FF
Unit ID
1 Byte, 0xFF = Master device
05
Function Code
1 Byte, 05 = Write single register
0064
Starting Address
2 Bytes, address of the first register
FF00
Data
2 Byte, FF00 indicates COM and NO is close
In the response from the device we get:
0x 000100000006FF050064FF00
Command
Field
Description
0001
Transaction ID
2 Bytes, identification of a Modbus Request/Response transaction
0000
Protocol ID
2 Bytes, 0000 = Modbus protocol
0006
Length Field
2 Bytes, number of following bytes
FF
Unit ID
1 Byte, 0xFF = Master device
05
Function Code
1 Byte, 05 = Write single register
0064
Starting Address
2 Bytes, address of the first register
FF00
Data
2 Byte, FF00 indicates COM and NO is close
Take the case of acquisition 1 channel DI as an example. The command is as follows:
0x 000100000006FF0200C80001
Command
Field
Description
0001
Transaction ID
2 Bytes, identification of a Modbus Request/Response transaction
0000
Protocol ID
2 Bytes, 0000 = Modbus protocol
0006
Length Field
2 Bytes, number of following bytes
FF
Unit ID
1 Byte, FF = Master device
02
Function Code
1 Byte, 02 = Read
00C8
Starting Address
2 Bytes, address of the first register
0001
Quantity of Registers
2 Bytes, the number of required registers
C2000-A1-SDD1010-AB3 User Manual
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