SR176 datasheet(8/35 Pages) STMICROELECTRONICS

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Data transfer

SR176

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Data transfer

3.1

Input data transfer from the Reader to the SR176 (request

frame)

The reader that accesses the SR176 must generate a 13.56 MHz sinusoidal carrier wave on

its antenna, with enough energy to “tele-power” the SR176 device. The energy received on

the SR176 antenna is transformed to a power supply voltage by a regulator, and to data bits

through the ASK demodulator. To decode correctly the information sent to the SR176, the

reader must use a 10% amplitude modulation of the 13.56 MHz wave, as represented

(though not to scale) in Figure 3. The data transfer rate is 106 Kbit/second.

Figure 3.

Received wave using ASK modulation

3.2

Character transmission format for request frame

Data Bytes are transmitted and received by the SR176 as 10-bit characters, as shown in

Figure 4, with the least significant bit (b0) transmitted first. These characters, with the

addition of the Start Of Frame (SOF) and the End Of Frame (EOF), are grouped to form a

Command Frame as shown in Figure 10. The frame includes an SOF, instructions,

addresses, data, a CRC and an EOF as defined by ISO 14443-3 Type B. If an error is

detected during the data transfer, no error frame is generated by the SR176, and the

instruction is not executed.

Each bit duration is referred to as an ETU (Elementary Time Unit). One ETU is equal to

9.44 µs (1/106 kHz).

3.3

Request start of frame

The SOF, as shown in Figure 5, consists of:

●

one falling edge

●

followed by 10 ETUs at logic 0

●

followed by one single rising edge

●

followed by at least 2 ETUs (but no more than 3 ETUs) at logic 1.

One bit time is 1/106kHz

AI09058

Data Bit Transmit

to the SR176

13.5MHz 10% ASK

Modulation Generated

by the Reader

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