3 delay functions in STM32

The first delay function:

void delay(u16 num)

{

  u16 i,j;

  for(i=0;i

    for(j=0;j<0x800;j++);

}

eg: delay(50);

The second delay function:

void Delayms(u16 ms)

{

  u16 i,j;

  u8k;

  for(i=0;i

    for(j=0;j<0x0500;j++) k++;

}

The third delay function:

static u8 fac_us=0;//us delay multiplier

static u16 fac_ms=0;//ms delay multiplier

//Initialize delay function

//SYSTICK clock is fixed to 1/8 of the HCLK clock

//SYSCLK: system clock

void delay_init(u8 SYSCLK)

{

SysTick->CTRL&=0xfffffffb;//Clear bit2, select external clock HCLK/8

fac_us=SYSCLK/8;    

fac_ms=(u16)fac_us*1000;

}    

//Delay nms

//Pay attention to the range of nms

//SysTick->LOAD is a 24-bit register, so the maximum delay is:

//nms<=0xffffff*8*1000/SYSCLK

//SYSCLK unit is Hz, nms unit is ms

//Under 72M conditions, nms<=1864 

void delay_ms(u16 nms)

{    

u32 temp;   

SysTick->LOAD=(u32)nms*fac_ms;//Time loading (SysTick->LOAD is 24bit)

SysTick->VAL =0x00; //Clear the counter

SysTick->CTRL=0x01; //Start the countdown  

do

{

temp=SysTick->CTRL;

}

while(temp&0x01&&!(temp&(1<<16))); //Wait for time to arrive   

SysTick->CTRL=0x00; //Close counter

SysTick->VAL =0X00; //Clear the counter      

}   

//Delay nus

//nus is the number of us to be delayed.       

void delay_us(u32 nus)

{

u32 temp;      

SysTick->LOAD=nus*fac_us; //Time loading    

SysTick->VAL=0x00; //Clear the counter

SysTick->CTRL=0x01; //Start the countdown  

do

{

temp=SysTick->CTRL;

}

while(temp&0x01&&!(temp&(1<<16))); //Wait for time to arrive   

SysTick->CTRL=0x00; //Close counter

SysTick->VAL =0X00; //Clear the counter  

}