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Tuan Thanh Tan
Tuan Thanh Tan

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Assembly Language Lab SPO600 - Lab 02

Hello everyone, I'm Tuan Thanh Tan aka Dustin. If you happen to read this blog. Thank you!

This is the lab 2 for my SPO course. This lab is about writing code in 6502 assembly language. One of the most difficult and cumbersome lab I've ever had.

lda #$00    ; set a pointer at $40 to point to $0200     
    sta $40 
    lda #$02 
    sta $41

    lda #$05    ; colour number

    ldy #$00    ; set index to 0

top: sta ($40), y;  

top:        sta ($40), y         ; set pixel 

              iny                      ; increment index

              cpy #$20            ; compare y value with 20. If the index is 20, end the loop

              bne top

              lda #$05

              sta $41               ; point the last page 

              lda #$06             ; set color blue
              ldy #$e0             ; set the index to indicate the last linex

bottom:  sta ($40), y      ; set pixel  
              iny                      ; increment index  
              bne bottom         ; continue until done the line
right_left: lda #$07         ; set index to 0 

              sta ($40), y          ; set the color yellow 

              tax                       ; transfer a to x   
              tya                       ; transfer y to a  
              clc                       ; clear carry flag to do ADC (add with carry) 
              adc #$1f              ; add with #$1f so it indicates the last line   

              tay                       ; transfer a to y  
              txa                       ; transfer x to a  

              lda #$04              ; set the color purple  

              sta ($40), y          ; set pixel            
              iny                       ; increment index  
              bne right_left       ; continue until done the page   : 2

              inc $41                ; increment the page      
              ldx $41                ; get the page      
              cpx #$06             ; compare with 6 (the last page is 05 so if it is 06, it means all pages are already painted)

              bne right_left       ; continue until done all page

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I found this language has a great deal of complexity and difficulties. But as time goes on, I'll get used to it.

For the performance, I used this website to get the number of circles of each instruction and sum it up. The result that I have is 106.

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