SPO600 Lab3 - Math Lab Update Kaleidoscope

Hello my friend, good to see you again here. Today I'm going to update the lab 3 that I started a couple weeks ago. Unfortunately, my group mates and I are unable to solve the Pong game by using 6502 Assembly language. Our problem is we are not sure how to make it bounce on a wall. So we decided to start a new project, if you are still interested in the Pong game and want to explore it further, click here. But now the new project is Kaleidoscope.

For this project we needed to create a project to draw the same shape in each quarter of the screen when pressing the arrow keys. This is the code:

define POINTER     $10      ;ptr: start of row
 define POINTER_H   $11 
define ROW     $20      ;current row
 define COL     $21         ; current column
 define DOT     $01         ; dot colour location
 define CURSOR      $05     ; green colour
setup: lda #$0f         ; initial ROW,COL
    sta ROW
    sta COL
    LDA #$01
    STA DOT
 draw:  jsr draw_cursor
 getkey:    lda $ff         ; get the keystroke
    ldx #$00            ; clear the key buffer
    stx $ff
    cmp #$30
    bmi getkey
    cmp #$40
    bpl continue
    SEC
    sbc #$30
    tay
    lda color_pallete, y
    sta DOT
    jmp done

continue:   cmp #$43    
    beq clear
    cmp #$63
    beq clear
    cmp #$80    
    bmi getkey
    cmp #$84
    bpl getkey
    pha    
    lda DOT
    sta (POINTER),y
    jsr draw_on_quads
    pla
    cmp #$80
    bne check1
    dec ROW  
    jmp done

 check1:    cmp #$81    ; right key
    bne check2
    inc COL     ; increment COL
    jmp done

 check2:    cmp #$82    ; down key
    bne check3
    inc ROW     ; increment ROW
    jmp done

 check3:    cmp #$83    ; left key
    bne done
    dec COL     ; decrement COL
    clc
    bcc done

 clear: lda table_low   ; clear screen
    sta POINTER
    lda table_high
    sta POINTER_H
    ldy #$00
    tya

 c_loop:    sta (POINTER),y
    iny
    bne c_loop
    inc POINTER_H
    ldx POINTER_H
    cpx #$06
    bne c_loop

 done:  clc   
    bcc draw

 draw_cursor:
    lda ROW     
    and #$0f
    sta ROW
    lda COL     
    and #$0f
    sta COL
    ldy ROW     
    lda table_low,y
    sta POINTER
    lda table_high,y
    sta POINTER_H
    ldy COL     
    lda #CURSOR
    sta (POINTER),y
    rts

 draw_on_quads:     
    LDA POINTER 
    PHA         
    LDA POINTER_H
    PHA
    LDA #$10
    CLC
    SBC COL
    CLC
    ADC #$10
    TAY
    LDA DOT
    STA (POINTER),y
    TYA
    PHA 
    lda #$10    
    CLC
    SBC ROW
    CLC
    ADC #$10
    TAY
    lda table_low,y
    sta POINTER
    lda table_high,y
    sta POINTER_H
    ldy COL     
    lda DOT
    sta (POINTER),y
    PLA
    TAY
    lda DOT
    sta (POINTER),y
    PLA
    STA POINTER_H
    PLA
    STA POINTER
    RTS
 table_high:
 dcb $02,$02,$02,$02,$02,$02,$02,$02
 dcb $03,$03,$03,$03,$03,$03,$03,$03
 dcb $04,$04,$04,$04,$04,$04,$04,$04
 dcb $05,$05,$05,$05,$05,$05,$05,$05,
table_low:
 dcb $00,$20,$40,$60,$80,$a0,$c0,$e0
 dcb $00,$20,$40,$60,$80,$a0,$c0,$e0
 dcb $00,$20,$40,$60,$80,$a0,$c0,$e0
 dcb $00,$20,$40,$60,$80,$a0,$c0,$e0
color_pallete:
dcb $01,$02,$03,$04,$05,$06,$07,$08,$09,$0a

This is a sample of the result:

Reflection

In this lab, we actually worked on a fully functional program, this program is available to receive user’s input and draw out a diagram. After I finished this lab, I learned how to work on subroutines and understand the syntax and logic of assembly language deeply. Assembly language is a low-level programming language which frequently and explicitly accesses the memory and registers. I hope this practice will help me to work on 6502 assembly language easier in the future.