Fuji Electric FRENIC-VG Series - CRC-16 Algorithm

5.3 Modbus RTU
5-41
Chap. 5 USING STANDARD RS-485
5.3.3.2 CRC-16 algorithm
The following diagram shows the CRC-16 calculation algorithm. Please also refer to the calculation
example in Section 5.3.3.3.
CRC DATA is 1 word of memory. It is updated in the calculation process and finally added to the
sent frame as a check code.
When the message is received, the same algorithm is used. The CRC calculated at the receiving side
must then be cross-checked with the CRC that was sent.
初期設定
余り R ← "FFFF"
生成多項式 P ← "A001"
ﾃﾞｰﾀ長ｶｳﾝﾀ n ← 0
ﾃﾞｰﾀ長計算 N←ﾃﾞｰﾀ長
n == N？
n++
A = n番目の送信ﾊﾞｲﾄを
ﾜｰﾄﾞﾃﾞｰﾀの下位ﾊﾞｲﾄに設定
上位ﾊﾞｲﾄは"00"
CRC DATA ← CRC DATA XOR A
Shift Count == 8？
Shift Count++
No
Yes
Bitｼﾌﾄ ｷｬﾘｰ有り？
No
CRC DATA ← CRC DATA XOR P
Shift Count == 0？
Yes
No
Shift Count ← 0
Yes
CRC DATAを
送信ﾌﾚｰﾑ最終段に付加
END
START
Yes
n == 1？
CRC DATA ← A XOR R
No
Yes
No
CRC DATA >> 1bitｼﾌﾄ
Default
Remainder R  “FFFF”
Generating polynomial P  “A001”
Data length counter n  0
Data length calc. N  Data length
Specify last byte of word data as:
A = n
th
sent byte
Top byte is “00”
CRC DATA >> 1 bit shift
Bit shift Carr
y
?
A
dd CRC DAT
A
to last level of
sent frame