Modicon M340 Resume Operation Status After Power Outage

Fellow PLC Lovers :nodi:,

Good day!

I'm back again for another question. This time for Modicon M340.

I am currently developing a user program for a Soda company using the said PLC system above.

The requirement I must meet is that whenever a power outage occurs, the process shall return to the step where it was interrupted after power restoration. I am currently looking at M340's System Bits %S1 (Warm Restart) , %S12 (PLC Running) , %S13 (First Cycle After Switching to Run) and %S21 (First Cycle Task) but still confused on how to implement them to meet such requirement.

Can anyone help me with this one? Thank you very much.

ry_fern;

if I disconnect the 24VDC power supply to an M340 PLC, wait 10s, and then restore the power, any state that was stored in the PLC such as the status of memory bits, values of memory integers, latches, and the current step of a SFC is the same as it was prior to disconnecting the power.

The M340 Power supply, rack and processor manual indicates the PLC has no battery and seems to use flash type memory.

When the power is returned to the PLC, the program scan will begin with the memory of the PLC and state of the program exactly as it was.

It will be up to the program to determine that the PLC has been powered down, know what it was doing before being powered down, and to examine the inputs to determine what the appropriate next action is based on the knowledge that some unknown amount of time has passed since the last program scan.