SRI4K datasheet(9/45 Pages) STMICROELECTRONICS

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SRI4K

Data transfer

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Data transfer

3.1

Input data transfer from the reader to the SRI4K (request

frame)

The reader must generate a 13.56 MHz sinusoidal carrier frequency at its antenna, with

enough energy to “remote-power” the memory. The energy received at the SRI4K’s antenna

is transformed into a supply voltage by a regulator, and into data bits by the ASK

demodulator. For the SRI4K to decode correctly the information it receives, the reader must

10% amplitude-modulate the 13.56 MHz wave before sending it to the SRI4K. This is

represented in Figure 3. The data transfer rate is 106 Kbits/s.

Figure 3.

10% ASK modulation of the received wave

3.1.1

Character transmission format for request frame

The SRI4K transmits and receives data bytes as 10-bit characters, with the least significant

bit (b0) transmitted first, as shown in Figure 4. Each bit duration, an ETU (elementary time

unit), is equal to 9.44 µs (1/106 kHz).

These characters, framed by a start of frame (SOF) and an end of frame (EOF), are put

together to form a command frame as shown in Figure 10. A frame includes an SOF,

commands, addresses, data, a CRC and an EOF as defined in the ISO 14443-3 Type B

Standard. If an error is detected during data transfer, the SRI4K does not execute the

command, but it does not generate an error frame.

Figure 4.

SRI4K request frame character format

DATA BIT TO TRANSMIT

TO THE

10% ASK MODULATION

OF THE 13.56MHz WAVE,

GENERATED BY THE READER

Transfer time for one data bit is 1/106 kHz

SRI4K

AI10880

ai07664

1 ETU

Start

"0"

Stop

"1"

MSb

LSb

Information Byte

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