mbed library sources
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Diff: targets/cmsis/TARGET_STM/TARGET_DISCO_F051R8/system_stm32f0xx.c.x
- Revision:
- 130:1dec54e4aec3
--- /dev/null Thu Jan 01 00:00:00 1970 +0000 +++ b/targets/cmsis/TARGET_STM/TARGET_DISCO_F051R8/system_stm32f0xx.c.x Fri Mar 21 11:45:09 2014 +0000 @@ -0,0 +1,319 @@ +/** + ****************************************************************************** + * @file system_stm32f0xx.c + * @author MCD Application Team + * @version V1.0.1 + * @date 12-January-2014 + * @brief CMSIS Cortex-M0 Device Peripheral Access Layer System Source File. + * This file contains the system clock configuration for STM32F0xx devices, + * and is generated by the clock configuration tool + * STM32F0xx_Clock_Configuration_V1.0.1.xls + * + * 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 + * 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_stm32f0xx.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 Range) is used as system clock source. + * Then SystemInit() function is called, in "startup_stm32f0xx.s" file, to + * configure the system clock before to branch to main program. + * + * 3. 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. + * + * 4. The default value of HSE crystal is set to 8MHz, refer to "HSE_VALUE" define + * in "stm32f0xx.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: + *============================================================================= + *============================================================================= + * System Clock source | HSI + *----------------------------------------------------------------------------- + * SYSCLK(Hz) | 8000000 + *----------------------------------------------------------------------------- + * HCLK(Hz) | 8000000 + *----------------------------------------------------------------------------- + * AHB Prescaler | 1 + *----------------------------------------------------------------------------- + * APB Prescaler | 1 + *----------------------------------------------------------------------------- + * HSE Frequency(Hz) | NA + *---------------------------------------------------------------------------- + * PLLMUL | NA + *----------------------------------------------------------------------------- + * PREDIV | NA + *----------------------------------------------------------------------------- + * Flash Latency(WS) | 0 + *----------------------------------------------------------------------------- + * Prefetch Buffer | ON + *----------------------------------------------------------------------------- + ****************************************************************************** + * @attention + * + * <h2><center>© COPYRIGHT(c) 2014 STMicroelectronics</center></h2> + * + * Redistribution and use in source and binary forms, with or without modification, + * are permitted provided that the following conditions are met: + * 1. Redistributions of source code must retain the above copyright notice, + * this list of conditions and the following disclaimer. + * 2. Redistributions in binary form must reproduce the above copyright notice, + * this list of conditions and the following disclaimer in the documentation + * and/or other materials provided with the distribution. + * 3. Neither the name of STMicroelectronics nor the names of its contributors + * may be used to endorse or promote products derived from this software + * without specific prior written permission. + * + * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" + * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE + * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE + * DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE + * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL + * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR + * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER + * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, + * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE + * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. + * + ****************************************************************************** + */ + +/** @addtogroup CMSIS + * @{ + */ + +/** @addtogroup stm32f0xx_system + * @{ + */ + +/** @addtogroup STM32F0xx_System_Private_Includes + * @{ + */ + +#include "stm32f0xx.h" + +/** + * @} + */ + +/** @addtogroup STM32F0xx_System_Private_TypesDefinitions + * @{ + */ + +/** + * @} + */ + +/** @addtogroup STM32F0xx_System_Private_Defines + * @{ + */ +/** + * @} + */ + +/** @addtogroup STM32F0xx_System_Private_Macros + * @{ + */ + +/** + * @} + */ + +/** @addtogroup STM32F0xx_System_Private_Variables + * @{ + */ +uint32_t SystemCoreClock = 8000000; +__I uint8_t AHBPrescTable[16] = {0, 0, 0, 0, 0, 0, 0, 0, 1, 2, 3, 4, 6, 7, 8, 9}; + +/** + * @} + */ + +/** @addtogroup