Delta ASD-A3-0121, User Manual

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ASDA-A3 MODBUS Communication
Revision December, 2017
9-11
9
LRC and CRC transmission error check
The error check in ASCII mode is LRC (Longitudinal Redundancy Check). In RTU mode, it is
CRC (Cyclical Redundancy Check). See the details below.
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
‘7’
‘F’
Function
‘0’
‘3’
Start Data Address
‘0’
‘5’
‘C’
‘4’
Data Number
‘0’
‘0’
‘0’
‘1’
LRC Check
‘B’
‘4’
End 1 (0DH) (CR)
End 0 (0AH) (LF)