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Perform RDREC Operation Using Library #325
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Hello, Later models of S7 devices (1200 and 1500) begin using "Instructions" in place of SZL requests. Is there any way to perform these instruction sets via the Snap-7 library? Specifically, I'm interested in the possibility of performing a RDREC Instruction (SFB 52) using python-snap7. If this is not possible, I suppose you would need read the values into global data blocks on the PLC and then pull from there. Thanks! |
Answered by
gijzelaerr
Mar 19, 2026
Replies: 1 comment
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RDREC (SFB 52) is a PLC-internal instruction that runs on the PLC CPU itself -- it cannot be invoked remotely via the S7 communication protocol. The correct approach is to have PLC logic execute RDREC and store the results in a global data block, then use client.db_read() to retrieve that data remotely. |
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gijzelaerr
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RDREC (SFB 52) is a PLC-internal instruction that runs on the PLC CPU itself -- it cannot be invoked remotely via the S7 communication protocol. The correct approach is to have PLC logic execute RDREC and store the results in a global data block, then use client.db_read() to retrieve that data remotely.