STM8 internal clock switching

Introduction: There is a clock switching function inside the STM8, which can change the clock frequency when needed. The board is STM8_Discovery, and the LED is PD0.

The procedure is as follows:

//Function: STM8 internal clock frequency division switch

#include "iostm8s105c6.h"

// Function: Delay function

// Input parameter: ms -- the number of milliseconds to delay, assuming the CPU frequency is 2MHZ

void DelayMS(unsigned int ms)

{

unsigned char i;

while(ms != 0)

{

for(i=0;i<250;i++)

{

}

for(i=0;i<75;i++)

{

}

ms--;

}

}

//GPIO port initialization

void GPIO_init(void)

{

PD_DDR = 0x01; //Configure the direction register PD0 output of the PD port

PD_CR1 = 0x01; //Set PD0 to push-pull output

PD_CR2 = 0x00;

}

// Clock initialization

void CLK_init(void)

{

CLK_SWR = 0xE1; //Select the 16MHZ RC oscillator inside the chip as the main clock

}

main()

{

int i;

GPIO_init();

CLK_init();

while(1) //Enter an infinite loop

{

//Set the CPU clock divider below so that CPU clock = main clock / 4

//Through the LED, we can see that the speed of the program has indeed dropped significantly

CLK_CKDIVR = 0x1A; // Main clock = 16MHZ/8 = 2MHz

//CPU clock = main clock / 4 = 500KHZ

for(i=0;i<10;i++)

{

PD_ODR = 0x01;

DelayMS(100);

PD_ODR = 0x00;

DelayMS(100);

}

// Set the CPU clock divider below so that the CPU clock = the main clock

CLK_CKDIVR = 0x0A; // Main clock = 16MHZ/2 = 8MHz

//CPU clock = main clock/4 = 2MHZ

for(i=0;i<10;i++)

{

PD_ODR = 0x01;

DelayMS(100);

PD_ODR = 0x00;

DelayMS(100);

}

}

}