Configuring Communication Connections
Notice
Remember that with this configuration on an
System Memory
You can access the following address areas in the system memory on the SIMATIC S7 PLC using FETCH or WRITE:
SData blocks (DB)
(When accessing DBs, remember that the highest DB number is 255.)
SBit memory (M, MB, MW, MD)
SProcess image input table (E)
SProcess image output table (A)
SI/O area inputs (PIW, PID, PIB)
SI/O area outputs (PQW, PQD, PQB)
SCounters (C)
STimers (T)
Links to Other Systems
The FETCH and WRITE modes supported on ISO transport connections and
To be able to use this type of access, for example for PC applications, you need to know the PDU structure of the jobs. The required S7 or S5 headers for request and response frames are 16 bytes long and their structure is described in the Appendix.
Messages in the Diagnostic Buffer
As a result of FETCH/WRITE access, negative acknowledgments from the S7 CPU are possible. This then leads to corresponding
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