Micromod MOD: Modcell 2050R MODBUS Communications - Manual (Page 40)

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
0 1 2 3 ... 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
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