Latched bits and EEPROM load on power loss

I have a SLC 5/03 set to load from EEPROM on power loss.
What happens to the bits that were latched, -(L)- , before the power loss?

I've read a lot of posts and can't find answer, Thanks.

When you load a program from EEPROM, it is as if you started over with a new program. If bits are latched in the EEPROM program, then they will be latched when the PLC switches back to RUN mode.

Thanks Lancie

Lancie1 said:

When you load a program from EEPROM, it is as if you started over with a new program. If bits are latched in the EEPROM program, then they will be latched when the PLC switches back to RUN mode.

Click to expand...

So after power cycle, the battery does not keep the bits latched even though it loads the 'new' program from the EEPROM?

even though it loads the 'new' program from the EEPROM?

Click to expand...

That is the key part. It DOES load a new program from the EEPROM, so whatever is in that program (it could be completely different) will now be in control. The old program that was in PLC memory is completely gone and all bits have been reset or replaced with what is in the current EEPROM program.

Loading from EEPROMs can be hazardous unless you know what is in the program in the EEPROM. Now if the EEPROM program was saved when the the same bits were latched as in the old program, then yes, they will be latched after the EEPROM load. Otherwise, not. In the usual case, some bits are on and some are off, depending exactly when the EEPROM program was captured. Is is usually best to save the EEPROM program with retentive outputs in a safe state.

In any case, the loading operation will not happen instantaneously, so there will be some seconds while the PLC outputs are off, until the new program is loaded and the PLC switches back to RUN mode.

Lancie1 said:

That is the key part. It DOES load a new program from the EEPROM, so whatever is in that program (it could be completely different) will now be in control. The old program that was in PLC memory is completely gone and all bits have been reset or replaced with what is in the current EEPROM program.

Loading from EEPROMs can be hazardous unless you know what is in the program in the EEPROM.

Click to expand...

Clear as a bell. Thanks a lot