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RTU mode:
A silent interval of more than 10 ms
START
Communication address:8-bit address
ADR
Command code:8-bit command
CMD
DATA(n-1)
Contents of data: n 8-bit data,n =25
......
DATA 0
CRC CHK Low
CRC check sum:
16-bit check sum consists of 2 8-bit characters
CRC CHK High
A silent interval of more than 10 ms
END
ADR (Communication Address)
Valid communication addresses are in the range of 0 to 254. An address
equals to 0 means a broadcast to all AC drives (AMD) in the network. In
this case, the AMD will not reply to the master device.
For example, communication to AMD with address 16 decimal:
ASCII mode: (ADR 1, ADR 0)='1'
'0' =>'1'=31H, '0'=30H
RTU mode: (ADR)=10H
Function (Function code) and DATA (data characters)
The format of data characters depends on the function code. The available
function codes are described as follows:
03H: read data from register
06H: write single data to register
10H: write multiple data to registers
Command code: 03H, read N words. The maximum value of N is 12.
For exam ple, rea ding continuous 2 words from starting address 2102H of
AMD with address 01H.
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Appendix
ASCII mode:
Command message:
Starting data address
RTU mode:
Command message:
Starting data address
STX
':'
'0'
ADR 1
ADR 0
'1'
'0'
CMD 1
CMD 0
'3'
'2'
'1'
'0'
'2'
'0'
Number of data
'0'
(count by word)
'0'
'2'
'D'
LRC CHK 1
LRC CHK 0
'7'
'CR'
END 1
END 0
'LF'
ADR
01H
CMD
03H
21H
02H
Number of data
00H
(count by word)
02H
CRC CHK Low
6FH
CRC CHK High
F7H
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Appendix
Response message:
STX
':'
'0'
ADR 1
ADR 0
'1'
'0'
CMD 1
CMD 0
'3'
Number of data
'0'
(count by byte)
'4'
'1'
Content of starting
'7'
data address
'7'
2102H
'0'
'0'
Content of
'0'
data address
'0'
2103H
'0'
'7'
LRC CHK 1
LRC CHK 0
'1'
CR
END 1
END 0
LF
Response message:
ADR
01H
CMD
03H
Number of data
04H
(count by byte)
17H
Content of data address
2102H
70H
00H
Content of data address
2103H
00H
FEH
CRC CHK Low
CRC CHK High
5CH
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