In order to ensure the correctness of the transmission process, it is necessary to perform errors control over the communication process. The most common method of error control is to automatically request the retransmission mode (ARQ), forward error correction mode (FEC) and mixed error correction (HEC). When the transmission process is relatively low, it is ideal with FEC mode. When the transmission process is high, it is easy to "chaos" phenomenon using FEC. HEC mode The combination of ARQ and FEC. In many digital communication, ARQ mode is widely used, and the error control at this time only needs to detect the error. There are many error-controlled methods that implement the error detection function. Traditional: parity, checksum detection, repetition check, expansion code check, row redundancy check, etc., these methods are redundant The balance is sent to the receiving end together. The received data is the same verification, and then the resulting check code is compared to the received check code, if the two consistent, it is considered to be correct. But these methods have their own disadvantages, and the probability of misjudgment is relatively high. When using a CRC check, the sender and the receiver use the same generated polynomial G (X), and the first bit of G (x) must be 1. The method of processing the CRC is that the sender removes T (X) by g (x) to obtain the remainder as a CRC check code. When the calibration is calculated as 0, it is determined whether the data frame is wrong. The CRC check can be detected by 100% of all odd random errors and lengths of less than or equal to K (k as g (x) steps). Therefore, the higher the class of the CRC generated polynomial, the smaller the probability of misjudgment.
Due to the reliability of CRC-32, the CRC-32 is used for important data transmission, so it is widely used in communication, computers. In some UART communication control chips (such as MC6582, Intel8273, and Z80-Si), CRC check code is used for error control; Ethernet card chips, MPEG decoding chips, also using CRC-32 in error control.
As can be seen from the CRC encoding rule, the CRC encoding is actually converted to the M-bit binary polynomial T (X) transmitted into a M R bit binary polynomial that can be removed by G (X), so it can be used when decoding The received data removal G (X), if the remaining number is zero, then the transmission process is not error; if the remainder is not zero, there is definitely an error during the transmission process. Many CRC hardware decoding circuits are detected in this way. It can also be seen as a combination of T (X) and CRC check code, so decoding the received binary data removes the R bit data of the tail, which is the original data.
