Alarm on S7 PLC going to STOP mode

[twinsen]

WinCC OA 3.14, S7 driver with first device and redundant device configured to connect to SIMATIC S7-400H PLC. The connection is fine, but I can't figure out
how to detect when one of the PLC's CPU goes from RUN to STOP mode. I want to have an alarm triggered in that case.
The driver's internal DP element ConnState is set only when the CPUs are disconnected from the network or powered off.
How to detect the STOP mode of SIMATIC PLCs?

[fmulder]

We were facing the same question and have eventually decided to implement a watchog. We poll an integer from the PLC. When the integer stops counting then we assume that 'something is wrong' and raise an alarm. We do not specifically look at status 'STOP'. (we just conclude that it probably has stopped for some reason)

Hope this helps

Share the fun
Frenk Mulder

[twinsen]

Thanks, Frenk! I though maybe WinCC OA could offer a more graceful solution, but looks like I'll have to implement a watchdog too.

[Gertjan van Schijndel]

The operating state of the plc is written on the 'OpState' element.

[twinsen]

Thanks for the tip! I'll use this element. But it works a bit differently than stated in the documentation, I got this:
0 - Both CPU are in STOP
2 - Only one CPU is in RUN
9 - Both CPU are in RUN

[agruber]

FYI, at least in 3.15 the documentation describes the states of the H-systems.

For you reference I copy them here:

When using redundant PLCs (H-System), different states will be sent by the driver:
0 UNKNOWN
1 CPU STOP (Updating)
2 CPU STOP (Full reset)
3 CPU STOP (Initializing)
4 CPU STOP (Both PLCs are running)
5 CPU START (Cold start)
6 CPU START (Warm start)
7 CPU START (Resuming)
8 RUN SOLO (Only one PLC is running)
9 RUN REDU (Both PLCs are running)
10 CPU HALT
11 CONNECTING
12 UPDATING
13 DEFECT
14 SELFTEST
15 NO POWER

BR,
Andreas
Customer Care

[twinsen]

Yep, I read that. But for some reason, in my case, RUN SOLO is indicated by value 2, not 8.

[nmnogueira]

For an H-system the following states apply:

0 - Stopped - Both CPUs in STOP
1 - Starting
2 - Run Solo - Only one CPU in RUN
3 - Stopped - Initializing
4 - Stopped - Both PLCs are running
5 - Starting - Cold start
6 - Starting - Warm start
7 - Starting - Resuming
8 - Run Solo - Only one CPU in RUN
9 - Run Redu - Both PLCs are running
10 - HALT
11 - Connecting
12 - Updating
13 - Defect
14 - Selftest
15 - No Power