MAS9191AJ MAS [Micro Analog systems], MAS9191AJ Datasheet - Page 17

• Manufacturer Part Number: MAS9191AJ
• Description: Single Chip AMPS/ETACS/NAMPS Audio/Data Processor
• Manufacturer: MAS [Micro Analog systems]

FUNCTIONS
◆
The RX audio block starts with switch S1. The switch
is controlled by bit S1 of register 0E
ALP is used for enabling the audio loopback mode.
In normal operation RX is used. Behind the switch is
amplifier GC1 with adjustable gain from -3dB to
+3dB. The gain is controlled with bits 0..3 in register
0E
second order lowpass filter F1. The cutoff frequency
of the filter is 50 kHz and the gain at 1kHz is 0dB.
The filter output is connected to data comparator C1
and to the SAT bandpass filter F2 and to the rest of
the RX audio block. The polarity of the received data
can be inverted with bit INVRX, which is located in
register 13
connected to the DPLL and Manchester decoder
blocks. The filter F2 is a 6kHz bandpass filter for
supervisory audio tone. The filter is a second order
SC filter. The filter output is connected to SAT
comparator C2 and the SAT detection block.
The signal from F1 is connected to filter F3 through a
switch which is used by the internal logic when the
AUMUT bit of register 13
HEX
RX Audio
SIDETONE
SIDEFB
BUZOUT
BUZFB
EARP2
EARP1
EXTERP
S4
.The amplifier output is connected to the
HEX
F5
. The data comparator output is
RXTST0
RXTST1
A2
S2
A3
A4
A5
C1 C2 F2
HEX
is active. In this case if
S9
F4
HEX
M1
S10
S11
. The input
Receiver
DTMF
Audio Receive Path
MICOUT
S7
F7
+
+
S6
GC2
the data is received on the voice channel the
lowpass filter F3 input is grounded automatically with
this switch. With switches S6 and S7 the received
audio and transmitted audio can be summed. The
control bits of the switches are located in register
03
receiver. The function of the DTMF receiver is
described in the next section RX de-emphasis filter
F4 has a -6dB/octave (±1dB) frequency response in
the range 300Hz ... 3kHz. The filter can be bypassed
with
RXTST1 is connected to the DEOUT pin. The
performance of C1, C2 and F2 can be monitored with
switch S2-RXTST0-RXTST1. Bits 5 and 6 in register
02
An external capacitor is needed between DEOUT
and RBPFIN. The RBPFIN input is connected to filter
F5, which is a 6th order bandpass filter. The gain of
this filter is 0dB at 1kHz. The filter can be bypassed
with switch S4. After S4 the signal is connected to
the RBPFOUT pin. An external capacitor is used to
connect the signal to the EXPIN input.
HEX
HEX
F3
. This signal is fed to F4 and to the DTMF
and bit 5 in register 0E
S2-RXTST0-RXTST1.
+
S8
RXMUTE
F6
RX data, SAT
F1
S5
EXPANDER
HEX
Switch
GC1
control this switch.
1:2
DA9191A.000
July 31, 1997
S1
S2-RXTST0-
ALP
RX
17