SRT512 datasheet(11/46 Pages) STMICROELECTRONICS

номер детали	SRT512

подробное описание детали	13.56 MHz short-range contactless memory chip with 512-bit EEPROM and anticollision functions

PDF	46 Pages

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производитель	STMICROELECTRONICS [STMicroelectronics]

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SRT512

Data transfer

Doc ID 13277 Rev 4

11/46

3.2

Output data transfer from SRT512 to reader (answer frame)

The data bits issued by the SRT512 use back-scattering. Back-scattering is obtained by

modifying the SRT512 current consumption at the antenna (load modulation). The load

modulation causes a variation at the reader antenna by inductive coupling. With appropriate

detector circuitry, the reader is able to pick up information from the SRT512. To improve

load-modulation detection, data is transmitted using a BPSK encoded, 847 kHz subcarrier

frequency ƒs as shown in Figure 7, and as specified in the ISO 14443-2 Type B standard.

Figure 7.

Wave transmitted using BPSK subcarrier modulation

3.2.1

Character transmission format for answer frame

The character format is the same as for input data transfer (Figure 4). The transmitted

frames are made up of an SOF, data, a CRC and an EOF (Figure 10). As with an input data

transfer, if an error occurs, the reader does not issue an error code to the SRT512, but it

should be able to detect it and manage the situation. The data transfer rate is

106 Kbits/second.

3.2.2

Answer start of frame

The SOF described in Figure 8 is composed of:

●

followed by 10 ETUs at logic-0

●

followed by 2 ETUs at logic-1

Figure 8.

Answer start of frame

AI13504b

Data Bit to be Transmitted

to the Reader

847-kHz BPSK Modulation

Generated by the SRT512

BPSK Modulation at 847 kHz

During a One-bit Data Transfer Time (1/106 kHz)

ai07665

ETU

b10

b11

0000000000

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