KE300A Inverter MODBUS Communication Protocol
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Chapter 9 MODBUS Communication Protocol
KE300A series inverter provides RS485 communication interface, and adopts MODBUS communication
protocol. User can realize centralized monitoring through PC/PLC, host computer, and also can set
inverter’s operating commands, modify or read function parameters, read operating status and fault
information, etc.
9.1 About Protocol
This serial communication protocol defines the transmission information and use format in the series
communication. It includes the formats of master-polling, broadcast and slave response frame, and master
coding method with the content including slave address (or broadcast address), command, transmiting
data and error checking. The response of slave adopts the same structure, including action confirmation,
returning the data and error checking etc. If slave takes place the error while it is receiving the information
or cannot finish the action demanded by master, it will send one fault signal to master as a response.
9.2 Application Method
The inverter could be connected into a “Single-master Multi-slave” PC/PLC control network with RS485
bus.
9.3 Bus Structure
(1) Interface mode
RS485
(2) Transmission mode
There provide asynchronous series and half-duplex transmission mode. At the same time, just one can
send the data and the other only receives the data between master and slave. In the series asynchronous
communication, the data is sent out frame by frame in the form of message.
(3) Topological structure
In Single-master Multi-slave system, the setup range of slave address is 0 to 247. 0 refers to broadcast
communication address. The address of slave must be exclusive in the network. That is basic condition of
MODBUS communication.
9.4 Protocol Description
KE300A series inverter communication protocol is a kind of asynchronous serial master-slave
communication protocol. In the network, only one equipment (master) can build a protocol (Named as
“Inquiry/Command”). Other equipments (slave) response “Inquiry/Command” of master only by providing
the data, or doing the action according to the master’s “Inquiry/Command”. Here, master is Personnel
Computer, Industrial control equipments or Programmable logical controller, and the slave is inverter or
other communication equipments with the same communication protocol. Master not only can visit some
slave separately for communication, but also sends the broadcast information to all the slaves. For the
single “Inquiry/Command” of master, all of slaves will return a signal that is a response; for the broadcast
information provided by master, slave needs not feedback a response to master.
