CRX14 datasheet(21/40 Pages) STMICROELECTRONICS

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CRX14

CRX14 ISO14443 TYPE-B RADIO FREQUENCY DATA TRANSFER

Output RF Data Transfer from the CRX14 to the

PICC (Request Frame)

The CRX14 output buffer is controlled by the

13.56MHz clock signal generated by the external

oscillator and by the request frame generator. The

CRX14 can be directly connected to an external

matching circuit to generate a 13.56MHz sinusoi-

dal carrier frequency on its antenna.

The current driven into the antenna coil is directly

generated by the CRX14 RFOUT output driver.

If the antenna is correctly tuned, it emits an H-field

of a large enough magnitude to power a contact-

less PICC from a short distance. The energy re-

ceived on the PICC antenna is converted to a

Power Supply Voltage by a regulator, and turned

into data bits by the ASK demodulator. The

CRX14 amplitude modulates the 13.56MHz wave

by 10% as represented in Figure 20. The data

transfer rate is 106 kbit/s.

Figure 20. Wave Transmitted using ASK Modulation

Transmission Format of Request Frame

Characters

The CRX14 transmits characters of 10 bits, with

the Least Significant Bit (b0) transmitted first, as

shown in Figure 21.

Several 10-bit characters, preceded by the Start

Of Frame (SOF) and followed by the End Of

Frame (EOF), constitute a Request Frame, as

shown in Figure 27.

A Request Frame includes the SOF, instructions,

addresses, data, CRC and the EOF as defined in

the ISO14443 type-B.

Each bit duration is called an Elementary Time

Unit (ETU). One ETU is equal to 9.44µs (1/

106kHz).

Figure 21. CRX14 Request Frame Character Format

DATA BIT TRANSMITTED

BY THE CRX14

10% ASK MODULATION

OF THE 13.56MHz WAVE,

GENERATED BY THE RFOUT

DRIVER

Transfer time for one data bit is 1/106 kHz

AI10912

10% ASK MODULATION

OF THE 13.56MHz WAVE,

GENERATED ON THE CRX14

ANTENNA

ETU

Start

'0'

LSB

MSB Stop

'1'

Information Byte

ai09250

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