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"

Include dependency graph for system_stm32f4xx.c:

Go to the source code of this file.

Macros
#define	PLL_M 8

#define	PLL_N 336

#define	PLL_P 2

#define	PLL_Q 7

#define	VECT_TAB_OFFSET 0x00

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	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...

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

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

uint32_t	SystemCoreClock = 168000000

Detailed Description

Author: MCD Application Team

Version: V1.0.0

Date

19-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 8 MHz, 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) | 8000000

PLL_M | 8

PLL_N | 336

PLL_P | 2

PLL_Q | 7

PLLI2S_N | NA

PLLI2S_R | NA

I2S input clock | NA

VDD(V) | 3.3

High Performance mode | Enabled

Flash Latency(WS) | 5

Prefetch Buffer | OFF

Instruction cache | ON

Data cache | ON

Require 48MHz for USB OTG FS, | Enabled

SDIO and RNG clock |