TOHO ELECTRONICS TTM200 - Manual (Page 18)

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6.3 Composition of an RTU request message (transmitted from a high-level
computer to this product)
 For codes a) through i), see "6.5 Description of RTU codes."
6.3.1 Composition of a read request message
a) Slave address 01H
b) Function code 03H
c) Register address
High level 00H
First register address
Low level 00H
d) Number of registers
High level 00H
Fixed at 2
Low level 02H
e) CRC-16
Low level 0BH
High level C4H
6.3.2 Composition of a write request message
a) Slave address 01H
b) Function code 10H
c) Register address
High level 00H
First register address
Low level 00H
d) Number of registers
High level 00H
Fixed at 2
Low level 02H
f) Number of byte items 04H Number of registers

2
g)
Data for the first register
(a low-level word)
High level 00H ③
Data composition is ①, ②, ③,
and ④H. (① represents 1
byte.) Low level 00H ④
Data for the first register
(a high-level word) High level 00H ①
Low level 00H ②
e) CRC-16
Low level 3FH
High level FEH
6.3.3 Composition of a store request message
a) Slave address 01H
b) Function code 10H
c) Register address
High level 02H
First register address
Low level 0EH
d) Number of registers
High level 00H
Fixed at 2
Low level 02H
f) Number of byte items 04H Number of registers

2
g)
Data for the first register
(a low-level word)
High level 00H
The data about the storage of settings
is arbitrary. Low level 00H
Data for the first register
(a high-level word)
High level 00H
Low level 00H
e) CRC-16
Low level E2H
High level EBH