DKM-40
7 Kullanım Kılavuzu V-1.1
29
The normal response will be:
Byte
Description
Value
0
Controller address
same as in the query
1
Function code
3
2
Data lenght in
bytes
(L)
number of registers * 2
3
High byte of 1st register
4
Low byte of 1st register
5
High byte of 2nd register
6
Low byte of 2nd register
....
L+1
High byte of the last register
L+2
Low byte of the last register
L+3
CRC low byte
See below for the checksum calculation
L+4
CRC high byte
The exceptional response will be:
Byte
Description
Value
0
Controller address
same as in the query
1
Function code
131 (function code + 128)
2
Exception code
2 (illegal address)
3
CRC low byte
See below for the checksum calculation
4
CRC high byte
Data Writing
The function 06 (write single register) function 10h (write multiple registers) are used for
data writing. A maximum of 32 registers can be written at a time.
The MODBUS master will send a query containing data to be written. The answer will be
one of the below:
-A normal response confirming successful write,
-An exceptional response indicating a write error.
Only some of the available registers are authorized to be written. An attempt to write a write
protected register will result to the exceptional response.
The query message specifies the register address and data. The message structure is
below:
Byte
Description
Value
0
Controller address
1 to 254
1
Function code
6
2
Register address high
See below the description of available registers
3
Register address low
4
Data high byte
5
Data low byte
6
CRC low byte
See below for the checksum calculation
7
CRC high byte
