Communication manual TOHO ELECTRONICS INC.
DWG.No. 4B-6829-A
- 13 -
Section
5
Explanation about MODBUS Protocol Communication
5.1.
MODBUS RTU
5.1.1.
Structure of Request Message (Data Transmission from Upper Computer to This Product)
5.1.1.1.
Structure of Read Request Message
a) Slave Address
01H
b) Function Code
03H
c) Register Address
Upper
00H
First register address
Lower
00H
d) Number of Registers
Upper
00H
2 (fixed)
Lower
02H
e) CRC-16
Lower
C4H
Upper
0BH
5.1.1.2.
Structure of Write Request Message
a) Slave Address
01H
b) Function Code
10H
c) Register Address
Upper
01H
First register address
Lower
00H
d) Number of Registers
Upper
00H
2 (fixed)
Lower
02H
f) Number of Bytes
04H
Number of Registers x 2
g)
Data for the first register
(Lower word)
Upper
00H
③
Data structure is ①②③④H.
(① represents 1 byte)
Lower
0DH
④
Data for the first register
(Upper word)
Upper
00H
①
Lower
00H
②
e) CRC-16
Lower
6FH
Upper
FCH
5.1.1.3.
Structure of Save Request Message
a) Slave Address
01H
b) Function Code
10H
c) Register Address
Upper
20H
First register address
Lower
0EH
d) Number of Registers
Upper
00H
2 (fixed)
Lower
02H
f) Number of Bytes
04H
Number of Registers x 2
g)
Data for the first register
(Lower word)
Upper
00H
Data for the saving of setting is
optional.
Lower
00H
Data for the first register
(Upper word)
Upper
00H
Lower
00H
e) CRC-16
Lower
EBH
Upper
E2H