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The relation of these three signals and character fonts on
the screen are as follows
1
TABLE 0-7
Signals and Character Fonts
Bit 3 of
GA Input
GAoutput
Selected
Selected
attribute
CHFO
CHFO
PDPO
INTE
CGM
Display
Display
byte
NTO
SL1
N1
01
Display
Display
80x25
0
H
H
H
H
H
LCD
8x8double
or
1
H
H
H
L
H
LCD
8x8single
40x25
L
H
LCD
8x8single
0
L
H
H
1
L
H
H
H
H
LCD
8x8double
80x25
0
H
L
X
H
H
CRT
8x8double
or
1
H
L
X
H
H
CRT
8x8 double(High)
40x25
L
L
L
H
CRT
8x8single
0
X
1
L
L
X
L
H
CRT
8x8 single (Hiah)
0.5.6 Clock input (2 lines)
OSCl4I : Oscillator 14 MHZ (Input)
This clock is the input signal to generate a video signal
for the CRT display.
The frequency of the clock must be l4.3l818MHZ.
OSC17l : Oscillator l7.SMHz (Input)
This clock is the input signal to generate a video signal
for the plasma display.
The frequency of the clock must be l7.SMHZ.
0.5.7 Other signals (5 lines)
DGDISI : GA Off (Input)
If this signal is at high level, the gate array is disabled.
This signal is used to disable the gate array in order to
connect another display adapter to the I/O expansion box.
In this system, this is fixed to "0".
DUTY: DUTY-LCD (Input)
This is SCAN DUTY select signal for the LCD display.
When this bit is "1", 1/200 duty is selected, and when "0",
1/100 duty is selected.
In this system, this bit is always set to "I".
D -
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