When bit 5 is set to a
"1"
colors are determined as follows.
The C 1
CO
Set selected are:
o 0 Background as defined
by
Bit 0-3
of
Port
'3D9'
o 1 Cyan
1 0
~agenta
1 1 White
When
bit 5 is set to a
"0"
Colors are determined as follows.
The
CO
Cl
Set selected are:
o 0 Background
as
dermed
by
Bit 0-3
of
Port
'3D9'
o 1 Green
1 0 Red
1 0 Yellow
Mode
Select
Register
This is a 6 bit output only register, it can not be read. Its address
is
X'3D8'.
It
can be written using the 8088
I/O
OUT
command.
The following is a description
of
the registers functions.
Bit 0
Bit 0
80
x 25 mode
Bit
1
Graphic Select
Bit 2
B
& W Select
Bit 3
Enable Video Signal
Bit 4
High Res
640
x 200 B & W
~ode
Bit 5
Change
BACKGROUND
INTENSITY
to Blink Bit
Bit 6
Not
Used
Bit
7
Not
Used
Bit 0
Selects between
40
x 25 and
80
x 25 alpha mode, a
"1"
sets it to
80
x 25 mode.
Bit 1 Selects between
ALPHA
mode and 320 x 200 graphics
mode, a
"I"
select 3 20 x
200
graphics mode.
Bit 2
Selects color
or
B & W mode, a
"1"
selects B & W.
Bit 3
Enables the video signal
at
certain times when modes are
Oeing
changed.
The
video signal should be disabled when
changing modes. A
"1"
enables the video signal.
Bit 4
When on, this bit selects the
640
x 200 B & W graphics
mode. One color
of
8
can
be selected on direct drive sets in
this mode
by
using register 3D9.
2-58
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