1 /**
2 ******************************************************************************
3 * @file system_stm32f0xx.c
4 * @author MCD Application Team
5 * @brief CMSIS Cortex-M0 Device Peripheral Access Layer System Source File.
6 *
7 * 1. This file provides two functions and one global variable to be called from
8 * user application:
9 * - SystemInit(): This function is called at startup just after reset and
10 * before branch to main program. This call is made inside
11 * the "startup_stm32f0xx.s" file.
12 *
13 * - SystemCoreClock variable: Contains the core clock (HCLK), it can be used
14 * by the user application to setup the SysTick
15 * timer or configure other parameters.
16 *
17 * - SystemCoreClockUpdate(): Updates the variable SystemCoreClock and must
18 * be called whenever the core clock is changed
19 * during program execution.
20 *
21 *
22 ******************************************************************************
23 * @attention
24 *
25 * Copyright (c) 2016 STMicroelectronics.
26 * All rights reserved.
27 *
28 * This software is licensed under terms that can be found in the LICENSE file
29 * in the root directory of this software component.
30 * If no LICENSE file comes with this software, it is provided AS-IS.
31 *
32 ******************************************************************************
33 */
34 /** @addtogroup CMSIS
35 * @{
36 */
37
38 /** @addtogroup stm32f0xx_system
39 * @{
40 */
41
42 /** @addtogroup STM32F0xx_System_Private_Includes
43 * @{
44 */
45
46 #include "stm32f0xx.h"
47
48 /**
49 * @}
50 */
51
52 /** @addtogroup STM32F0xx_System_Private_TypesDefinitions
53 * @{
54 */
55
56 /**
57 * @}
58 */
59
60 /** @addtogroup STM32F0xx_System_Private_Defines
61 * @{
62 */
63 #if !defined (HSE_VALUE)
64 #define HSE_VALUE ((uint32_t)8000000) /*!< Default value of the External oscillator in Hz.
65 This value can be provided and adapted by the user application. */
66 #endif /* HSE_VALUE */
67
68 #if !defined (HSI_VALUE)
69 #define HSI_VALUE ((uint32_t)8000000) /*!< Default value of the Internal oscillator in Hz.
70 This value can be provided and adapted by the user application. */
71 #endif /* HSI_VALUE */
72
73 #if !defined (HSI48_VALUE)
74 #define HSI48_VALUE ((uint32_t)48000000) /*!< Default value of the HSI48 Internal oscillator in Hz.
75 This value can be provided and adapted by the user application. */
76 #endif /* HSI48_VALUE */
77 /**
78 * @}
79 */
80
81 /** @addtogroup STM32F0xx_System_Private_Macros
82 * @{
83 */
84
85 /**
86 * @}
87 */
88
89 /** @addtogroup STM32F0xx_System_Private_Variables
90 * @{
91 */
92 /* This variable is updated in three ways:
93 1) by calling CMSIS function SystemCoreClockUpdate()
94 2) by calling HAL API function HAL_RCC_GetHCLKFreq()
95 3) each time HAL_RCC_ClockConfig() is called to configure the system clock frequency
96 Note: If you use this function to configure the system clock; then there
97 is no need to call the 2 first functions listed above, since SystemCoreClock
98 variable is updated automatically.
99 */
100 uint32_t SystemCoreClock = 8000000;
101
102 const uint8_t AHBPrescTable[16] = {0, 0, 0, 0, 0, 0, 0, 0, 1, 2, 3, 4, 6, 7, 8, 9};
103 const uint8_t APBPrescTable[8] = {0, 0, 0, 0, 1, 2, 3, 4};
104
105 /**
106 * @}
107 */
108
109 /** @addtogroup STM32F0xx_System_Private_FunctionPrototypes
110 * @{
111 */
112
113 /**
114 * @}
115 */
116
117 /** @addtogroup STM32F0xx_System_Private_Functions
118 * @{
119 */
120
121 /**
122 * @brief Setup the microcontroller system
123 * @param None
124 * @retval None
125 */
SystemInit(void)126 void SystemInit(void)
127 {
128 /* NOTE :SystemInit(): This function is called at startup just after reset and
129 before branch to main program. This call is made inside
130 the "startup_stm32f0xx.s" file.
131 User can setups the default system clock (System clock source, PLL Multiplier
132 and Divider factors, AHB/APBx prescalers and Flash settings).
133 */
134 }
135
136 /**
137 * @brief Update SystemCoreClock variable according to Clock Register Values.
138 * The SystemCoreClock variable contains the core clock (HCLK), it can
139 * be used by the user application to setup the SysTick timer or configure
140 * other parameters.
141 *
142 * @note Each time the core clock (HCLK) changes, this function must be called
143 * to update SystemCoreClock variable value. Otherwise, any configuration
144 * based on this variable will be incorrect.
