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55 lines
1.5 KiB
ArmAsm
55 lines
1.5 KiB
ArmAsm
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.export check_for_abort_key
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.export abort_key
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.exportzp abort_key_default = $3f
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.exportzp abort_key_disable = $ff
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.data
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abort_key: .byte $3f ; RUN/STOP
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.code
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; check whether the abort key is being pressed
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; inputs: none
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; outputs: sec if abort key pressed, clear otherwise
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check_for_abort_key:
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lda $cb ; current key pressed
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cmp abort_key
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bne no_key
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@flush_loop:
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ldy #$ff
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jsr $f142 ; not officially documented - where F13E (GETIN) falls through to if device # is 0 (KEYBD)
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cpy #$ff ; Y gets modified iff there's a character available - this approach allows to read ^@ as 0
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bne @flush_loop
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lda $cb ; current key pressed
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cmp abort_key
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beq @flush_loop
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sec
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rts
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no_key:
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clc
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rts
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; -- LICENSE FOR c64_input.s --
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; The contents of this file are subject to the Mozilla Public License
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; Version 1.1 (the "License"); you may not use this file except in
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; compliance with the License. You may obtain a copy of the License at
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; http://www.mozilla.org/MPL/
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;
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; Software distributed under the License is distributed on an "AS IS"
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; basis, WITHOUT WARRANTY OF ANY KIND, either express or implied. See the
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; License for the specific language governing rights and limitations
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; under the License.
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;
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; The Original Code is ip65.
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;
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; The Initial Developer of the Original Code is Jonno Downes,
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; jonno@jamtronix.com.
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; Portions created by the Initial Developer are Copyright (C) 2009
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; Jonno Downes. All Rights Reserved.
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; -- LICENSE END --
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