10

AT88RF020

2010C–RFID–2/06

A valid READ command response is a 12-byte frame sent from the PICC to the PCD

and is formatted as shown in Table 5.

Both the ACK and NACK responses consist of a 4-byte frame sent from the PICC to the

PCD and are formatted as shown in Table 6.

There are two parts to the second byte of the ACK and NACK response commands (see

Table 6): the most significant nibble and the least significant nibble.

For each command, the most significant nibble is not guaranteed, and therefore the

reader/writer should mask this field when assessing whether an ACK or a NACK has

been issued by the PICC. As indicated in Table 6, the least significant nibble of the sec-

ond byte will always be a “0” for an ACK and a “1” for a NACK.

For an ACK, the most significant nibble of the second byte will be undefined. For a

NACK, the most significant nibble of the second byte contains an error feedback code.

This error code represents the error that caused the NACK response command.

Electrical

This device includes a voltage reference to ensure that the chip operates only when the

power supply voltage on the chip is above a required level of 1.8 – 2.0 volts. Memory

writes are guaranteed above this voltage level. The on-chip regulator will ensure that the

VDD voltage will be within the range of 2.1 – 2.5 volts.

The chip is specified to operate over the temperature range of 0

°C to 70°C (junction

temperature). The coil pads (ac1 and ac2) offer ESD protection at levels greater than 2

kV.

The input capacitance of the coil pins will be 82 pf and may vary by ±10% over process,

temperature, voltage and frequency. Internal power supply bypass capacitance is inte-

grated on the chip.

Table 5. PICC Frame Format

Commands

1st Byte

2nd Byte

3rd–10th Bytes

11th Byte

12th Byte

READ

CID | 0x4

Address

64 bits data

CRC_0

CRC_1

Table 6. ACK and NACK

Description

1st Byte

2nd Byte

3rd Byte

4th Byte

ACK

CID | COP

0xX0

CRC_0

CRC_1

NACK

CID | COP

0xX1

CRC_0

CRC_1

Table 7. Error Codes

ACK/NACK 2nd Byte

Command Decode

XXXX

0000

ACK, no errors detected

00010001

NACK, attempted write to locked page

X

X

100001

NACK, terminal count reached or attempted

operation to invalid address

01000001

NACK, invalid password attempted

10000001

NACK, low-voltage condition detected