9

AT88RF020

2010B–RFID–03/02

If the write cannot take place (because Counter has a value of 0x8000, Page 2 is locked

or no password has been sent), then a NACK command will be issued by the PICC; oth-

erwise, an ACK command will be transmitted after the write has completed.

Data Transfer

Command Formats

The first byte of each command includes the CID as the least significant nibble followed

by the command opcode (COP) as the most significant nibble. COP is encoded accord-

ingtoTable 3.

All these commands consist of 12 bytes to be sent to the PICC by the PCD. CID is the

card ID byte as received by the PICC during the anticollision sequence. The address

field in the following chart is a 5-bit value, and the device ignores the most significant

three bits of the byte. Therefore, the device will interpret a value of 0xFF as 0x1F.

The command bytes are shown in Table 4.

Table 3. Command Summary

LSB

MSB

Command

Description

0010

READ

64-bit page from memory

1100

WRITE

64-bit page to memory

0100

LOCK

Data is ORed with existing LockBits value

0110

CHECK PASSWORD

0101

DESELECT

0111

COUNT

Table 4. Command Bytes

Commands

1st Byte

2nd Byte

3rd–10th Bytes

11th Byte

12th Byte

READ

CID | 0x4

Address

Ignored

CRC_0

CRC_1

WRITE

CID | 0x3

Address

64 bits data

CRC_0

CRC_1

LOCK

CID | 0x2

Ignored

32 bits ignored, 32 bits data

CRC_0

CRC_1

CHECK PASSWORD

CID | 0x6

Ignored

64 bits data

CRC_0

CRC_1

DESELECT

CID | 0xA

Ignored

Ignored

CRC_0

CRC_1

COUNT

CID | 0xE

Ignored

16 bits ignored, 48 bits data

CRC_0

CRC_1