Communication Protocol
Bit socket tray uses Modbus-RTU protocol.
If several bit socket trays are connected, send a message to one bit socket tray and do not send a message until a response is received. (Timeout: 200ms)
Modbus-RTU
Request Message
Data Length High
Data Length Low
CRC (RTU) Low
CRC (RTU) High
Slave address
Function Code
Address High
Address Low
1. Slave address: It means comm ID. 2. Function code: It means the kind of command. (4: read, 6: write) 3. Address: It means target address. (2 byte) 4. Data length: It means the number of data to be read. (2 byte) 5. CRC: Error detection
Data Length High
Data Length Low
CRC (RTU) Low
CRC (RTU) High
Slave Address
Function Code
Address High
Address Low
e.g. (Hex)
01
04
0C
80
00
01
33
72
Response Message
Data Byte Length
CRC (RTU) Low
CRC (RTU) High
Slave Address
Function Code
Data High
Data Low
1. Data byte length: Byte number of data 2. Data: value 1
Data Byte Length
CRC (RTU) Low
CRC (RTU) High
Slave Address
Function Code
Data High
Data Low
e.g. (Hex)
01
04
02
00
01
78
F0
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