Sound Processing - NEC DTE-25G5THS Service Manual

Service Manual CP-785A
High impedance
This mode can be used for input only operation of the port.
Special port for LED
Pin 10 and 11 have the same functionality as the general I/O pins but in addition, their current source and
sink capacity is 8 mA instead of 4 mA. These pins are used for driving LED' s via a series current
limiting resistor.
-Controller I/O pin configuration and function table
pin name
1 n.u.
2 SCL
3 SDA
4
5 OCP
6 -
7 Key in
8 S/SW
10 Red LED
11 Green LED
62 Audio mute

5-5 Sound processing

Analogue sound IF - input section
The input pins ANA_IN1+ and ANA_IN- offer the possibility to connect sound IF sources to the MSP
3415D. The analogue-to-digital conversion of the preselected sound IF signal is done by an A/D
converter, whose output is used to control an analogue automatic gain circuit (AGC), providing an
optimal level for a wide range of input levels.
Quadrature Mixers
The digital input coming from the integrated A/D converter may contain audio information at a frequency
range of theoretically 0 to 9 MHz corresponding to the selected standards. By means of two
programmable quadrature mixers, two different audio sources ; for example, NICAM and FM-mono,
may be shifted into baseband position.
Phase and AM discrimination
The filtered sound IF signals are demodulated by means of the phase and amplitude discriminator block.
On the output, the phase and amplitude is available for further processing. AM signals are derived from
the amplitude information, whereas the phase information serves for FM and NICAM demodulation.
configuration
Stand by
High impedance
Open Drain
Open Drain
High impedance
High impedance
High impedance
High impedance
High impedance
Open Drain
Push Pull
TV ON
High impedance
Open Drain
Open Drain
High impedance
High impedance
High impedance
See table above
Open Drain
High impedance
Push Pull
-36-
description
not used
Serial clock line
Serial data line
Over Current Protection
( Switch the set OFF if
the voltage on this pin is
<2.33V )
For factory use only
Local keyboard input
external video switch
High in stand by mode