A Cyclic Redundancy Check is a powerful error-detection coding.

A CRC check is performed in the Ethernet and 802.11 WiFi frame.
For a CRC-n check, n+1 bits are used in the generator bit pattern G.

TLDR

  • Append n bits to the data D
  • Divide D with G (align the first ‘1’, then XOR)

  • Continue until the remainder is given

  • R == 0 - successful verification

  • R != 0 - data has been corrupted

http://www.sunshine2k.de/articles/coding/crc/understanding_crc.html

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Input data is the byte 0xC2 = b11000010.
As generator polynomial (=divisor), let's use b100011101.
The divisor has 9 bits (therefore this is a CRC-8 polynomial), so append 8 zero bits to the input pattern.
Align the leading '1' of the divisor with the first '1' of the dividend and perform a step-by-step school-like division, using XOR operation for each bit:

ABCDEFGHIJKLMNOP
1100001000000000
100011101
---------
010011001
 100011101
 ----------
 000101111
    100011101           (*)
    ---------
    001100101
      100011101
      ---------
      010001001
       100011101
       ---------
       000001111 = 0x0F
ABCDEFGHIJKLMNOP