Definitions and terms, Data type definitions, Glossary – Comtrol Modbus TCP User Guide User Manual
Page 14: Data type definitions 1.5.2. glossary

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Chapter 1. Introduction
DeviceMaster UP Modbus/TCP User Guide: 2000447 Rev. I
Definitions and Terms
1.5. Definitions and Terms
This section describes the Modbus/TCP definitions and terms included in the Modbus/TCP interface and
supported by the DeviceMaster UP.
1.5.1. Data Type Definitions
The following list defines the available data types.
1.5.2. Glossary
The following list defines terms associated with Modbus/TCP.
Data Type
Definition
BYTE
Bit String (8-bits)
DINT
Signed Double Integer (32-bits)
DWORD
Bit String (32-bits)
INT
Signed Integer (16-bits)
STRING
Character String (1-byte per character)
UDINT
Unsigned Double Integer (32-bits)
USINT
Unsigned Short Integer (8-bits)
WORD Unsigned
Integer
(16-bits)
Term
Definition
Alias Device ID
The device ID that the original received ID is changed to when an Alias Device ID is
configured.
Device ID
The address of the slave device and the term is identical to Unit Identifier and Slave
Address.
Ethernet Device A device that communicates through an Ethernet TCP/IP connection.
Master Device
A device that transmits Modbus/TCP messages to slave devices and receives the
corresponding responses.
Modbus
An application layer messaging protocol that provides client/server communications
between devices connected on different types of buses.
Modbus Serial
The Modbus protocol over a serial connection.
Modbus/ASCII
Modbus Serial in ASCII format. This form of Modbus communication requires two
characters for each byte.
Modbus/RTU
Modbus Serial in binary format.
Modbus/TCP
The Modbus protocol over an Ethernet TCP/IP connection. Also known as Modbus over
Ethernet.
Raw Serial
Device
A common serial device that communicates over serial ports through plain byte or ASCII
data messages.
Slave Address
The address of the slave device. This term is identical to Unit Identifier and Device ID.
Slave Device
A device that only responds to Modbus messages.
Socket Port
The Ethernet socket port that is used to communicate to an Ethernet device.