Parameterization Of The Modbus Communication - Siemens SIMATIC S7 Manual

4

Parameterization of the Modbus Communication

General
Information
Connection
Description DB
MODBUS_PARAM
MODBUS / TCP communication via the integrated PN interface of the CPU
2XV9450-1MB02; Manual edition 2.1
For the communication via the integrated PN interface of the PLC, a network
configuration in NetPro is not necessary. The connections are established
and terminated by means of the function blocks TCON (FB65) und TDISCON
(FB66).
Several connections to different communication partners can be
parameterized and established at the same time. The maximal number of
coexistent connections depends on the PLC.
The parameters to establish a connection and to execute the Modbus
communication are defined as a structure in a parameter DB called
MODBUS_PARAM. At first the connection parameters are defined,
subsequently, the Modbus parameters are defined.
For each logical connection, a separate structure is required. This structure
contains the connection parameters of both communication partners and the
Modbus parameters. For each additional connection, the parameter data
block must be expanded by or a new data block created with the structure for
connection parameters and the Modbus parameters.
The parameter data block can contain parameter information of all defined
connections. It is also possible to use a separate parameter data block for
each connection.
A prepared structure is part of the library "MODBUS_PN_CPU" and can be
used as a sample.
Structure of DB MODBUS_PARAM:
Address Name
STRUCT
+0.0 Connection 1: Connection parameters
+64.0 Connection 1: Modbus parameters
END_STRUCT
STRUCT
+650.0 Connection 2: Connection parameters
+714.0 Connection 2: Modbus parameters
END_STRUCT
... ...
STRUCT
650*i Connection i+1: Connection parameters (65+i)
650*i+64 Connection i+1: Modbus parameters
END_STRUCT
Parameterisation of the Modbus Communication
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