Chapter 6 RS485 Communication protocol
FC300
CHAPTER 6 RS485 COMMUNICATION PROTOCOL
6.1 Support Protocol
Support Modbusprotocol,RTU mode.Broadcast address 0, slave address can be set as1 255.
6.2 Interface Mode
RS485: asynchronous half-duplex the lowest effective bit is sent outby priority.High byteis in
front, low byte is at back.
Default data format:1-8-N-2, 38400 bps
Function parameters:P150, Communication configuration.Composed by four hexadecimal
digits[D3 D2 D1 D0], default value is 0x0301.
Their respective effects are as below:
D3
Data format
0 1-8-2 mode, no verification
1 1-8-1 mode, even verification
2 1-8-1 mode, odd verification
D2
Baud rate
0
4800
1
9600
2
19200
3
38400
D1
D0
Two hexadecimal digits
mean hostaddress, range
01-FF, i.e. decimal 1-255.
6.3 Protocol Format
ADU(Application Data Unit) check is obtained through the first three parts of the CRC16 check
of ADU and exchanging high and low bytes. When operation request fails PDU Protocol Data
Unit responds as error code or exception code.Error code is equal to function code +0x80
while exception code indicates specific error reasons. Examples for abnormal codes are listed
below.
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