Using SysCtlClockGet() to generate different clock; error

Hi Amit,

Ok , does not mean even if those parameters are not used for particular setting but we should mention them. right?

1. Case1 : Internal 16Mhz crystal as system clock
SysCtlClockSet(SYSCTL_SYSDIV_2_5 | SYSCTL_USE_OSC | SYSCTL_OSC_INT| SYSCTL_XTAL_16MHZ );


2. Case2 : 80Mhz as system clock using Internal 16Mhz crystal
SysCtlClockSet(SYSCTL_SYSDIV_2_5 | SYSCTL_USE_PLL | SYSCTL_OSC_INT| SYSCTL_XTAL_16MHZ);


3. Case3 : External 16Mhz crystal as system clock
SysCtlClockSet(SYSCTL_SYSDIV_2_5 |SYSCTL_USE_OSC |SYSCTL_OSC_MAIN | SYSCTL_XTAL_16MHZ );


4. Case4 : 80Mhz as system clock using External 16Mhz crystal
SysCtlClockSet(SYSCTL_SYSDIV_2_5 | SYSCTL_USE_PLL | SYSCTL_OSC_MAIN | SYSCTL_XTAL_16MHZ );

Hi Amit,

I think I have done it wrong.

Today i have configured the systick timer & inverted a pin to measure the exact clock freq.

I think to correctly configure the clock to make it 16Mhz external crystal the correct setting would be:

SysCtlClockSet(SYSCTL_SYSDIV_1 |SYSCTL_USE_OSC |SYSCTL_OSC_MAIN | SYSCTL_XTAL_16MHZ );

1. If I had used SYSCTL_SYSDIV_1  , the on/off time of pin is 1ms, which is correct. because I had write 16000 in systick load register. 

But if I use SYSCTL_SYSDIV_2_5 , the on/off time comes out to be 3ms which is wrong.

Below is the code which I have used.

void SysTick_Handler(void)
{
    GPIOF_AHB->DATA ^= REG32_BIT_2;         /* invert the bit */
}


void func(void)
{
/* set clock */
	SysCtlClockSet(SYSCTL_SYSDIV_1 | SYSCTL_USE_OSC | SYSCTL_OSC_INT  | SYSCTL_XTAL_16MHZ );   /* 16Mhz internal */
	//SysCtlClockSet(SYSCTL_SYSDIV_2_5 | SYSCTL_USE_OSC | SYSCTL_OSC_INT  | SYSCTL_XTAL_16MHZ );   /* wrong */
	
/* PF2 as output low */    
    SYSCTL->RCGCGPIO |= REG32_BIT_5;                /* enable PORTF clock */
    while(! (SYSCTL->PRGPIO & REG32_BIT_5));        /* while periph ready */
    SYSCTL->GPIOHBCTL |= REG32_BIT_5;               /* enable access to AHB bus  */

    GPIOF_AHB->DATA     &= (u32_t)(~REG32_BIT_2);  /* pin low on output */  
    GPIOF_AHB->DIR      |= REG32_BIT_2;            /* make as output */
    GPIOF_AHB->AFSEL    &= (u32_t)(~REG32_BIT_2);  /* used as GPIO */
    GPIOF_AHB->PUR      &= (u32_t)(~REG32_BIT_2);  /* pull up disabled */
    GPIOF_AHB->PDR      &= (u32_t)(~REG32_BIT_2);  /* pull down disabled */
    GPIOF_AHB->ODR      &= (u32_t)(~REG32_BIT_2);  /* not open drain */
    GPIOF_AHB->AMSEL    &= (u32_t)(~REG32_BIT_2);  /* analog function disabled */  
    GPIOF_AHB->DR2R     |= REG32_BIT_2;            /* 2mA drive enable */
    GPIOF_AHB->SLR      &= (u32_t)(~REG32_BIT_2);  /* slew disabled */
    GPIOF_AHB->DEN      |= REG32_BIT_2;            /* digital function enabled */
	
	
/* systick regsiter */
    SysTick->CTRL &= ((uint32_t)~REG32_BIT_1);   /* disable systick */
    SysTick->CTRL |= REG32_BIT_2;                /* sysytem clock as clock source */
    SysTick->CTRL |= REG32_BIT_1;                /* enable systick interrupt */
    SysTick->VAL = 0U;                           /* clesr counter */
    SysTick->LOAD = 15999U;                      /* (15999 + 1) / 16  = 1000us */
    SysTick->CTRL |= REG32_BIT_0;                /* start the counter */

    while(1)
    {
    }    	

}