Response PDU
Function code
1 byte
0x03
Byte count
1 byte
2 x
N*
Register value
N*
x 2 bytes
*N = Quantity of registers
Exception Response PDU
Error code
1 byte
0x83 (=0x03 + 0x80)
Exception code
1 byte
01 or 02 or 03 or 04
Here is an example of a request to read the parameters
(register 9).
Request
Response
Field name
(Hex)
Field name
(Hex)
Function
03
Function
03
Starting address Hi
00
Byte count
04
Starting address Lo
07
Register 8 value Hi
03
No. of registers Hi
00
Register 8 value Lo
E8
No. of registers Lo
02
Register 9 value Hi
05
Register 9 value Lo
DC
parameter (register 8) contains
the value 03 E8 hex, i.e. 1000 in decimal notation;
parameter (register 9) contains the value 05 DC hex, i.e. 1500 in decimal
notation.
MAN RD6 MB E 1.1
Modbus® interface
54 of 92
RD6 Modbus®