Advanced
BIOS
Functions
DIRECT
CRT
I/O
COMMANDS
CMD# 0 - Display Video Memory Format Data
on
CRT
This
function
displays the
data,
starting
from the positions specified
by
LA
and
CA
for the length in NOC,
on
the CRT. The display
data
must be in video memory
format.
The contents
of
the display request block for this
command
follow.
CMD#
LA
CA
NOC
o
Range is 0-24, binary. Values greater
than
24
are
converted to 24.
Range is
0-79, binary. Values greater
than
79
are converted
to
79.
If
the
number
of
data
items to be displayed exceeds the display
area
on
the
CRT,
the overflow
data
is
ignored.
If
NOC
is
0, the
cursor
is
positioned
at
LA,CA
and
no other action is taken.
display The starting address should be located
at
an
even
memory
address
data
buffer
(DMA
controller's restriction).
If
the base address
is
0,
no
display
address da ta
is
transferred.
attribute
If
the base address IS 0, attribute
data
is
not
transferred.
data
buffer
address
If
the base addresses
of
both
display
data
and
attribute
data
are
0, the effect
is
the
same as setting
NOC
to
O.
The
cursor
is positioned
at
LA,CA
and
no
data
is
transferred.
After
data
is
transferred, the
cursor
is positioned
at
the next cursor position.
If
the
cursor
is
positioned
on
the last screen position (25,80) when the call
is
issued, the
command
is
executed, the screen rolls up one line,
and
the cursor
is
positioned
on
the
first
column
of
the
bottom
line.
6-23
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