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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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