Comb Filter (V Models); 8-Bit A/D Converter - Sony KP-43T70 Training Manual

Comb Filter (V Models)

Overview
The digital 3D Comb Filter is used to separate the Y and C signals con-
tained in the composite video signal. IC203 D/A Converter, IC204 3D
Comb Filter and IC202 4MB EDO Memory are used to accomplish this.
IC203 8-Bit A/D Converter
Before the composite signal is input to IC204 3D Comb Filter, IC203 ADC
digitizes it. The composite video signal is input at IC203/4 from the Y
buffer circuit. In addition to the video signal input, IC203 ADC needs a
clock and clamp pulse input. The clock input is a 4fsc (14.28 MHz) sine
wave signal, which is sent from IC204/75 ALTF to IC203/24 CLK. The
clamp pulse is sent from IC204/61 to IC203/6 PCL. This signal is at the H
rate. The digital output from IC203 ADC is output from pins 13 – 17 and
20 – 22 to IC204 3D Comb Filter.
IC204 3D Comb Filter
The data from IC203 ADC is input to IC204/67-74 DYC02 – DYC09. This
data is synchronized to IC204/76 CSI, the composite sync input, and also
by IC204/50 FSCI. The input at IC204/76 is the composite sync input
from the main Y buffer and controls the timing generator inside of IC204
3D Comb Filter. IC204/50 FSCI receives a 3.58 MHz signal, which origi-
nates at IC205/57. IC205 is the YCJ. This signal controls the system
clock internal to IC204 3D Comb Filter.
Once the digitized video data is received by IC204 3D Comb Filter, it is
written into IC204 internal EDO memory controller. The EDO control reads
and writes data into and out of IC202 Frame Memory and also controls
the addressing, write enable and refreshing of the frame memory. Data is
read in and out between IC204/13-28 and IC202/2-5, 7-10, 39-36 and 34-
31. Addressing is done between IC204/9-2 and 99 and IC202/16-19 and
26-22. The write enable signal is sent from IC204/11 MWE to IC202/13
WE. The memory controller inside IC204 writes data to the locations
addressed while WE is LOW. IC204/12 MOE is the output enable line
and allows IC204 3D Comb filter to read data from it by IC202 3D Frame
Memory. This line is connected to IC202/27 OE.
9
IC202 Frame Memory is four Meg of EDO memory. Since IC202 Frame
Memory is EDO type memory, it needs to be refreshed constantly. This is
done using the RAS (Row Address Strobe) and CAS (Column Address
Strobe) lines. IC204/10 MCAS outputs a CAS signal to IC202/28 and 29
UCAS and LCAS. IC204/98 MRAS is output to IC202/14 RAS. These
lines are always active and keep the memory constantly refreshed.
The comb filter uses the memory controller for three different purposes.
The first is to feed signals that are delayed by 1H and 2H into the line (2D)
comb filter. The second is to feed signals that are delayed by 1H and 526
H into the frame (3D) comb filter. The third section is the motion detector
block that looks at all of the signals and determines if there is motion.
This circuit is connected to a mixer that outputs either the output from the
line comb filter if there is motion, or the output from the frame comb filter
if no motion is detected.
After the filtering is complete, the separate Y and C components are input
to noise reduction circuits. Noise is subtracted out of the signals and then
they are ready to be output. Analog Y is output from IC204/84 AYO to the
filter network consisting of FL202, Q203 and Q207. The Y signal is then
passed through buffers Q211 and Q214. This signal is then sent to IC1410
Y Switch. IC1410 Y S witch is used to select either the Y signal from the
3D comb filter or the Y signal that is input from an S video or component
video input. IC002/30 Killer controls this switching. IC002 (not shown) is
the System Control IC. The main Y signal is sent to IC1402/34 Main
Decoder Y In for PIP processing, to IC1404 YUV Switch for component
PIP processing and to IC1407 YUV Controller for main picture process-
ing.
The C signal is output from IC204/83 ACO to the filter network FL201,
Q202 and Q208. It is then sent through buffers Q209 and Q213. This
signal is sent to the switching circuit on the U board. It is switched back to
CN401/16 Main C. The Main C signal is then sent to IC1402/32 (not
shown) Main Decoder C In through buffer Q1403 to be used for PIP. The
Main C signal is also sent to IC206/5 (not shown) YCJ C In for the main
picture.