1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
|
/**
******************************************************************************
* @file system_stm32f0xx.c
* @author MCD Application Team
* @brief CMSIS Cortex-M0 Device Peripheral Access Layer System Source File.
*
* 1. This file provides two functions and one global variable to be called from
* user application:
* - SystemInit(): 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) 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. This file configures the system clock as follows:
*=============================================================================
* Supported STM32F0xx device
*-----------------------------------------------------------------------------
* System Clock source | HSI
*-----------------------------------------------------------------------------
* SYSCLK(Hz) | 8000000
*-----------------------------------------------------------------------------
* HCLK(Hz) | 8000000
*-----------------------------------------------------------------------------
* AHB Prescaler | 1
*-----------------------------------------------------------------------------
* APB1 Prescaler | 1
*-----------------------------------------------------------------------------
*=============================================================================
******************************************************************************
* @attention
*
* <h2><center>© Copyright (c) 2016 STMicroelectronics.
* All rights reserved.</center></h2>
*
* This software component is licensed by ST under BSD 3-Clause license,
* the "License"; You may not use this file except in compliance with the
* License. You may obtain a copy of the License at:
* opensource.org/licenses/BSD-3-Clause
*
******************************************************************************
*/
/** @addtogroup CMSIS
* @{
*/
/** @addtogroup stm32f0xx_system
* @{
*/
/** @addtogroup STM32F0xx_System_Private_Includes
* @{
*/
#include "stm32f0xx.h"
/**
* @}
*/
/** @addtogroup STM32F0xx_System_Private_TypesDefinitions
* @{
*/
/**
* @}
*/
/** @addtogroup STM32F0xx_System_Private_Defines
* @{
*/
#if !defined (HSE_VALUE)
#define HSE_VALUE ((uint32_t)8000000) /*!< Default value of the External oscillator in Hz.
This value can be provided and adapted by the user application. */
#endif /* HSE_VALUE */
#if !defined (HSI_VALUE)
#define HSI_VALUE ((uint32_t)8000000) /*!< Default value of the Internal oscillator in Hz.
This value can be provided and adapted by the user application. */
#endif /* HSI_VALUE */
#if !defined (HSI48_VALUE)
#define HSI48_VALUE ((uint32_t)48000000) /*!< Default value of the HSI48 Internal oscillator in Hz.
This value can be provided and adapted by the user application. */
#endif /* HSI48_VALUE */
/**
* @}
*/
/** @addtogroup STM32F0xx_System_Private_Macros
* @{
*/
/**
* @}
*/
/** @addtogroup STM32F0xx_System_Private_Variables
* @{
*/
/* This variable is updated in three ways:
1) by calling CMSIS function SystemCoreClockUpdate()
2) by calling HAL API function HAL_RCC_GetHCLKFreq()
3) each time HAL_RCC_ClockConfig() is called to configure the system clock frequency
Note: If you use this function to configure the system clock there is no need to
call the 2 first functions listed above, since SystemCoreClock variable is
updated automatically.
*/
uint32_t SystemCoreClock = 8000000;
const uint8_t AHBPrescTable[16] = {0, 0, 0, 0, 0, 0, 0, 0, 1, 2, 3, 4, 6, 7, 8, 9};
const uint8_t APBPrescTable[8] = {0, 0, 0, 0, 1, 2, 3, 4};
/**
* @}
*/
/** @addtogroup STM32F0xx_System_Private_FunctionPrototypes
* @{
*/
/**
* @}
*/
/** @addtogroup STM32F0xx_System_Private_Functions
* @{
*/
/**
* @brief Setup the microcontroller system.
* @param None
* @retval None
*/
void SystemInit(void)
{
/* NOTE :SystemInit(): 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.
User can setups the default system clock (System clock source, PLL Multiplier
and Divider factors, AHB/APBx prescalers and Flash settings).
*/
}
/**
* @brief 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.
*
* @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_hal.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_hal.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, predivfactor = 0;
/* Get SYSCLK source -------------------------------------------------------*/
tmp = RCC->CFGR & RCC_CFGR_SWS;
switch (tmp)
{
case RCC_CFGR_SWS_HSI: /* HSI used as system clock */
SystemCoreClock = HSI_VALUE;
break;
case RCC_CFGR_SWS_HSE: /* HSE used as system clock */
SystemCoreClock = HSE_VALUE;
break;
case RCC_CFGR_SWS_PLL: /* PLL used as system clock */
/* Get PLL clock source and multiplication factor ----------------------*/
pllmull = RCC->CFGR & RCC_CFGR_PLLMUL;
pllsource = RCC->CFGR & RCC_CFGR_PLLSRC;
pllmull = ( pllmull >> 18) + 2;
predivfactor = (RCC->CFGR2 & RCC_CFGR2_PREDIV) + 1;
if (pllsource == RCC_CFGR_PLLSRC_HSE_PREDIV)
{
/* HSE used as PLL clock source : SystemCoreClock = HSE/PREDIV * PLLMUL */
SystemCoreClock = (HSE_VALUE/predivfactor) * pllmull;
}
#if defined(STM32F042x6) || defined(STM32F048xx) || defined(STM32F072xB) || defined(STM32F078xx) || defined(STM32F091xC) || defined(STM32F098xx)
else if (pllsource == RCC_CFGR_PLLSRC_HSI48_PREDIV)
{
/* HSI48 used as PLL clock source : SystemCoreClock = HSI48/PREDIV * PLLMUL */
SystemCoreClock = (HSI48_VALUE/predivfactor) * pllmull;
}
#endif /* STM32F042x6 || STM32F048xx || STM32F072xB || STM32F078xx || STM32F091xC || STM32F098xx */
else
{
#if defined(STM32F042x6) || defined(STM32F048xx) || defined(STM32F070x6) \
|| defined(STM32F078xx) || defined(STM32F071xB) || defined(STM32F072xB) \
|| defined(STM32F070xB) || defined(STM32F091xC) || defined(STM32F098xx) || defined(STM32F030xC)
/* HSI used as PLL clock source : SystemCoreClock = HSI/PREDIV * PLLMUL */
SystemCoreClock = (HSI_VALUE/predivfactor) * pllmull;
#else
/* HSI used as PLL clock source : SystemCoreClock = HSI/2 * PLLMUL */
SystemCoreClock = (HSI_VALUE >> 1) * pllmull;
#endif /* STM32F042x6 || STM32F048xx || STM32F070x6 ||
STM32F071xB || STM32F072xB || STM32F078xx || STM32F070xB ||
STM32F091xC || STM32F098xx || STM32F030xC */
}
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;
}
/**
* @}
*/
/**
* @}
*/
/**
* @}
*/
/************************ (C) COPYRIGHT STMicroelectronics *****END OF FILE****/
|
