Appendix 2 Modbus Communication Protocol 51
EV3200 Door Control Inverter User Manual
Appendix 2 Modbus Communication Protocol
Network Topology
:
RS232
Master: PC
RS485
EV3200
EV3100
EV1000
EV2000
RS232
EV3200
Single master multi-slave
or
RS485
232-485 adapter
Master: PLC
Master: PC
Single master single slave
232-485 adapter
Interfaces
RS485 or RS232: asynchronous, half-duplex.
Default: 8-N-2, 19200bps. See parameter settings of parameter group F8.
Communication mode
1. The protocol is Modbus protocol.
2. The inverter 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.
3. In the case of multi-inverter communication or long-distance transmission, connecting a 100 ~ 120
Ω
resistor in parallel with
the master signal line will help to enhance the immunity to interference.
Protocol format:
Modbus protocol supports both RTU and ASCII mode. The frame format is illustrated as follows:
Start, at least 3.5 bits
of vacancy
Slave
address
Function
code
Data
Check
End, at least 3.5
bits of vacancy
Modbus data frame
RTU mode
Start: "0
×
3A"
Slave
address
Function
code
Data
Check
End: "0
×
D, 0
×
A"
Modbus data frame
ASCII mode
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 idle time between frames is decided by the bigger value between parameter setting and the Modbus
minimum idle time. The minimum Modbus 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 the examples given
in the end of this appendix for details on CRC Check. 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 Inverter No. 1.
Address
Function parameter
Register address
Quantity of inputs
Check sum
0x01
0x03
0x00 0x02 0x00 0x01
0x25 0xCA