knowledge of Siemens PCS7 and WinCC?


Thread Starter


We are using the latest in Siemens technology which are PCS7 for the hardware and WinCC for the HMI. There are two redundant CPUs for each
plant and we all know that when the primary (Master) fails, the second CPU will take over. At first, the process seem alright. Until
recently, when the master CPU experienced a fault, naturally it will go into STOP mode. But the second CPU did not take over. This is very
alarming for a redundant system to shutdown at the same time. We tried to figure out all the diagnostics, check the time of scanning but all
seem okay. Is there any apparent reason for this simultaneous shutdown of CPU? Thanks in advance..

Jeff Winborn

I was curious about what version of firmware you have and when you last compiled/downloaded the entire program. Firmware updates can be
downloaded from the Siemens customer support web site:


Of course, you will need a RAM card and a programming device. The Siemens hotline will usually program the RAM card for you. There are
explanations included on bug fixes for each release. Be forewarned that the absolute latest firmware version (3.0) is meant for PCS7 v5.2. I
don't know if there are any compatibility issues with older versions of PCS7. I have experienced similar problems which were resolved by
updating firmware and compiling/downloading the complete program. Too many incremental compiles/downloads have caused problems in the past.
Have you tried putting the master in stop just to see if the role swap occurs? Is it one particular fault that causes this problem?
Hi Jeff,
Thank you for the reply. Our hardware/firmware was up-to-date with the latest version which was downloaded by Siemens Germany last three months ago. I also thought that the problem will be resolved after the download. I think that the
problem is really internal because the master CPU can transfer to the slave when we shutdown the first one. Meaning, there's nothing wrong with the
redundancy when simulating the transfer mode (that is, shutting down the master. It will automatically transfer to the slave and the slave will eventually become the master). The problem lies inside which was not properly logged by the diagnostic. We were very alarmed because the system is now ONLINE and generating 55 MW of power (this is actually installed in a power plant). Siemens Germany has not resolved this problem yet. We are using S7-400 CPUs. There are three plantstations and are communicating with each other via a hub (connected to a telephone). I think the problem lies in the CPU. We tried to
swap the CPU (say, from A to B). A was originally the problematic CPU and it became B after the swap. So, I am certain that the problem is in the CPU. The watchdog tried to shutdown the master when the error triggered. But the absurd thing is, the slave also fails (as if the watchdog also was triggered by the same error as with the master).


We are currently busy with a project where we use 4 417h plc's with pcs7. During the last weeks we have had the same problems, we are still developping and commissioning. Each time the problem was unique. 1st: The driver we developed for the siemens vsd's (redundant) was the problem, when more than 10 of the slave's drop communication to the plc, both plc's went down. This was a software problem. 2nd: Still not sure but after downloading the network connections the problem was solved. When downloading hardware after overall reset it is adviced to download the network connections as well, for wincc is
connected as a named connection. 3d: Hardware settings, make sure that ob 85 is only call on incomming and outgoing events.(Clock settings)