Omron V530-R2000 User Manual page 145

SECTION 9
Appendix
n FCS Calculation
FCS (Frame Check Sequence) is the result of taking the XOR for each byte between
the prefix and suffix (8 bits) and converting to 2-character ASCII.
The FCS can be attached to output data to improve communications.
Each time data is received, the Host Link system calculates the FCS and checks it
against the FCS attached to the sent data so that the sent data can be checked for
errors.
An FCS can be appended only if the communications mode is set to Normal.
n Example FCS Calculation
Example read data: ABCDEFG
The details of the read data and calculation method are as follows:
Read data
Prefix
· Calculation
Read data
A
B
C
D
E
F
G
V530-R2000
128
User's Manual
p.40
A B C D E F G 4 0
Read data
ASCII
Conversion to
ASCII:
Suffix
FCS
41
Conversion to
42
hexadecimal:
43
44
45
46
47
FCS data: 4 0
Hexadecimal
0100 0001
XOR
0100 0010
XOR
0100 0011
XOR
0100 0100
XOR
0100 0101
XOR
0100 0110
XOR
0100 0111
Obtaining the exclu-
sive logical OR:
0100 0000
On conversion
to ASCII: