User Manual

IB-23C650M
MODBUS PROTOCOL
Message Formats
The following message formats are used to transfer information between the
controller and a host. Refer to the message format example for format details.
Read Coil Status, Read Input Status
Master Message Format Bytes
0 1 2 & 3 4 & 5 6 & 7
Device Address Function Code Starting Coil Number Number of Coils CRC
Slave Response Bytes
0123
...
x
x+1 &
x+2
Device
Address
Function
Code
Number of
Data Bytes
Data byte #1 ... Data Byte #n CRC
Read Holding Registers, Read Input Registers
Master Message Format Bytes
0 1 2 & 3 4 & 5 6 & 7
Device Address Function Code Starting Register Number Number of Registers CRC
Slave Response Bytes
0 1 2 3 & 4
...
x & x+1
x+2 &
x+3
Device
Address
Function
Code
Number of
Data Bytes
Register #1
data
... Register #n
data
CRC
Force Single Coil
Master Message Format Bytes
0 1 2 & 3 4 & 5 6 & 7
Device Address Function Code Coil Number Coil Data
ON = FF00
OFF =0000
CRC
Slave Response (simple echo) Bytes
0 1 2 & 3 4 & 5 6 & 7
Device Address Function Code Coil Number Coil Data
ON = FF00
OFF =0000
CRC
36