【经验分享】STM32F103固件库源码解析——RCC_APB2PeriphClockCmd

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STMCU小助手发布时间：2022-5-2 09:13

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文章简介:	STM32F103固件库源码解析——RCC_APB2PeriphClockCmd

RCC_APB2PeriphClockCmd函数用来开启或关闭APB2外设时钟，

该函数总览如下，

/**
* @brief Enables or disables the High Speed APB (APB2) peripheral clock.
* @param RCC_APB2Periph: specifies the APB2 peripheral to gates its clock.
* This parameter can be any combination of the following values:
* @arg RCC_APB2Periph_AFIO, RCC_APB2Periph_GPIOA, RCC_APB2Periph_GPIOB,
* RCC_APB2Periph_GPIOC, RCC_APB2Periph_GPIOD, RCC_APB2Periph_GPIOE,
* RCC_APB2Periph_GPIOF, RCC_APB2Periph_GPIOG, RCC_APB2Periph_ADC1,
* RCC_APB2Periph_ADC2, RCC_APB2Periph_TIM1, RCC_APB2Periph_SPI1,
* RCC_APB2Periph_TIM8, RCC_APB2Periph_USART1, RCC_APB2Periph_ADC3,
* RCC_APB2Periph_TIM15, RCC_APB2Periph_TIM16, RCC_APB2Periph_TIM17,
* RCC_APB2Periph_TIM9, RCC_APB2Periph_TIM10, RCC_APB2Periph_TIM11
* @param NewState: new state of the specified peripheral clock.
* This parameter can be: ENABLE or DISABLE.
* @retval None
*/
void RCC_APB2PeriphClockCmd(uint32_t RCC_APB2Periph, FunctionalState NewState)
{
/* Check the parameters */
assert_param(IS_RCC_APB2_PERIPH(RCC_APB2Periph));
assert_param(IS_FUNCTIONAL_STATE(NewState));
if (NewState != DISABLE)
{
RCC->APB2ENR |= RCC_APB2Periph;
}
else
{
RCC->APB2ENR &= ~RCC_APB2Periph;
}
}

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如下，FunctionalState是枚举类型，DISABLE 值为0，ENABLE 值为1，使用该参数判断是否要开相应的时钟。

typedef enum {DISABLE = 0, ENABLE = !DISABLE} FunctionalState;

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在stm32f10x_rcc.h中，有APB2_peripheral的宏定义。

/** @defgroup APB2_peripheral
* @{
*/
#define RCC_APB2Periph_AFIO ((uint32_t)0x00000001)
#define RCC_APB2Periph_GPIOA ((uint32_t)0x00000004)
#define RCC_APB2Periph_GPIOB ((uint32_t)0x00000008)
#define RCC_APB2Periph_GPIOC ((uint32_t)0x00000010)
#define RCC_APB2Periph_GPIOD ((uint32_t)0x00000020)
#define RCC_APB2Periph_GPIOE ((uint32_t)0x00000040)
#define RCC_APB2Periph_GPIOF ((uint32_t)0x00000080)
#define RCC_APB2Periph_GPIOG ((uint32_t)0x00000100)
#define RCC_APB2Periph_ADC1 ((uint32_t)0x00000200)
#define RCC_APB2Periph_ADC2 ((uint32_t)0x00000400)
#define RCC_APB2Periph_TIM1 ((uint32_t)0x00000800)
#define RCC_APB2Periph_SPI1 ((uint32_t)0x00001000)
#define RCC_APB2Periph_TIM8 ((uint32_t)0x00002000)
#define RCC_APB2Periph_USART1 ((uint32_t)0x00004000)
#define RCC_APB2Periph_ADC3 ((uint32_t)0x00008000)
#define RCC_APB2Periph_TIM15 ((uint32_t)0x00010000)
#define RCC_APB2Periph_TIM16 ((uint32_t)0x00020000)
#define RCC_APB2Periph_TIM17 ((uint32_t)0x00040000)
#define RCC_APB2Periph_TIM9 ((uint32_t)0x00080000)
#define RCC_APB2Periph_TIM10 ((uint32_t)0x00100000)
#define RCC_APB2Periph_TIM11 ((uint32_t)0x00200000)
#define IS_RCC_APB2_PERIPH(PERIPH) ((((PERIPH) & 0xFFC00002) == 0x00) && ((PERIPH) != 0x00))

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APB2 外设时钟使能寄存器(RCC_APB2ENR)如下，可见APB2_peripheral的宏定义正好对应了寄存器RCC_APB2ENR的对应位。

IS_RCC_APB2_PERIPH(PERIPH)宏定义实现了输入判断，当输入参数不符合RCC_APB2Periph的数据格式时，返回0。

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if (NewState != DISABLE)
{
RCC->APB2ENR |= RCC_APB2Periph;
}
else
{
RCC->APB2ENR &= ~RCC_APB2Periph;
}

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这段代码是开启对应APB2外设时钟的主要实现语句。

如下，RCC是指向RCC_TypeDef结构体类型的指针，RCC_BASE就是RCC寄存器的映射地址，也就是RCC指针的值。

#define RCC ((RCC_TypeDef *) RCC_BASE)

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RCC_TypeDef结构体的定义如下，

/**
* @brief Reset and Clock Control
*/
typedef struct
{
__IO uint32_t CR;
__IO uint32_t CFGR;
__IO uint32_t CIR;
__IO uint32_t APB2RSTR;
__IO uint32_t APB1RSTR;
__IO uint32_t AHBENR;
__IO uint32_t APB2ENR;
__IO uint32_t APB1ENR;
__IO uint32_t BDCR;
__IO uint32_t CSR;
#ifdef STM32F10X_CL
__IO uint32_t AHBRSTR;
__IO uint32_t CFGR2;
#endif /* STM32F10X_CL */
#if defined (STM32F10X_LD_VL) || defined (STM32F10X_MD_VL) || defined (STM32F10X_HD_VL)
uint32_t RESERVED0;
__IO uint32_t CFGR2;
#endif /* STM32F10X_LD_VL || STM32F10X_MD_VL || STM32F10X_HD_VL */
} RCC_TypeDef;