STM8S的时钟配置通过：CLK_CKDIVR寄存器，而CLK_CKDIVR一个是配置HSI分频，另一个是配置CPU的分频
static void CLK_Config(void)
{
CLK_DeInit();
/* Clock divider to HSI/1 */
CLK_HSIPrescalerConfig(CLK_PRESCALER_HSIDIV1); // 只配置HSI分频率，CPU分频率１
/* Output Fcpu on CLK_CCO pin */
CLK_CCOConfig(CLK_OUTPUT_MASTER);
}
/**
* @brief Configure system clock to run at Maximum clock speed and output the
* system clock on CCO pin
* @param None
* @retval None
*/
static void CLK_Config(void)
{
ErrorStatus status = FALSE;
CLK_DeInit();
/* Configure the Fcpu to DIV1*/
CLK_SYSCLKConfig(CLK_PRESCALER_CPUDIV1); // 配置CPU分频
/* Configure the HSI prescaler to the optimal value */
CLK_SYSCLKConfig(CLK_PRESCALER_HSIDIV1); // 配置HSI分频
/* Output Fcpu on CLK_CCO pin */
CLK_CCOConfig(CLK_OUTPUT_CPU);
/* Configure the system clock to use HSE clock source and to run at 24Mhz */
status = CLK_ClockSwitchConfig(CLK_SWITCHMODE_AUTO, CLK_SOURCE_HSE, DISABLE, CLK_CURRENTCLOCKSTATE_DISABLE);
while (ButtonPressed == FALSE)
{
}
/* Configure the system clock to use HSI clock source and to run at 16Mhz */
status = CLK_ClockSwitchConfig(CLK_SWITCHMODE_AUTO, CLK_SOURCE_HSI, DISABLE, CLK_CURRENTCLOCKSTATE_DISABLE);
}
// CLK_SYSCLKConfig通过CLK_Prescaler值的最高位来区分是配置HSI分频，还是CPU分频的。这个函数有两个功能。而CLK_HSIPrescalerConfig是直接配置HSI分频的，CPU分频配置成１
void CLK_SYSCLKConfig(CLK_Prescaler_TypeDef CLK_Prescaler)
{
/* check the parameters */
assert_param(IS_CLK_PRESCALER_OK(CLK_Prescaler));
if (((uint8_t)CLK_Prescaler & (uint8_t)0x80) == 0x00) /* Bit7 = 0 means HSI divider */
{
CLK->CKDIVR &= (uint8_t)(~CLK_CKDIVR_HSIDIV);
CLK->CKDIVR |= (uint8_t)((uint8_t)CLK_Prescaler & (uint8_t)CLK_CKDIVR_HSIDIV);
}
else /* Bit7 = 1 means CPU divider */
{
CLK->CKDIVR &= (uint8_t)(~CLK_CKDIVR_CPUDIV);
CLK->CKDIVR |= (uint8_t)((uint8_t)CLK_Prescaler & (uint8_t)CLK_CKDIVR_CPUDIV);
}
}