LRIS2K datasheet(26/102 Pages) STMICROELECTRONICS

26 / 102 page

Communications signal from LRIS2K to VCD

LRIS2K

26/102

Communications signal from LRIS2K to VCD

The LRIS2K has several modes defined for some parameters, owing to which it can operate

in different noise environments and meet different application requirements.

6.1

Load modulation

The LRIS2K is capable of communication to the VCD via an inductive coupling area

whereby the carrier is loaded to generate a subcarrier with frequency fS. The subcarrier is

generated by switching a load in the LRIS2K.

The load-modulated amplitude received on the VCD antenna must be of at least 10mV

when measured as described in the test methods defined in International Standard

ISO10373-7.

6.2

Subcarrier

The LRIS2K supports the one-subcarrier and two-subcarrier response formats. These

formats are selected by the VCD using the first bit in the protocol header. When one

subcarrier is used, the frequency fS1 of the subcarrier load modulation is 423.75 kHz (fC/32).

When two subcarriers are used, the frequency fS1 is 423.75 kHz (fC/32), and frequency fS2

is 484.28 kHz (fC/28). When using the two-subcarrier mode, the LRIS2K generates a

continuous phase relationship between fS1 and fS2.

6.3

Data rates

The LRIS2K can respond using the low or the high data rate format. The selection of the

data rate is made by the VCD using the second bit in the protocol header. It also supports

the x2 mode available on all the Fast commands. Table 11 shows the different data rates

produced by the LRIS2K using the different response format combinations.

Table 11.

Response data rates

Data rate

One subcarrier

Two subcarriers

Low

Standard commands

6.62 Kbits/s (fc/2048)

6.67 Kbits/s (fc/2032)

Fast commands

13.24 Kbits/s (fc/1024)

not applicable

High

Standard commands

26.48 Kbits/s (fc/512)

26.69 Kbits/s (fc/508)

Fast commands

52.97 Kbits/s (fc/256)

not applicable

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