Siemens SIMATIC ET 200SP System Manual page 121

Types of event sources
MC interpolator interrupt
Programming error (only for
global error handling)
I/O access error (only for
global error handling)
* If OB was not configured
** For these event sources, apart from the permanently assigned OB numbers (see column: possible OB numbers), you
can also assign OB numbers in STEP 7 from the range ≥ 123.
*** If the cycle monitoring time is exceed twice within a cycle, the CPU always switches to STOP, regardless of whether
OB80 was configured.
Assignment between event source and OBs
The type of OB determines where you make the assignment between OB and event source:
● With hardware interrupts and isochronous mode interrupts, the assignment is made
during the configuration of the hardware or when the OB is created.
● STEP 7 automatically assigns OBs 91/92 to the MC servo interrupt and MC interpolator
interrupt as soon as you add a technology object.
● For all other types of OB, the assignment is made when the OB is created, where
applicable after you have configured the event source.
For hardware interrupts, you can change an assignment which has already been made
during runtime with the instructions ATTACH and DETACH. In this case, only the actually
effective assignment changes, and not the configured assignment. The configured
assignment takes effect after loading, and at startup.
The CPU ignores hardware interrupts to which you did not assign an OB in your
configuration or which occur after the DETACH instruction. The check as to whether an OB
is assigned to an event does not take place when the associated event occurs, but only
when the hardware interrupt actually has to be executed.
Distributed I/O system
System Manual, 12/2015, A5E03576849-AF
Possible priorities (default
priority)
16 to 26 (24)
2 to 26 (7)
2 to 26 (7)
Possible OB num- Default system
bers reaction*
92 Not applicable
121 STOP
122 Ignore
Basics of program execution
7.1 Events and OBs
Number of OBs
0 or 1
0 or 1
0 or 1
121