Chapter 10. Plc Programming For Modbus Object (44 Hex); Read Discrete Inputs Service (4B Hex) - Comtrol DeviceMaster EtherNet/IP-Modbus EIP-MOD User Manual

Chapter 10. PLC Programming for Modbus Object (44
Hex)
The CIP Modbus Object is supported on the DeviceMaster EtherNet/IP-
Modbus gateway. This functionality provides the ability to send read
and write messages directly to the Shared Memory or a Modbus slave
device. Each EtherNet/IP MSG instruction requires some setup. The
following is a programming guide to how to set up MSG instructions
and message data for each Modbus function.
The provided PLC example program utilizes standard MSG
instructions and User Defined data structures to format the Modbus
request and response parameters.
The list (right) of the User Defined data structures from the example
PLC program.

10.1. Read Discrete Inputs Service (4B Hex)

This service reads one or more discrete inputs from the Modbus
Discrete Inputs table. This service results in the DeviceMaster EIP-
MOD issuing a Read Discrete Inputs function (function code 0x02) to
either the Shared Memory or the Modbus Message Routing subsystem.
Refer to CIP Standard Vol1_3.22 Section 5B-3 and/or MODBUS
Application Protocol Specification V1.1b3.pdf at
more details.
Parameter
Service Code
Instance
DeviceMaster EIP-MOD User Guide: 2000664 Rev. A
Value
4b Hex
1
www.modbus.org for
Directly corresponds to Modbus function code:
Read Discrete Inputs (function code 2)
Modbus Device ID of 1
(Valid Range = 1 to 255)

Chapter 10. PLC Programming for Modbus Object (44 Hex) - 127

Description