Hello guys,

I need your advice. Recently I encountered a problem regarding communication break between S7412 CPU and some external devices in the field. Communication is established via CP440 (440-1CS00-0YE0). The communication worked without any problem until supply voltage was switched off from the devices in the field.

Now, when power was restored, communication is OFF. Actually the data read by RECV_440 (FB9) are all zeros. I have tried warm and cold PLC restarts and even turned off the PLCs power supply unit, but that didn't solve the problem.

I'm very inexperienced when it comes to communication between PLC and some external devices. There is one example for set up connection for CP440 here:

https://support.industry.siemens.com/cs/attachments/88867653/88867653_FAQ_en.pdf

This worked before and then stopped after power down od field devices. What can I try in order to find out what is the reason. Unfortunately, because of the safety reasons I cannot switch off power on filed devices again.

What else can I try? I don’t want to make changes in the PLC program because it worked before. In the HW Config in CP440 module properties I have saw option: Reaction to CPU STOP set to “Continue”. But I have already tried to power off complete PLC (via turn off PSU) and that didn’t help.

Any advice would be highly appreciated.

Not really sure if this is relevant, but this is extract from the diagnostic buffer of the CP:

6ES7 440-1CS00-0YE0               Hardware                          1
- - -                             Firmware                          V 1.0.0

Rack:                             0
Slot:                             4

Event 1 of 8:  Event ID 16# F5C8:0008
Mode transition: CPU in RUN
Internal error, Incoming event

Event 2 of 8:  Event ID 16# F5C8:0004
IF 1: Module parameters already on CP (same time stamp)
Internal error, Incoming event

Event 3 of 8:  Event ID 16# F5C8:0007
Mode transition: CPU in STOP
Internal error, Incoming event

Event 4 of 8:  Event ID 16# F5C8:0008
Mode transition: CPU in RUN
Internal error, Incoming event

Event 5 of 8:  Event ID 16# F5C8:0004
IF 1: Module parameters already on CP (same time stamp)
Internal error, Incoming event

Event 6 of 8:  Event ID 16# F5C8:0003
IF 1: Module parameters accepted by CP
Internal error, Incoming event

Event 7 of 8:  Event ID 16# F5C8:0007
Mode transition: CPU in STOP
Internal error, Incoming event

Event 8 of 8:  Event ID 16# F5C8:0001
CP initialization terminated
Internal error, Incoming event

Like I said before, I have tried several times to restart PLC (via Warm and Cold restart) but without any success.