Modbus Communication
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3 Modbus Communication
3.1 Introduction
With the RS485 communication interface, the MD520 series AC drive connects as a
communication slave to the PC/PLC control network with a single master and
multiple slaves, which allows centralized control by using a PC or PLC. You can set the
operation commands, modify or read parameters, and read the operating status and
fault information of the AC drive through the communication protocol.
The AC drive supports the Modbus RTU and Modbus ASCII slave communication
protocols. These protocols define the content and format of messages transmitted
during serial communication. If the slave has an error upon receiving a message or
fails to complete the action required by the master, it responds with a fault message
to the master.
3.2 Networking and Interfaces
In a network with a single master and multiple slaves, one of the devices works as the
communication master (typically a PC host controller, PLC, or HMI), and the other
devices work as communication slaves. The communication master initiates
communication actively to read or write to parameters of communication slaves, and
the slaves respond to queries or communication operations from the master. At the
same moment, either the master or the slave transmits data and the other can only
receive data.
Each communication slave has a unique slave address, which ranges from 1 to 247. 0
indicates the broadcast address.
Communication Interface
The MD38TX1 communication card required for Modbus communication is specially
designed for the MD520 series AC drive to provide the RS485 communication function.
It adopts the isolation scheme and its electrical parameters conform to international
standards. You can use it as required to control operation and parameter setting of
the AC drive through the remote serial interface. See the following figure.
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