Dear all, 

i am wondering if you could assist me. In our system we have a dual redundant 412-5H PLC. Everything was operating fine until we performed the following changes:

• Changed all the IP addresses to the CPU and all the CP443-1 cards. The IP ranges were completely changed.
• Modified a Modbus TCP connection.

Since then, the following behaviour occurs:

Upon HW config download to the standby PLC , the stop light just flashes and the PLC does not go to run. The error code is 16#49A1 which means Stop caused by parameter assignment error:memory reset request. I am performing a factory reset to the unit and also deleting the data from flash card. Then I am downloading the HW again and i am getting the same result. 

The strange thing is that even if there is no code in the flash card the error is starting occurring straight after the HW config download.

The netPro compiles without any errors and the Master PLC operates in solo mode without any problems. All the comms (Modbus TCP etc.) to the Master PLC are ok.

Has anyone witnessed this behaviour before. I feel i am running into circles. 

I hope i have explain my situation clearly above. Any assistance will be much appreciated.

Thank you in advance.

Hi Tolis,

Can u share HW configuration? The parameters of both redundant CPUs must be identical in order to run H-redundancy. How many CPs u r using? For more availability, CPs should have different subnet name but identical IP addresses. Please refer STEP 7 - Fault-Tolerant Systems(S7hvsysb.pdf )manual [installed after Step-7 in documentation].

Also note that parameter assignment error also comes if there is wrong parameters for IO modules. Please share diagnostics buffer log.