问怎样用pwm控制步进电机?

#include <mega128.h> void delly(unsigned char A); void drlly(unsigned char B); void main(void) { DDRB=0xff; //PORTB=0xff; delly(1); drlly(1); } void delly(unsigned char A) {TCCR0=0x00; ASSR=0x01; TCNT0=A; OCR0=255-A; // TIFR=0X03; TCCR0=0X7a; // while(!(TIFR&0x02)); } void drlly(unsigned char B) {TCCR2=0x00; ASSR=0x01; TCNT2=B; OCR2=255-B; // TIFR=0X03; TCCR2=0X7a; // while(!(TIFR&0x02)); }