LRIS2K-W4 datasheet(21/102 Pages) STMICROELECTRONICS

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LRIS2K

Data rate and data coding

21/102

Data rate and data coding

The data coding implemented in the LRIS2K uses pulse position modulation. Both data

coding modes that are described in the ISO15693 are supported by the LRIS2K. The

selection is made by the VCD and indicated to the LRIS2K within the start of frame (SOF).

5.1

Data coding mode: 1 out of 256

The value of one single byte is represented by the position of one pause. The position of the

pause on 1 of 256 successive time periods of 18.88 µs (256/fC), determines the value of the

byte. In this case the transmission of one byte takes 4.833 ms and the resulting data rate is

1.65 kbits/s (fC/8192).

Figure 5 illustrates this pulse position modulation technique. In this figure, data E1h (225

decimal) is sent by the VCD to the LRIS2K.

The pause occurs during the second half of the position of the time period that determines

the value, as shown in Figure 6.

A pause during the first period transmits the data value 00h. A pause during the last period

transmit the data value FFh (255 decimal).

Figure 5.

1 out of 256 coding mode

AI06656

0 1

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4.833 ms

18.88 µs

9.44 µs

Pulse

Modulated

Carrier

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