EXPERT Standard Series User Manual
212
Annex Communication Protocol
Interfacing method
RS485: Asynchronous, half duplex Default: 8-N-2, 9600bps.See group FB
description for parameter settings.
Communication method
1. Communication protocol of the drive is the Modbus protocol, except for
supporting common register read and write, partial commands are also expanded to
carry out management on drive function codes.
2. The drive is the slave, master-slave point to point communication. When the
master sends commands using broadcast address, the slave will not respond.
3. During multi-machine communication or long distance communication,
connecting a resistance of 120Ω at both ends of the communication could improve the
communication’s interference rejection.
Protocol format
Modbus protocol supports both RTU mode and ASCII mode, and corresponding
frame format is as follows:
Modbus adopts the “Big Endian” coding method, which sends high bit bytes first,
and then low bit bytes.
RTU method: Under RTU method, idle time between frames could select function
code setting or observe inner conventions of Modbus. Min. frame idle agreed inside
Modbus is as follows: Frame head and end use bus idle time larger than or equal to
3.5 bytes to determine the frame. Data check adopts CRC-16, and the entire
information participates in check, while high and low bits of checksum need to be sent
