Debugging functions, diagnostics and troubleshooting
10.7 Diagnostics of DP CPUs
S7-300, CPU 31xC and CPU 31x: Installation
10-20 Operating Instructions, Edition 08/2004, A5E00105492-05
Event detection
The table below shows how a CPU 31x-2 operating as DP master detects operating mode
transitions of a CPU operating as DP slave, or data exchange interruptions.
Table 10-10 Event detection of CPU 31x2 operating as DP master
Event What happens in the DP master?
Bus interrupt (short-
circuit, connector
removed)
• Call of OB 86 with the message Station failure (incoming event;
diagnostic address of Slot 0 of the DP slave that is assigned to the
DP master)
• with I/O access: call of OB 122 (I/O access error)
DP slave: RUN → STOP
• Call of OB 82 with the message Module error
(incoming event; diagnostic address of Slot 2 of the DP slave that is
assigned to the DP master; Variable OB82_MDL_STOP=1)
DP slave: RUN → STOP
• Call of OB 82 with the message Module OK
(outgoing event; diagnostic address of Slot 2 of the DP slave that is
assigned to the DP master; Variable OB82_MDL_STOP=0)
Evaluation in the user program
The table below shows how you can, for example, evaluate RUN to STOP transitions of the
DP slave in the DP master.
Table 10-11 Evaluating RUN to STOP transitions of the DP slave in the DP master
In the DP master In the DP slave (CPU 31x-2 DP)
Diagnostic addresses: (Example)
Master diagnostic address = 1023
Slave diagnostic address = 1022
(Slot 0 of slave)
(Diagnostic) address for "Slot 2"= 1021
(Slot 2 of slave)
Diagnostic addresses: (Example)
Slave diagnostic address = 422
Master diagnostic address = irrelevant
The CPU calls OB82 with the following information:
• OB82_MDL_ADDR:= 1021
• OB82_EV_CLASS:=B#16#39 (incoming event)
• OB82_MDL_DEFECT: = Module error
Tip: The CPU diagnostic buffer also contains this
information
In the user program you should also include SFC
13 "DPNRM_DG" for reading out DP slave
diagnostic data.
CPU: RUN -> STOP
The CPU generates a DP slave diagnostics
message frame
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