RKC INSTRUMENT Z-TIO-G, Instruction Manual

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7. MODBUS
7-8
IMS01T28-E4
7.2 Register Read and Write
7.2.1 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 two holding registers from 0000H to 0001H are the read out from slave
address 2.
Query message
Slave address 02H
Function code 03H
Starting No. High 00H
Low 00H
Quantity High 00H
Low 02H
CRC-16 High C4H
Low 38H
Normal response message
Slave address 02H
Function code 03H
Number of data 04H
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 C9H
Low 5FH
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