Delta ASD-A2-0121 Series User Manual page 609

ASDA-A2

LRC and CRC transmission Error Checking
The error checking in ASCII communication mode is LRC (Longitudinal Redundancy Check);
CRC (Cyclical Redundancy Check) is for RTU communication mode. The algorithm of both is as
the following.
LRC (ASCII mode):
Start
Slave address
Function
Starting data address
Number of data
LRC Check
End 1
End 0
The LRC algorithm is: add all bytes, round down the carry, and take 2's complement. For example,
7FH + 03H + 05H + C4H + 00H + 01H = 14CH, round down the carry 1 and take 4CH.
2's complement of 4CH is B4H.
9-14
':'
'7'
'F'
'0'
'3'
'0'
'5'
'C'
'4'
'0'
'0'
'0'
'1'
'B'
'4'
(0DH)(CR)
(0AH)(LF)
Chapter 9 Communications