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Appendix 1 Modbus Communication Protocol
1. Networking mode
The drive has two networking modes: single host/multiple slaves mode and single host/single slave mode.
2. Interface mode
RS485 interface: asynchronous and half-duplex. Default: 1-8-N-2, 9600bps, RTU. Refer to Group P15
function code for the parameter setting.
3. Communication mode
1. The communication protocol of the drive is Modbus protocol, which does not only support common register
reading and writing, but also expands some commands to manage the drive function codes.
2. The drive is slave, adopting host/salve mode P2P communication. The drive will not response to the
command sent by the host via broadcast address.
3. In multiple units communication or long-distance communication, parallel connecting the resistance of 100
to 120 ohms with the positive end and negative end of the communication signal line of the host station can
enhance its immunity to interference.
4. MV600 provides RS485 interface only. If the communication interface of the external equipment is RS232,
the RS232/RS485 conversion equipment is needed.
4. Protocol format
Modbus protocol supports both RTU mode and ASCII mode, and the corresponding frame format is as shown
in the Attached Fig.1-1.
Attached Fig.1-1 Modbus protocol format
Start (at least 3.5
bytes of idle time)
Slave
address
Command
code
Data
Check code
End (at least 3.5
bytes of idle time)
Modbus data frame
RTU mode
Start
(
0x3A
)
Data
End
Modbus data frame
SCII mode
Slave
address
Command
code
Check code
(0x0D, frame trail byte)