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Chapter 7 Modbus Communication Protocol
Slave address
Command code
Write data address high bit
Write data address low bit
Data content high bit
Data content low bit
CRC CHK low bit
CRC CHK high bit
END
RTU slave response information (when normal):
START
Slave address
Command code
Write data address high bit
Write data address low bit
Data content high bit
Data content low bit
CRC CHK low bit
CRC CHK high bit
END
RTU slave response information (when abnormal):
START
Slave address
Command code
Error code
CRC CHK low bit
CRC CHK high bit
END
Loop self-test command code: 06H, sending back the same slave response information as the
master command information, used to detect whether the signal transmission between the master
and the slave is normal, the detection code and data can be set arbitrarily, the detection code has
nothing to do with the parameter address of the AC drive.
For example, 5000 (1388H) is written to the 0000H detection code of the slave address 1 AC
drive. Then the structure of the frame is described as follows:
RTU master command information:
START
Slave address
Command code
Detection code high bit
Detection code low bit
Data high bit
Data low bit
CRC CHK low bit
CRC CHK high bit
END
RTU slave response information (when normal):
START
Slave address
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
3.5 bytes transmission time
69
01H
06H
30H
00H
13H
88H
8BH
9CH
01H
06H
30H
00H
13H
88H
8BH
9CH
01H
86H
01H
83H
A0H
01H
08H
00H
00H
13H
88H
EDH
5DH
01H
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