Comtrol DeviceMaster EtherNet/IP-Modbus EIP-MOD User manual

DeviceMaster®EIP-MOD
EtherNet®/IP - Modbus®
User Guide

Trademark Notices
Comtrol, DeviceMaster, and PortVision are trademarks owned by Pepperl + Fuchs, GmbH and are used
under license by Pepperl + Fuchs Comtrol, Inc.
Concept is a trademark of Schneider Electric.
Modbus is a registered trademark of Schneider Electric.
ControlLogix, PLC-5 and Rockwell Automation are registered trademarks of Rockwell Automation.
MicroLogix, RSLinx, RSLogix 5, RSLogix 500, RSLogix 5000 and SLC are trademarks of Rockwell
Automation.
PLC is a registered trademark of Allen-Bradley Company, Inc.
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Software, Inc. All Rights Reserved.
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Other product names mentioned herein may be trademarks and/or registered trademarks of their respective
owners.
First Edition, April 3, 2019
Copyright © 2019. Pepperl + Fuchs Comtrol, Inc. 
All Rights Reserved.
Pepperl + Fuchs Comtrol, Inc. makes no representations or warranties with regard to the contents of this
document or to the suitability of the Pepperl + Fuchs Comtrol, Inc. product for any particular purpose.
Specifications subject to change without notice. Some software or features may not be available at the time of
publication. Contact your reseller for current product information.
Document Number: 2000664 Rev A

DeviceMaster EIP-MOD User Guide: 2000664 Rev. A Table of Contents - 3
Table of Contents
Chapter 1. Introduction........................................................................................................7
1.1. EtherNet/IP-Modbus Gateway Overview.......................................................................................... 7
1.2. System Architecture .............................................................................................................................. 9
1.3. EtherNet/IP to Modbus Translation Layer Architecture............................................................ 10
1.4. Translation Layer Connections ........................................................................................................ 11
1.4.1. Connection Methods Table............................................................................................................. 11
1.4.2. EtherNet/IP Controllers Class1 to/from Shared Memory ............................................................ 12
1.4.3. EtherNet/IP Controllers via Data Mapping to/from Tag/File ...................................................... 12
1.4.4. EtherNet/IP Controllers CIP Modbus Object via MSG Instructions........................................... 13
1.5. Data Type Definitions ......................................................................................................................... 13
1.5.1. Terms and Definitions.................................................................................................................... 14
1.6. What is Modbus? ................................................................................................................................... 16
1.6.1. Modbus/RTU ................................................................................................................................... 16
1.6.2. Modbus/ASCII................................................................................................................................. 17
1.6.3. Modbus/TCP.................................................................................................................................... 18
1.7. Locating the Latest Software and Documentation ...................................................................... 19
Chapter 2. EtherNet/IP Interface Profile (ControlLogix)...........................................21
2.1. Modbus Object (44 Hex, 1 Instance) ................................................................................................. 21
2.1.1. Class Attributes.............................................................................................................................. 21
2.1.2. Instance Attributes......................................................................................................................... 21
2.1.3. Common Services............................................................................................................................ 21
2.1.4. Object Specific Services (Instance Specific) .................................................................................. 22
2.1.4.0.1. Read Discrete Inputs Service (4B Hex) ..................................................................................................22
2.1.4.0.2. Read Coils Service (4C Hex)....................................................................................................................22
2.1.4.0.3. Read Input Registers Service (4D Hex)..................................................................................................22
2.1.4.0.4. Read Holding Registers Service (4E Hex) ..............................................................................................23
2.1.4.0.5. Write Coils Service (4F Hex)...................................................................................................................23
2.1.4.0.6. Write Holding Registers Service (50 Hex)..............................................................................................23
2.1.4.0.7. Modbus Passthrough Service (51 Hex)...................................................................................................23
2.1.4.0.8. Vendor Specific Write Single Coil Service (70 Hex)...............................................................................23
2.1.4.0.9. Vendor Specific Write Single Register Service (71 Hex) .......................................................................23
2.1.4.0.10. Vendor Specific Write Mask Register (72 Hex)....................................................................................23
2.1.4.0.11. Vendor Specific Read/Write Holding Registers (73 Hex) ....................................................................24
2.2. Informational Objects ......................................................................................................................... 24
2.2.1. Identity Object (01 Hex, 1 Instance).............................................................................................. 24
2.2.1.1. Class Attributes .................................................................................................................... 24
2.2.1.2. Instance Attributes ............................................................................................................... 24
2.2.1.3. Status Word........................................................................................................................... 25
2.2.1.4. Common Services .................................................................................................................. 26
2.2.2. Message Router Object (02 Hex).................................................................................................... 27
2.2.2.1. Class Attributes .................................................................................................................... 27
2.2.2.2. Instance Attributes ............................................................................................................... 27
2.2.2.3. Common Services .................................................................................................................. 27
2.2.3. Connection Manager Object (06 Hex)............................................................................................ 28
2.2.3.1. Class Attributes Object (06 hex) .......................................................................................... 28
2.2.3.2. Instance Attributes (06 hex)................................................................................................. 28
2.2.3.3. Common Services Object (06 hex) ........................................................................................28
2.2.4. Port Object (F4 Hex - 1 Instance) .................................................................................................. 29
2.2.4.1. Class Attributes .................................................................................................................... 29
2.2.4.2. Instance Attributes (F4 Hex, Instance 1) ............................................................................ 29
2.2.4.3. Instance Attributes (F4 Hex, Instance 2) ............................................................................ 30

