AM79213 Legerity, AM79213 Datasheet - Page 13

• Manufacturer Part Number: AM79213
• Description: (AM79C203/031 / AM79213) PCM CODEC
• Manufacturer: Legerity

ASLIC/ASLAC DEVICES FUNCTIONAL
DESCRIPTION
The ASLIC/ASLAC devices chip set integrates all func-
tions of the subscriber line. The chip set comprises an
ASLIC device and an ASLAC device. The set provides
two basic functions: 1) the ASLIC device, a high-voltage,
bipolar device that drives the subscriber line, maintains
longitudinal balance, and senses line conditions; and 2)
the ASLAC device, a low-voltage CMOS device that
combines CODEC, DC Feed control, and line supervi-
sion. A complete schematic of a linecard using the
ASLIC/ASLAC devices chip set is shown in the Figure 7.
The ASLIC device uses reliable, bipolar technology to
provide the power necessary to drive a wide variety of
subscriber lines. It can be programmed by the ASLAC
device to operate in eight different states that control
Power Consumption and Signaling states. This enables
full control over the subscriber loop. The ASLIC device
is customized to be used exclusively with the ASLAC
device, providing a two-chip universal line interface. The
ASLIC device requires only a +5 V power supply and a
negative battery supply for its operation.
The ASLIC device implements a linear loop current
feeding method with the enhancement of thermal man-
agement to limit the amount of power dissipated on the
ASLIC device by dissipating excess power in an external
resistor.
The ASLAC device is a high-performance, CMOS CO-
DEC/filter device with additional digital filters and cir-
cuits that allow software control of transmission, DC
Feed, and supervision.
Advanced CMOS technology makes the ASLAC device
an economical device that has both the functionality and
the low power consumption required by linecard design-
ers to maximize linecard density at minimum cost.
When used with an ASLIC device, the ASLAC device
provides a complete software-configurable solution to
linecard functions. In addition, the ASLIC/ASLAC devic-
es chip set provides system-level solutions for loop su-
pervisory functions and metering. In total, the ASLIC/
ASLAC devices chip set provides a programmable so-
lution that can satisfy worldwide linecard requirements
by software configuration.
All software-programmed coefficients and DC Feed pa-
rameters are easily calculated with the AmSLAC3
ware. This software is provided free of charge and runs
on an IBM-compatible PC. It allows the designer to enter
a description of system requirements, then the software
returns the necessary coefficients and the predicted
system response.
The ASLAC device uses the industry standard micro-
processor (MPI) and PCM interfaces to communicate
with the system and for interfacing to the 64 kilobit per
second voice network.
ASLIC/ASLAC Products
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soft-
The ASLIC device interface unit inside the ASLAC device
processes information regarding line voltages, loop cur-
rents, and battery voltage levels. These inputs allow the
ASLAC device to place several key ASLIC device perfor-
mance parameters under programmable supervision.
The main functions that can be observed and/or controlled
through the ASLAC device control interface are:
















To accomplish these functions, the ASLAC device col-
lects the following information from the ASLIC device
and the Central Office system:




The outputs supplied by the ASLAC device are then:






The ASLAC device performs the CODEC and filter func-
tions associated with the four-wire section of the sub-
scriber line circuitry in a digital switch. These functions
involve converting an analog voice signal into digital
PCM samples and converting digital PCM samples back
into an analog signal. During conversion, digital filters
are used to band-limit the voice signals.
The user-programmable filters set the receive and
transmit gain, perform the transhybrid balancing func-
tion, permit adjustment of the two-wire termination im-
pedance, and provide frequency response adjustment
(equalization) of the receive and transmit paths. Adap-
tive transhybrid balancing is also included.
DC Feed characteristics
Ground-key detection
Off-hook detection
Metering signal
Longitudinal operating point
Subscriber line voltage and currents
Ring trip
Abrupt and smooth battery polarity reversal
The sum and difference of the currents in each loop
leg, ISUM, and IDIF
Currents proportional to the:
— voltage across the loop (IAB)
— battery voltage (IBAT)
— ringing current in the loop (IRTA – IRTB)
A current proportional to the desired DC loop cur-
rent (IDC)
A voltage proportional to the desired longitudinal off-
set voltage (VLBIAS)
A 12/16 kHz metering signal (appears on VM for
12/16 kHz teletax)
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