Communication Protocol; What This Chapter Contains; Brief Introduction To Modbus Protocol; Application Of The Inverter - INVT Goodrive300-19 Series Operation Manual

Goodrive300-19 series open loop vector inverter special for hosit

Communication protocol

Communication protocol 10

10.1 What this chapter contains

This chapter describes the communication protocol of Goodrive300-19 series inverters.
Goodrive300-19 series inverters provide RS485 communication interface and adopt international
standard Modbus communication protocol to perform master-slave communication. The user can
realize centralized control through PC/PLC, upper computer control, etc. (set the control command,
running frequency of the inverter, modify relevant function codes, monitor and control the operating
state and fault information of the inverter and so on) to adapt specific application requirements.

10.2 Brief introduction to Modbus protocol

Modbus protocol is a software protocol and common language which is applied in the electrical
controller. With this protocol, the controller can communicate with other devices via the channel of
signal transmission. And with this industrial standard, the controlling devices of different
manufacturers can be connected to an industrial network for the convenience of being monitored.
There are two transmission modes for Modbus protocol: ASCII mode and RTU (Remote Terminal
Units) mode. On one Modbus network, all devices should select the same transmission mode and
their basic parameters, such as baud rate, digital bit, check bit and stop bit should have no difference.
Modbus network is a controlling network with single master and multiple slaves, which means that
only one device is the master and the others are the slaves on one Modbus network. The master can
either communicate with any slave independently or send broadcasting messages to all slaves. For
the independent access command, the slave will send a response message; for the broadcasting
message from the master, the slave will not need to make any response message.

10.3 Application of the inverter

The Modbus protocol of the inverter is RTU mode and the physical layer is RS485.
10.3.1 RS485
The interface of 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
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