3

AT88RF020

2010C–RFID–2/06

Signature: This field is written unmodified into the first six bytes of Page 2 via the

COUNT instruction. It is expected that this value will be related to the count and may be

encrypted by the reader/writer. In this manner, the Counter and Signature fields together

can provide an additional level of security from tampering.

Pages 0, 1 and 2 can always be read by the system; Page 3 may never be read by the

system; and all remaining pages can be read only after the proper password has been

sent to the chip. The LockBits field within Page 0 can be modified only through the use

of the LOCK command and only after the proper password has been sent to the chip.

The contents of Page 2 can only be modified using the COUNT command—again, only

after the proper password has been sent to the chip.

All other pages (1 and 3 through 31) can be written to only after the proper password

has been validated by the chip. The first four bytes of Page 0 comprise the serial num-

ber (PUPI) and, although the adjacent LockBits field is updateable, the serial number

can never be changed during any kind of operation.

Communications

The electrical signaling of the chip is fully compatible with ISO 14443-2, “Radio Fre-

quency Power and Signal Interface,” version 1999(e) for Type B only. Anticollision

operation and frame formatting is compatible with ISO 14443-3 Type B, “Initialization

and Anticollision,” version 2000(e), Type B only.

Command/Data

Transmission Frame

All data sent between the PICC and PCD is sent as characters (see ISO 14443-3, sec-

tion 7.1.1). The character is composed of a start bit (logic “0”), 8 bits of data and a stop

bit (logic “1”).

Between characters is an extra guard time (EGT) that must not exceed 6 ETUs (~57

microseconds (µs)) for data sent to the PICC and will be two ETUs for data sent to the

PCD (see ISO 14443-3, section 7.1.2).

The PICC will automatically resynchronize character reception (internal clocks) with the

start bit of each incoming character.

Groups of characters exchanged between the PCD and PICC comprise a frame, which

is delimited by a Start of Frame (SOF) and an End of Frame (EOF) signal protocol (see

ISO 14443-3, sections 7.1.3–7.1.5).

After the READ command has been received by the PICC, the PICC will respond with

the data frame following a delay of 8 ETUs (~75.5 µs) and transmit a sub carrier for a

period of 10 ETUs (~94.4 µs) with no phase changes (see ISO 14443-3, section 7.1.6,

and ISO 14443-2, section 9.2.5.).

Note:

This device ignores attempts to reduce the minimum TR0 and TR1 values from the ISO

14443-2 defaults as may be specified by the PCD in the ATTRIB command (see ISO

14443-3, sections 7.10.3.1 and 7.10.3.2.).

CRC

A 2-byte CRC code is included in all frame transmissions. The CRC polynomials are

defined as:

This is a hex polynomial of 1021. The CRC register is initialized to 0xFFFF. When

receiving information from the system, the device computes the CRC on the incoming

command, data and CRC bytes (start/stop bits, SOT, EOT and EGT are ignored). When

the last bit of the CRC has been received, the value in the CRC register should be

0x0000. When the device transmits data, the CRC is computed based on all outgoing

data bits.