M580 Standby CPU Index Overrun Error

[AvinashPatil]

Hello Forum,

We have been successfully operating HSBY M580 PLCs for several weeks, but recently the standby PLC encountered an error. The CPU module's LEDs were green, and the corresponding NOC communication module was blinking green and getting all the alarms related to redundancy failure from running master PLC. After restarting the power, the standby PLC resumed functioning and communicated with the Master PLC without any errors. This issue has occurred twice in the past two weeks and we did the same exercise.

Upon reviewing the diagnostic file, we found that the system word indicates %SW125 = DEF3, which corresponds to 'Index overflow/overrun.'

Could someone clarify what 'index overrun' means? also, I would appreciate any guidance on how to resolve this system error.

Thank you for your assistance!

Regards,

Avinash Patil

[Michael_Chan]

Perhaps this is the course. An "index overrun" or "index overflow" occurs when a program tries to access an array element outside its valid range. This typically happens when the index used is either negative or greater than the array's maximum size. Imagine trying to put more data into a container than it can hold; the excess data spills over into adjacent memory locations, potentially causing unpredictable behavior, data corruption, or system crashes.