92 lines
2.3 KiB
C
92 lines
2.3 KiB
C
/*
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* =====================================================================================
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*
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* ________ .__ __ ________ ____ ________
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* \_____ \ __ __|__| ____ | | __\______ \ _______ _/_ |/ _____/
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* / / \ \| | \ |/ ___\| |/ / | | \_/ __ \ \/ /| / __ \
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* / \_/. \ | / \ \___| < | ` \ ___/\ / | \ |__\ \
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* \_____\ \_/____/|__|\___ >__|_ \/_______ /\___ >\_/ |___|\_____ /
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* \__> \/ \/ \/ \/ \/
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*
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* www.optixx.org
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*
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*
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* Version: 1.0
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* Created: 07/21/2009 03:32:16 PM
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* Author: david@optixx.org
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*
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* =====================================================================================
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*/
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#include <stdint.h>
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#include <stdio.h>
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#include <avr/io.h>
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#include <avr/io.h>
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#include <avr/interrupt.h> /* for sei() */
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#include "debug.h"
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#include "info.h"
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#include "sram.h"
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extern uint8_t snes_reset_line;
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#ifndef OCR1A
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#define OCR1A OCR1 // 2313 support
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#endif
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#ifndef WGM12
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#define WGM12 CTC1 // 2313 support
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#endif
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// #define XTAL 11059201L // nominal value
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#define XTAL 20000000UL
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#define DEBOUNCE 500L // debounce clock (256Hz = 4msec)
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#define uint8_t unsigned char
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#define uint unsigned int
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uint16_t prescaler;
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uint16_t volatile second; // count seconds
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ISR(SIG_OUTPUT_COMPARE1A)
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{
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#if XTAL % DEBOUNCE // bei rest
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OCR1A = 20000000UL / DEBOUNCE - 1; // compare DEBOUNCE - 1 times
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#endif
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if (--prescaler == 0) {
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prescaler = (uint16_t) DEBOUNCE;
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second++; // exact one second over
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#if XTAL % DEBOUNCE // handle remainder
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OCR1A = XTAL / DEBOUNCE + XTAL % DEBOUNCE - 1; // compare once per second
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#endif
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}
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}
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void timer_start(void)
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{
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TCCR1B = (1 << WGM12) | (1 << CS10); // divide by 1
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// clear on compare
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OCR1A = XTAL / DEBOUNCE - 1UL; // Output Compare Register
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TCNT1 = 0; // Timmer startet mit 0
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second = 0;
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prescaler = (uint16_t) DEBOUNCE; // software teiler
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TIMSK1 = 1 << OCIE1A; // beim Vergleichswertes Compare Match
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// Interrupt (SIG_OUTPUT_COMPARE1A)
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sei();
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}
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uint16_t timer_stop_int(void)
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{
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uint16_t t = ((DEBOUNCE - prescaler) / DEBOUNCE) + second;
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return t;
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}
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