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2.2.4.4. Common Services .................................................................................................................. 31
2.2.5. TCP Object (F5 Hex - 1 Instance) .................................................................................................. 31
2.2.5.1. Class Attributes .................................................................................................................... 31
2.2.5.2. Instance Attributes ............................................................................................................... 31
2.2.5.3. Common Services .................................................................................................................. 33
2.2.6. Ethernet Link Object (F6 Hex) ...................................................................................................... 33
2.2.6.1. Class Attributes .................................................................................................................... 33
2.2.6.2. Instance Attributes ............................................................................................................... 34
2.2.6.3. Common Services .................................................................................................................. 35
2.2.7. Assembly Object (For Class 1 Interface) ....................................................................................... 35
2.2.7.1. Class Attributes .................................................................................................................... 35
2.2.7.2. Instance Attributes ............................................................................................................... 35
2.2.7.2.1. Instance Attribute Definitions: Attribute 3-Request/Write Data .........................................................36
2.2.7.2.2. Instance Attribute Definitions: Attribute 4-Data Length .....................................................................36
2.2.7.3. Common Services .................................................................................................................. 36
2.2.7.4. Instance Definitions.............................................................................................................. 36
2.2.7.4.1. Instance Definitions (Default).................................................................................................................36
2.2.7.4.2. All Available Instance Definitions..........................................................................................................37
Chapter 3. Configuration Overview ................................................................................41
3.1. Home Page ............................................................................................................................................. 41
3.2. Serial Port - Configuration Overview ............................................................................................. 43
3.3. Modbus Over TCP Overview - Configuration Overview............................................................. 45
Chapter 4. Serial Menus .....................................................................................................47
4.1. Serial Port Overview Page................................................................................................................. 47
4.2. Serial Port Configuration Page ........................................................................................................ 48
Chapter 5. Modbus Menus..................................................................................................53
5.1. Modbus over TCP (not Modbus/TCP) Overview ........................................................................... 53
5.2. Modbus over TCP (not Modbus/TCP) Socket Configuration Page ........................................... 54
5.3. Modbus/TCP Configuration Page ..................................................................................................... 56
5.4. Remote Modbus/TCP Device Configuration .................................................................................. 57
5.5. Modbus Alias Configuration .............................................................................................................. 59
Chapter 6. Network Menus ................................................................................................61
6.1. Network Configuration Page............................................................................................................. 61
6.2. Password Page ...................................................................................................................................... 63
6.3. Security Settings Page ........................................................................................................................ 64
6.4. Key and Certificate Management Page........................................................................................... 65
6.5. EtherNet/IP Stack Configuration..................................................................................................... 67
Chapter 7. Data Mapping Menus ......................................................................................69
7.1. Modbus to EtherNet/IP Tag/File Configuration Page ................................................................. 69
7.2. EtherNet/IP Tag/File to Modbus Configuration Page ................................................................. 72
7.3. Modbus to Modbus Configuration Page.......................................................................................... 75
7.4. Shared Memory Configuration Page ............................................................................................... 78
7.5. EtherNet/IP Class 1 Page.................................................................................................................... 83
7.5.1. Active Class1 Interface Page ......................................................................................................... 83
7.5.2. All Shared Memory Class1 Interface Page ................................................................................... 84
7.6. Data Mapping Verification Page ...................................................................................................... 85
7.7. Shared Memory Map Page ................................................................................................................. 87

