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PSB4595

Analog Line Interface Solution ALIS

Siemens AG 

PSB 4595 / PSB 4596

Analog Line Interface Solution

ALIS Implementation

4

ALIS Implementation

The ALIS chip set replaces all the major parts of a conventional front end for modem

solutions. The circuit consists of two major parts, a DSP-based codec and an electronic

DAA. Advanced features such as ring detection, pulse dialing and caller ID are

integrated on-chip. Additional operating modes such as sleep mode or ringing mode are

implemented to minimize power consumption.

4.1 ALIS Block Diagram

The tip/ring telephone line interface is connected mainly with the ALIS-A. It is also

connected with the ALIS-D for Caller ID functions..

Control Data

Isolation

Control Interface

DSP

HW -

Filter

Cap. Interface

Data Interface

ALIS-D

Caller ID

I/O

Vdd

Control

A/D

Hybrid

and

Filters

D/A

ALIS-A

Control

TIP/RING

Transmit/Receive Data

Figure 9 ALIS Block Diagram

The analog front end (ALIS-A) is connected to the line via TIP/RING. The programmable

supply voltage for ALIS-A is generated from the line by the Vdd control. Two/four wire

conversion is implemented in the hybrid circuit. Analog anti-aliasing pre-filters (PREFI)

and smoothing post-filters (POFI) are included for signal conditioning. High-performance

over-sampling analog-to-digital converters (ADCs) and digital-to-analog converters

(DACs) assure the required conversion accuracy. The ADCs and DACs are connected

to the digital signal processor (DSP) on the digital part (ALIS-D) via a dedicated capacitor

interface which also provides the required isolation to the line. Special hardware filters

perform filtering functions such as interpolation and decimation. The DSP handles all the

necessary algorithms. These include bandpass filtering, sample rate conversion, ringing

detection, and caller ID decoding. All programmable filters and functions are also

controlled and processed by the DSP. The control interface allows external control of the

ALIS features and provides transparent access to ALIS commands and signaling pins.

Thus pre-calculated sets of coefficients can be downloaded from the system to the on-

Semiconductor Group

20

Data Sheet 06.98

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