Table of Contents
Advertisement
13.15
Matrix
Circuit
•
RB
Generator
Circuit
and
Matrix
(see Fig.
13-50)
The
video
signal
output
from
the
computer
consists
of
Y
(luminance
signal),
R-Y
(red/lumi-
nance
difference
signal)
and
B-Y
(blue/luminance
difference
signal)
components from
the
VDP
(TMS9129).
The
RGB
mixing
ratio in
each
signal
is
decided
by
the following equations
(1),
(2),
and
(3),
the
RB
signal
being obtained
by
adding the
R-Y
and
Y,
and
B-Y
and
Y
signals
on
a 1
:1 basis.
(1)
Y
= 0.30R + 0.59G + 0.11B
,
—
,
(2)
R-Y
= 0.70R
—
0.59G
—
0.11B
R
—
—
Lr
(3)
B-Y
=
—
0.30R
—
0.59G + 0.89B
B
—
'
-B
The
R
signal
is
obtained
by
adding
Y
and
R-Y
on
a 1:1
basis in
R210/R205
before being applied
to
pin 5
of IC105, and the
B
signal
is
obtained
by
adding
Y
and
B-Y
on
a
1:1
basis in
R209/R204
before being applied
to
pin
3 of
IC105. These
signals
are
then
compared
with
the
L
level
on
VR104,
and
are
obtained
as
respective negative
outputs
from
pins 1
and
7 of IC105.
The
negative
R
and
B
signals
are
subsequently
inverted in the
inverted
output
buffer
IC106
to
obtain
positive
R
and
B
signals
from
the
RGB OUTPUT
pins
6 and
8
(see
Photo. 13-8
and
Photo.
13-9).
•
G
and
OV
LYF
Gene
rator Circuit
(see
Fig.
13-50)
The
G
and
OVLYF
signals
are
obtained
from
the
three
Y, R-Y,
and B-Y
outputs
from
the
VDP
(TMS9129)
described
above.
The
G
signal
is
obtained
by
addition to the other
signals in
accord-
ance with the
following equation.
(4)
G
=
Y
-
[0.51(R-Y)
+
0.19(B-Y)]
The
0.51(R-Y)
+
0.19(B-Y)
addition
is
executed
by R207/R208,
and
the
inverted
signal
is
formed
by Q205/Q206. The
Y
signal
is
added by R215/
R216,
the
result
being
added
to pin
3
of
IC104 and
the
output
being obtained
from
pin
1.
The
G
output
is
then
inverted
by
the
output
inverter
buffer
IC106
to
become
the
positive polarity
G
signal
which
is
obtained
from
the pin
7
RGB
OUTPUT
terminal
(see
Photo.
13-10).
•
OVLYF
The
overlay
flag
is
included
in
the
R-Y
and
B-Y
output
signals
during
VDP
(TMS9129)
external
synchronizing
m
ode (SU
PERIMPOSE,
VIDEO),
and
in
the PX-7,
OVLYF
is
obtained
from
the
B-Y
signal.
Since
OVLYF
is
used
at
the
same com-
parator
level as
the
G
signal,
the
B-Y
signal
is
subject to
a
positive
voltage
shift
(since
the
flag
is
included
as
a negative
signal in
the
color difference
signal)
befo
re
being applied to pin 5 of
IC104
to
obtain the
OVLYF
signal (see
Photo. 13-11
and
and
Photo.
13-12).
i
os
Advertisement
Table of Contents
