Distributed I/O system
150 System Manual, 12/2016, A5E03576849-AG
Basics of program execution
Events and OBs
Response to triggers
The occurrence of a start event results in the following reaction:
● If the event comes from an event source to which you have assigned an OB, this event
triggers the execution of the assigned OB. The event is positioned in a queue according
to its priority.
● If the event comes from an event source to which you have not assigned an OB, the CPU
executes the default system reaction.
Note
Some event sources, such as startup, pull/plug, exist even if you do not configure them.
The table below provides an overview of the start events, including the possible values for
OB priority, possible OB numbers, default system reaction and number of OBs. The table is
sorted in ascending order by OB numbers.
Possible priorities (default
priority)
Default system
response
1)
2)
2)
2)
2)
Cyclic interrupt
2)
2 to 24 (8 to 17, frequency
30 to 38, ≥ 123 Not applicable 0 to 20
2)
Manufacturer-specific or
profile-specific interrupt
2 to 24 (4) 57 Ignore 0 or 1
Synchronous cycle interrupt
3)
22 80
0 or 1
Cycle monitoring time ex-
STOP
Pull/plug interrupt for mod-
2 to 26 (6) 83 Ignore 0 or 1
Rack error 2 to 26 (6) 86 Ignore 0 or 1
4)