gray@strawberry.it.udel.edu (Scott Gray) (02/27/90)
I have been working on an assembly routine to scroll a portion (window) of
an EGA/VGA screen but have run up against something that just is not doc-
umented well in very many reference manuals.
First off, under the various read/write modes what happens when I read a
byte from the display memory? (i.e. MOV DS,[VIDEO_MEMORY_ADDR]
MOV SI,0
very loose assembly code --> MOV DI,[VARIABLE]
MOVSB
after doing all your settings of read/write modes)
In other words, what will will the byte variable [VARIABLE] hold? Two pixels?
Eight bits from bitplane 'n'? One latch? What?
Also, in my readings, some books suggest doing a screen to main memory copy
of the block then from main memory back to screen memory again. Apparently
screen-screen memory moves are too slow. Any input on this?
Finaly, if anyone already has a routine to do this and would like to save
me the trouble of having to learn new information, feel free to send me a
copy. (actually I would like to know this.)
-- Scott --
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+ SCOTT - gray@freezer.it.udel.edu | "I'm, BORED BORED BORED BORED!" +
+ or god@vax1.acs.udel.edu | - Vivian +
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