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https://github.com/deater/dos33fsprogs.git
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110 lines
1.3 KiB
ArmAsm
110 lines
1.3 KiB
ArmAsm
GBASL = $26
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GBASH = $27
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HGRPAGE = $E6
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HGR_BITS = $1C
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HGR_X = $E0
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HGR_Y = $E2
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HGR_COLOR = $E4
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TEMP = $FE
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OLD = $FF
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PAGE0 = $C054
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PAGE1 = $C055
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HGR = $F3E2
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HGR2 = $F3D8
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HCLR = $F3F2
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HPLOT0 = $F457 ;; plot at (Y,X), (A)
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WAIT = $FCA8 ;; delay 1/2(26+27A+5A^2) us
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;.zeropage
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;.globalzp xx_smc,yy_smc
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tiny:
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jsr HGR2 ; clear page1
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; A is 0 after
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tiny_yloop:
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; lda #0
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; sta XX ; XX doesn't really matter where starts
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; sta YY ; start at top of screen
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tiny_xloop:
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txa
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; lda xx_smc+1
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;===============here
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; and yy_smc+1
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eor yy_smc+1
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;===============================
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; modulo 9
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;===============================
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; value in A
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mod_9:
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; Divide by 9
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; 17 bytes, 30 cycles
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; by Omegamatrix https://forums.nesdev.com/viewtopic.php?t=11336
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sta OLD
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sta TEMP
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lsr
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lsr
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lsr
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adc TEMP
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ror
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adc TEMP
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ror
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adc TEMP
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ror
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lsr
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lsr
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lsr
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; A is ORIG/9, mod = OLD-(A*9)
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sta TEMP
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asl
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asl
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asl
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clc
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adc TEMP
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eor #$ff
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sec
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adc OLD
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;
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; beq store_color
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; lda #$7f
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store_color:
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sta HGR_COLOR
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ldy #0
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;xx_smc:
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; ldx #0
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yy_smc:
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lda #0
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jsr HPLOT0 ; plot at (Y,X), (A)
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; at begin, stores A to HGR_Y
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; X to HGR_X and Y to HGR_X+1
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; destroys X,Y,A
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; Y is XX/7
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ldx HGR_X
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inx
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; inc xx_smc+1
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bne tiny_xloop
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inc yy_smc+1
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bne tiny_xloop
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; should we over-write brk handler to restart?
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