User manual

IEC61131 User and Reference Manual
April 22, 2008
79
Modbus RTU in UDP
Modbus RTU in UDP protocol is similar to Modbus RTU in TCP protocol. It has the same
message format as the RTU in TCP message. The only difference between them is one
uses TCP protocol and another uses UDP protocol.
 To configure a Modbus RTU in UDP protocol connection, highlight Modbus RTU in
UDP in the Communication Protocols window and click the Configure button. The
Modbus RTU in UDP Configuration window is displayed.
 To select a configured Modbus RTU in UDP protocol connection, highlight Modbus
RTU in UDP in the Communication Protocols window and click the OK button.
 To close the dialog, without making a selection click the Cancel button.
General Parameters
When Modbus RTU in UDP is selected for configuration the Modbus RTU in UDP
Configuration dialog is opened with the General tab selected as shown below.
Figure 29: Modbus RTU in UDP Configuration (General) Dialog Box
The Modbus Communication Settings grouping contains Modbus specific communication
settings including the addressing mode, the station address, the timeout interval as well as
the number of attempts.
The Addressing parameter selects standard or extended Modbus addressing. Standard
addressing allows 255 stations and is compatible with standard Modbus devices. Extended
addressing allows 65534 stations, with stations 1 to 254 compatible with standard Modbus
devices. The default is Standard.