mirror of https://github.com/mre/mos6502.git
34 lines
731 B
Plaintext
34 lines
731 B
Plaintext
; euclid.a65
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; A program to find the greatest common divisor of two numbers
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.ORG $1000
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; .algo
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LDA $00 ; Load from F to A
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; .algo_
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sec ; Set carry flag
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SBC $01 ; Subtract S from the number in A (from F)
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BEQ end ; Jump to .end if the difference is zero
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BMI swap ; Jump to .swap if the difference is negative
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STA $00 ; Load A to F
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JMP algo_ ; Jump to .algo_
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; .end
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end:
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LDA $00 ; Load from F to A
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BRK ; Break (end program)
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; .swap
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swap:
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LDX $00 ; Load F to X
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LDY $01 ; Load S to Y
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STX $01 ; Store X to S
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STY $00 ; Store Y to F
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JMP algo ; Jump to .algo
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algo:
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JMP algo ; Infinite loop to prevent program from ending
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algo_:
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JMP algo_ ; Infinite loop to prevent program from ending
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