Goodrive300-01 inverter for air compressor Communication protocol
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Appendix A Communication protocol
A.1 Application mode of the inverter
The Modbus protocol adopted by this inverter is RTU mode and the network line is RS485.
A.1.1 RS485
RS485 interface works on semiduplex and its data signal applies differential transmission which is
called balance transmission, too. It uses twisted pairs, one of which is defined as A (+) and the other
is defined as B (-). Generally, if the positive electrical level between sending drive A and B is among
+2~+6V, it is logic“1”, if the electrical level is among -2V~-6V; it is logic“0”.
485+ on the terminal board corresponds to A and 485- to B.
Communication baud rate (P14.01) means the binary bit number transmitted in one second. The unit
is bit/s (bps). The higher the baud rate, the quicker the transmission speed and the weaker the
anti-interference ability. If the twisted pairs of 0.56mm (24AWG) is applied as the communication
cables, the Max. Transmission distance is as below:
Baud rate
Max. transmission distance
Baud rate Max. transmission distance
2400BPS
1800m
9600BPS
800m
4800BPS
1200m
19200BPS
600m
It is recommended to use shielded cables and make the shield layer as the grounding wires during
RS485 remote communication.
In the cases with less devices and shorter distance, it is recommended to use 120Ω terminal resistor
as the performance will be weakened if the distance increase even though the network can perform
well without load resistor.
A.2 RTU command code and communication data
A.2.1 Command code: 03H, read N words (read 16 words continuously at most)
Command code 03H means that if the master read data from the inverter, the number being read (16
words at most)
depends on the “data number” in the command and the parameter address being read
must be continuous. The byte length of every data is 2 (one word).
This command code is used to read the parameters and working stage of the inverter.
A.2.2 Command code: 06H, write one word
This command means that the master write data to the inverter and one command can write one data
only other than multiple data. Its role is to change the parameters and working mode of the inverter.
A.2.3 Command code: 08H, diagnosis function
Meaning of sub-function codes
Sub-function Code
Description
0000
Return to inquire information data
A.2.4 The definition of data address
The address definition of the communication data in this part is to control the running of the inverter
and get the state information and relative function parameters of the inverter.
A.2.4.1 The rules of address of the function codes
