AVR 單片機(jī)初值計(jì)算

ID:83710 · 發(fā)表于 2015-6-24 21:25

使用芯片 AT Mega16    外部晶振 4.00MHz
定時(shí)器1 （16位定時(shí)器）寄存器 TCCR1B = 0x04 設(shè)定 256預(yù)分頻
要利用定時(shí)器定時(shí)1秒
1，4000000 / 256 = 15625 說明定時(shí)器每當(dāng) 1/15625 秒就會觸發(fā)一次中斷
2，65535 - 15625 = 49910 計(jì)算出要累加多少次才能在1秒后出發(fā)定時(shí)器1的溢出中斷
3，49910 <==> C2 F6          將計(jì)算后的值換算成16進(jìn)制
4， TCNT1H = 0xC2 ;          對寄存器賦值
   TCNT1L = 0xF6 ;

=============================================================================
例如用16位定時(shí)器TIMER1,4MHZ晶振，256分頻，100ms定時(shí)，如何求得初值賦給TCNT1?
65536-(4M/256)*0.1=63973.5
其中，4M是晶體頻率，0.1是定時(shí)時(shí)長單位秒。
對于8位的定時(shí)器
T=(2^8-計(jì)數(shù)初值)*晶振周期*分頻數(shù)=(2^8-計(jì)數(shù)初值)/晶振頻率*分頻數(shù)
計(jì)數(shù)初值=2^8-T/晶振周期/分頻數(shù)=2^8-T*晶振頻率/分頻數(shù)
因?yàn)锳VR一指令一周期

ID:690448 · 發(fā)表于 2020-11-19 18:52

ICC-AVR application builder 點(diǎn)幾下鼠標(biāo)就可完成

推薦大家試一試

//ICC-AVR application builder : 2020/11/19 18:50:34
// Target : M16
// Crystal: 4.0000Mhz
#include <iom16v.h>
#include <macros.h>
void port_init(void)
{
PORTA = 0x00;
DDRA = 0x00;
PORTB = 0x00;
DDRB = 0x00;
PORTC = 0x00; //m103 output only
DDRC = 0x00;
PORTD = 0x00;
DDRD = 0x00;
}
//TIMER1 initialize - prescale:256
// WGM: 0) Normal, TOP=0xFFFF
// desired value: 1Sec
// actual value: 1.000Sec (0.0%)
void timer1_init(void)
{
TCCR1B = 0x00; //stop
TCNT1H = 0xC2; //setup
TCNT1L = 0xF7;
OCR1AH = 0x3D;
OCR1AL = 0x09;
OCR1BH = 0x3D;
OCR1BL = 0x09;
ICR1H = 0x3D;
ICR1L = 0x09;
TCCR1A = 0x00;
TCCR1B = 0x04; //start Timer
}
#pragma interrupt_handler timer1_ovf_isr:iv_TIM1_OVF
void timer1_ovf_isr(void)
{
//TIMER1 has overflowed
TCNT1H = 0xC2; //reload counter high value
TCNT1L = 0xF7; //reload counter low value
}
//call this routine to initialize all peripherals
void init_devices(void)
{
//stop errant interrupts until set up
CLI(); //disable all interrupts
port_init();
timer1_init();
MCUCR = 0x00;
GICR = 0x00;
TIMSK = 0x04; //timer interrupt sources
SEI(); //re-enable interrupts
//all peripherals are now initialized
}
//
void main(void)
{
init_devices();
//insert your functional code here...
}

復(fù)制代碼

ID:739227 · 發(fā)表于 2020-4-27 19:30

非常好！不錯(cuò)！非常感謝樓主

ID:808608 · 發(fā)表于 2020-10-10 14:23

非常好！不錯(cuò)！非常感謝師傅

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AVR 單片機(jī)初值計(jì)算

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