DeviceMaster EIP-MOD User Guide: 2000664 Rev. A Table of Contents - 5
Chapter 8. Diagnostic Menus ............................................................................................91
8.1. Serial Communication Statistics Page............................................................................................ 92
8.2. Modbus RTU/ASCII over Ethernet TCP Statistics Page ............................................................. 94
8.3. Serial Interface Logs ........................................................................................................................... 96
8.4. Known Modbus Slave Device List .................................................................................................... 97
8.5. Modbus/TCP and Serial Modbus Master Statistics Page.......................................................... 100
8.6. Modbus/TCP Connections Page ...................................................................................................... 104
8.7. Modbus Alias Device ID Statistics Page ....................................................................................... 106
8.8. Shared Memory Contents................................................................................................................. 107
8.8.1. Shared Holding Block Register Blocks ........................................................................................ 107
8.8.2. Shared Coil Blocks........................................................................................................................ 109
8.9. Ethernet/IP Interface Statistics Page ........................................................................................... 111
8.10. Modbus to EtherNet/IP Tag/File Diagnostics Page.................................................................. 113
8.11. EtherNet/IP Tag/File to Modbus Diagnostics Page.................................................................. 115
8.12. Modbus to Modbus Diagnostics Page .......................................................................................... 116
8.13. System Log ......................................................................................................................................... 118
Chapter 9. System Menus .................................................................................................119
9.1. Update Firmware ............................................................................................................................... 119
9.2. Configuration File Page.................................................................................................................... 121
9.2.1. Saving a Configuration File ......................................................................................................... 121
9.2.2. Loading a Configuration File ....................................................................................................... 122
9.3. System Snapshot Page ...................................................................................................................... 123
9.4. Restore Defaults Page ....................................................................................................................... 124
9.5. Reboot ................................................................................................................................................... 125
Chapter 10. PLC Programming for Modbus Object (44 Hex)...................................127
10.1. Read Discrete Inputs Service (4B Hex)....................................................................................... 127
10.2. Read Coils Service (4C Hex) .......................................................................................................... 129
10.3. Read Input Registers Service (4D Hex) ...................................................................................... 131
10.4. Read Holding Registers Service (4E Hex) .................................................................................. 133
10.5. Write Coils Service (4F Hex).......................................................................................................... 135
10.6. Write Holding Registers Service (50 Hex) ..................................................................................137
10.7. Vendor Specific Write Single Coil Service (70 Hex)................................................................. 141
10.8. Vendor Specific Write Single Register Service (71 Hex) ........................................................ 143
10.9. Vendor Specific Write Mask Register (72 Hex) ......................................................................... 145
10.10. Vendor Specific Read/Write Holding Registers (73 Hex)...................................................... 148
Chapter 11. Class 1 Interface Definition.......................................................................151
11.1. Configuring an I/O Ethernet Module on a ControlLogix PLC............................................... 151
Chapter 12. Troubleshooting and Technical Support ...............................................155
12.1. Troubleshooting Checklist ............................................................................................................ 155
12.2. General Troubleshooting ............................................................................................................... 156
12.3. Daisy-Chaining DeviceMaster EIP-MOD Units With Two Ethernet Ports ......................... 157
12.4. Technical Support............................................................................................................................ 158

