User Manual of EM730/EM730E Series Inverter
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Chapter 11
MODBUS Communication Protocol
11.1
Applicable scope
1
、
Applicable series: EM730/EM730E series
2
、
Applicable network: Support the “single-master multi-slave” communication network
with MODBUS-RTU protocol and RS-485 bus.
A+
A-
Host
A+
A-
Inverter 1#
A+
A-
Inverter 2#
A+
A-
Inverter n#
A-
A+
11.2
Interface mode
RS-485 asynchronous half-duplex communication mode, with the least significant bit sent
first;
RS-485 network address: 1-247; 0 is the broadcast address;
Default data format of RS-485 terminal: 1-8-N-1
[
2
]
(options: 1-8-E-1, 1-8-O-1, 1-8-N-2,
1-8-E-2 and 1-8-O-2);
Default baud rate of RS-485 terminal: 9600bps (options: 4800bps, 19200bps, 38400bps,
57600bps and 115200bps)
It is recommended to use twisted-pair shielded cable as the communication cable to reduce
the impact of external interference on communication.
[2]
:
1-8-N-1, meaning 1 start bit - 8 characters per byte of data - no parity - 1 stop bit.
E:
even parity.
O: odd parity.
11.3
Protocol Format
11.3.1
Message format
As shown in Fig. 12-20, a standard MODBUS message includes a start tag, RTU (Remote
Terminal Unit) message, and end tag.
