M24LR04E-R datasheet(52/142 Pages) STMICROELECTRONICS

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Communication signal from M24LR04E-R to VCD

M24LR04E-R

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Doc ID 022208 Rev 5

Communication signal from M24LR04E-R to VCD

The M24LR04E-R has several modes defined for some parameters, owing to which it can

operate in various noise environments and meet various application requirements.

10.1

Load modulation

The M24LR04E-R 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 M24LR04E-R.

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

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

ISO10373-7.

10.2

Subcarrier

The M24LR04E-R 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 M24LR04E-R generates a

continuous phase relationship between fS1 and fS2.

10.3

Data rates

The M24LR04E-R 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. For fast

commands, the selected data rate is multiplied by two. Table 20 shows the different data

rates produced by the M24LR04E-R using the different response format combinations.

Table 20.

Response data rates

Data rate

One subcarrier

Two subcarriers

Low

Standard commands

6.62 Kbit/s (fc/2048)

6.67 Kbit/s (fc/2032)

Fast commands

13.24 Kbit/s (fc/1024)

not applicable

High

Standard commands

26.48 Kbit/s (fc/512)

26.69 Kbit/s (fc/508)

Fast commands

52.97 Kbit/s (fc/256)

not applicable

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