6 - Table of Contents DeviceMaster EIP-MOD User Guide: 2000664 Rev. A

DeviceMaster EIP-MOD User Guide: 2000664 Rev. A Chapter 1. Introduction - 7
Chapter 1. Introduction
This document describes how to configure the DeviceMaster EIP-MOD for the EtherNet/IP-Modbus after
basic DeviceMaster EIP-MOD installation and configuration procedures.
•EtherNet/IP Interface Profile (ControlLogix) on Page 21
•Configuration Overview on Page 41
•Serial Menus on Page 47
•Modbus Menus on Page 53
•Network Menus on Page 61
•Diagnostic Menus on Page 91
•System Menuson Page 119
See Locating the Latest Software and Documentation on Page 19 to locate the latest firmware, documentation,
and tools.
1.1. EtherNet/IP-Modbus Gateway Overview
The DeviceMaster EtherNet/IP-Modbus gateway provides the following functionality.
EtherNet/IP interface support:
• Supports all fully CIP compliant controllers including Rockwell ControlLogix, CompactLogix, SoftLogix,
Schneider Electric, Omron, and GE PLCs, OPC Servers, SCADA systems, HMIs and many more.
• Supports PCCC based PLCs such as MicroLogix, SLC 5/05 and PLC-5.
• EtherNet/IP Interface specifics:
- Maximum CIP sessions = 128
- Maximum CIP input (to PLC) connections = 128
- Maximum CIP output (from PLC) connections = 16
- Write-to-Tag/File and Read-from-Tag/File support
- CIP Modbus Object support. Custom service codes support additional Modbus function codes.
• EtherNet/IP controllers can communicate to:
• Shared Memory
• A wide variety of Modbus slave devices:
- Local serial Modbus/RTU and Modbus/ASCII slave devices
- Modbus/TCP slaves
- Remote serial Modbus/RTU and Modbus/ASCII devices connected to other gateways
• A wide variety of Modbus masters via Shared Memory:
- Modbus/TCP masters
- Modbus/RTU and Modbus/ASCII masters over Ethernet TCP connections
- Serial Modbus/RTU and Modbus/ASCII masters
• Other EtherNet/IP controllers via Shared Memory
- Via Class1 connections to Shared memory
- CIP Modbus Object messages

8 - Chapter 1. Introduction DeviceMaster EIP-MOD User Guide: 2000664 Rev. A
EtherNet/IP-Modbus Gateway Overview
- Via Read-from-Tag/File and Write-to-File/Tag configurations
The most extensive Modbus functionality in the industry:
• Up to 96 Modbus/TCP connections
• Support up to eight unique Modbus TCP socket port numbers. (i.e. 502, 503, 505, etc.)
• Multiple Modbus/RTU and/or Modbus/ASCII over Ethernet TCP connections
• Local serial Modbus/RTU and Modbus/ASCII slave devices
• Maximum sized Modbus messages
• Serial Modbus/RTU and Modbus/ASCII masters
• Shared Memory that can be configured to provide communication interfaces between a vast array of
Modbus slaves, Modbus masters and EtherNet/IP controllers.
• Modbus Alias functionality
• Remote Modbus device connectivity
• Modbus slave to Modbus slave communication
• Private Modbus serial bus connectivity – A serial port connected to a serial master and one or more serial
slave devices
A Data Mapping process that provides:
• EtherNet/IP Tag/File to Modbus connectivity - to either Modbus device(s) or Shared memory
• Modbus to EtherNet/IP Tag/File connectivity - from either Modbus device(s) or Shared memory
• Modbus to Modbus connectivity
- Can read from multiple Modbus devices into Shared Memory.
- Can write from Shared memory to multiple Modbus devices.
- Can read directly from one Modbus slave device to another Modbus slave device anywhere on the
Modbus network. These devices can be of any supported type, local or remote.
- Can convert from Modbus register type to another automatically.
• A Data Mapping verification web page that checks for possible Modbus write conflicts, incorrect
configuration and write violations.
• A Shared Memory map web page that displays the Shared Memory read and write memory blocks as
defined utilized by the Data Mapping.

