纳闷的PWM问题

只看该作者 · 2007-6-3 21:22

如何使用PWM中的方式15?原程序如下:
//ICC-AVR application builder : 2007-5-28 19:25:02
// Target : T2313
// Crystal: 7.3728Mhz

#include <iot2313v.h>
#include <macros.h>
#pragma ctask timer1_init,port_init,uart0_init,init_devices,interrupt_handler timer1_capt_isr

unsigned char icpl,icph,flag;

void port_init(void)
{
PORTA = 0x00;
DDRA  = 0x00;
PORTB = 0x00;
DDRB  = 0x10;
PORTD = 0x00;
DDRD  = 0x3C;
}

//TIMER1 initialize - prescale:1
// WGM: 15) PWM fast, TOP=OCRnA
// desired value: 550uSec
// actual value: 549.995uSec (0.0%)

void timer1_init(void)
{
TCCR1B = 0x00; //stop timer
TCNT1H = 0x00; //set count value
TCNT1L = 0x00;
  OCR1AH  = 0xFF; //set compare value
OCR1AL  = 0xFF;
OCR1BH  = 0xF0; //set compare value
OCR1BL  = 0x29;
TCCR1A = 0x23;
TCCR1B = 0x99; //start Timer

}

#pragma  interrupt_handler timer1_capt_isr:4
void timer1_capt_isr(void)
{
//timer 1 input capture event, read (int)value in ICR1 using;
if(!flag)
{
icpl=ICR1L;   //Read low byte first (important)
icph=ICR1H;    //Read high byte and shift into top byte
flag=1;
}
}

/*
#pragma interrupt_handler timer1_compb_isr:13
void timer1_compb_isr(void)
{ //compare occured TCNT1=OCR1A
}

#pragma interrupt_handler timer1_ovf_isr:6
void timer1_ovf_isr(void)
{
//TIMER1 has overflowed
TCNT1H = 0xF0; //reload counter high value
TCNT1L = 0x2A; //reload counter low value
}
*/

//UART0 initialize
// desired baud rate: 19200
// actual: baud rate:19200 (0.0%)
void uart0_init(void)
{
UCSRB = 0x00; //disable while setting baud rate

UCSRA = 0x00;
UCSRC = 0x06;
UBRRH = 0x00; //set baud rate upper
UBRRL = 0x17; //set baud rate lower
UCSRB = 0x18; //enable
}

//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();
uart0_init();

MCUCR = 0x00;
GIMSK = 0x00;
TIMSK = 0x08;
SEI(); //re-enable interrupts
//all peripherals are now initialized
}

//
void main(void)
{
init_devices();
//insert your functional code here...
while(1)
{
if(flag)
{
while(!(UCSRA&0x20));
UDR=icph;
while(!(UCSRA&0x20));
UDR=icpl;
flag=0;
}

}

}

软件仿真调试时虽然设置的还是模式15,但是却变成模式9下工作,硬件运行时用示波器观察波形周期,也是在模式9下工作.OCRA和OCRB的高6位被舍弃一样，为什么？

只看该作者 · 2007-6-3 21:40

的问题，

只看该作者 · 2007-6-4 11:01

2楼的兄弟，我有证据认为不是AVRSTUDIO的问题。我把程序写到ATTINY2313中去，用面包板搭建一个硬件测试电路，晶振用的是11.059MHz的（程序是用7.3728Mhz),然后测试PWM管脚输出波形，测得周期为93us，对照晶振频率，TOP计数值（OCR1A）大约就在1024左右（0x3ff），而用AVRSTUDIO软件仿真时初始化中OCR1A被设置成0XFFFF，过后不知为何自己就变成了0x3fff,而前6位变成空的且不可设置。两种试验方法结果都一样。
我测试高电平时间为3.8us，相当于计数值为0x29，而OCR1B中设置的是OXF029，用AVRSTUDIO软件仿真时初始化中OCR1B被设置成0XF029，过后OCR1A变成了0x3fff的同时OCR1B变成了0X0029。
我的程序是否有问题还是AVR单片机根本就不支持PWM模式15？