Yokogawa Touch Screen GP20 - Manual (Page 328)

4-8
IM 04L51B01-01EN
4.3 Using Modbus to Enable Other Devices to Read
Data from and Write Data to the GX/GP (Modbus
slave function)
The GX/GP can operate as a Modbus slave device.
Other devices (Modbus master devices) can carry out the following operations on the GX/
GP.
• Read I/O channel and math channel (/MT option) data (input register)
• Read communication channel (/MC option) data (hold register)
• Write communication channel (/MC option) data (hold register)
• Start and stop recording, write messages, and perform other operations (using the hold
register)
• Load the recording start/stop condition, message strings, and other types of data (using
the hold register)
Modbus master device
Modbus slave
Serial communication
GX/GP
Command
Input register
Hold register Read
Write
Read
3XXXXX
4XXXXX Write
Read
Read
GX/GP internal register Master
4.3.1 Setting Serial Communication Conditions
Description
• Configure the receiver function
• Set data transfer conditions
For details on the settings, see page 1-138 in section 1.17.1, “Setting Basic Communication
Conditions”.
4.3.2 Reading from and Writing to the GX/GP from Other Devices
Other devices (master devices) can transmit commands to the GX/GP to read data from and
write data to the GX/GP. By writing data to the GX/GP registers, you can control the GX/GP
(such as start recording).
For details on the function codes that the GX/GP supports and the GX/GP registers that
master devices can access, see page 4-11 in section 4.5, “Modbus Function and Register
Assignments”.