41 lines
942 B
ArmAsm
41 lines
942 B
ArmAsm
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.if CODESEG = 1
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.segment "CODE1"
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.endif
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.export _getkey
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.export _count
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.export _key
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KBDCR = $D011 ; Apple I got key?
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KBDDATA = $D010 ; The key pressed
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_count: .byte 0,0,0,0
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_key: .byte 0
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_getkey:
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LDA KBDCR ; cycles 4 got key?
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BMI DONE ; cycles 2 if neg, got key goto DONE
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CLC ; cycles 2 clear carry
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LDA #1 ; cycles 2 A = 1
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ADC _count+0 ; cycles 4 LSB += A
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STA _count+0 ; cycles 4
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LDA #0 ; cycles 2 A = 0
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ROL A ; cycles 2 A = carry, carry = 0
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ADC _count+1 ; cycles 4
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STA _count+1 ; cycles 4
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LDA #0 ; cycles 2 A = 0
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ROL A ; cycles 2 A = carry, carry = 0
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ADC _count+2 ; cycles 4
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STA _count+2 ; cycles 4
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LDA #0 ; cycles 2 A = 0
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ROL A ; cycles 2 A = carry, carry = 0
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ADC _count+3 ; cycles 4
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STA _count+3 ; cycles 4
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CLC ; cycles 2 clear carry
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BCC _getkey ; cycles 2 + 1 back to checking for key
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; total = 59
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DONE: LDA KBDDATA ; get key value
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AND #$7F ; 7th bit to 0
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STA _key ; store in _key
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RTS
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