APPENDIX. HOST COMMUNICATION PROTOCOL
IMR02E20-E1
131
A.3.6 Register read and write
Read holding registers [03H]
The query message specifies the starting register address and quantity of registers to be read.
The contents of the holding registers are entered in the response message as data, divided into two
parts: the high-order 8-bit and the low-order 8-bit, arranged in the order of the register numbers.
Example: The contents of the four holding registers from 01FCH to 01FFH are the read out
from slave address 2.
Query message
Slave address
02H
Function code
03H
Starting number
High
01H
Low
FCH
Quantity High
00H
Low
04H
CRC-16 High
85H
Low
F6H
Normal response message
Slave address
02H
Function code
03H
Number of data
08H
First holding register contents
High
01H
Low
24H
Next holding register contents
High
01H
Low
1BH
Next holding register contents
High
01H
Low
2BH
Next holding register contents
High
01H
Low
22H
CRC-16 High
AAH
Low
F3H
Error response message
Slave address
02H
80H + Function code
83H
Error code
03H
CRC-16 High
F1H
Low
31H
First holding register address
The setting must be between 1 (0001H) and
125 (007DH).
Number of holding registers
2
