PLC concepts
4.1 Execution of the user program
S7-1200 Programmable controller
92 System Manual, 03/2014, A5E02486680-AG
Table 4- 7 Start information for pull or plug of modules OB
Event_Class Byte 16#38: module inserted
Rack or station failure OB
The "Rack or station failure" OB executes when the CPU detects the failure or
communication loss of a distributed rack or station.
Rack or station failure event
The CPU generates a rack or station failure event when it detects one of the following:
● The failure of a DP master system or of a PROFINET IO system (in the case of either an
incoming or an outgoing event).
● The failure of a DP slave or of an IO device (in the case of either an incoming or an
outgoing event)
● Failure of some of the submodules of a PROFINET I-device
If you have not programmed this OB, the CPU changes to STOP mode when any of these
conditions occur.
Table 4- 8 Start information for rack or station failure OB
Event_Class Byte 16#32: Activation of a DP slave or an IO device
16#33: Deactivation of a DP slave or an IO device
16#38: outgoing event
Time of day OBs execute based on configured clock time conditions. The CPU supports two
time of day OBs.
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