6502 Math Lab (Week 3 Lab)

Hello everybody, and welcome to the third lab of SPO600.

After studying 6502 directives last class, specifically DCB, we're going to use it this lab in our very first creative piece of work using 6502.

The objective in this lab is to create a graphic animation using the 6502 emulator colors. We're given four options to achieve this:

1. Bouncing Graphic
2. Numeric Display
3. Pong
4. Kaleidoscope

I've decided to go with the bouncing graphic.

To achieve my design, I copied the code example to display a ball on the screen. This code sample uses DCB to pre-define all the locations and load them into the a register.

define WIDTH 	4 ; width of graphic
define HEIGHT 	4 ; height of graphic
 
 
 	lda #$25	; create a pointer at $10
 	sta $10		;   which points to where
 	lda #$02	;   the graphic should be drawn
 	sta $11
 
 	lda #$00	; number of rows we've drawn
 	sta $12		;   is stored in $12
 
 	ldx #$00	; index for data
 	ldy #$00	; index for screen column
 
 draw:	lda data,x
 	sta ($10),y
 	inx
 	iny
 	cpy #WIDTH
 	bne draw
   
 	inc $12		; increment row counter
 
 	lda #HEIGHT	; are we done yet?
 	cmp $12
 	beq done	; ...exit if we are
 
 	lda $10		; load pointer
 	clc
 	adc #$20	; add 32 to drop one row
 	sta $10
 	lda $11	; carry to high byte if needed
 	adc #$00
 	sta $11
 
 	ldy #$00
 	beq draw
 
 done:	brk		; stop when finished
 
 data:
 dcb 00,03,03,00
 dcb 07,00,00,07
 dcb 07,00,00,07
 dcb 00,03,03,00