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Chapter 7 Modbus Communication Protocol
Chapter 7 Modbus Communication Protocol
ACH200 series AC drive is equipped with RS485 communication interface as standard, and
master-slave communication using international standard Modbus communication protocol. Users
can realize centralized control (setting AC drive control commands, operating frequency,
modification of relevant function code parameters, monitoring of AC drive operating status and fault
information, etc.) through PC/PLC, host computer, master AC drive, etc. to meet specific application
requirements.
7.1 Rules of Communication
The MODBUS communication format is shown in the table below.
Project
Interface
Synchronization method
Communication frames
Communication protocols
Note: ACH200 series only supports RTU mode.
7.2 Information Format
In RTU mode, a new frame starts with a transmission time pause interval of at least 3.5 bytes.
The data fields transmitted immediately afterwards are, in order: slave address, operation command
code, data and check word, and at the completion of the last byte transmission, another transmission
time pause interval of at least 3.5 bytes indicates the end of the frame. the RTU data frame format
is shown in the figure below.
Start，need at least
3.5 characters of free
memory space
ACH200 Series High Voltage Variable Frequency Speed Control System Operating Manual
Description
RS-485 (RS232 interface requires additional RS232/RS485
converter)
Asynchronous
Baud rate:1200、2400、4800、9600、19200、38400、57600bps
Data length: 8-bit (fixed)
Check: odd, even, none
Stop bit: 1-bit (fixed)
Modbus protocol (RTU (mode) only)
RTU data frame format
MODBUS messages
Slave address
Command code
Figure.7-1
65
Data
Check
Over，need at least
3.5 characters of free
memory space
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