Lab 02: 6502 Assembly Language Lab
Paste this code into the emulator: lda #$00 ; set a pointer at $40 to point to $0200 sta $40 lda #$02 sta $41 lda #$07 ; colour ldy #$00 ; set index to 0 loop: sta ($40),y ; set pixel iny ; increment index bne loop ; continue until done the page inc $41 ; increment the page ldx $41 ; get the page cpx #$06 ; compare with 6 bne loop ; continue until done all pages Add this instruction after the loop: label and before the sta ($40),y instruction: tya What visual effect does this cause, and how many colours are on the screen? Why? Answer: The bitmap would display columns of 16 colors repeating once. The reason is because we use "lda #$07" to load accumulator "a" as our designated color, when we add "tya" at the start of our loop, we transfer "y" to "a". So as "y" increment, so does our color "a". And since the max number of "y" we have is 32, it would repeat the color ...