Object Specific Services (Instance Specific); Read Discrete Inputs Service (4B Hex); Read Coils Service (4C Hex); Read Input Registers Service (4D Hex) - Comtrol DeviceMaster EtherNet/IP-Modbus EIP-MOD User Manual

| Modbus Object (44 Hex, 1 Instance) | Object Specific Services (Instance Specific) | |

2.1.4. Object Specific Services (Instance Specific)

These services are provided to implement the supported Modbus functions. All Modbus Object services, as
specified in Volume 7: Integration of Modbus Devices into the CIP Architecture, are supported as well as
several additional services.
Service Code
4B hex Read Discrete Inputs
4C hex Read Coils
4D hex Read Input Registers
4E hex Read Holding Registers
4F hex Write Coils
50 hex Write Holding Registers
51 hex Modbus Pass through
70 hex ** Write Single Coil
71 hex ** Write Single Register
72 hex ** Mask Write Register
73 hex ** Read/Write Holding Registers
** = Vendor specific services provided to support additional Modbus functions.
Note: In order to use these services, the Enable Vendor Specific Modbus Object Services option on the
EtherNet/IP Stack Configuration web page must be selected.

2.1.4.0.1. 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

2.1.4.0.2. Read Coils Service (4C Hex)

This service reads one or more coils from the Modbus Coils table. This service results in the DeviceMaster
EIP-MOD issuing a Read Coils function (function code 0x01) 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

2.1.4.0.3. Read Input Registers Service (4D Hex)

This service reads one or more input registers from the Modbus Input Register table. This service results in
the DeviceMaster EIP-MOD issuing a Read Input Registers function (function code 0x04) 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
22 - Chapter 2. EtherNet/IP Interface Profile (ControlLogix)
Service Name
www.modbus.org
Service Description
Reads one or more contiguous discrete input(s).
Reads one or more contiguous coil(s).
Reads one or more contiguous input register(s).
Reads one or more contiguous holding register(s).
Writes one or more contiguous coil(s).
Writes one or more contiguous holding register(s).
Provides encapsulation of any public or private
Modbus function.
Writes a single coil.
Writes a single holding register.
Perform a mask write operation on a single holding
register.
Writes one or more holding register(s) and reads one
or more holding register(s).
www.modbus.org for more details.
for more details.
www.modbus.org for more details.
DeviceMaster EIP-MOD User Guide: 2000664 Rev. A