system_stm32f1xx.c File Reference

CMSIS Cortex-M3 Device Peripheral Access Layer System Source File. More...

#include "stm32f1xx.h"

Go to the source code of this file.

Macros
#define	HSE_VALUE   8000000U
#define	HSI_VALUE   8000000U

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

Variables
uint32_t	SystemCoreClock = 8000000
const uint8_t	AHBPrescTable [16U] = {0, 0, 0, 0, 0, 0, 0, 0, 1, 2, 3, 4, 6, 7, 8, 9}
const uint8_t	APBPrescTable [8U] = {0, 0, 0, 0, 1, 2, 3, 4}

Detailed Description

CMSIS Cortex-M3 Device Peripheral Access Layer System Source File.

Author

MCD Application Team

1. 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 factors, AHB/APBx prescalers and Flash settings). This function is called at startup just after reset and before branch to main program. This call is made inside the "startup_stm32f1xx_xx.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.
2. After each device reset the HSI (8 MHz) is used as system clock source. Then SystemInit() function is called, in "startup_stm32f1xx_xx.s" file, to configure the system clock before to branch to main program.
3. The default value of HSE crystal is set to 8 MHz (or 25 MHz, depending on the product used), refer to "HSE_VALUE". 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.

Attention

Copyright (c) 2017-2021 STMicroelectronics. All rights reserved.

This software is licensed under terms that can be found in the LICENSE file in the root directory of this software component. If no LICENSE file comes with this software, it is provided AS-IS.

Definition in file system_stm32f1xx.c.