SRT512 datasheet(12/46 Pages) STMICROELECTRONICS

12 / 46 page

Data transfer

SRT512

12/46

Doc ID 13277 Rev 4

3.2.3

Answer end of frame

The EOF shown in Figure 9 is composed of:

●

followed by 10 ETUs at logic-0,

●

followed by 2 ETUs at logic-1.

Figure 9.

Answer end of frame

3.3

Transmission 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 SRT512 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 SRT512 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 SRT512.

Figure 10.

Example of a complete transmission frame

ai07665

ETU

b10

b11

0000000000

12 bits

10 bits

Sync

128/fs

fs=847.5kHz

SOF

Cmd

Data

CRC

EOF

10 bits

12 bits

10 bits

Data CRC CRC

SOF

EOF

12 bits

SOF

Ai13506b

Input data transfer using ASK

Output data transfer using BPSK

Sent by the

Reader

Sent by

SRT512

at 106kb/s

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