NFC Digital Protocol - CWI

NFC-A TechnologyRequirements 23: Format of SDD_RES Response (Incomplete NFCID1 Only)Poll Mode4.7.2.8 The NFC Forum Device MUST beready to receive an SDD_RESResponse containing 40-n databits, where n is the number of databits following the SEL_PAR in theSDD_REQ Command previouslysent.The NFC Forum Device MUSTtreat an SDD_RES Responsecontaining a different number ofdata bits as Protocol Error.4.7.2.10 The NFC Forum Device MUSTverify the BCC included in theSDD_RES Response. Verificationdata MUST be the first 4 bytes ofthe NFCID1 CLn (i.e., theconcatenation of the data bitsfollowing the SEL_PAR in thepreceding SDD_REQ Commandand the SDD_RES Responseexcluding the BCC).The NFC Forum Device MUSTtreat an incorrect BCC as aTransmission Error.Listen Mode4.7.2.9 If the first n bits of the NFCForum Device's NFCID1 in therespective cascade level are equalto the n data bits following theSEL_PAR in the precedingSDD_REQ Command, then theNFC Forum Device MUST returnthe remaining 40-n bits of itsNFCID1 in the respective cascadelevel.Otherwise, the NFC ForumDevice MUST ignore theSDD_REQ Command.4.7.2.11 The NFC Forum Device MUSTcalculate a BCC as exclusive-orover the first 4 bytes of theNFCID1 CLn (from which a partis returned in the SDD_RESResponse).4.8 SEL_REQUse the SEL_REQ Command to select the NFC Forum Device in Listen Mode by means of itsNFCID1.4.8.1 SEL_REQ CommandTable 15 specifies the code for the SEL_REQ Command.Table 15: Format of SEL_REQ CommandByte 1 Byte 2 Bytes 3 - 6 Byte 7SEL_CMD 70h NFCID1 CLn BCCThe SEL_CMD byte is coded as is shown in Table 10.BCC is a checksum calculated as exclusive-or over the 4 bytes of the NFCID1 CLn.The format of NFCID1 CLn is specified in Table 16.NFC Digital Protocol Page 34