5

AT88RF020

2010C–RFID–2/06

The PICC ignores all the PARAM bytes with the exception of the least significant four

bits of PARAM4, which are stored within the chip as the CID for future responses. Any

higher layer INF command is also ignored.

The PICC response to a valid ATTRIB command is always three bytes long. The first

byte contains the CID in the lower nibble and 0x0 in the upper nibble. The next two bytes

are the CRC.

HLTB Command

The HLTB command is used to set the PICC to the HALT state, after which only the

WUPB command will be acknowledged. The format of this 7-byte command is 0x50,

PUPI (4 bytes), CRC (2 bytes). The chip always responds to a valid HLTB command

with the 3-byte sequence: 0x00, CRC_0 and CRC_1. The HLTB command is not valid if

the PICC is in the ACTIVE state (see ISO 14443-3 sections 7.4.7 and 7.12 for additional

information).

SlotMARKER Command

The SlotMARKER command provides a way for the reader to query those cards for

which the generated random number R is greater than 1. It is a 3-byte command, the

last two of which are the CRC bytes. The least significant nibble of the first byte is the

slot number, and if this matches the generated random number, then the ATQB

response is generated. The chip will truncate the slot number field to match the value of

N provided in the REQB command. The most significant nibble of this command is fixed

at 0xA.