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Chapter 7 Modbus Communication Protocol
7.4 Communication Instructions
Read slave parameter command code: 03H, reads N words (Word), and can read up to 20
consecutive words.
For example, if the AC drive with slave address 01H and memory start address 2100H ([C-00])
reads 3 consecutive words, the structure of the frame is described as follows:
RTU Master Command Information:
START
Slave address
Command code
Start address high bit
Start address low bit
Number of data high bit
Number of data low bit
CRC CHK low bit
CRC CHK high bit
END
RTU slave response information (when normal):
START
Slave address
Command code
Number of bytes low
Data address 2100H high bit
Data address 2100H low bit
Data address 2101H high bit
Data address 2101H low bit
Data address 2102H high bit
Data address 2102H low bit
CRC CHK low bit
CRC CHK high bit
END
RTU slave response information (when normal):
START
Slave address
Command code
Error code
CRC CHK low bit
CRC CHK high bit
END
Write slave parameter command code: 06H, writes a word data (Word) to the specified data
address, which can be used to modify the AC drive parameter value.
For example, write 5000 (1388H) to the 3000H address of the slave address 1 AC drive. Then
the structure of the frame is described as follows:
RTU master command information:
START
ACH200 Series High Voltage Variable Frequency Speed Control System Operating Manual
3.5 bytes transmission time
3.5 bytes transmission time
3.5 bytes transmission time
3.5 bytes transmission time
3.5 bytes transmission time
3.5 bytes transmission time
3.5 bytes transmission time
68
01H
03H
21H
00H
00H
03H
0FH
F7H
01H
03H
06H
13H
88H
00H
00H
00H
00H
90H
A6H
01H
83H
04H
40H
F3H
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