Siemens SIMATIC S7-400 Reference Manual page 75

Interrupts with the S7/M7 DP Master
In the CPU 41x as a DP slave you can trigger a process interrupt in the DP master
from the user program. You can trigger an OB 40 in the user program of the DP
master by calling SFC 7 "DP_PRAL". Using SFC 7 you can forward interrupt
information in a double word to the DP master, which you can evaluate in OB 40 in
the OB40_POINT_ADDR variable. You can program the interrupt information as
you choose. You will find a detailed description of SFC 7 "DP_PRAL" in the System
Software for S7-300/400, System and Standard Functions Reference Manual.
Interrupts with another DP Master
If you are running the CPU 41x with another DP master, these interrupts are
reflected in the station diagnosis of the CPU 41x. You have to process the relevant
diagnostic events in the DP master's user program.
Note
Note the following in order to be able to evaluate diagnostic interrupts and process
interrupts by means of the station diagnosis when using a different DP master:
•
The DP master should be able to store the diagnostic messages; in other
words, the diagnostic messages should be stored in a ring buffer in the DP
master. There are more diagnostic messages than the DP master can store,
only the last diagnostic message received would be available for evaluation, for
example.
•
You must query the relevant bits in the station diagnosis at regular intervals in
your user program. You must also take the PROFIBUS DP bus cycle time into
consideration so that you can query the bits at least once synchronously with
the bus cycle time, for example.
•
You cannot use process interrupts in the station diagnosis with an IM 308-C as
the DP master, because only incoming – and not outgoing – interrupts are
reported.
Automation System S7-400 CPU Specifications
A5E00165965-01
Structure of a CPU 41x
1-63