Communication Protocol
108
10. COMMUNICATION PROTOCOL
10.1 Interfaces
RS485: asynchronous, half-duplex.
Default: 8-E-1, 19200bps. See Group PC parameter settings.
10.2 Communication Modes
10.2.1 The protocol is Modbus protocol. Besides the common register Read/Write
operation, it is supplemented with commands of
parameters management.
10.2.2 The drive is a slave in the network. It communicates in ‘point to point’ master-slave
mode. It will not respond to the
command sent by the master via broadcast address.
10.2.3 In the case of multi-drive communication or long-distance transmission,
connecting a 100~120Ω resistor in parallel with the
master signal line will help to enhance the immunity to interference.
10.3 Protocol Format
Modbus protocol supports both RTU and ASCII mode. The frame format is illustrated as
follows:
Modbus adopts “Big Endian” representation for data frame. This means that when a
numerical quantity larger than a byte is transmitted, the most significant byte is sent first.
RTU mode
In RTU mode, the Modbus minimum idle time between frames should be no less than 3.5
bytes. The checksum adopts CRC-16 method. All data except checksum itself sent will be
counted into the calculation. Please refer to section: CRC Check for more information.
Note that at least 3.5 bytes of Modbus idle time should be kept and the start and end idle
time need not be summed up to it.
The table below shows the data frame of reading parameter 002 from slave node address
1.
To Next Page
Loading...
Need help?
General