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2.Data transmission system
Com system：Half-duplex asynchronous system (Boring selecting system）
Com. distance：Max. 500m （depending on influences from the environment）
Connection method：Multidrop system (Max 1 :31 stations）
Start bit：1 bit
Transmission code： ASCII (ASCII mode)
Binary (RTU mode)
Error check： LRC (ASCII mode)
CRC-16 (RTU mode)
3.Frame configuration
The RTU mode consists of a message portion only.
The ASCII mode consists of a starting character "：(colon, 3AH)", a message and a terminating
character "CR (carriage return, ODH) + LF(line feed), OAH".
RTU mode：
ASCII mode：
4.Message configuration
The configuration of an MODBUS message is as follows for both RTU & ASCII modes:
Slave address
Function code
Data
Error check
Message
： ｜ Message
｜ CR
4. Operating procedures
Setting external communication
｜ LF
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