SRI512 Data transfer
Doc ID 13263 Rev 5 9/47
3 Data transfer
3.1 Input data transfer from the reader to the SRI512 (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 SRI512’s
antenna is transformed into a supply voltage by a regulator, and into data bits by the ASK
demodulator. For the SRI512 to decode correctly the information it receives, the reader must
10% amplitude-modulate the 13.56 MHz wave before sending it to the SRI512. 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 SRI512 transmits and receives data bytes as 10-bit characters, with the least significant
bit (b
0
) 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 SRI512 does not execute the
command, but it does not generate an error frame.
Figure 4. SRI512 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
SRI512
Ai10796
ai07664
1 ETU
Start
"0"
Stop
"1"
MSbLSb Information Byte
b0 b1 b2 b3 b4 b5 b6 b7 b8 b9
