S7 General

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The S7 protocol is used to communicate with S7 PLCs and with CPs capable of using the S7 protocol.

The S7 protocol can be used in conjunction with TCP/IP, H1, or MPI.

Read (Fetch active) and Write (Write active)

•	When communicating with S7 PLCs, it is generally possible to both read and write data over a single connection.

•	Usually, the parameterization of the S7 protocol is based on RFC 1006.

•	Besides the S7 PLC address (IP address or MAC address), a read and write TSAP is required. When using MPI, enter the MPI address of the CPU.

•	To read and write data from and to an S7 PLC (layer 7 communication), the following can be used:

o	non-parameterizable connections

o	parameterizable connections

Non-parameterizable connections

Only on the Engine side will a connection be set up and NOT on the PLC side.

Standard connections are required, which are handled via standard TSAPs or standard ports.

There are only a limited number of standard connections available. If these are not sufficient, "parameterizable connections" must be used.

Standard connections to Siemens CPs are handled via RFC1006 or H1 (see TSAP, TSAP for S7 Connection and Routing TSAPs.

Parameterizable connections

The connection must be configured on both sides of the communication (a fetch / write active connection in the Engine AND a fetch / write-passive connection in the S7-CP).

If the communication is via the Engine, parameterizable connections are required.

Note:

For communication with S7 controllers, both the S7 Item Syntax and the S5 Item Syntax can be used.