循环冗余校验（CRC）

CRCisoneofthemostversatileerrorchecking

algorithmusedinvariousdigitalcommunication

systems.CRCstandsforCyclicRedundancyCode

CheckorsimplyCyclicRedundancyCheck.

Mostofthepopularcommunicationprotocols,like

CAN,USB,IrDA

Æ

,SDLC,HDLCandEthernet,employ

CRCforerrordetection.

Normally,fortheerrordetectionindigital

communicationsystems,achecksumiscomputedon

themessagethatneedstobetransmitted.Thecom-

putedchecksumisthenappendedattheendofthe

messagestreamandistransmitted.Atthereceiving

end,themessagestreamíschecksumiscomputedand

comparedwiththetransmittedchecksum.Ifbothare

equal,thenthemessagereceivedistreatedaserror

free.

CRCworksinasimilarway,butithasgreater

capabilitiesforerrordetectionthantheconventional

forms.DifferentCRCpolynomialsareemployedfor

errordetection.ThesizeofCRCdependsuponthe

polynomialchosen.

ThisapplicationnotedescribestheCRCoperationand

itsimplementationusingadedicatedhardwaremodule.AN1148CyclicRedundancyCheck(CRC)Author:SudhirBommenaConsideramessageof‘M’of‘k’bitsandgeneratorMicrochipTechnologyInc.polynomial‘G’of‘n+1’bits.Dividingthemessagebythegeneratorwillyieldaremainder‘R’of‘n’bits.There-fore,M=GQ+R;whereQisthequotientobtainedINTRODUCTIONwhenMisdividedbyG.CRCisoneofthemostversatileerrorchecking