LRI2K datasheet(19/89 Pages) STMICROELECTRONICS

19 / 89 page

LRI2K

Communications signal from LRI2K to VCD

19/89

Communications signal from LRI2K to VCD

The LRI2K has several modes defined for some parameters, owing to which it can operate

in different noise environments and meet different application requirements.

4.1

Load modulation

The LRI2K is capable of communication with 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 LRI2K.

The load-modulated amplitude received on the VCD antenna shall be at least 10 mV when

measured as described in the test methods defined in International Standard ISO 10373-7.

4.2

Subcarrier

The LRI2K 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, frequency fS1 is 423.75 kHz (fC/32), and frequency fS2 is

484.28 kHz (fC/28). When using the two-subcarrier mode, the LRI2K generates a

continuous phase relationship between fS1 and fS2.

4.3

Data rates

The LRI2K 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 4 shows the different data rates produced

by the LRI2K using the different response format combinations.

Table 4.

Response data rate

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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