Chapter 3: Circuit Description; Video Signal Processing; Input Signals; Displayed Colors - Zenith ZVM-1380 Service Manual

Refer to the block diagram and the schematics in
Chapter 4, while reading the following material.
Video Signal Processing
The RGBI inputs are all TTL level, digital signals sup-
plied by the computer. These signals are listed in Table
3-1.
PIN NO.
1
2
3
4
5
6
7
8
9
Table 3-1
Input Signals
MODE 1
Ground.
Ground.
A.
G.
B.
Intensity.
Monochrome Video*
Horizontal Sync.
Vertical Sync.
MODE 2
Ground.
R'.
A.
G.
B.
G'.
B'.
Horizontal Sync.
Vertical Sync.
NOTE: Secondary red (R'), green (G'), and blue (B') signals are
indicated by the lower case r, g, and b throughout this manual.
*
Present, but not used by this monitor.
The monitor determines the mode of operation by de-
coding the vertical sync Signal. A positive polarity di-
rects the monitor into mode 1 and a negative polarity
directs the monitor into mode 2. The RGB (red, green,
and blue) signals contain the primary color information.
In mode 1, the intensity bit is used to enhance the
hue of a particular color by providing additional drive
to the displayed color. In this manner, as many as
16 different colors can be displayed.
Chapter 3
Circuit Descriptions
In mode 2, additional color information is contained
in the secondary colors r,g,and b. These bits of data
are used in a similar manner as the intensity bit in
mode 1. They are used to enhance the hue of a pri-
mary color by providing additional drive to the color
Signal. 64 color combinations are available using 6
input bits. The 16 colors and the input signal combina-
tions required to generate those colors for both modes
are listed in Table 3-2.
Table 3-2
Displayed Colors
MODE 1 MODE 2
Color RGBI RrGgBb
Black 0000 000000
Gray 0001 000010
Blue 0010 00 10 00
Light blue 0011 001010
Green 0100 100000
Light green 0101 100010
Cyan 0110 100100
Light cyan 01 1 1 101010
Red 1000 01 01 01
Light red 1001 01 01 11
Magenta
1010
01 11 01
Light magenta 1 01 1 01 11 11
Yellow 1100 11 01 01
Light yellow
1 1 01 11 01 11
White 1 1 1 0 11 11 01
Intensified white 1 1 1 1 111111
0= No signal.
1 = Signal active.