ST75C520 datasheet(35/45 Pages) STMICROELECTRONICS

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VIII.2.2 - Power Estimation

The Power estimation Cell is needed to measure

the amplitude of the different tones. It is run on a

sample basis.

Z -1

OUT

ABS(.)

Z -1

Figure 3 : Power Estimator

The corresponding transfer function is :

Out

| Input| ⋅ z±1 ⋅

±(1 ± P1) ⋅ z±1

VIII.2.3 - Static Level

A single Threshold level is associated with each

Cell. It can be use to compare the outputof a Power

Estimation with an Absolute Value.

VIII.2.4 - Comparator

The Comparator computes, on a baud basis, the

difference of the signal on its Positive and Negative

Inputs. If the result is Higher that zero it sets the

corresponding bit into the TONEDET[0..1] word; if

not it clear this bit.

VIII.2.5 - Wiring

The user must specify the connection (wiring) be-

tween the input/outputof the Filter, the input/output

of the Power estimator, the output of the static

levels and the two inputs of the Comparators.

The output signals have an absolute address:

Node Address

Signal

Name

Address

Description

Ground

Signal always equal to 0000

RxSig

Receive signal from the

Analog front end

RxSig2

Receive signal multiplied by 2

RxSig4

Receive signal multiplied by 4

04..0F

Reserved

Filter[0..F]

10..1F

Biquadratic Filter Outputs

Power[0..F]

20..2F

Power Estimator Outputs

Level[0..F]

30..3F

Static Levels

The user will specify the inputs of the filters, Power

and Comparator. At leastone input must come from

the RxSig (node 01, 02 or 03). It is mandatory to

connect all unused cell inputs to the Ground signal

(node 00).

ST75C520

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