9 Modbus/TCP
9.1 Protocol Configuration
For Modbus/TCP, three IP addresses need to be set via parameters:
● IP address H3.03
● Subnet mask H3.04
● Gateway address H3.05
A Modbus/TCP client can connect to default TCP port 502. Additionally, a user
can specify another port by writing a port number to parameter H3.51. However,
only one client connection is accepted by the MEP card.
9.2 System Configuration
The process data configuration is setting via the parameters H3.30 and H3.31,
respectively for the input and output.
The following Modbus/TCP transactions are supported by the MEP card:
Modbus Function Code Transaction Name Max. Value of N
3 Read N register words 16
6 Write one register word -
16 Write N register words 16
23 Read / write N register words 16 / 16
43
(sub-function code 14)
Read Device Identification -
Tab. 9-1: Modbus / TCP transactions
Besides accessing parameters by their function code virtual address, there are
some special register addresses, that can be used, e.g. for reading/writing the
complete process data image. The following table gives an overview:
Register Address
Contents
0x7F00 Control word H0.00
0x7F01 Frequency command value H0.10
0x7FA0 Status word H0.01
0x7FE0 Input Process Data Image as specified by H3.30
0x7FF0 Output Process Data Image as specified by H3.31
Tab. 9-2: Overview of special register addresses
Bosch Rexroth AG
Modbus/TCP
Multi-Ethernet Card
46/61
DOK-RCON0*-XFCX610*MUL-IT02-EN-P
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