crc32b

Cyclic Redundancy Check 32-bit Byte

crc32b RA, RS

Accumulates a CRC32 checksum using the low byte of RS.

Encoding

Binary Layout

31

0:5

RS

6:10

RA

11:15

0

16:20

522

21:30

/

31

 

Format X-form

Opcode 0x7C00020A

Extension Base

Operands

• RA
  Target/Accumulator
• RS
  Data

Example

crc32b r4, r3

Related

More in Base

Reference

View in PowerISA v3.1C Specification ↗ OPF Power ISA v3.1C

Description

Accumulates a 32-bit CRC checksum using the low byte (bits 56-63) of RS, with the running CRC value in RA. The updated CRC result is written to RA. This is a Base-category instruction with no CR, XER, or FPSCR updates.

Operation

byte_val ← RS[56:63]; crc ← RA ⊕ (byte_val || [0]*24); for i in 0 to 7 do; if (crc[31] = 1) then crc ← (crc << 1) ⊕ 0x04C11DB7; else crc ← crc << 1; crc ← crc ∧ 0xFFFFFFFF; RA ← crc;