timer_counter_1.c

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/*
 * SPDX-License-Identifier: GPL-3.0-only
 * This file is part of Lazuli.
 */

#include <stdint.h>

#include <Lazuli/config.h>

#include <Lazuli/sys/arch/AVR/timer_counter_1.h>

#define TIMER_COUNTER_1_PRESCALER (8)

#define COMPARE_MATCH_REGISTER_VALUE                                    \
  ((uint16_t)((LZ_CONFIG_MACHINE_CLOCK_FREQUENCY /                      \
               (TIMER_COUNTER_1_PRESCALER *                             \
                LZ_CONFIG_SYSTEM_CLOCK_RESOLUTION_FREQUENCY)) - 1))     \

void
Arch_InitSystemTimer(void)
{
  const uint16_t compareMatchRegisterValue = COMPARE_MATCH_REGISTER_VALUE;

  TCCR1A = 0;
  TIMSK1 = 0;
  TIFR1 = 0;
  TCNT1H = 0;
  TCNT1L = 0;
  TCCR1B = TCCR1B_WGM12; /* CTC mode, TOP is OCR1A */
  OCR1AH = HI8(compareMatchRegisterValue);
  OCR1AL = LO8(compareMatchRegisterValue);
}

void
Arch_StartSystemTimer(void)
{
  /* Enable output compare A match interrupt */
  TIMSK1 |= TIMSK1_OCIE1A;

  /* Clock select : system clock, prescale by 8 */
  TCCR1B |= TCCR1B_CS11;
}