Appendix B Communication Protocol Shenzhen Hpmont Technology Co., Ltd.
- 144 - HD3N Series User Manual V1.1
Protocol Format
The MODBUS protocol simultaneously supports RTU mode and ASCII mode, with corresponding Frame
format as shown below:
MODBUS adopts “Big Endian” encoding mode, higher byte prior to lower byte at sending.
• The idle time of Frame head and Frame tail passing bus should be not less than 3.5 bytes.
• Slave address = 0, it means broadcast address.
• Data checking relies on CRC-16. The whole information need be checked. The concrete CRC
checking is referred to the page 150.
For example
: To read the slave internal register F00.08 = 50.00Hz of No. 1 address:
Command
Frame
Address Parameter Register Address Read char no. Checksum
0x01 0x03 0x00 0x08 0x00 0x01 0x05 0xC8
Response
Frame
Address Parameter Response Byte Content of register Checksum
0x01 0x03 0x02 0x13 0x88 0xB5 0x12
2. Scaling of Drive Transmitting Values
Except the parameters of the remarks, all other function codes can define the scaling relationship of
the specified function code via referring the manual’s minimum unit.
Remarks:
1. 0-2000 of F04.03, F21.01, F16.05, F16.08, F16.22, F16.24 correspond to -1000 - +1000.
2. Communication data 0 - 16000 of status parameter 0x3318 correspond to -8000 - +8000.
3. Output data 0 –2000 of status parameter (process PID setting, process PID feedback, process PID
tolerance, process PID integral and process PID output) correspond to-1000 - + 1000.
Modbus data frame
RTU model
Slave
address
Frame head (at least
3.5 character spacing)
Frame head (at least
3.5 character spacing)
Function
code
Data Checking
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