Explanation Of Modbus Rtu Communication - Toho Electronics TTX-800 Operation Manual

3.3

Explanation of MODBUS RTU Communication

3.3.1 Structure of MODBUS RTU Request Message (Data Transmission from the Upper Computer to This Product)
■ See "3.3.3
Explanation of MODBUS RTU Codes" for codes a) to g).
3.3.1.1 Structure of Read Request Message
a) Slave Address
b) Function Code
c) Register Address
d) Number of Registers
e) CRC-16
3.3.1.2 Structure of Write Request Message
a) Slave Address
b) Function Code
c) Register Address
d) Number of Registers
f) Number of Bytes
Data for the First Register
(Lower Word)
g)
Data for the First Register
(Upper Word)
e) CRC-16
3.3.1.3 Structure of Save Request Message
a) Slave Address
b) Function Code
c) Register Address
d) Number of Registers
f) Number of Bytes
Data for the First Register
(Lower Word)
g)
Data for the First Register
(Upper Word)
e) CRC-16
01H
03H
Upper 00H
First register address
Lower 00H
Upper 00H 2 (fixed)
※ Except for communication monitor
Lower 02H
register address
Lower C4H
Upper 0BH
01H
10H
Upper 01H
First register address
Lower 00H
Upper 00H
2 (fixed)
Lower 02H
04H Number of Registers x 2
Upper 00H ③
Lower 00H ④
Data structure is ①②③④H.
Upper 00H ①
(① represents 1 byte)
②
Lower 00H
Lower FEH
Upper 3FH
01H
10H
Upper 09H
First register address
Lower 0CH
Upper 00H
2 (fixed)
Lower 02H
04H Number of Registers x 2
Upper 00H
Lower 00H
Data for saving the setting is
Upper 00H
optional.
Lower 00H
Lower E8H
Upper E2H
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