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Ralph Mowery

In article ,
says...

When I worked for a paper mill we had a machine lose memory, lightning storm I think. The Allen Bradley PLC had an EEPROM backup so we uploaded the program from it.

Counterintuitively to the maintenance section, "upload" to A-B means upload FROM the PLC, not TO the PLC. So we loaded the empty program into the EPROM, erasing it.

Not a problem, we had another EEPROM safely locked in a cabinet in the office.

Of course we repeated the same mistake on our only backup.

Where I worked we had lots of the AB PLCs. Seems to me that they did
many things backwards from more normal thinking,or what other companies
were doing.

What I really hated about them was if a card went bad you had to shut
down the whole PLC system. Something difficult to do and keep the
process from going bad. Much perferred some of the other equipment
where you could hot swap the bad card. When there are 30 to 50 cards
involved and each one has 8 to 16 production items on it, it can make a
mess out of production.