有如下两个程序，RCC_Configuration用于配置Clock,Timer2_Configuration配置TIM2,能在A0管脚输出10K的PWM波形；把RCC_PCLK1Config(RCC_HCLK_Div4)改成RCC_PCLK1Config(RCC_HCLK_Div2)，能输出20K的PWM波，符合期望；但是改成RCC_PCLK1Config(RCC_HCLK_Div1)后，应该输出40K的PWM波形，结果却是20K的PWM；请问是什么原因。
多谢帮助！
void RCC_Configuration(void)
{
/* RCC system reset(for debug purpose) */
RCC_DeInit();
RCC_HSICmd(ENABLE);
/* PLLCLK = 8MHz * 9 = 72 MHz */
RCC_PLLConfig(RCC_PLLSource_HSI_Div2, RCC_PLLMul_9);
/* Enable PLL */
RCC_PLLCmd(ENABLE);
FLASH_SetLatency(FLASH_Latency_2);
/* Enable Prefetch Buffer */
FLASH_PrefetchBufferCmd(FLASH_PrefetchBuffer_Enable);
RCC_HCLKConfig(RCC_SYSCLK_Div1);
/* PCLK2 = HCLK */
RCC_PCLK2Config(RCC_HCLK_Div1);
/* PCLK1 = HCLK */
RCC_PCLK1Config(RCC_HCLK_Div4);
/* Wait till PLL is ready */
while(RCC_GetFlagStatus(RCC_FLAG_PLLRDY) == RESET)
{
}
/* Select PLL as system clock source */
RCC_SYSCLKConfig(RCC_SYSCLKSource_PLLCLK);
/* Wait till PLL is used as system clock source */
while(RCC_GetSYSCLKSource() != 0x08)
{
}
/* TIM2 clock enable */
RCC_APB1PeriphClockCmd(RCC_APB1Periph_TIM2, ENABLE);
/* GPIOA and GPIOB clock enable */
RCC_APB2PeriphClockCmd(RCC_APB2Periph_GPIOA|RCC_APB2Periph_GPIOC, ENABLE);
/* Enable GPIOA, GPIOB and AFIO clocks */
RCC_APB2PeriphClockCmd(RCC_APB2Periph_GPIOA | RCC_APB2Periph_GPIOB |RCC_APB2Periph_AFIO, ENABLE);
}
void Timer2_Configuration(void)
{
GPIO_InitStructure.GPIO_Pin = GPIO_Pin_0;
GPIO_InitStructure.GPIO_Mode = GPIO_Mode_AF_PP;
GPIO_InitStructure.GPIO_Speed = GPIO_Speed_50MHz;
GPIO_Init(GPIOA, &GPIO_InitStructure);
/* Time base configuration */
TIM_TimeBaseStructure.TIM_Period = 1800;
TIM_TimeBaseStructure.TIM_Prescaler = 0x00;
TIM_TimeBaseStructure.TIM_ClockDivision = 0x0;
TIM_TimeBaseStructure.TIM_CounterMode = TIM_CounterMode_Up;
TIM_TimeBaseInit(TIM2, &TIM_TimeBaseStructure);
/* Output Compare */
TIM_OCInitStructure.TIM_OCMode = TIM_OCMode_PWM1;
TIM_OCInitStructure.TIM_OutputState = TIM_OutputState_Enable;
TIM_OCInitStructure.TIM_Pulse = 900;
TIM_OCInitStructure.TIM_OCPolarity = TIM_OCPolarity_High;
TIM_OC1Init(TIM2, &TIM_OCInitStructure);
TIM_OC1PreloadConfig(TIM2, TIM_OCPreload_Enable);
TIM_ARRPreloadConfig(TIM2, ENABLE);
TIM_Cmd(BUCK_PWM_TIM, ENABLE);
} |
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