1us

//适配主频为120MHz的单片机
void Delay_us(int16_t nus) 
{int32_t temp; SysTick->LOAD = nus*15; //120MHzSysTick->VAL=0X00;SysTick->CTRL=0X01;do { temp=SysTick->CTRL;}while((temp&0x01)&&(!(temp&(1<<16))));SysTick->CTRL=0x00; SysTick->VAL =0X00; 
}

1ms

void Delay_ms(int16_t t)
{unsigned long a;a = t;while(a--){Delay_us(1000);}
}