Siemens Simatic S7-300 CPU 31xC Series Installation And Operating Instructions Manual page 149

Commissioning
Commission the DP CPU as a DP master in the PROFIBUS subnet as follows:
1. Download the PROFIBUS subnet configuration created with STEP 7 (preset
2. Switch on all of the DP slaves.
3. Switch the DP CPU from STOP to RUN.
Start-up of DP CPU as DP master
During start-up, the DP CPU checks the configured preset configuration of its DP master
system against the actual configuration.
If preset configuration = actual configuration, the CPU switches to RUN mode.
If the preset configuration ≠ to the actual configuration, the configuration of parameter
Start-up if preset configuration ≠ actual configuration determines the start-up behavior of the
CPU.
Startup when the preset configuration ≠ actual
configuration = yes (default setting)
DP CPU switches to RUN.
(BUSF LED flashes if any of the DP slaves
cannot be addressed)
Recognizing the operating state of DP slaves (Event recognition)
The table below shows how the DP CPU operating as a DP master recognizes operating
mode transitions of a CPU operating as a DP slave or data exchange interruptions.
Table 8-8
Event
Bus failure interrupt
(short-circuit,
connector unplugged)
DP slave:
RUN → STOP
DP slave:
RUN → STOP
S7-300, CPU 31xC and CPU 31x: Installation
Operating Instructions, Edition 08/2004, A5E00105492-05
configuration) from the PG to the DP CPU.
Event recognition by CPUs 31x-2 DP/31xC-2 DP operating as DP master
What happens in the DP master?
Call of OB86 with the message Station failure
•
(coming event; diagnostic address of the DP slave assigned to the DP
master)
With I/O access: call of OB 122
•
(I/O access error)
Call of OB82 with the message Module error
•
(incoming event; diagnostic address of the DP slave assigned to the DP
master; Variable OB82_MDL_STOP=1)
Call of OB82 with the message Module OK
•
(outgoing event; diagnostic address of the DP-Slave assigned to the DP
master; Variable OB82_MDL_STOP=0)
8.5 Commissioning PROFIBUS DP
Startup when the preset configuration ≠ actual
configuration = no
DP CPU remains in STOP mode, and the BUS
LED flashes after the set Monitoring time for
transfer of parameters to modules.
The flashing BUSF LED indicates that at least
one DP slave cannot be accessed. In this case,
check whether all DP slaves are switched on or
correspond with your configuration, or read out
the diagnostic buffer with STEP 7.
Commissioning
8-25