2-Wire Rs485 - INVT Goodrive100 Series Instruction Manual

Goodrive100 inverters Communication protocol

7.2.1 2-wire RS485

The interface of 2-wire RS485 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 means the binary bit number in one second. The unit is bit/s (bps). The higher the
baud rate is, the quicker the transmission speed is and the weaker the anti-interference is. If the twisted
pairs of 0.56mm（24AWG）is applied as the communication cables, the Max. Transmission distance is as
below:
Max.transmissi Max.transmissi Max.transmissi Max.transmissi
Baud Baud Baud Baud
on on on on
rate rate rate rate
distance distance distance distance
2400BP 4800BP 9600BP 19200BP
1800m 1200m 800m 600m
S S S S
It is recommended to use shield 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.
7.2.1.1 Single application
Figure 1 is the site Modbus connection figure of single inverter and PC. Generally, the computer does not
have RS485 interface, the RS232 or USB interface of the computer should be converted into RS485 by
converter. Connect the A terminal of RS485 to the 485+ terminal of the inverter and B to the 485- terminal. It
is recommended to use the shield twisted pairs. When applying RS232-RS485 converter, if the RS232
interface of the computer is connected to the RS232 interface of the converter, the wire length should be as
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