STM32F0xx_System_Private_FunctionPrototypes + * @{ + */ + +static void SetSysClock(void); + +/** + * @} + */ + +/** @addtogroup STM32F0xx_System_Private_Functions + * @{ + */ + +/** + * @brief Setup the microcontroller system. + * Initialize the Embedded Flash Interface, the PLL and update the + * SystemCoreClock variable. + * @param None + * @retval None + */ +void SystemInit (void) +{ + /* Set HSION bit */ + RCC->CR |= (uint32_t)0x00000001; + + /* Reset SW[1:0], HPRE[3:0], PPRE[2:0], ADCPRE and MCOSEL[2:0] bits */ + RCC->CFGR &= (uint32_t)0xF8FFB80C; + + /* Reset HSEON, CSSON and PLLON bits */ + RCC->CR &= (uint32_t)0xFEF6FFFF; + + /* Reset HSEBYP bit */ + RCC->CR &= (uint32_t)0xFFFBFFFF; + + /* Reset PLLSRC, PLLXTPRE and PLLMUL[3:0] bits */ + RCC->CFGR &= (uint32_t)0xFFC0FFFF; + + /* Reset PREDIV1[3:0] bits */ + RCC->CFGR2 &= (uint32_t)0xFFFFFFF0; + + /* Reset USARTSW[1:0], I2CSW, CECSW and ADCSW bits */ + RCC->CFGR3 &= (uint32_t)0xFFFFFEAC; + + /* Reset HSI14 bit */ + RCC->CR2 &= (uint32_t)0xFFFFFFFE; + + /* Disable all interrupts */ + RCC->CIR = 0x00000000; + + /* Configure the System clock frequency, AHB/APBx prescalers and Flash settings */ + SetSysClock(); +} + +/** + * @brief Update SystemCoreClock 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. + * + * @note Each time the core clock (HCLK) changes, this function must be called + * to update SystemCoreClock variable value. Otherwise, any configuration + * based on this variable will be incorrect. + * + * @note - The system frequency computed by this function is not the real + * frequency in the chip. It is calculated based on the predefined + * constant and the selected clock source: + * + * - If SYSCLK source is HSI, SystemCoreClock will contain the HSI_VALUE(*) + * + * - If SYSCLK source is HSE, SystemCoreClock will contain the HSE_VALUE(**) + * + * - If SYSCLK source is PLL, SystemCoreClock will contain the HSE_VALUE(**) + * or HSI_VALUE(*) multiplied/divided by the PLL factors. + * + * (*) HSI_VALUE is a constant defined in stm32f0xx.h file (default value + * 8 MHz) but the real value may vary depending on the variations + * in voltage and temperature. + * + * (**) HSE_VALUE is a constant defined in stm32f0xx.h file (default value + * 8 MHz), user has to ensure that HSE_VALUE is same as the real + * frequency of the crystal used. Otherwise, this function may + * have wrong result. + * + * - The result of this function could be not correct when using fractional + * value for HSE crystal. + * @param None + * @retval None + */ +void SystemCoreClockUpdate (void) +{ + uint32_t tmp = 0, pllmull = 0, pllsource = 0, prediv1factor = 0; + + /* Get SYSCLK source -------------------------------------------------------*/ + tmp = RCC->CFGR & RCC_CFGR_SWS; + + switch (tmp) + { + case 0x00: /* HSI used as system clock */ + SystemCoreClock = HSI_VALUE; + break; + case 0x04: /* HSE used as system clock */ + SystemCoreClock = HSE_VALUE; + break; + case 0x08: /* PLL used as system clock */ + /* Get PLL clock source and multiplication factor ----------------------*/ + pllmull = RCC->CFGR & RCC_CFGR_PLLMULL; + pllsource = RCC->CFGR & RCC_CFGR_PLLSRC; + pllmull = ( pllmull >> 18) + 2; + + if (pllsource == 0x00) + { + /* HSI oscillator clock divided by 2 selected as PLL clock entry */ + SystemCoreClock = (HSI_VALUE >> 1) * pllmull; + } + else + { + prediv1factor = (RCC->CFGR2 & RCC_CFGR2_PREDIV1) + 1; + /* HSE oscillator clock selected as PREDIV1 clock entry */ + SystemCoreClock = (HSE_VALUE / prediv1factor) * pllmull; + } + break; + default: /* HSI used as system clock */ + SystemCoreClock = HSI_VALUE; + break; + } + /* Compute HCLK clock frequency ----------------*/ + /* Get HCLK prescaler */ + tmp = AHBPrescTable[((RCC->CFGR & RCC_CFGR_HPRE) >> 4)]; + /* HCLK clock frequency */ + SystemCoreClock >>= tmp; +} + +/** + * @brief Configures the System clock frequency, AHB/APBx prescalers and Flash + * settings. + * @note This function should be called only once the RCC clock configuration + * is reset to the default reset state (done in SystemInit() function). + * @param None + * @retval None + */ +static void SetSysClock(void) +{ +/******************************************************************************/ +/* HSI used as System clock source */ +/******************************************************************************/ + + /* At this stage the HSI is already enabled and used as System clock source */ + + /* Enable Prefetch Buffer and Flash 0 wait state */ + FLASH->ACR = FLASH_ACR_PRFTBE; + + /* HCLK = SYSCLK / 1 */ + RCC->CFGR |= (uint32_t)RCC_CFGR_HPRE_DIV1; + + /* PCLK = HCLK / 1 */ + RCC->CFGR |= (uint32_t)RCC_CFGR_PPRE_DIV1; + +} + +/** + * @} + */ + +/** + * @} + */ + +/** + * @} + */ + +/************************ (C) COPYRIGHT STMicroelectronics *****END OF FILE****/ +