The User Manual of JAC200 Series General Frequency Converter
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Appendix C: JAC
200
Modbus Communication Protocol
JAC200 series frequency converter provides RS485 communication protocol, and supports Modbus-RTU
slave machine communication protocol. THE user can realize the centralized control though station or PLC,
and by the communication protocol, the user can set the run command for the frequency converter, modify
or read the function code parameters, and read the working condition and failure of frequency converter,
etc.
C.1 Protocol content
The serial communication protocol defines the transmission information content and the using format in the
serial communication. They include: master polling (or broadcast) format; the coding method for master,
and the content includes: the function codes, data transmission and error verification and so on for the
requested action, The response of the slave machine also uses the same structure, and its content include:
action confirmation, data returning and error checking, etc. Whether error happens when the salve station
receives the information, or it cannot complete the actions requested by the master, it shall organize a failure
as the response to feed back to the master machine.
C.1.1 Application mode
The frequency converter is accessed into the “single principal line and multiple affiliated lines” PC/PLC
control network equipped with RS485 bus and used as a communication salve computer.
C.1.2 Bus structure
(1) Hardware interface
The main board interface labels are 485+ and 485-.
(2) Topological structure
System of single main station and multiple slave machines Each communication equipment in the
network has an exclusive slave machine address, among which, one of the equipment, used as the
communication master (normally are flat PC upper station, PLC, and HMI, etc.), launch the communication
proactively and make read or write operation to the parameters for the slave machine, while the other
equipment, used as the communication slave machines, response the inquiry or communication operations
against the station by the master. At the same time, only one of the equipment can send the data, while the
other equipment is in the accepting state.
The setting arrange for the slave machine is 1~247, and 0 is the broadcast communication address. The
slave machine address in the network must be exclusive.
(3) Communication transmission mode
Asynchronous serial and half-duplex transmission mode During the serial asynchronous communication
