香主，关于STM32F100用新固件库配置系统时钟的问题

只看该作者 · 2011-1-22 09:21

最近有一项目，综合比较下各方面，选择了STM32F100 的片子，也是现学现用，今天想做个SysTick的精准延时，发现新的固件库（3.0的貌似）中SysTick的函数和旧的不一样了，新的函数库中只有SysTick_Config（）这个函数了，而里面的系统时钟貌似只有
//以下为选择CPU的运行频率,系统已经默认了用户是使用8M的晶振了.
//#define SYSCLK_FREQ_HSE HSE_Value //这个值系统默认为8M
//#define SYSCLK_FREQ_20MHz  20000000
//#define SYSCLK_FREQ_36MHz  36000000
//#define SYSCLK_FREQ_48MHz  48000000
#define SYSCLK_FREQ_56MHz  56000000
//#define SYSCLK_FREQ_72MHz  72000000
这几种，然后新库函数中提供的定义如下：
/*******************************************************************************
*  Clock Definitions
*******************************************************************************/
#ifdef SYSCLK_FREQ_HSE
  const uint32_t SystemFrequency       = SYSCLK_FREQ_HSE;       /*!< System Clock Frequency (Core Clock) */
  const uint32_t SystemFrequency_SysClk  = SYSCLK_FREQ_HSE;       /*!< System clock                      */
  const uint32_t SystemFrequency_AHBClk  = SYSCLK_FREQ_HSE;       /*!< AHB System bus speed             */
  const uint32_t SystemFrequency_APB1Clk = SYSCLK_FREQ_HSE;       /*!< APB Peripheral bus 1 (low)  speed */
  const uint32_t SystemFrequency_APB2Clk = SYSCLK_FREQ_HSE;       /*!< APB Peripheral bus 2 (high) speed */
#elif defined SYSCLK_FREQ_20MHz
  const uint32_t SystemFrequency       = SYSCLK_FREQ_20MHz;    /*!< System Clock Frequency (Core Clock) */
  const uint32_t SystemFrequency_SysClk  = SYSCLK_FREQ_20MHz;    /*!< System clock                      */
  const uint32_t SystemFrequency_AHBClk  = SYSCLK_FREQ_20MHz;    /*!< AHB System bus speed             */
  const uint32_t SystemFrequency_APB1Clk = SYSCLK_FREQ_20MHz;    /*!< APB Peripheral bus 1 (low)  speed */
  const uint32_t SystemFrequency_APB2Clk = SYSCLK_FREQ_20MHz;    /*!< APB Peripheral bus 2 (high) speed */
#elif defined SYSCLK_FREQ_36MHz
  const uint32_t SystemFrequency       = SYSCLK_FREQ_36MHz;    /*!< System Clock Frequency (Core Clock) */
  const uint32_t SystemFrequency_SysClk  = SYSCLK_FREQ_36MHz;    /*!< System clock                      */
  const uint32_t SystemFrequency_AHBClk  = SYSCLK_FREQ_36MHz;    /*!< AHB System bus speed             */
  const uint32_t SystemFrequency_APB1Clk = SYSCLK_FREQ_36MHz;    /*!< APB Peripheral bus 1 (low)  speed */
  const uint32_t SystemFrequency_APB2Clk = SYSCLK_FREQ_36MHz;    /*!< APB Peripheral bus 2 (high) speed */
#elif defined SYSCLK_FREQ_48MHz
  const uint32_t SystemFrequency       = SYSCLK_FREQ_48MHz;    /*!< System Clock Frequency (Core Clock) */
  const uint32_t SystemFrequency_SysClk  = SYSCLK_FREQ_48MHz;    /*!< System clock                      */
  const uint32_t SystemFrequency_AHBClk  = SYSCLK_FREQ_48MHz;    /*!< AHB System bus speed             */
  const uint32_t SystemFrequency_APB1Clk = (SYSCLK_FREQ_48MHz/2);  /*!< APB Peripheral bus 1 (low)  speed */
  const uint32_t SystemFrequency_APB2Clk = SYSCLK_FREQ_48MHz;    /*!< APB Peripheral bus 2 (high) speed */
#elif defined SYSCLK_FREQ_56MHz
  const uint32_t SystemFrequency       = SYSCLK_FREQ_56MHz;    /*!< System Clock Frequency (Core Clock) */
  const uint32_t SystemFrequency_SysClk  = SYSCLK_FREQ_56MHz;    /*!< System clock                      */
  const uint32_t SystemFrequency_AHBClk  = SYSCLK_FREQ_56MHz;    /*!< AHB System bus speed             */
  const uint32_t SystemFrequency_APB1Clk = (SYSCLK_FREQ_56MHz/2);  /*!< APB Peripheral bus 1 (low)  speed */
  const uint32_t SystemFrequency_APB2Clk = SYSCLK_FREQ_56MHz;    /*!< APB Peripheral bus 2 (high) speed */
#elif defined SYSCLK_FREQ_72MHz
  const uint32_t SystemFrequency       = SYSCLK_FREQ_72MHz;    /*!< System Clock Frequency (Core Clock) */
  const uint32_t SystemFrequency_SysClk  = SYSCLK_FREQ_72MHz;    /*!< System clock                      */
  const uint32_t SystemFrequency_AHBClk  = SYSCLK_FREQ_72MHz;    /*!< AHB System bus speed             */
  const uint32_t SystemFrequency_APB1Clk = (SYSCLK_FREQ_72MHz/2);  /*!< APB Peripheral bus 1 (low)  speed */
  const uint32_t SystemFrequency_APB2Clk = SYSCLK_FREQ_72MHz;    /*!< APB Peripheral bus 2 (high) speed */
#else /*!< HSI Selected as System Clock source */
  const uint32_t SystemFrequency       = HSI_Value;             /*!< System Clock Frequency (Core Clock) */
  const uint32_t SystemFrequency_SysClk  = HSI_Value;             /*!< System clock                      */
  const uint32_t SystemFrequency_AHBClk  = HSI_Value;             /*!< AHB System bus speed             */
  const uint32_t SystemFrequency_APB1Clk = HSI_Value;             /*!< APB Peripheral bus 1 (low)  speed */
  const uint32_t SystemFrequency_APB2Clk = HSI_Value;             /*!< APB Peripheral bus 2 (high) speed */
#endif

我的问题是，STM32F100的最大频率只有24M，在这里要怎么选择呢？
看了网上有人试验过，说只有在选择56M 的时候SysTick延时稳定，但STM32F100最大只有24M，选56M 的话这算正常工作么？

有点不解，所以还请论坛各位朋友帮忙看看。。
香主可以讲讲么？