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42 lines
1.3 KiB
NASM
42 lines
1.3 KiB
NASM
****************************************************************
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*
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* KeyPress - Check to see if a key has been pressed
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*
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* Outputs:
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* A - 1 (true) if pressed, else 0
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*
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****************************************************************
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*
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KeyPress start
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keyBoard equ $C000 keyboard location
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sep #$30 use short regs for load
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lda >keyBoard load keyboard value
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asl A shift sign bit into bit 0
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rol A
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rep #$30 back to long regs
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and #1 and out all but the bit we want
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rtl
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end
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****************************************************************
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*
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* ReadChar - return the last character typed on the keyboard
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*
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* Outputs:
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* A - character typed
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*
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****************************************************************
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*
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ReadChar start
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keyBoard equ $C000 keyboard location
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strobe equ $C010 strobe location
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sep #$30 use short regs
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sta >strobe clear strobe
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lda >keyBoard load character
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rep #$30 back to long regs
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and #$007F and out high bits
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rtl
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end
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