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44 lines
729 B
ArmAsm
44 lines
729 B
ArmAsm
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.importzp sp, sreg, tmp1
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.import addysp1
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.import addysp
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.import popax
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.include "ieee754.inc"
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.import ftosaddeax
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.export ftossubeax
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ftossubeax:
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; FIXME
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rts
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; found at https://github.com/CrashAndSideburns/6502ieee754/blob/main/arithmetic/addition.s
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; subtraction:
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; Pull MSB of second parameter off of stack, flip sign bit, and push back to stack.
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; Proceed to addition.
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; TSX
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; TXA
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; CLC
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; ADC #$05
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; TAX
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; TXS
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; PLA
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; EOR #$80
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; PHA
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; TXA
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; SEC
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; SBC #$05
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; TAX
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; TXS
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pha
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ldy #3
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lda (sp),y ; msb
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eor #$80
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sta (sp),y ; msb
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pla
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jmp ftosaddeax
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