ico*_*eep 3 assembly 6502 delay
我是ASM的新手,我正在努力研究如何为以下代码创建延迟:
org $1000
loop: inc $d021
jmp loop
我猜,评论很清楚.
每帧改变颜色的代码示例(1/50秒)
sei ; enable interrupts
loop1: lda #$fb ; wait for vertical retrace
loop2: cmp $d012 ; until it reaches 251th raster line ($fb)
bne loop2 ; which is out of the inner screen area
inc $d021 ; increase background color
lda $d012 ; make sure we reached
loop3: cmp $d012 ; the next raster line so next time we
beq loop3 ; should catch the same line next frame
jmp loop1 ; jump to main loop
用于每秒更改颜色的代码示例
counter = $fa ; a zeropage address to be used as a counter
lda #$00 ; reset
sta counter ; counter
sei ; enable interrupts
loop1: lda #$fb ; wait for vertical retrace
loop2: cmp $d012 ; until it reaches 251th raster line ($fb)
bne loop2 ; which is out of the inner screen area
inc counter ; increase frame counter
lda counter ; check if counter
cmp #$32 ; reached 50
bne out ; if not, pass the color changing routine
lda #$00 ; reset
sta counter ; counter
inc $d021 ; increase background color
out:
lda $d012 ; make sure we reached
loop3: cmp $d012 ; the next raster line so next time we
beq loop3 ; should catch the same line next frame
jmp loop1 ; jump to main loop