galep-4 programmer, but the meter was having none of it when I installed the DS1220AD.

I contacted Prema in Germany and they advised me to use an ST M48Z02-150 as the DS1220AD was known not to work.

I installed the M48Z02 into the meter with the rear panel switch in the "Cal" position, which wrote the original factory calibration constants for THIS meter from the EPROM into the NVRAM.

When I compared this data with what I'd previously read from the DS1220Y, it was pretty much the same (only ten bytes different), so I stored the data from the DS1220Y into the M48Z02 and put it back in the meter.

PS does anyone know the format and location of the date code printed on an M48Z02, as the current ST datasheet is silent on this issue.

HtH
Dave
So

[stj]

i would also like to know the date coding,
i think one of the big u.k. suppliers is shipping 10year old parts!

btw, dont throw the old part away - try to open it to remove the original cell and replace it with a coincell-holder.
if you fail - you lose nothing, but if you manage then it will be better than the factory part that has a smaller battery of unknown age.