Siemens SIMATIC CM35, Manual

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CM35 Counter Module
(4) J31069-D0416-U001-A5-7618
4.3.5 Evaluating a Hardware Interrupt in OB 40
Depending on the set operating mode and the selected parameterization, you
can specify that a hardware interrupt is to be triggered when certain events
occur. In this case, a hardware interrupt OB (OB 40) must exist on the CPU.
When a hardware interrupt occurs, the user program is interrupted, the data
of the module are transferred to the start information of OB 40, and OB 40 is
called. The hardware interrupt is acknowledged when OB 40 is exited.
The following local data are located in the start information of OB 40.
-- OB 40_MDL_ADDR: The base address of the module which trig-
gered the interrupt
-- OB 40_POINT_ADDR: Information on the event which triggered the
interrupt
Variable OB40_POINT_ADDR consists of four bytes. The process
interrupt information of the CM35 is entered in the low word (local data
bytes 10 and 11 of OB 40). For the allocation and description of this interrupt
information, see the description of the particular operating mode.
For a description of OB 40, see STEP 7 reference manual /235/.
Data Communication with the CM35