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Fabricante

PEB3065

Signal Processing Subscriber Line Interface Codec Filter

Siemens AG 

PEB 3065

PEF 3065

SLICOFI® Principles

3

SLICOFI® Principles

Five Oversampling AD/DA converters are necessary for data conversion to gain the

aspired programmability in the DSP. Generally the SLICOFI can be divided between the

AC-Loop which is handling the voice and additionally teletax and the DC-Loop for line

feeding, ringing injection and supervision.

3.1

SLICOFI® Signal Flow Graph: AC

AGX TTXFI

ITAC

A

D

Transmit Path

XFIX2

X1 AX2 +

IMFIX3

AGR

V2W

+

IMFIX2

IMFIX1

IM2 IM1

RFIX2

D

A

+

+

D

A

TTGEN

AGTTX

THFIX

TH

AR2

Receive Path

DHPX

XFIX1

PCM

Output

FRX AX1 CMP

TG1 TG2

RFIX1

FRR AR1

PCM

Input

EXP

DHPR

User Programmable Block

Figure 2

Functional Block

Fixed Filter Block

ITS10183

Transmit Path

The analog input signal has to be connected to pin 21 (ITAC) by an external capacitor

(680 nF - 1 µF) for AC/DC separation. After passing a simple initializing prefilter (PREFI)

the voice signal is converted to a 1-bit digital data stream in the Σ∆-converter. The first

down sampling steps are done in fast running digital hardware filters. The following steps

are implemented in the micro code which has to be executed by the central Digital Signal

Processor. This DSP-machine is able to handle the workload for the DC-loop as well. At

the end the fully processed signal (flexibly programmed in many parameters) is

transferred to the IOM-2 Interface in a PCM-compressed signal representation.

Receive Path

The digital input signal is received via the IOM-2 Interface. Expansion,

PCM-lowpass-filtering, gain correction and frequency response correction are the next

Semiconductor Group

12

01.98

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