7. MODBUS
IMS01J02-E2
115
7.2 Message Format
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 three holding registers from 006BH to 006DH are the read out from
slave address 2.
Query message
Slave address
02H
Function code
03H
Starting No.
High
00H
Low
6BH
Quantity High
00H
Low
03H
CRC-16 High
74H
Low
24H
Normal response message
Slave address
02H
Function code
03H
Number of data
06H
First holding
High
02H
register contents
Low
2BH
Next holding
High
00H
register contents
Low
00H
Next holding
High
00H
register contents
Low
63H
CRC-16 High
50H
Low
48H
Error response message
Slave address
02H
80H
+
Function code
83H
Error code
03H
CRC-16 High
F1H
Low
31H
First holding register address
Number of holding registers
×
2
The setting must be between 1 (0001H)
and 125 (007DH).