mirror of https://github.com/cc65/cc65.git
70 lines
2.0 KiB
ArmAsm
70 lines
2.0 KiB
ArmAsm
;
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; Karri Kaksonen, Harry Dodgson 2006-01-07
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;
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; char cgetc (void);
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;
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.export _cgetc
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.import _kbhit
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.import KBEDG
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.import KBSTL
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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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_cgetc:
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jsr _kbhit ; Check for char available
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beq _cgetc
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ora KBSTL
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ldx #0
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and #1
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beq @L5
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lda KBEDG ; Pause button is pressed
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and #$0c
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beq @L2
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ora KBSTL
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@L1:
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bit #$04
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beq @L3 ; Pause + Opt 1 = Reset
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bit #$08
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beq @L4 ; Pause + Opt 2 = Flip
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lda #'?' ; All buttons pressed
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bra reset_and_exit
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@L2:
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lda KBSTL ; Pause alone was the last placed button
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and #$0c
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bne @L1
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lda #'P' ; Pause pressed
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bra reset_and_exit
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@L3:
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lda #'R' ; Reset pressed
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bra reset_and_exit
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@L4:
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lda #'F' ; Flip pressed
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bra reset_and_exit
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@L5:
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lda KBEDG ; No Pause pressed
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ora KBSTL
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bit #$08
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beq @L7
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bit #$04
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beq @L6
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lda #'3' ; opt 1 + opt 2 pressed
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bra reset_and_exit
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@L6:
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lda #'1' ; opt 1 pressed
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bra reset_and_exit
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@L7:
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lda #'2' ; opt 2 pressed
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reset_and_exit:
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stz KBEDG
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rts
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