DeviceMaster EIP-MOD User Guide: 2000664 Rev. A Chapter 1. Introduction - 9
System Architecture
1.2. System Architecture
The DeviceMaster EtherNet/IP-Modbus firmware utilizes the following architecture.
The firmware architecture is designed to take full advantage of a broad range of EtherNet/IP and Modbus
routing functionality supported by the DeviceMaster EtherNet/IP-Modbus gateway.

10 - Chapter 1. Introduction DeviceMaster EIP-MOD User Guide: 2000664 Rev. A
EtherNet/IP to Modbus Translation Layer Architecture
1.3. EtherNet/IP to Modbus Translation Layer Architecture
The following image illustrates the EtherNet/IP to/from Modbus translation layer.

DeviceMaster EIP-MOD User Guide: 2000664 Rev. A Chapter 1. Introduction - 11
Translation Layer Connections
1.4. Translation Layer Connections
The following connections are possible through the translation layer.
1.4.1. Connection Methods Table
This table lists the possible connections and the methods available for a wide variety of EtherNet/IP and
Modbus interfaces.
Write (To)
EtherNet/IP PLC(s) via
Class1 Connection
EtherNet/IP PLC(s)
via Tag/File
EtherNet/IP PLC(s)
via Modbus Object
Modbus/TCP Master(s)
Modbus RTU/ASCII
Serial Master(s)
Modbus RTU/ASCII
Over Ethernet TCP Master(s)
Modbus RTU/ASCII
Serial Slave(s)
Modbus/TCP Slave(s)
Remote Modbus RTU/ASCII
Serial Slave(s)
Read (From)
EtherNet/IP PLC(s) via
Class1 Connection 232222333
EtherNet/IP PLC(s) via Tag/
File 3333333,43,43,4
EtherNet/IP PLC(s) via
Modbus Object 2322221,31,31,3
Modbus/TCPMaster(s)2322221,31,31,3
Modbus RTU/ASCII Serial
Master(s) 2322221,31,31,3
Modbus RTU/ASCII Over
Ethernet TCP Master(s) 2322221,31,31,3
Modbus RTU/ASCII Serial
Slave(s) 3 3,4 1,3 1,3 1,3 1,3 3,4 3,4 3,4
Modbus/TCP Slave(s) 3 3,4 1,3 1,3 1,3 1,3 3,4 3,4 3,4
Remote Modbus RTU/ASCII
Serial Slave(s) 3 3,4 1,3 1,3 1,3 1,3 3,4 3,4 3,4
Where the method is:
1 = via direct message to Modbus slave device
2 = via Shared Memory
3 = via Shared Memory and use of Data Mapping
4 = via use of only Data Mapping

