[time-nuts] PM6681 and Timelab (was: PM6680 or 53131A for TimePod)

[Mark Sims]

Not only battery backed up SRAM but EEPROM config data has problems.   I'm a bit of a mass nut and have seen lots of old precision balances (i.e. Sartorious and Mettler) that used first gen serial EEPROMs to save their cal/config data.  Lots of these are going senile.   I had to build programmers for the SDA2006 and MCM2801 (?) chips since no commercial programmers support them.  They require 3 or 4 different voltages to program.  
Whenever I get in a scale I dump the old eeprom and rewrite it.  If the old eeprom already croaked,  I use a backup dump from a different scale.   Sometimes that causes issues if the scale has an internal cal weight that was calibrated at the factory...  then one gets to try and adjust the internal cal weight to match the weight specified in backup device data.