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DRX-1
determine the antenna signal strength after a buffer [7705]
with the signal AGC_MUTE. In the opposite direction this
line may be used to mute the demodulator to avoid cross
talk in all cases, where the tuner signal is not needed. In
this case a „high" signal is sent via AGC_MUTE and the
conducting diode [6703] to pin4. The video trap [1703]
reduces adjacent channel video and sound carrier
remainders in the video for BG standards. For all other
standards the switch [7704] and signal TS "low" bypass
this trap. In this cases the selectivity of the SAW filter
[1700] is sufficient. A frequency response correction is
achieved by the inductance [5009] for not BG standards.
This correction is not preferred for SECAM L' and
therefore shorts circuited by [7709], if the signal SB1 is
"high". The demodulated video signal VFV is available
after the buffer and limiting stage for noise peaks [7706].
The FM-PLL demodulator function of TDA 9818 is not
used and deactivated by the resistor [3726].
Audio Demodulator
Sound processor MSP 3415G
The MSP 3415G [7600] is a multistandard sound
processor which can demodulate FM Mono/Stereo,
NICAM and AM signals. The incoming signal is first
controlled and then digitised. The digital signal is then
demodulated in 2 separate channels. In the first MSP
channel, FM and NICAM (B/G/I/D/K) are demodulated,
whereas in the second MSP channel, FM and are
demodulated again (NICAM L corresponds to NICAM B/
G). These demodulated signals are selected digitally in
the I/O and switched to the D/A converter on the outputs.
Amplitude and bandwidth of the demodulated audio
signals can be determined in the MSP using the
corresponding commands via the I2C bus. The audio
signal from the tuner is available at the pins 30 AFER and
31 AFEL.
3.9 Input/Output Video-Routing (A, B, G models)
General Description:
The complete Video- I/O-switching is basically realised by
the I/O switch STV6410A. It is controlled via IIC-Bus-0
(SDA/SCL) by the all in one C on the analogue board. The
STV 6410 has three YCVBS switches, three chroma
switches and one RGB switch. All switches have 6-dB
amplification on the outputs.
The YCVBS inputs have bottom clamp, the chroma inputs
have average clamp, and the RGB inputs have bottom
clamp circuits at the inputs. The R/C inputs can be
switched to average clamp for chroma signals via I2C bus.
The IC has also one slow blanking monitor and one fast
blanking switch for fast RGB insertion (see detailed
description in chapter 1.5). Two pre-selectors BA 7652 are
additionally used: One for switching between Rear CVBS,
Y- Rear and Front, the second for switching between
Chroma- Rear and Front signal. Both pre-selectors are
controlled via IS1 and IS2 from the analogue board C.
CVBS Signals:
There are four CVBS input connection possibilities: Front
76
chinch (E6), Rear Chinch (E4), Scart 1 (E1) and Scart 2 (E2).
Rear Chinch In is routed via the pre selector BA 7652; the
other signals are connected direct to the STV 6410. The
selected CVBS signal is routed to Rear Chinch Out (via BA
7660, 6dB amplification, 75 Ohm driver) and to Scart 1.
Independent of the input signal quality (CVBS, S-Video or
RGB) the digital board supplies also S-Video and RGB
signals to the corresponding socket.
S-Video Signals:
There are also four S-Video input connection possibilities:
Front In (E5), Rear In (E3), Scart 1 and Scart 2. For S-
Video from Scart this option has to be switched on in the
OSD menu.
The pre-selectors and the STV 6410 do the signal
selection (for detailed routing see overview). Also the
video quality will be S-Video, the digital board supplies
also CVBS to the corresponding sockets. The S-Video
signal that is coming from the digital board is routed via BA
7660 (6-dB amplification and 75-Ohm driver) to the S-
Video Rear Out socket.
RGB Signals:
The Scart 2 RGB input signal (Decoder socket) is
connected to the RGB switch of STV 6410 and to the
digital board in parallel.
The RGB from Scart 2 is routed to Scart 1 in low power
standby mode. The direct connection (not via STV 6410) is
for loop through and REC. The RGB signal, which is
coming from the digital board, is connected to the RGB
encoder input of the STV6410 and is routed to Scart 1 in
all other modes.
As the Scart-connection can carry either RGB- or Y/C-
signals it is necessary to define the available and selected
signal-property.
While Pin15 of Scart (Red or Chroma-upstream) is fully
handled via STV6410A the Pin7 (Blue or Chroma-
downstream) has to be extra set.
• Scart1: Pin42 of C (SC1YC_H-line):
– Low ( Blue-Out on SC1
– High ( Chroma-In on SC1
• Scart2: Pin41 of C (SC2RGB_H-line):
– Low ( Chroma-Out on SC2
– High ( Blue-In on SC2
Detection of Status-Information
Pin-8 (Slow-Blank):
Level-detection of Pin-8 (Scart-1 and -2) is realised by
using STV6410A. It can be readout via IIC-Bus by the CC-
C. To obtain the status of Scart1-Pin8, Bit 0 & 1 of register
06h must be set to 0 (Input-mode). The corresponding bits
for verification of Scart2-Pin8-status are set to input-mode
as default.
Meaning of Read-Register-Bits:
• Bit 7 & 6: not used
• Bit 5 & 4: Status Scart-2/Pin8:
– 0 1 Low-level
– 1 0 Medium-level (16:9)
– 1 1 High-level (4:3)
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