VD560 Series Inverter User Manual Communication Protocol
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Chapter 9 Communication Protocol
VD560 series inverter provides RS485 communication interface, and adopts Modbus-RTU
communication protocol. User can carry out centralized monitoring through PC/PLC to get operating
requirements.
9.1 About Protocol
This Modbus serial communication protocol defines the frame content of asynchronous transmission
information and use format in the series communication and it includes master-polling (or broadcast
address) executive command, data and error checking. The response of slave is the same structure,
and it includes 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 Methods
VD560 series inverter will be connected into a “Single-master Multi-slave” control net with RS485 bus.
9.3 Bus Structure
(1) Interface mode RS-485 Hardware interface.
(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 mode
In Single-master system, the setup range of slave address is 0 to 247. Zero refers to broadcast
communication address. The address of slave must is exclusive in the network. That is the basis to
guarantee the Modbus serial communication.
9.4 Protocol Description
VD560 series inverter communication protocol is a kind of serial master-slave communication
protocol, in the network, only one equipment (master) can build a protocol, (Named as
“Inquire/Command”). Other equipment (slave) only by providing the data response
“Inquire/Command” or doing the action according to the master’s “Inquiry/Command”. Here, master is
personnel computer (PC), industrial control machine or programmable logical controller(PLC) etc.,
and the slave refers to the VD560 series inverter or other control equipment with the same
communication protocol. Master not only visits some slave, but also sends the broadcast information
to all the slaves. For the single master “Inquiry/Command”, 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 machine.
9.5 Communication Frame Structure
Modbus protocol communication frame format of VD560 series of inverter is shown as following: (In
RTU mode, messages start with a interval of at least 3.5 character times. This is most easily
implemented as a multiple of character times at the baud rate that is being used on the network.
(shown as T1-T2-T3-T4 in the figure below). The first field then transmitted is the device address. The
allowable characters transmitted for all fields are hexadecimal 0 ... 9, A ... F. Networked devices
monitor the network bus continuously, including during the silent intervals.
When the first field (the address field) is received, each device decodes it to find out if it is the
addressed device. Following the last transmitted character, a similar interval of at least 3.5 character
