Delta ASDA-A3 Series User Manual page 616

ASDA-A3
LRC and CRC transmission error check
The error check in ASCII mode is LRC (Longitudinal Redundancy Check) and in RTU mode,
it is CRC (Cyclical Redundancy Check). See the following details.
LRC (ASCII mode):
To calculate the LRC: add all the bytes, round down the carry, and take the two's complement.
For example: 7FH + 03H + 05H + C4H + 00H + 01H = 14CH, round down the carry 1 and take
4CH. The two's complement of 4CH is B4H.
Start
Slave Address
Function
Start Data Address
Data Number
LRC Check
End 1
End 0
MODBUS Communication
':'
'7'
'F'
'0'
'3'
'0'
'5'
'C'
'4'
'0'
'0'
'0'
'1'
'B'
'4'
(0DH) (CR)
(0AH) (LF)
9
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