(ii) Appending the CRC to the end of the data unit must result in the bit sequence which is exactly divisible by the divisor. (i) It must have exactly one less bit than divisor. It is the CRC.Ī CRC will be valid if and only if it satisfies the following requirements: (i) We divide the data unit by a predetermined divisor. The redundancy bits used by CRC may be derived by following the procedure given below : Such an erroneous data unit is then rejected. But, a non-zero remainder indicates presence of errors in the received data unit. At the receiver, this data unit is divided by the same binary number There is no error if this division does not yield any remainder. The resulting data unit after adding CRC remainder becomes exactly divisible by another predetermined binary number. A sequence of redundant bits called CRC or CRC remainder is appended at the end of a data unit such as byte. This technique is more powerful than the parity check and checksum error detection. A codeword can be generated for a given dataword (message) polynomial M(x) with the help of long division. For CRC code, the sender and receiver must agree upon a generator polynomial G(x). Polynomial arithmetic uses a modulo-2 arithmetic i.e., addition and subtraction are identical to E-XOR. This is a type of polynomial code is which a bit string is represented in the form of polynomials with coefficients of 0 and 1 only. Cyclic Redundancy Check (CRC), crc calculation step by step, what is polynomial code circuit ?
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