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 -- -=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=- + SCOTT - gray@freezer.it.udel.edu | "I'm, BORED BORED BORED BORED!" + + or god@vax1.acs.udel.edu | - Vivian + -=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-