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Appendix A Modbus Communication Protocol
116
Appendix A Modbus Communication Protocol
1. Support Protocol
Support Modbus protocol, RTU format, Broadcast address 0, slave address “1
−
247”, “248
−
255” for
reservation.
2. Interface mode
RS485: Asynchronous, half duplex, LSB sending priority. Low byte is after the high byte.
Inverter communication port A (RJ45) default data format: 8
−
N
−
1, 38400 bps
It is recommended to adopt EIA/TIA T568B, the lead of port A is defined as:
Attached Fig. 1 RJ45 interface
Lead of
communication
port A
1
2
3
4
5
6
7
8
Signal of
communication
port A
+5V
GND
485+
485
−
485+
485
−
GND
+5V
EIA/TIA T568A
White
green
Green
White
orange
Blu
e
Whit
e blue
Orang
e
Whit
e
brown
Brow
n
EIA/TIA T568B
White
orange
Orang
e
White
green
Blu
e
Whit
e blue
Green
Whit
e
brown
Brow
n
3. Protocol Format
Check sun
The initial
space of the
frame is 4
characters or
above
Data
Slave address
Function code
ADU
PDU
The end space
of the frame is
4 characters or
above
Attached Fig.2 Protocol Format
ADU (Application Data Unit) check is the CRC16 check of the first three parts of ADU and obtained
through exchange of high/low bytes.
If the operation request is rejected, the feedback of PDU(Protocol Data Unit) will be error code or
abnormal code. Error code equals to function code +0x80, abnormal code shows the error cause in
detail.
1
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