ST STM32F31xx - System AHB, APB1 and APB2 Busses Clocks Configuration Functions

Reset and clock control (RCC)
UM1581
322/584
DocID023800 Rev 1
Function Name
void RCC_MCOConfig ( uint8_t RCC_MCOSource)
Function Description
Selects the clock source to output on MCO pin (PA8).
Parameters
 RCC_MCOSource : specifies the clock source to output.
This parameter can be one of the following values:
 RCC_MCOSource_NoClock : No clock selected.
 RCC_MCOSource_LSI : LSI oscillator clock selected.
 RCC_MCOSource_LSE : LSE oscillator clock selected.
 RCC_MCOSource_SYSCLK : System clock selected.
 RCC_MCOSource_HSI : HSI oscillator clock selected.
 RCC_MCOSource_HSE : HSE oscillator clock
selected.
 RCC_MCOSource_PLLCLK_Div2 : PLL clock
selected.
Return values
 None.
Notes
 PA8 should be configured in alternate function mode.
 The MCOF flag is set once the MCO clock source switch is
effective.
18.2.7 System AHB, APB1 and APB2 busses clocks configuration functions
18.2.7.1 RCC_SYSCLKConfig
Function Name
void RCC_SYSCLKConfig ( uint32_t RCC_SYSCLKSource)
Function Description
Configures the system clock (SYSCLK).
Parameters
 RCC_SYSCLKSource : specifies the clock source used as
system clock source This parameter can be one of the
following values:
 RCC_SYSCLKSource_HSI : HSI selected as system
clock source
 RCC_SYSCLKSource_HSE : HSE selected as system
clock source
 RCC_SYSCLKSource_PLLCLK : PLL selected as
system clock source
Return values
 None.
Notes
 The HSI is used (enabled by hardware) as system clock
source after startup from Reset, wake-up from STOP and
STANDBY mode, or in case of failure of the HSE used
directly or indirectly as system clock (if the Clock Security
System CSS is enabled).
 A switch from one clock source to another occurs only if the
target clock source is ready (clock stable after startup delay or
PLL locked). If a clock source which is not yet ready is