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Chapter 8 MODBUS Communications|ASDA-AB Series
Revision January 2009 8-13
RTU Mode:
Command message: Response message:
ADR 01H ADR 01H
CMD 06H CMD 06H
02H (Upper bytes) 02H (Upper bytes)
Starting data
address
00H (Lower bytes)
Starting data
address
00H (Lower bytes)
00H (Upper bytes) 00H (Upper bytes)
Content of data
64H (Lower bytes)
Content of data
64H (Lower bytes)
CRC Check Low 89H (Lower bytes) CRC Check Low 89H (Lower bytes)
CRC Check High 99H (Upper bytes) CRC Check High 99H (Upper bytes)
LRC (ASCII Mode):
LRC (Longitudinal Redundancy Check) is calculated by summing up, module 256, the values of the bytes
from ADR to last data character then calculating the hexadecimal representation of the 2’s-complement
negation of the sum.
For example, reading 1 word from address 0201H of the ASDA-AB series AC servo drive with address 01H.
STX ‘:’
‘0’
ADR
‘1’
‘0’
CMD
‘3’
‘0’
‘2’
‘0’
Starting data address
‘1’
‘0’
‘0’
‘0’
Number of data
‘1’
‘F’
LRC Check
‘8’
End 1 (0DH)(CR)
End 0 (0AH)(LF)
01H+03H+02H+01H+00H+01H = 08H, the 2’s complement negation of 08H is F8H.
Hence, we can know that LRC CHK is ’F’,’8’.