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56 lines
1.0 KiB
NASM
56 lines
1.0 KiB
NASM
// Tests simple word pointer math
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// Commodore 64 PRG executable file
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.file [name="word-pointer-math.prg", type="prg", segments="Program"]
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.segmentdef Program [segments="Basic, Code, Data"]
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.segmentdef Basic [start=$0801]
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.segmentdef Code [start=$80d]
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.segmentdef Data [startAfter="Code"]
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.segment Basic
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:BasicUpstart(main)
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.segment Code
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main: {
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.label SCREEN = $400
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.label w = 3
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.label idx = 2
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lda #0
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sta.z idx
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tax
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__b1:
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// words+i
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txa
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asl
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// w = *(words+i)
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tay
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lda words,y
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sta.z w
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lda words+1,y
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sta.z w+1
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// <w
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lda.z w
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// SCREEN[idx++] = <w
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ldy.z idx
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sta SCREEN,y
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// SCREEN[idx++] = <w;
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iny
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// >w
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lda.z w+1
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// SCREEN[idx++] = >w
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sta SCREEN,y
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// SCREEN[idx++] = >w;
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iny
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tya
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// idx++;
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clc
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adc #1
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sta.z idx
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// for( byte i: 0..3)
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inx
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cpx #4
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bne __b1
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// }
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rts
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.segment Data
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// Clever word array that represents C64 numbers 0-7
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words: .word $3130, $3332, $3534, $3736
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}
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