Configuring Communication Connections
“S7 Addressing Mode” Option
When you configure the FETCH ACTIVE / WRITE ACTIVE modes, you can select the addressing mode. This specifies how the addresses will be interpreted in the FETCH/WRITE call in the SIMATIC S7 station:
SS7 addressing mode: byte address
SS5 addressing mode: word address
This makes it possible for applications to access S5 or S7 stations without needing to adapt the addresses. This is particularly interesting for existing S5 applications than can be used unchanged to access S7 stations.
As default, the addressing mode for access to SIMATIC S7 is set (option selected).
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 (I, IB, IW, ID)
SProcess image output table (Q, QB, QW, QD)
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.
SIMATIC NET NCM S7 for Industrial Ethernet | 141 |
Release 6/2003 |
