61 lines
1.6 KiB
ArmAsm
61 lines
1.6 KiB
ArmAsm
; timer routines
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;
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; the timer should be a 16-bit counter that's incremented by about
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; 1000 units per second. it doesn't have to be particularly accurate,
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; if you're working with e.g. a 60 Hz VBLANK IRQ, adding 17 to the
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; counter every frame would be just fine.
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;
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; this is generic timer routines, machine specific code goes in drivers/<machinename>timer.s
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.include "../inc/common.inc"
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.export timer_timeout
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.import timer_read
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.bss
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time: .res 2
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.code
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; check if specified period of time has passed yet
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; inputs: AX - maximum number of milliseconds we are willing to wait for
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; outputs: carry flag clear if timeout occured, set otherwise
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timer_timeout:
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pha
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txa
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pha
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jsr timer_read
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stax time
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pla
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tax
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pla
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sec ; subtract current value
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sbc time
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txa
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sbc time + 1
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rts ; clc = timeout, sec = no timeout
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; -- LICENSE FOR timer.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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