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56 lines
1.1 KiB
ArmAsm
56 lines
1.1 KiB
ArmAsm
;
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; Karri Kaksonen, Harry Dodgson 2006-01-06
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;
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; unsigned char kbhit (void);
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;
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.export _kbhit
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.export KBEDG
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.export KBSTL
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.import return0, return1
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; --------------------------------------------------------------------------
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; The Atari Lynx has a very small keyboard - only 3 keys
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; Opt1, Opt2 and Pause.
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; But the designers have decided that pressing Pause and Opt1 at the
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; same time means Restart and pressing Pause and Opt2 means Flip screen.
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; For "easter egg" use I have also included all three keys pressed '?'
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; and Opt1 + Opt2 pressed '3'.
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; So the keyboard returns '1', '2', '3', 'P', 'R', 'F' or '?'.
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.data
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KBTMP: .byte 0
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KBPRV: .byte 0
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KBEDG: .byte 0
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KBSTL: .byte 0
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KBDEB: .byte 0
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KBNPR: .byte 0
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.code
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_kbhit:
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lda $FCB0 ; Read the Opt buttons
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and #$0c
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sta KBTMP
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lda $FCB1 ; Read Pause
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and #1
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ora KBTMP ; 0000210P
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tax
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and KBPRV
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sta KBSTL ; for multibutton
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txa
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and KBDEB
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sta KBEDG ; for just depressed
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txa
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and KBNPR
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sta KBDEB ; for debouncing
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txa
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eor #$ff
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sta KBNPR ; inverted previous ones pressed
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stx KBPRV
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lda KBEDG
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beq @L1
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jmp return1 ; Key hit
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@L1:
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jmp return0 ; No new keys hit
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