system_stm32f1xx.c File Reference

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

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Detailed Description

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

Author:

MCD Application Team

Version:

V4.1.0

Date:

29-April-2016 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.

4. 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.

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Definition in file system_stm32f1xx.c.