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ICDM-RX/MOD User Manual
Overview
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 Modbus/TCP and can
be also used for transferring Modbus/RTU and Modbus/ASCII messages.
Local Slave Device A local slave device is one that is connected directly to a serial port on the gateway.
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.
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/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/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.
Public Slave
Device
A public slave device is one that can communicate to all master(s) on the Modbus
network.
Note:
If a device is not specifically specified as a “public” or “private” slave device,
then it can be assumed to be a public device.
Private Slave
Device
A private slave device is one that can only communicate to a master that is connected
on the same serial bus, such as RS-485 or RS-422. Private slave device cannot
communicate to other masters on the Modbus network.
Received Device
ID
The original device ID received in the Modbus message from a Modbus master.
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.
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.
Sockets
The method used to communicate between devices while communicating over
Ethernet TCP/IP.
Term
Definition
