Interrupts On The Dp Master - Siemens CPU 313C Hardware And Installation Manual

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If the CPU 31x-2 is used as the DP slave, you can trigger a process interrupt on
the DP master from the user program.
When you call SFC 7 "DP_PRAL", you trigger an OB40 in the user program on the
DP master. The SFC 7 allows you to forward interrupt information to the DP master
in a double word. This information can then be evaluated in the
OB40_POINT_ADDR variable in the OB40. The interrupt information can be freely
programmed as required. The 6\VWHP 6RIWZDUH IRU 6  6\VWHP DQG
6WDQGDUG )XQFWLRQV - Reference Manual contains a detailed description of SFC 7
"DP_PRAL".
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In the CPU 31x-2 operated as a DP slave, you can trigger user-defined interrupts
from the DP master from the user program. SFB 75 "SALRM" is used to send a
process or diagnostic interrupt from a slot in the transfer area (virtual slot) to the
associated DP master from the user program on an intelligent slave. This starts the
associated OB on the DP master.
Interrupt-specific additional information may be sent at the same time. You can
read all this additional information in the DP master using SFB 54 "RALRM".
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When CPU 31x-2 operates with another DP master, an image of these interrupts is
created in the device-specific diagnostic data of CPU 31x-2. You must post-
process the relevant diagnostic events in the DP master's user program.
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Before you can evaluate diagnostic and process interrupts using the device-
specific diagnostics function on another DP master, you must make sure that:
The DP master is able to store the diagnostic messages, i.e. the diagnostic
messages should be stored in a ring buffer on the DP master. For example, if the
DP master can not store diagnostic messages, only the last incoming diagnostic
message would be stored.
In your user program, you must query the relevant bits in device-specific diagnostic
data. Here you must take the PROFIBUS DP cycle time into account, for example,
to be able to query these bits at least once and in synchronism to bus cycle time.
With an IM 308-C operating as DP master you cannot utilize process interrupts in
device-specific diagnostics, because only incoming events are reported rather than
outgoing events.
S7-300 Automation System, Hardware and Installation: CPU 31xC and CPU 31x
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