nes-proj/cpu/avr/dev/clock.c

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#include "sys/clock.h"
#include "sys/etimer.h"
#include <avr/io.h>
#include <avr/interrupt.h>
2007-01-23 12:24:35 +00:00
static volatile clock_time_t count;
/*---------------------------------------------------------------------------*/
SIGNAL(SIG_OUTPUT_COMPARE0)
{
++count;
if(etimer_pending()) {
etimer_request_poll();
}
}
/* External clock source does not work ? */
#if 0
void
clock_init(void)
{
cli ();
TIMSK &= ((unsigned char)~(1 << (TOIE0)));
TIMSK &= ((unsigned char)~(1 << (OCIE0)));
/* Disable TC0 interrupt */
/**
* set Timer/Counter0 to be asynchronous
* from the CPU clock with a second external
* clock(32,768kHz)driving it
*/
ASSR |= (1 << (AS0));
TCCR0 = _BV (CS02) | _BV (CS01) | _BV (WGM1);
TCNT0 = 0;
OCR0 = 128;
TIMSK |= (1 << (OCIE0));
TIMSK |= (1 << (TOIE0));
sei ();
}
#endif
/*---------------------------------------------------------------------------*/
void
clock_init(void)
{
cli ();
/* Select internal clock */
ASSR = 0x00;
/* Set counter to zero */
TCNT0 = 0;
/*
* Set comparison register:
* Crystal freq. is 16000000,
* pre-scale factor is 1024, i.e. we have 125 "ticks" / sec:
* 16000000 = 1024 * 125 * 125
*/
OCR0 = 125;
/*
* Set timer control register:
* - prescale: 1024 (CS00 - CS02)
* - counter reset via comparison register (WGM01)
*/
TCCR0 = _BV(CS00) | _BV(CS01) | _BV(CS02) | _BV(WGM01);
/* Clear interrupt flag register */
TIFR = 0x00;
/*
* Raise interrupt when value in OCR0 is reached. Note that the
* counter value in TCNT0 is cleared automatically.
*/
TIMSK = _BV (OCIE0);
/*
* Counts the number of ticks. Since clock_time_t is an unsigned
* 16 bit data type, time intervals of up to 524 seconds can be
* measured.
*/
count = 0;
sei ();
}
/*---------------------------------------------------------------------------*/
clock_time_t
clock_time(void)
{
return count;
}
/*---------------------------------------------------------------------------*/
/**
* Delay the CPU for a multiple of TODO
*/
void
clock_delay(unsigned int i)
{
for (; i > 0; i--) { /* Needs fixing XXX */
unsigned j;
for (j = 50; j > 0; j--)
asm volatile("nop");
}
}
/*---------------------------------------------------------------------------*/
/**
* Wait for a multiple of 1 / 125 sec = 0.008 ms.
*
*/
void
clock_wait(int i)
{
clock_time_t start;
start = clock_time();
while(clock_time() - start < (clock_time_t)i);
}
/*---------------------------------------------------------------------------*/
void
clock_set_seconds(unsigned long sec)
{
// TODO
}
unsigned long
clock_seconds(void)
{
return count / CLOCK_SECOND;
}