12 - Chapter 1. Introduction DeviceMaster EIP-MOD User Guide: 2000664 Rev. A
EtherNet/IP Controllers Class1 to/from Shared Memory
1.4.2. EtherNet/IP Controllers Class1 to/from Shared Memory
The following provides information about EtherNet/IP controllers Class1 to and from shared memory.
• Combined with the Data Mapping Modbus to Modbus functionality:
- Local serial Modbus/RTU and Modbus/ASCII slave devices.
- Remote serial Modbus/RTU and Modbus/ASCII slave devices (via additional gateways).
- Remote Modbus/TCP slaves.
• Modbus Controllers:
- Modbus/TCP masters
- Modbus/RTU and Modbus/ASCII over Ethernet TCP masters
- Serial Modbus/RTU and Modbus/ASCII masters
• Other EtherNet/IP controllers:
- Utilizing Class1 connections
- Combined with the Data Mapping Read Tag/File Write Modbus functionality
- Combined with the Data Mapping Read Modbus Write Tag/File functionality
1.4.3. EtherNet/IP Controllers via Data Mapping to/from Tag/File
The following provides information about EtherNet/IP controllers via data mapping to and from Tag/File.
• Directly to/from Modbus slave devices:
- Local serial Modbus/RTU and Modbus/ASCII slave devices.
- Remote serial Modbus/RTU and Modbus/ASCII slave devices (via additional gateways).
- Modbus/TCP slaves.
• Through Shared Memory:
- Combined with the Data Mapping Modbus to Modbus functionality:
- Local serial Modbus/RTU and Modbus/ASCII slave devices.
- Remote serial Modbus/RTU and Modbus/ASCII slave devices (via additional gateways).
- Remote Modbus/TCP slaves.
- Modbus Masters:
- Modbus/TCP masters
- Modbus/RTU and Modbus/ASCII over Ethernet TCP masters
- Serial Modbus/RTU and Modbus/ASCII masters
- Other EtherNet/IP controllers:
- Utilizing Class1 connection(s)
- Combined with the Data Mapping Read Tag/File Write Modbus functionality
- Combined with the Data Mapping Read Modbus Write Tag/File functionality

DeviceMaster EIP-MOD User Guide: 2000664 Rev. A Chapter 1. Introduction - 13
EtherNet/IP Controllers CIP Modbus Object via MSG Instructions
1.4.4. EtherNet/IP Controllers CIP Modbus Object via MSG Instructions
The following provides information about EtherNet/IP controller CIP Modbus object via MSG instructions.
• Directly to/from Modbus slave devices:
- Local serial Modbus/RTU and Modbus/ASCII slave devices.
- Remote serial Modbus/RTU and Modbus/ASCII slave devices (via additional gateways).
- Modbus/TCP slaves.
• Through Shared Memory:
- Combined with the Data Mapping Modbus to Modbus functionality:
- Local serial Modbus/RTU and Modbus/ASCII slave devices.
- Remote serial Modbus/RTU and Modbus/ASCII slave devices (via additional gateways).
- Remote Modbus/TCP slaves.
- Modbus Masters:
- Modbus/TCP masters
- Modbus/RTU and Modbus/ASCII over Ethernet TCP masters
- Serial Modbus/RTU and Modbus/ASCII masters
- Other EtherNet/IP controllers:
- Utilizing Class1 connection(s)
- Combined with the Data Mapping Read Tag/File Write Modbus functionality
- Combined with the Data Mapping Read Modbus Write Tag/File functionality
1.5. Data Type Definitions
The following list defines the available data types.
Data Type Definition
USINT Unsigned short integer (8-bits)
UINT Unsigned integer (16-bit)
UDINT Unsigned double integer (32-bits)
INT Signed integer (16-bits)
DINT Signed double integer (32-bits)
BYTE Bit string (8-bits)
WORD Bit string (16-bits)
DWORD Bit string (32-bits)
STRING Character string (1-byte per character)

