TOHO ELECTRONICS TTM200 - Manual (Page 19)

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6.4 Composition of an RTU response message (transmitted from this product
to a high-level computer)
 For codes a) through h), see "6.5 Description of RTU codes."
6.4.1 Response message for a read request message
a) Slave address 01H
b) Function code 03H
d) Number of byte items 04H Number of registers

2
g)
Data for the first register
(a low-level word)
High level 0AH ③
Data composition is ①, ②, ③,
and ④H. (① represents 1
byte.) Low level A1H ④
Data for the first register
(a high-level word)
High level 00H ①
Low level 00H ②
e) CRC-16
Low level 09H
High level A8H
6.4.2 Response message for a write/store request message
a) Slave address 01H
b) Function code 10H
c) Register address
High level 01H
First register address
Low level 00H
d) Number of registers
High level 00H
Fixed at 2
Low level 02H
e) CRC-16
Low level 34H
High level 40H
6.4.3 Response message in the case of an error
a) Slave address 01H
b) Function code 83H

In the case of an error, the function
for the request message + 80H is
entered.
h) Error code 03H
e) CRC-16
Low level 31H
High level 01H