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<title>CMSIS-Core (Cortex-M): System Configuration Files system_<device>.c and system_<device>.h</title>
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<div id="projectname">CMSIS-Core (Cortex-M)
 <span id="projectnumber">Version 5.3.0</span>
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<div id="projectbrief">CMSIS-Core support for Cortex-M processor-based devices</div>
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<div class="title">System Configuration Files system_<device>.c and system_<device>.h </div> </div>
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<div class="textblock"><p>The <a class="el" href="system_c_pg.html">System Configuration Files system_<device>.c and system_<device>.h</a> provides as a minimum the functions described under <a class="el" href="group__system__init__gr.html">System and Clock Configuration</a>. These functions are device specific and need adaptations. In addition, the file might have configuration settings for the device such as XTAL frequency or PLL prescaler settings.</p>
<p>For devices with external memory BUS the system_<device>.c also configures the BUS system.</p>
<p>The silicon vendor might expose other functions (i.e. for power configuration) in the system_<device>.c file. In case of additional features the function prototypes need to be added to the system_<device>.h header file.</p>
<h1><a class="anchor" id="system_Device_sec"></a>
system_Device.c Template File</h1>
<p>The <a class="el" href="system_c_pg.html#system_Device_sec">system_Device.c Template File</a> for the Cortex-M3 is shown below.</p>
<pre class="fragment">/**************************************************************************//**
* @file system_<Device>.c
* @brief CMSIS Cortex-M# Device Peripheral Access Layer Source File for
* Device <Device>
* @version V5.00
* @date 10. January 2018
******************************************************************************/
/*
* Copyright (c) 2009-2018 Arm Limited. All rights reserved.
*
* SPDX-License-Identifier: Apache-2.0
*
* Licensed under the Apache License, Version 2.0 (the License); you may
* not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an AS IS BASIS, WITHOUT
* WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
#include <stdint.h>
#include "<Device>.h"
/*----------------------------------------------------------------------------
Define clocks
*----------------------------------------------------------------------------*/
/* ToDo: add here your necessary defines for device initialization
following is an example for different system frequencies */
#define XTAL (12000000U) /* Oscillator frequency */
#define SYSTEM_CLOCK (5 * XTAL)
/*----------------------------------------------------------------------------
System Core Clock Variable
*----------------------------------------------------------------------------*/
/* ToDo: initialize SystemCoreClock with the system core clock frequency value
achieved after system intitialization.
This means system core clock frequency after call to SystemInit() */
uint32_t SystemCoreClock = SYSTEM_CLOCK; /* System Clock Frequency (Core Clock)*/
/*----------------------------------------------------------------------------
Clock functions
*----------------------------------------------------------------------------*/
void SystemCoreClockUpdate (void) /* Get Core Clock Frequency */
{
/* ToDo: add code to calculate the system frequency based upon the current
register settings.
This function can be used to retrieve the system core clock frequeny
after user changed register sittings. */
SystemCoreClock = SYSTEM_CLOCK;
}
void SystemInit (void)
{
/* ToDo: add code to initialize the system
do not use global variables because this function is called before
reaching pre-main. RW section maybe overwritten afterwards. */
SystemCoreClock = SYSTEM_CLOCK;
}
</pre><h1><a class="anchor" id="system_Device_h_sec"></a>
system_Device.h Template File</h1>
<p>The system_<device>.h header file contains prototypes to access the public functions in the system_<device>.c file. The <a class="el" href="system_c_pg.html#system_Device_h_sec">system_Device.h Template File</a> is shown below.</p>
<pre class="fragment">/**************************************************************************//**
* @file system_<Device>.h
* @brief CMSIS Cortex-M# Device Peripheral Access Layer Header File for
* Device <Device>
* @version V5.00
* @date 10. January 2018
******************************************************************************/
/*
* Copyright (c) 2009-2018 Arm Limited. All rights reserved.
*
* SPDX-License-Identifier: Apache-2.0
*
* Licensed under the Apache License, Version 2.0 (the License); you may
* not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an AS IS BASIS, WITHOUT
* WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
#ifndef SYSTEM_<Device>_H /* ToDo: replace '<Device>' with your device name */
#define SYSTEM_<Device>_H
#ifdef __cplusplus
extern "C" {
#endif
#include <stdint.h>
extern uint32_t SystemCoreClock; /*!< System Clock Frequency (Core Clock) */
/**
\brief Setup the microcontroller system.
Initialize the System and update the SystemCoreClock variable.
*/
extern void SystemInit (void);
/**
\brief Update SystemCoreClock variable.
Updates the SystemCoreClock with current core Clock retrieved from cpu registers.
*/
extern void SystemCoreClockUpdate (void);
#ifdef __cplusplus
}
#endif
#endif /* SYSTEM_<Device>_H */
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