14 - Chapter 1. Introduction DeviceMaster EIP-MOD User Guide: 2000664 Rev. A
Terms and Definitions
1.5.1. Terms and Definitions
This section uses the following terms and definitions.
Term Definition
Class 1
Otherwise called implicit messaging, is a method of communication between
EtherNet/IP controllers and devices that:
• Uses Ethernet UDP messages.
• Is cyclic in nature. Input and/or output data is exchanged between the
controllers and devices at regular time intervals.
Class 3
Otherwise called explicit messaging, is a method of communication between
EtherNet/IP controllers and devices that:
• Uses Ethernet TCP/IP messages.
• By itself is not cyclic in nature. The controller and devices must send
individual messages to each other.
EtherNet/IP An Ethernet based industrial communication protocol utilized to communicate
between controllers, often times PLCS, and devices.
Ethernet TCP/IP Standard Ethernet communications protocol utilizing socket communication
interfaces that guarantees delivery to the intended device.
Ethernet UDP/IP
Standard Ethernet communications protocol utilizing socket communication
interfaces that does not guarantee delivery. The data may or may get to the
intended device.
Multicast
Multicast addressing involves Ethernet devices sending messages to each other
using a multicast address. Multicast addressing:
• Uses a specified IP address range designated for multicast communication.
• Allows either one or multiple devices to receive the same messages.
Point-to-Point
Point-to-Point, otherwise called unicast, addressing involves Ethernet devices
sending messages directly to each other using their own IP addresses. Messages
are sent to only one device.
Master (or Client)
Mode
The method of operation when a PLC, a gateway, or an application is operating
as a Master or the message originator.
Slave (or Server)
Mode The method of operation when a PLC, a gateway, or an application is operating as a Slave or the message receiver.
Device ID
The Modbus device identification number. Device IDs include:
• 0 = Broadcast
• 1-247 = Standard device IDs
• 248-255 = Reserved device IDs (generally used for vendor specific gateway
functions)
Device ID Offset An offset applied at the slave serial port interface that changes the message
device ID range to match the serial device(s) device ID range.
Received Device ID The original device ID received in the Modbus message from a Modbus master.
Alias Device ID The device ID that the original received ID is changed to when an Alias Device
ID is configured.
Local Slave Device A local slave device is one that is connected directly to a serial port on the
gateway.
Remote Slave
Device
A remote slave device is either a slave Modbus/TCP device or a serial slave
device attached to another gateway and accessed as a remote Modbus/TCP
device.

DeviceMaster EIP-MOD User Guide: 2000664 Rev. A Chapter 1. Introduction - 15
Terms and Definitions
Modbus/RTU
The standard Modbus messages, in hexadecimal format, that are typically
transmitted over serial lines but can also be transmitted over other
communication methods such as wireless or Ethernet TCP/IP socket
connections.
Note: Modbus/RTU over Ethernet TCP/IP is not the same as Modbus TCP.
Modbus/ASCII An ASCII, or character based, form of Modbus. The base message is the same as
Modbus/RTU, but the format is somewhat different.
Modbus/TCP An Ethernet based form of Modbus communication. The base message is the same as Modbus/RTU, but a special Modbus header is included for packet
identification and routing purposes.
Polling
The process where a PLC or Application requests data on a continual basis. In
this operation the Master sends the request messages while the Slave responds
to the messages.
Ethernet TCP/IP A form of Ethernet connectivity that provides a level of guaranteed delivery and
data verification. This is used for many upper layer protocols such as Modbus/
TCP and can be also used for transferring Modbus/RTU and Modbus/ASCII.
messages.
Term Definition (Continued)

16 - Chapter 1. Introduction DeviceMaster EIP-MOD User Guide: 2000664 Rev. A
What is Modbus?
1.6. What is Modbus?
This subsection discusses:
•Modbus/RTU
•Modbus/ASCII on Page 17
•Modbus/TCP on Page 18
1.6.1. Modbus/RTU
Modbus/RTU is native Modbus in hexadecimal format. These are the base Modbus messages that contain
simple read and write requests. The format is as follows:
Where:
•ThetermsMaster or Client are used to identify the sender of the message.
•ThetermsSlave or Server are used to identify the devices responding to the message.
Modbus/RTU is used primarily for:
• Serial port connectivity
RS-485 is the most common serial mode, but RS-232 and RS-422 are also widely used. Commonly used by
both Master and Slave devices.
• Ethernet TCP/IP socket connections
This is not the same as Modbus/TCP on Page 18, but does provide a very simple method of interfacing to
remote devices. It is used by many applications and some OPC servers.
Note: This communication method typically is not supported by PLCs.