145 *
146 * @note - The system frequency computed by this function is not the real
147 * frequency in the chip. It is calculated based on the predefined
148 * constant and the selected clock source:
149 *
150 * - If SYSCLK source is HSI, SystemCoreClock will contain the HSI_VALUE(*)
151 *
152 * - If SYSCLK source is HSE, SystemCoreClock will contain the HSE_VALUE(**)
153 *
154 * - If SYSCLK source is PLL, SystemCoreClock will contain the HSE_VALUE(**)
155 * or HSI_VALUE(*) multiplied/divided by the PLL factors.
156 *
157 * - If SYSCLK source is HSI48, SystemCoreClock will contain the HSI48_VALUE(***)
158 *
159 * (*) HSI_VALUE is a constant defined in stm32f0xx_hal_conf.h file (default value
160 * 8 MHz) but the real value may vary depending on the variations
161 * in voltage and temperature.
162 *
163 * (**) HSE_VALUE is a constant defined in stm32f0xx_hal_conf.h file (its value
164 * depends on the application requirements), user has to ensure that HSE_VALUE
165 * is same as the real frequency of the crystal used. Otherwise, this function
166 * may have wrong result.
167 *
168 * (***) HSI48_VALUE is a constant defined in stm32f0xx_hal_conf.h file (default value
169 * 48 MHz) but the real value may vary depending on the variations
170 * in voltage and temperature.
171 *
172 * - The result of this function could be not correct when using fractional
173 * value for HSE crystal.
174 *
175 * @param None
176 * @retval None
177 */
SystemCoreClockUpdate(void)178 void SystemCoreClockUpdate (void)
179 {
180 uint32_t tmp = 0, pllmull = 0, pllsource = 0, predivfactor = 0;
181
182 /* Get SYSCLK source -------------------------------------------------------*/
183 tmp = RCC->CFGR & RCC_CFGR_SWS;
184
185 switch (tmp)
186 {
187 case RCC_CFGR_SWS_HSI: /* HSI used as system clock */
188 SystemCoreClock = HSI_VALUE;
189 break;
190 case RCC_CFGR_SWS_HSE: /* HSE used as system clock */
191 SystemCoreClock = HSE_VALUE;
192 break;
193 case RCC_CFGR_SWS_PLL: /* PLL used as system clock */
194 /* Get PLL clock source and multiplication factor ----------------------*/
195 pllmull = RCC->CFGR & RCC_CFGR_PLLMUL;
196 pllsource = RCC->CFGR & RCC_CFGR_PLLSRC;
197 pllmull = ( pllmull >> 18) + 2;
198 predivfactor = (RCC->CFGR2 & RCC_CFGR2_PREDIV) + 1;
199
200 if (pllsource == RCC_CFGR_PLLSRC_HSE_PREDIV)
201 {
202 /* HSE used as PLL clock source : SystemCoreClock = HSE/PREDIV * PLLMUL */
203 SystemCoreClock = (HSE_VALUE/predivfactor) * pllmull;
204 }
205 #if defined(STM32F042x6) || defined(STM32F048xx) || defined(STM32F071xB) || defined(STM32F072xB) || defined(STM32F078xx) || defined(STM32F091xC) || defined(STM32F098xx)
206 else if (pllsource == RCC_CFGR_PLLSRC_HSI48_PREDIV)
207 {
208 /* HSI48 used as PLL clock source : SystemCoreClock = HSI48/PREDIV * PLLMUL */
209 SystemCoreClock = (HSI48_VALUE/predivfactor) * pllmull;
210 }
211 #endif /* STM32F042x6 || STM32F048xx || STM32F071xB || STM32F072xB || STM32F078xx || STM32F091xC || STM32F098xx */
212 else
213 {
214 #if defined(STM32F042x6) || defined(STM32F048xx) || defined(STM32F070x6) \
215 || defined(STM32F078xx) || defined(STM32F071xB) || defined(STM32F072xB) \
216 || defined(STM32F070xB) || defined(STM32F091xC) || defined(STM32F098xx) || defined(STM32F030xC)
217 /* HSI used as PLL clock source : SystemCoreClock = HSI/PREDIV * PLLMUL */
218 SystemCoreClock = (HSI_VALUE/predivfactor) * pllmull;
219 #else
220 /* HSI used as PLL clock source : SystemCoreClock = HSI/2 * PLLMUL */
221 SystemCoreClock = (HSI_VALUE >> 1) * pllmull;
222 #endif /* STM32F042x6 || STM32F048xx || STM32F070x6 ||
223 STM32F071xB || STM32F072xB || STM32F078xx || STM32F070xB ||
224 STM32F091xC || STM32F098xx || STM32F030xC */
225 }
226 break;
227 default: /* HSI used as system clock */
228 SystemCoreClock = HSI_VALUE;
229 break;
230 }
231 /* Compute HCLK clock frequency ----------------*/
232 /* Get HCLK prescaler */
233 tmp = AHBPrescTable[((RCC->CFGR & RCC_CFGR_HPRE) >> 4)];
234 /* HCLK clock frequency */
235 SystemCoreClock >>= tmp;
236 }
237
238 /**
239 * @}
240 */
241
242 /**
243 * @}
244 */
245
246 /**
247 * @}
248 */
249
250
