ST20CX 查看數據表（PDF） - STMicroelectronics

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ST20CX

Instruction Set Reference Manual

STMicroelectronics 

crcbyte

crcbyte

calculate CRC on byte

Code: 27 F5

Description: Generate a CRC (cyclic redundancy check) checksum from the most

significant b yte of Areg. Breg contains the previously accumulated checksum and

Creg the polynomial divisor (or ‘generator’). The new CRC checksum, the polynomial

remainder, is calculated by repeatedly (8 times) shifting the accumulated checksum

left, shifting in successive bits from the Areg and if the bit shifted out of the checksum

was a 1, then the generator is exclusive-ored into the checksum.

Definition:

Areg′ ← temp(8)

Breg′ ← Creg

Creg′ ← undefined

where

temp(0) = Breg

for i = 1 .. 8

temp(i) = (temp(i -1) << 1) + AregBitsPerWord-i)

⊗ (Creg × temp(i −1)BitsPerWord-1)

Error signals: none

Comments:

Secondary instruction.

See also: crcword

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