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1MAC052634-MB D
Section 3
3.1
3.1.1
3.1.1.1
615/620 series ANSI
Communication Protocol Manual
Vendor-specific implementation
Modbus link alternatives
Modbus communication is possible over the serial communication interface, over the
Ethernet interface, or over both interfaces simultaneously.
Serial link
Modbus serial communication requires that the IED variant is equipped with a serial
interface card at the slot X000. The serial interface card can contain one or two serial
interfaces.
The Modbus link mode can be either Modbus RTU or Modbus ASCII.
Modbus serial communication can run on two separate serial ports simultaneously. The
Modbus serial link characteristics can be different on the two ports. This applies also to the
Modbus RTU and ASCII link modes and the unit address.
Documentation concerning the Modbus serial link messages and the
Modbus standard can be obtained from www.modbus.org.
Modbus serial link parameters
Serial link setting parameters can be accessed with PST or via the LHMI path
Configuration > Communication > Modbus.
In the LHMI parameter names end either with number 1 or with number 2.
The numbers refer to two separate serial ports, that is the instances 1 and 2.
Address
Each serial link can be given a separate unit address.
End delay
The end of message delay, or timeout, is used only in the Modbus RTU link mode.
According to the Modbus standard, an idle period of 3.5 characters, that is the time it takes
to transmit 3.5 characters with the used baud rate, defines the end of a Modbus RTU frame
in the RTU mode. This parameter can be given with the accuracy of one character. The
default setting is three characters but the user can increase or decrease the value.
Vendor-specific implementation
Section 3
9
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