DPR-350 User Manual Ver_01 Firmware V-1.0
K91D01-EN - 63 -
Record reading is performed using function code 03 (read multiple registers). The MODBUS master
device sends a query. The response can be either the required data or an error message. Up to 123
registers can be read at once. If a query for more than 123 registers is made, an error message is sent as
a reply. Message structure is as follows.
BYTE
DESCRIPTION
VALUE
0
Device Address
1-253
1
Function Code
3
2
Starting
Address (Top)
Detailed explanation given below
3
Starting
Address
(Bottom)
Detailed explanation given below
4
Number of
Registers (Top)
0
5
Number of
Registers
(Bottom)
Max 7Bh (123 decimal)
6
CRC Bottom
Byte
CRC calculation is explained below in detail
7
CRC Top Byte
CRC calculation is explained below in detail
An example for reading 16 registers starting with the address 20h (32 decimal) is explained below.
01 03 00 20 00 10 45 CC (each byte is expressed by 2 hexadecimal characters)
Expected reply:
BYTE DESCRIPTION
VALUE
0
Device Address
Same as query
1
Function Code
3
2
Data Byte Size
Number of Registers x 2
3
1
st
Register Top
Byte
4
1
st
Register
Bottom Byte
5
2
nd
Register Top
Byte
6
2
nd
Register
Bottom Byte
…
…
…
L+1
Last Register Top
Byte
L+2
Last Register
Bottom Byte
L+3
CRC Bottom Byte CRC calculation is explained below
L+4
CRC Top Byte
CRC calculation is explained below
22.3. READING DATA
