Input Interface; Mhz Clock Generator - Loewe Q2500B Serviceanleitung

Technology of Q 2500 colour TV set
72
Chroma
Input
interface
73
CVBS/Y
AV3/Synch
74
auf Y
AGC
2 x ADC
75
H-Synch
VGA
1
B
2
G
AV2 RGB/YUV
3
R
Input
29
FB
interface
4
U/B
AV3
5
Y/G
4 x ADC
DVB
6
V/R
The functions in the VPC 3230 can be roughly
summarised into 9 blocks:
- Input interface with signal selection
and two precision 8 bit A/D converters

- 20.25 MHz clock generator

- high quality, adaptive 4 line
comb filter
- Multistandard colour decoder for PAL,
NTSC and SECAM
- Letterbox detector
- Output format conversion
(Output formatter)
- I²C bus interface
- Synchronisation block
- RGB/YUV interface
Document Q 2500
VPC 3230 block diagram
4 line
comb
filter
NTSC
PAL
RGB/YUV - Interface
Y/G
U/B
Matrix
V/R
FB
Multi-
Y
standard
colour-
decoder
Cr Cr
Mixer
NTSC
Cb Cb
PAL
SECAM
Y
Cr
Cb
FB
4.3.1

Input interface

On signal board Q 2500, the input multiplexer
is switched in such a way that a choice can be
made between two pairs of signals. If an
FBAS signal, for example, is supplied by a
receiver unit or a Y/C signal is fed to an inter-
face, pin 73 for the FBAS/Y signal and pin 72
for the chroma signal are switched.
So that the signals from the ADC can be cor-
rectly digitised, two conditions must be ful-
filled. The d.c. level and the amplitude of the
signals must be adapted to the ADC . The d.c.
level is defined by a signal clamp. For this
there is a clamp circuit in the FBAS/Y path
that clamps the signal to the rear black shoul-
der.
85
Line
Y
Output
compress.
Formatter
/de-
compress.
Memory
Letterbox-
Control
detector
I 2271
VPC 3230
2
I C Bus
Synch
+
Clock
Generation
Clock
Gen.
62
63 17
V Synch
20.25 MHz 2
I C Bus VGA
© Loewe ProCollege
LM0-7
8
FIFO
CNTL
3
28
LL Clock
54
H Synch
57
V Synch