Main/Sub Ntsc Decoders; Pip/Pop Circuitry - Mitsubishi Electric VS-45605 Technical Training Manual

Main/Sub NTSC
Decoders
Figure 7-2 shows a more detailed
diagram of the NTSC Decoder cir-
cuits. In the Main NTSC De-
coder, IC6C01, (VZ7+ only) the
internal switches select the path of
the Main Y and C signals. The
Main-Y signal passes through
Delay circuitry, is amplified and
then output from the IC.
The Main-C signal is applied to the
NTSC Decoder where it is de-
modulated, and the following Ma-
trix outputs U and V signals. The
signals then pass through color
amplifiers and are output from the
IC.
The Side by Side main picture
Color and Tint adjustments take
place in IC6C01. The MAIN-
SDA line from the Control cir-
cuitry controls the adjustments
through the Digital to Analog
Converter in IC2Y02.
The analog voltage from pin 14 of
IC2Y02 sets the tint of the Side
by Side main picture, and the voltage from pin 13
sets the color level. Both these adjustments are per-
formed to match color of the Side by Side main pic-
ture to that of the sub picture.
IC6C02 is the Sub Picture NTSC Decoder. Since
the sub picture signal is composite video, the inter-
nal input signal path in the IC differs from that of the
main picture Decoder. The sub picture Video is in-
put to the IC at pin 13 and then takes two paths:
1) Through a Chroma Trap, removing chroma
signal, and then to the Y Delay circuitry.
2) Through a Bandpass Filter, removing the
luminance (Y) signal, and then to the NTSC
Decoder.
The sub picture Color and Tint are also set through
IC2Y02. Pin 12 of IC2Y02 sets the sub picture tint,
and pin 11 the sub picture color level. The adjust-
ments are performed in the Single Insert mode, and
must be performed before the Side by Side picture
color adjustments.
Figure 7-3 illustrates a simplified functional diagram
of the PIP/POP circuitry in IC6P01.
PIP insert mode
The sub picture YUV input signals are converted to
digital and are written into memory. The memory is
then read at a rate to produce the insert picture(s).
Page 7-4

PIP/POP Circuitry