am79d2251 Advanced Micro Devices, am79d2251 Datasheet - Page 9

• Manufacturer Part Number: am79d2251
• Description: Dual Intelligent Subscriber Line Audio-processing Circuit Islac
• Manufacturer: Advanced Micro Devices

GENERAL DESCRIPTION
The Intelligent Access voice chipsets integrate all functions of the subscriber line for two subscriber
lines. One or more of two chip types are used to implement the linecard; an ISLIC device and a dual
ISLAC device. These provide the following basic functions:
1. The ISLIC device: A high voltage, bipolar IC that drives the subscriber line, maintains
2. The dual ISLAC device: A low voltage CMOS IC that provides conversion and DSP functions
Complete schematics of linecards using the Intelligent Access voice chipsets for internal and external
ringing are shown in Figure 4 and Figure 5.
The ISLIC device uses reliable, bipolar technology to provide the power necessary to drive a wide
variety of subscriber lines. It can be programmed by the ISLAC device to operate in eight different
modes that control power consumption and signaling modes. This enables it to have full control over
the subscriber loop. The ISLIC device is customized to be used exclusively with the ISLAC device
as part of a multiple-line chipset. The ISLIC device requires only +5 V power and the battery supplies
for its operation.
The ISLIC device implements a linear loop-current feeding method with the enhancement of
intelligent thermal management in a controlled manner. This limits the amount of power dissipated
on the ISLIC chip by dissipating excess power in external resistors.
Each ISLAC device contains high-performance codec circuits that provide A/D and D/A conversion
for voice (codec), DC-feed and supervision signals for two subscriber channels. The ISLAC device
contains a DSP core that handles signaling, DC-feed, supervision and line diagnostics for both
channels.
The DSP core selectively interfaces with three types of backplanes:
The Intelligent Access voice chipset provides a complete software configurable solution to the
BORSCHT functions as well as complete programmable control over subscriber line DC-feed
characteristics, such as current limit and feed resistance. In addition, these chipsets provide system
level solutions for the loop supervisory functions and metering. In total, they provide a programmable
solution that can satisfy worldwide linecard requirements by software configuration.
Software programmed filter coefficients, DC-feed data and supervision data are easily calculated
with the WinSLAC software. This PC software is provided free of charge. It allows the designer to
enter a description of system requirements. WinSLAC then computes the necessary coefficients
and plots the predicted system results.
The ISLIC interface unit inside the ISLAC device processes information regarding the line voltages,
loop currents and battery voltage levels. These inputs allow the ISLAC device to place several key
ISLIC performance parameters under software control.
Standard PCM/MPI
Standard GCI
Modified GCI with a single analog line per GCI channel
longitudinal balance and senses line conditions.
for 2 channels.
Am79D2251
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