4
MODBUS(R) STANDARD FUNCTIONS
4.2 Frame Specifications
4.2.1 Frame mode
4
- 12
1
O
VER
VIE
W
2
SYS
T
E
M
CO
NF
IG
U
R
A
T
IO
N
3
S
P
E
CIFICA
TI
ONS
4
MODB
US
(R)
S
TAN
DAR
D
FUN
C
TIO
N
S
5
FUNC
TI
ON
6
PR
E
-O
PER
A
T
ION
AL
P
R
OCED
URE
S A
ND
SE
TTINGS
7
P
A
RA
MET
E
R S
E
TTI
N
G
8
UTIL
ITY P
A
CK
AGE
(G
X Co
nf
ig
u
rat
o
r-M
B)
The following is a calculation example in the case where function code 07
H
is sent to
station No. 2.
Table4.5 CRC calculation procedures
CRC error check procedure
16-bit register (MSB)
Flag
(Load the register whose 16 bits are all "1")
02
H
(Station No.)
Exclusive OR (XOR)
1111
1111
1111
1111
1111
0000
1111
1111
0010
1101
Shift 1
Generator polynomial
Exclusive OR (XOR)
0111
1010
1101
1111
0000
1111
1111
0000
1111
1110
0001
1111
1
Shift2
Generator polynomial
Exclusive OR (XOR)
0110
1010
1100
1111
0000
1111
1111
0000
1111
1111
0001
1110
1
Shift3
Shift4
Generator polynomial
Exclusive OR (XOR)
0110
0011
1010
1001
0111
0011
0000
0011
1111
1111
0000
1111
1111
1111
0001
1110
0
1
Shift5
Shift6
Generator polynomial
Exclusive OR (XOR)
0100
0010
1010
1000
1001
0100
0000
0100
1111
1111
0000
1111
1111
1111
0001
1110
0
1
Shift7
Shift8
Generator polynomial
Exclusive OR (XOR)
0100
0010
1010
1000
0010
0001
0000
0001
0111
0011
0000
0011
1111
1111
0001
1110
0
1
07
H
(Function)
Exclusive OR (XOR)
1000
0001
0000
0011
0111
1001
Shift 1
Generator polynomial
Exclusive OR (XOR)
0100
1010
1110
0000
0000
0000
1001
0000
1001
1100
0001
1101
1
Shift2
Generator polynomial
Exclusive OR (XOR)
0111
1010
1101
0000
0000
0000
0100
0000
0100
1110
0001
1111
1
Shift3
Generator polynomial
Exclusive OR (XOR)
0110
1010
1100
1000
0000
1000
0010
0000
0010
0111
0001
0110
1
Shift4
Shift5
Generator polynomial
Exclusive OR (XOR)
0110
0011
1010
1001
0100
0010
0000
0010
0001
0000
0000
0000
0011
1001
0001
1000
0
1
Shift6
Shift7
Shift8
0100
0010
0001
1001
0100
0010
0000
1000
0100
0100
0010
0001
0
0
0
CRC value
12
H
41
H
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