INVT GD300-004G-4, Руководство по эксплуатации

Страница: 238 / 312

Goodrive300 inverters Communication protocol
237
Communication protocol 10
10.1 What this chapter contains
This chapter describes the communication protocol of Goodrive300 series inverters.
The Goodrive300 series inverters provide RS485 communication interface. It adopts
international standard ModBus communication protocol to perform master-slave
communication. The user can realize centralized control through PC/PLC, upper control PC,
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 instruction 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
network (the channel of signal transmission or the physical layer, such as RS485). And with
this industrial standard, the controlling devices of different manufacturers can be connected
to an industrial network for the convenient 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 same transmission
mode and their basic parameters, such as baud rate, digital bit, check bit, and stopping bit
should have no difference.
Modbus network is a controlling network with single-master and multiple slaves, which
means that there is only one device performs as the master and the others are the slaves on
one Modbus network. The master means the device which has active talking right to sent
message to Modbus network for the controlling and inquiring to other devices. The slave
means the passive device which sends data message to the Modbus network only after
receiving the controlling or inquiring message (command) form the master (response). After
the master sends message, there is a period of time left for the controlled or inquired slaves
to response, which ensure there is only one slave sends message to the master at a time for
the avoidance of singles impact.
Generally, the user can set PC, PLC, IPC and HMI as the masters to realize central control.
Setting certain device as the master is a promise other than setting by a bottom or a switch
or the device has a special message format. For example, when the upper monitor is