ACD320 user manual
Appendix
Chapter 9 Appendix
Appendix 1 ACD320 series serial communication protocol
The ACD320 series inverter provides RS485 communication ports, and adopts the standard
ModBus communication protocol for master/slave communications. The user can use PC/PLC or
control upper computer to implement centralized control (setting inverter control command,
operating frequency, modificationof related functional code parameters,working status of inverter,
and fault message monitoring), to meet special application requirement.
1、 Protocol Content
The Modbus serial communication protocol defines frame content and use format of
asynchronous transmission in serial communications. Including: polling and broadcast
frame of the master, and reply frame format of the slave. The frame content of the master
includes: address (broadcast address) of the slave, execution command, data, error
check,and so on. The response of the slave also adopts the same structure. Itscontent
includes:action confirmation, return data, error check, and so on. If an error occurs when the
slave is receiving a frame or the slave cannot complete the action required by the master, the
slave will organize a fault frame and send it to the master as a response message.
2、 Application Mode
The ACD320 series inverters access to the "single-master multi-slave" control network with
RS232/RS485 bus.
3、 Bus Structure
(1)Interface mode
RS485 hardware interface
(2)Transmission mode
Asynchronous serial and half-duplex transmission mode.At the same moment, only one of the
master and slave sends data, while the other receives data. Data is sent frame by frame in form of
packets during asynchronous serial communications.
(3)System topology:
"single master multi-slave". The addresses of the slaves range from 1 through 247.Where "0"
is the broadcast communication address.The address of each slave over the network is a unique
one. This is the basis for ensuring ModBus serial communications.
4、 Protocol Description
The communication protocol for ACD320 inverters is a asynchronous serial master/slave
ModBus communication protocol. Only one device (the master) can establish a protocol (called
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