SHENZHEN ENCOM ELECTRIC TECHNOLOGIES CO. EN500 Series Service Manual page 240

A.8.2 ACSII Mode
Host read Slave，command code: 03
Send
1 2
byte
Remark:
Begin symbol:
The lower computer judge the frame header of ASCII based on this.
It is:':'
Slave address:
Single inverter ID code，range:0~247.
Thereinto, 0 is broadcast address. Broadcast address can control all
the lined Slave simultaneously，and the Slave will not send back
any Data to the host. That means the Slave only accept and do not
send.
Modbus protocol without host address.
Command code:
Reading the command of parameter or data from inverter ，the
value is:'0''3'.
Register address:
The internal memory address of inverter function parameter is of 4
byte, which is ASCII mode transformed from Hexadecimal.
Corresponding relation between specific parameters and
memory address can be seen in the later table.
Register number:
The number of parameters read by a frame, it is 4 byte. It is ASCII
mode transformed from Hexadecimal.
Checksum:
From "slave address" to the character before checksum, the LRC
checksum of the character string. Function terminal can be seen on
the end of the text.
The host frame
The host frame format
2 4
Appendix A Modbus communication protocol
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