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3 modbus protocol specifications, 3 modbus protocol specifications -3, App index – Yokogawa Value Series FX1000 User Manual

Page 177: Modbus client function

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IM 04L21B01-17EN

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Index

6.3 Modbus Protocol Specifications

Modbus Client Function

Basic Operation

• The FX, as a Modbus client device, communicates with Modbus servers periodically

by sending commands at specified intervals.

• The Modbus client function operates independently from the Modbus master function

via the serial communication.

• The supported functions are “reading data from the input registers and hold registers

on the server” and “writing data into the hold registers on the server.”

Modbus Client Specifications

Communicate via ModbusTCP
Communication media: Ethernet 10Base-T
Read cycle:

Select from the following:

1 s, 2 s, 5 s, and 10 s

Connection retry:

Select the reconnection interval after disconnecting the
connection after the connection wait time has elapsed from the
following:

OFF, 10 s, 20 s, 30 s, 1 min, 2 min, 5 min, 10 min, 20 min, 30
min, and 1 h

Connection timeout value: 1 min

However, when the IP address is not established with DHCP, a
communication error results immediately.

Command timeout value: 10 s
Server:

Set up to 16 servers

Supported functions:

Supported Modbus client functions are as follows:

The server device must support these functions.

Function Code

Function

Operation

3

Read the hold register

(4XXXX, 4XXXXX)

The FX reads the hold register of the server

device into the communication input data.

4

Read the input register

(3XXXX, 3XXXXX)

The FX reads the input register of the server

device into the communication input data.

16

Write to the hold register

(4XXXX, 4XXXXX)

The FX writes the measured or computed data to

the hold register of the server device.