Technical data

Table Of Contents
DPV1 SFBs According to PNO AK 1131
System Software for S7-300/400 System and Standard Functions - Volume 1/2
A5E00709327-01
8-21
8.4 Sending an Interrupt to the DP Master with SFB 75
"SALRM"
Note
The SFB 75 "SALRM" interface is identical to the FB "SALRM" defined in the
standard "PROFIBUS Guideline PROFIBUS Communication and Proxy Function
Blocks according to IEC 61131-3"
Description
SFB 75 "SALRM" sends an interrupt for a slot from the user program of an
intelligent slave to the associated DP master, which accesses it in the transitional
area (virtual slot). This starts the associated OB at the DP master.
You can send additional interrupt-specific information along with the interrupt. At
the DP master, you can use SFB 54 "RALRM" to read all the additional information.
SFB 75 can only be used in S7-compatible mode.
DP: The master uses a GSD file to integrate the I-slave.
S7-compatible: The I-slave is linked to a master in STEP 7 via HW Config.
Operating principle
SFB 75 "SALRM" is an is an asynchronous SFB, which means that its processing
extends over several SFB calls. Call SFB 75 with REQ = 1 to start the transfer of
the interrupt.
The send procedure remains active until interrupt processing is either
acknowledged or canceled by the DP master.
Output parameter BUSY and bytes 2 and 3 of the output parameter STATUS
indicate the job status, whereby STATUS bytes 2 and 3 correspond to the
RET_VAL output parameter of the asynchronously operating SFCs (see also
Meaning of the Parameters REQ, RET_VAL and BUSY with Asynchronous SFCs
The transfer of the interrupt is concluded when the output parameter BUSY =
FALSE.