CMSIS Cortex-M4 Device Peripheral Access Layer System Source File. This file contains the system clock configuration for STM32F4xx devices, and is generated by the clock configuration tool stm32f4xx_Clock_Configuration_V1.0.0.xls. More...

#include "stm32f4xx.h"

Macros
#define	VECT_TAB_OFFSET 0x00

#define	PLL_M 4

#define	PLL_N 168

#define	PLL_P 2

#define	PLL_Q 7

Functions
static void	SetSysClock (void)
	Configures the System clock source, PLL Multiplier and Divider factors, AHB/APBx prescalers and Flash settings This function should be called only once the RCC clock configuration is reset to the default reset state (done in SystemInit() function). More...

void	SystemInit (void)
	Setup the microcontroller system Initialize the Embedded Flash Interface, the PLL and update the SystemFrequency variable. More...

void	SystemCoreClockUpdate (void)
	Update SystemCoreClock variable according to Clock Register Values. The SystemCoreClock variable contains the core clock (HCLK), it can be used by the user application to setup the SysTick timer or configure other parameters. More...

Variables
uint32_t	SystemCoreClock = 168000000

__I uint8_t	AHBPrescTable [16] = {0, 0, 0, 0, 0, 0, 0, 0, 1, 2, 3, 4, 6, 7, 8, 9}

Detailed Description

CMSIS Cortex-M4 Device Peripheral Access Layer System Source File. This file contains the system clock configuration for STM32F4xx devices, and is generated by the clock configuration tool stm32f4xx_Clock_Configuration_V1.0.0.xls.

Author: MCD Application Team

Version: V1.0.0

Date

30-September-2011

This file provides two functions and one global variable to be called from user application:
- SystemInit(): Setups the system clock (System clock source, PLL Multiplier and Divider factors, AHB/APBx prescalers and Flash settings), depending on the configuration made in the clock xls tool. This function is called at startup just after reset and before branch to main program. This call is made inside the "startup_stm32f4xx.s" file.
- SystemCoreClock variable: Contains the core clock (HCLK), it can be used by the user application to setup the SysTick timer or configure other parameters.
- SystemCoreClockUpdate(): Updates the variable SystemCoreClock and must be called whenever the core clock is changed during program execution.
After each device reset the HSI (16 MHz) is used as system clock source. Then SystemInit() function is called, in "startup_stm32f4xx.s" file, to configure the system clock before to branch to main program.
If the system clock source selected by user fails to startup, the SystemInit() function will do nothing and HSI still used as system clock source. User can add some code to deal with this issue inside the SetSysClock() function.
The default value of HSE crystal is set to 25MHz, refer to "HSE_VALUE" define in "stm32f4xx.h" file. When HSE is used as system clock source, directly or through PLL, and you are using different crystal you have to adapt the HSE value to your own configuration.

5. This file configures the system clock as follows:

=============================================================================

Supported STM32F4xx device revision | Rev A

System Clock source | PLL (HSE)

SYSCLK(Hz) | 168000000

HCLK(Hz) | 168000000

AHB Prescaler | 1

APB1 Prescaler | 4

APB2 Prescaler | 2

HSE Frequency(Hz) | 16000000

PLL_M | 16

PLL_N | 336

PLL_P | 2

PLL_Q | 7

PLLI2S_N | NA

PLLI2S_R | NA

I2S input clock | NA

VDD(V) | 3.3

Main regulator output voltage | Scale1 mode

Flash Latency(WS) | 5

Prefetch Buffer | OFF

Instruction cache | ON

Data cache | ON

Require 48MHz for USB OTG FS, | Enabled

SDIO and RNG clock |

=============================================================================

Attention

THE PRESENT FIRMWARE WHICH IS FOR GUIDANCE ONLY AIMS AT PROVIDING CUSTOMERS WITH CODING INFORMATION REGARDING THEIR PRODUCTS IN ORDER FOR THEM TO SAVE TIME. AS A RESULT, STMICROELECTRONICS SHALL NOT BE HELD LIABLE FOR ANY DIRECT, INDIRECT OR CONSEQUENTIAL DAMAGES WITH RESPECT TO ANY CLAIMS ARISING FROM THE CONTENT OF SUCH FIRMWARE AND/OR THE USE MADE BY CUSTOMERS OF THE CODING INFORMATION CONTAINED HEREIN IN CONNECTION WITH THEIR PRODUCTS.

Definition in file cmsis_system.c.

Function Documentation

static void SetSysClock ( void )

static

Configures the System clock source, PLL Multiplier and Divider factors, AHB/APBx prescalers and Flash settings This function should be called only once the RCC clock configuration is reset to the default reset state (done in SystemInit() function).

Return values

None

Definition at line 345 of file cmsis_system.c.

Macros

Functions

Variables