DeviceMaster EIP-MOD User Guide: 2000664 Rev. A Chapter 1. Introduction - 17
Modbus/ASCII
1.6.2. Modbus/ASCII
Modbus/ASCII is native Modbus in ASCII format. This protocol is used primarily by legacy devices and is no
longer supported as widely as Modbus/RTU.
Like Modbus/RTU, Modbus/ASCII contains the base Modbus messages that contain simple read and write
requests. The differences between Modbus/ASCII and Modbus/RTU are:
1. The message data is sent in ASCII format, so the message length is twice as long. It requires two ASCII
characters for each byte of data.
2. An 8-bit LRC is attached to verify the message instead of a 16-bit CRC. The LRC is also transmitted in
ASCII format.
3. There are defined starting and ending characters to determine a Modbus/ASCII messages.
The format is as follows:
Where:
•ThetermsMaster or Client are used to identify the sender of the message.
•ThetermsSlave or Server are used to identify the devices responding to the message.
Modbus/ASCII is used primarily for:
• Serial port connectivity
RS-485 is the most common serial mode, but RS-232 and RS-422 are also used. Used primarily by legacy
Slave devices.
• Ethernet TCP/IP socket connections
This is not the same as Modbus/TCP, but does provide a very simple method of interfacing to remote
devices. It is used by some applications and some OPC servers.
Note: This communication method typically is not supported by PLCs.

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Modbus/TCP
1.6.3. Modbus/TCP
Modbus/TCP is an Ethernet network based protocol that contains a Modbus/RTU message, with the exception
of the 2-byte CRC. The Modbus/TCP message contains a header with information designed to provide
message identification and routing information. The format is as follows:
Where:
•ThetermsMaster or Client are used to identify the sender of the message.
•ThetermsSlave or Server are used to identify the devices responding to the message.
• Modbus/TCP messages are typically sent to and received on a defined Ethernet TCP/IP socket of 502.
• Modbus/TCP implementations provide more capability, but also require more processing than simpler
Modbus/RTU implementations.
Modbus/TCP is used for connecting advanced Ethernet based devices, such as PLCs, HMIs, SCADA Systems,
and most OPC Servers to:
• Other Ethernet devices supporting Modbus/TCP.
• Remote serial Modbus/RTU and/or Modbus/ASCII devices through gateways (such as the DeviceMaster
EIP-MOD running the EtherNet/IP-Modbus or Modbus/TCP applications).
• Remote serial or Ethernet TCP/IP ASCII devices (barcode scanners, printers, RFID readers, visions
systems, etc) through a gateway (such as the DeviceMaster EIP-MOD running the Modbus/TCP
application).

DeviceMaster EIP-MOD User Guide: 2000664 Rev. A Chapter 1. Introduction - 19
Locating the Latest Software and Documentation
1.7. Locating the Latest Software and Documentation
You can use the links in this table to check for updated software or documentation.
Software and Documentation FTP
PortVision DX
(Windows)
Use PortVision DX to manage Pepperl+Fuchs Comtrol, Inc. Ethernet-
attached devices to:
• Scan the network for attached devices
• View networked devices in real-time
• Access product-specific network settings configurations
• Assign IP addresses and network settings to one or multiple
devices
• Upload the latest firmware or Bootloader
• Save and load configuration files
• Access DeviceMaster EIP-MOD configuration web pages
• Access Telnet/SSH sessions
• Remotely reboot devices
• Download technical documentation
• Enable event logging to assist in monitoring and troubleshooting
• Create shortcuts to quickly access your favorite applications
• Organize devices into folders and create multiple views
• Enter notes about a folder or device
EtherNet/IP-Modbus
Firmware
This is the application that may or may not have been loaded on the
DeviceMaster EIP-MOD depending on the model that was ordered.
You may need to use PortVision DX to load this firmware.
EtherNet/IP-Modbus
Hardware Installation and
Configuration Guide
This contains hardware installation, configuration information, and
connector information.
This includes using PortVision DX to configure the IP address and if
necessary, how to update the firmware.
EtherNet/IP-Modbus User
Guide
(this guide)
This User Guide contains detailed information about the EtherNet/IP-
Modbus (application) firmware, which includes additional information
about the web configuration interface.

20 - Chapter 1. Introduction DeviceMaster EIP-MOD User Guide: 2000664 Rev. A
Locating the Latest Software and Documentation