srt512 STMicroelectronics, srt512 Datasheet - Page 11

• Manufacturer Part Number: srt512
• Description: 13.56 Mhz Short-range Contactless Memory Chip With 512-bit Eeprom And Anticollision Functions
• Manufacturer: STMicroelectronics

SRT512
3.2
3.2.1
3.2.2
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 ƒ
Figure 7.
Character transmission format for Answer Frame
The character format is the same as for input data transfer
frames are made up of an SOF, data, a CRC and an EOF
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.
Answer Start Of Frame
The SOF described in
Figure 8.
followed by 10 ETUs at logic-0
followed by 2 ETUs at logic-1
847-kHz BPSK Modulation
Generated by the SRT512
Data Bit to be Transmitted
ETU
s
Wave transmitted using BPSK subcarrier modulation
Answer Start Of Frame
as shown in
to the Reader
0
b0
b1
0
Figure 8
Or
Figure
0
b2
is composed of:
7, and as specified in the ISO14443-2 Type B Standard.
During a One-bit Data Transfer Time (1/106 kHz)
0
b3
0
b4
BPSK Modulation at 847 kHz
0
b5
0
b6
(Figure
(Figure
0
b7
b8
0
10). As with an input data
4). The transmitted
0
b9
Data transfer
1
b10
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AI13504b
b11
1
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