Posted By
George
on 2011-09-11
16:36:03
 |  Re: Draw a single pixel in assembler
Hi gerliczer,
Yes, it helped. thank you very much. I think this init will be standard for my examples..
Another question:
This is the Code from Csabo which draws the one pixel
; draw a pixel at 160, 100 (center)
LDX #160
LDY #100
JSR drawpixel
; #################################################
drawpixel
TXA
AND #$07
STA tempx+1
;
TXA
AND #$F8
STA ptr
LDA #$00
STA ptr+1
;
TYA
AND #$07
STA tempy+1
;
TYA ; y=y/8
AND #$F8
LSR a
LSR a
LSR a
ASL a ; y=y*2
TAY
LDA ptr
CLC
ADC mul320,y
STA ptr
LDA ptr+1
ADC mul320+1,y
CLC
ADC #$20
STA ptr+1
after that i try to make a loop for a line from x=1 to 200, which does not work.
What i am doing wrong? Can i compare X or Y register direct with a value?
LDX #1
LDY #100
loop01
; loop
JSR drawpixel
INX
TXA
AND #200
BNE loop01
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