84 lines
2.3 KiB
C
84 lines
2.3 KiB
C
/***************************************************************************
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* __________ __ ___.
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* Open \______ \ ____ ____ | | _\_ |__ _______ ___
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* Source | _// _ \_/ ___\| |/ /| __ \ / _ \ \/ /
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* Jukebox | | ( <_> ) \___| < | \_\ ( <_> > < <
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* Firmware |____|_ /\____/ \___ >__|_ \|___ /\____/__/\_ \
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* \/ \/ \/ \/ \/
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* $Id$
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*
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* Copyright (C) 2005 Jens Arnold
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*
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* This program is free software; you can redistribute it and/or
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* modify it under the terms of the GNU General Public License
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* as published by the Free Software Foundation; either version 2
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* of the License, or (at your option) any later version.
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*
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* This software is distributed on an "AS IS" basis, WITHOUT WARRANTY OF ANY
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* KIND, either express or implied.
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*
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****************************************************************************/
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#include "cpu.h"
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#include "system.h"
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#include "timer.h"
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void IMIA4(void) __attribute__((interrupt_handler));
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void IMIA4(void)
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{
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if (pfn_timer != NULL)
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pfn_timer();
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and_b(~0x01, &TSR4); /* clear the interrupt */
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}
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bool timer_set(long cycles, bool start)
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{
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int phi = 0; /* bits for the prescaler */
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int prescale = 1;
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while (cycles > 0x10000)
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{ /* work out the smallest prescaler that makes it fit */
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phi++;
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prescale <<= 1;
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cycles >>= 1;
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}
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if (prescale > 8)
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return false;
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if (start)
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{
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if (pfn_unregister != NULL)
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{
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pfn_unregister();
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pfn_unregister = NULL;
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}
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and_b(~0x10, &TSTR); /* Stop the timer 4 */
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and_b(~0x10, &TSNC); /* No synchronization */
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and_b(~0x10, &TMDR); /* Operate normally */
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TIER4 = 0xF9; /* Enable GRA match interrupt */
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}
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TCR4 = 0x20 | phi; /* clear at GRA match, set prescaler */
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GRA4 = (unsigned short)(cycles - 1);
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if (start || (TCNT4 >= GRA4))
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TCNT4 = 0;
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and_b(~0x01, &TSR4); /* clear an eventual interrupt */
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return true;
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}
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bool timer_start(void)
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{
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IPRD = (IPRD & 0xFF0F) | 1 << 4; /* interrupt priority */
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or_b(0x10, &TSTR); /* start timer 4 */
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return true;
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}
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void timer_stop(void)
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{
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and_b(~0x10, &TSTR); /* stop the timer 4 */
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IPRD = (IPRD & 0xFF0F); /* disable interrupt */
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}
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