ST25TB02K datasheet(8/47 Pages) STMICROELECTRONICS

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3.2.3

Answer end of frame

The EOF shown in Figure 9 is composed of:

•

one falling edge,

•

followed by 10 ETUs at logic-0,

•

followed by 2 ETUs at logic-1.

Figure 9. Answer end of frame

ETU

b10

b11

3.3

Trasmission frame

Between the request data transfer and the answer data transfer, all ASK and BPSK modulations are suspended

for a minimum time of t0 = 128/ƒS. This delay allows the reader to switch from Transmission to Reception mode.

It is repeated after each frame. After t0, the 13.56 MHz carrier frequency is modulated by the ST25TB02K at

847 kHz for a period of t1 = 128/ƒS to allow the reader to synchronize. After t1, the first phase transition generated

by the ST25TB02K forms the start bit (‘0’) of the answer SOF. After the falling edge of the answer EOF, the reader

waits a minimum time, t2, before sending a new request frame to the ST25TB02K.

Figure 10. Example of a complete transmission frame

Sent by the

Reader

Sent by the

ST25TBxxx

12 bits

Sync

fS = 847.5 kHz

SOF

Cmd

Data

CRC

EOF

Data CRC

CRC

SOF

EOF

SOF

Input data transfer using ASK

Output data transfer using BPSK

at 106 kb/s

10 bits

12 bits 10 bits 10 bits 10 bits 12 bits

ST25TB02K

Trasmission frame

DS11469 - Rev 7

page 8/47

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