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Код: Выделить всё

#include <avr/io.h>
#include <avr/interrupt.h>
#include <avr/boot.h>

#define OUTPIN_MASK  _BV(PB3)
#define HALF_PERIOD   500 // 500 ms, 1 Hz

// Timer/Counter Compare Match A
// Every 1 ms
ISR(TIM0_COMPA_vect)
{
  static uint16_t cntr = 0;
  if(++cntr >= HALF_PERIOD) {
    PINB |= OUTPIN_MASK;
    cntr = 0;
  }
}

int main(void)
{
  uint8_t prescaler = 0;
  uint8_t f_low  = boot_lock_fuse_bits_get(GET_LOW_FUSE_BITS);
  uint8_t f_cksel = ~(FUSE_CKSEL0 & FUSE_CKSEL1) & f_low;
  switch(f_cksel) {
  case (uint8_t)~(FUSE_CKSEL0 & FUSE_CKSEL1):  // Internal 128 kHz Oscillator
    // Fcpu clkIO/2 = 64 kHz
    prescaler = _BV(CLKPS0);
    // T = (64*(0+1)) / 64000 Hz  = 1 ms
    OCR0A = 0;
    break;
  case (uint8_t)~FUSE_CKSEL1:  // 9.6 MHz
    // Fcpu clkIO/2 = 4.8 MHz
    prescaler = _BV(CLKPS0);
    // continue in 4.8 MHz section
  case (uint8_t)~FUSE_CKSEL0:  // 4.8 MHz
    // T = (64*(74+1)) / 4800000 Hz = 1 ms
    OCR0A = 74;
    break;
  }
  // prescaler
  if(prescaler) {
    CLKPR = _BV(CLKPCE);
    CLKPR = prescaler;
  }
  // Timer0 CTC mode 2, Toggle OC0A on Compare Match
  TCCR0A = _BV(COM0A0) | _BV(WGM01);
  // Timer0 clkIO/64
  TCCR0B = _BV(CS01) | _BV(CS00);
  // Timer/Counter0 Output Compare Match A Interrupt Enable
  TIMSK0 = _BV(OCIE0A);
  // output
  DDRB |= OUTPIN_MASK;
  // enable interrupts
  sei();
  while(1) {
    ;
  }
}

Код: Выделить всё

;26.03.2022

.INCLUDE "tn13def.inc"
;.INCLUDE "tn13Adef.inc"

.equ	Fo=9600000
;.equ	Fo=1200000
.equ	Fout=273	; задаваемая частота на выходе *100

.CSEG

.ORG $000
RESET:
	RJMP	START

.ORG $006
T0_COMPA:
	SBIW	YL,1
	BRCS	COMPA_OUT
	BRNE	PC+2
	OUT	OCR0A,R17	; длительность последнего интервала в полупериоде
	RETI
COMPA_OUT:
	SBI	PINB,0
	RET
;*******************
START:
	SBI	DDRB,0
GO:
	LDI	R17,(50*Fo/Fout-(50*Fo/Fout/128-1)*128-1)

	LDI	YH,HIGH(50*Fo/Fout/128-1)
	LDI	YL,LOW(50*Fo/Fout/128-1)

	LDI	R16,1<<SE
	OUT	MCUCR,R16

	LDI	R16,128-1
	OUT	OCR0A,R16
	LDI	R16,1<<WGM01
	OUT	TCCR0A,R16

	LDI	R16,1<<OCIE0A
	OUT	TIMSK0,R16
	OUT	TIFR0,R16

	LDI	R16,1<<CS00
	OUT	TCCR0B,R16

	SEI
WAIT_05P:
	SLEEP
	BRIE	WAIT_05P
		
	RJMP	GO
.EXIT