Hitachi EH-150 Series - Page 169

Appendix
A - 5
(2) CRC check
The error check field based on the CRC system is included in the message frame in RTU mode. The target of CRC
calculation is all messages (Device No., Function code, Data).
The CRC code is 16-bit data generated to the block of any data length of a 8-bit unit, which is calculated by
generation polynomial of CRC-16(X
16
+X
15
+X
2
+1).
CRC-16 calculation
Target data
exist ?
YES
NO
CRC* = HFFFF
CRC = CRC XOR Target data
8bit shift
complete?
CRC = Shift CRC to the right (1bit)
bit which
overflowed by shift
CRC = CRC XOR HA001
“0”
“1”
YES
NO
High byte and the Low byte
of CRC are swapped.
END
Target data is shifted by 1 byte.
Low
CRC register (2 byte)
High
* CRC :
Figure A.3 Calculation procedure of CRC-16
Ex ) The calculation method is explained using 2 bytes of data (0x0207) .
Procedure
CRC(Calculation middle)
Flag
Procedure
CRC(Calculation middle)
Flag
CRC
1111
1111
1111
1111
1000
0001
0011
1110
02
0000
0010
07
0000
0111
XOR
1111
1111
1111
1101
XOR
1000
0001
0011
1001
Shift right(1)
0111
1111
1111
1110
1
Shift right (1)
0100
0000
1001
1100
1
XOR 0xA001
1010
0000
0000
0001
XOR 0xA001
1010
0000
0000
0001
1101
1111
1111
1111
1110
0000
1001
1101
Shift right (2)
0110
1111
1111
1111
1
Shift right (2)
0111
0000
0100
1110
1
XOR 0xA001
1010
0000
0000
0001
XOR 0xA001
1010
0000
0000
0001
1100
1111
1111
1110
1101
0000
0100
1111
Shift right (3)
0110
0111
1111
1111
0
Shift right (3)
0110
1000
0010
0111
1
Shift right (4)
0011
0011
1111
1111
1
XOR 0xA001
1010
0000
0000
0001
XOR 0xA001
1010
0000
0000
0001
1100
1000
0010
0110
1001
0011
1111
1110
Shift right (4)
0110
0100
0001
0011
0
Shift right (5)
0100
1001
1111
1111
0
Shift right (5)
0011
0010
0000
1001
1
Shift right (6)
0010
0100
1111
1111
1
XOR 0xA001
1010
0000
0000
0001
XOR 0xA001
1010
0000
0000
0001
1001
0010
0000
1000
1000
0100
1111
1110
Shift right (6)
0100
1001
0000
0100
0
Shift right (7)
0100
0010
0111
1111
0
Shift right (7)
0010
0100
1000
0010
0
Shift right (8)
0010
0001
0011
1111
1
Shift right (8)
0001
0010
0100
0001
XOR 0xA001
1010
0000
0000
0001
1
2
4
1
1000
0001
0011
1110
CRC
4
1
1
2