TOHO ELECTRONICS TRM-006A - Manual (Page 21)

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6.3 Composition of an RTU request message (transmitted from a high-level
computer to this product)
n For codes a) through i), see "6.5 Description of RTU codes."
6.3.1 Composition of a read request message
a) Slave address 1BH
b) Function code 03H
High level 00H
c) Register address
Low level 00H
First register address
High level 00H
d) Number of registers
Low level 02H
Fixed at 2
High level C6H
e) CRC-16
Low level 31H
6.3.2 Composition of a write request message
a) Slave address 03H
b) Function code 10H
High level 00H
c) Register address
Low level C0H
First register address
High level 00H
d) Number of registers
Low level 02H
Fixed at 2
f) Number of data items 04H Number of registers
×
2
High level 00H ③
Data for the first register
(a low-level word)
Low level 6FH ④
High level 00H ①
g)
Data for the first register + 1
(a high-level word)
Low level 00H ②
When writing ①, ②, ③, and
④ H in the data, write them in
the order described on the
left-hand side. (① represents 1
byte.)
High level C4H
e) CRC-16
Low level 5AH