AM79C32A Advanced Micro Devices, AM79C32A Datasheet - Page 24

• Manufacturer Part Number: AM79C32A
• Description: Digital Subscriber Controller (DSC) Circuit
• Manufacturer: Advanced Micro Devices

Main Audio Processor (MAP)
(Am79C30A only)
Overview
The MAP, as illustrated in Figure 3, implements au-
dio-band analog-to-digital (ADC) and digital-to-analog
(DAC) conversions together with a wide variety of audio
support functions. Analog interfaces are provided for a
handset earpiece, a handset mouthpiece, a micro-
phone, and a loudspeaker. A programmable analog
preamplifier is included in front of the A/D converter.
The codec and filter functions are implemented using
digital signal processing (DSP) techniques to provide
operational stability and programmable features. There
is one programmable digital gain stage in the transmit
path and two in the receive path to allow precise signal
level control. Sidetone attenuation is programmable,
and programmable equalization filters are present in
both the receive and transmit paths in order to modify
the frequency response of either or both paths. Tone
generation capability is included to allow generation of
ringing signals, DTMF tones, and call progress signals.
MAP operation is described in detail in the following
sections.
24
AINA
AINB
AREF
EAR1
EAR2
Notes:
GX
GER
GR
STG
GA
ASTG
*Programmable
**These registers can also be programmed for infinite attenuation to break the signal path if desired.
LS1
LS2
CAP1
CAP2
Sidetone
Analog
Gain*
GA*
Minimum
–10 dB**
–12 dB**
–18 dB**
–27 dB**
0 dB**
0 dB
STR*
DAC
ADC
Default
–18 dB
0 dB
0 dB
0 dB
0 dB
Loopback 2
8
Figure 3. Main Audio Processor Block Diagram
Digital
Digital
Loopback 1
Interpolators, LPF
Maximum
12 dB
18 dB
24 dB
–6 dB
0 dB
0 dB
Am79C30A/32A Data Sheet
Decimators, BPF
(A) DTMF
GEN.
0.5 dB
0.5 dB
0.5 dB
0.5 dB
6.0 dB
1.5 dB
Step
(C)
R*
Audio Inputs
The audio input port consists of two inputs (AINA and
AINB) which are selectable, one at a time, by register
programming. Signals applied to these inputs must be
AC-coupled.
Earpiece and Loudspeaker Drivers
The earpiece and loudspeaker drivers each consist of
amplifiers with differential, low-impedance outputs. The
MAP receive path signal may be routed to either of
these outputs, or to both outputs simultaneously. Alter-
natively, the MAP receive path may be routed to the
EAR outputs while the Secondary Tone Ringer (STR)
is routed to the LS outputs. The EAR drivers can drive
loads Š130 ohms between the EAR1 and EAR2 pins,
while the LS drivers can drive loads Š40 ohms between
the LS1 and LS2 pins. The maximum capacitive-load-
ing between EAR1 and EAR2 or between LS1 and LS2
is 100 pF. The EAR outputs are high-impedance when
the MAP is disabled. The LS outputs are high imped-
ance when both the MAP and the Secondary Tone
Ringer are disabled.
Ringer
Tone*
GER*
X*
Sidetone
PEAKX
Tone*
Gen.
Gain*
+
GX*
GR*
(B)
PEAKR
COMP*
EXP*
Transmitter
Receiver
Ba channel
Ba channel
MUX
09893H-4
MUX
from
to