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Chapter 8 MODBUS Communications|ASDA-B Series
8-10 Revision January 2009
STX (Communication Start)
ASCII Mode: ’:’ character
RTU Mode: A silent interval of more than 10ms
ADR (Communication Address)
The valid communication addresses are in the range of 1 to 254.
For example, communication to AC servo drive with address 16 decimal:
ASCII Mode: ADR=’1’,’0’ => ‘1’=31H，’0’=30H
RTU Mode: ADR = 10H
CMD (Command Codes) and DATA (Data Characters)
The format of data characters depends on the command code. The available command codes and examples
for AC servo drive are described as follows:
Command code: 03H, read N words. The maximum value of N is 10.
For example, reading continuous 2 words from starting address 0200H of AC servo drive with address 01H.
ASCII Mode:
Command message: Response message:
STX ‘:’ STX ‘:’
‘0’ ‘0’
ADR
‘1’
ADR
‘1’
‘0’ ‘0’
CMD
‘3’
CMD
‘3’
‘0’ ‘0’
‘2’
Number of data
(Count by byte)
‘4'
‘0’ ‘0’
Starting data
address
‘0’ ‘0’
‘0’ ‘B’
‘0’
Contents of starting
data address
0200H
‘1’
‘0’ ‘1’
Number of data
‘2’ ‘F’
‘F’ ‘4’
LRC Check
‘8’
Contents of second
data address
0201H
‘0’
End 1 (0DH)(CR) ‘E’
End 0 (0AH)(LF)
LRC Check
‘8’
End 1 (0DH)(CR)
End 0 (0AH)(LF)