/**
  @page RTC_Tamper RTC example
  
  @verbatim
  ******************** (C) COPYRIGHT 2017 STMicroelectronics *******************
  * @file    Examples_LL/RTC/RTC_Tamper/readme.txt 
  * @author  MCD Application Team
  * @version V1.0.0
  * @date    14-April-2017
  * @brief   Description of the RTC example.
  ******************************************************************************
  *
  * 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.
  *
  ******************************************************************************
  @endverbatim

@par Example Description

This example guides you through the different configuration steps by mean of LL API 
to ensure Tamper configuration using the RTC peripheral. Peripheral initialization 
done using LL unitary services functions for optimization purpose (performance and size).

In this example, after start-up, SYSCLK is configured to the max frequency using the PLL with
HSE as clock source.

The RTC peripheral configuration is ensured by the Configure_RTC() function 
(configure of the needed RTC resources according to the used hardware CLOCK, 
PWR, RTC clock source and BackUp). You may update this function to change RTC configuration.

The associated firmware performs the following:
1. It configures the Tamper pin to be falling edge, and enables the Tamper 
   interrupt.
2. It writes the data to all RTC Backup data registers, then check whether the
   data were correctly written. If yes, LED1 toggles with a fast period,
   otherwise LED1 toggles with a period of 1s.
3. Applying a low level on the KEY_BUTTON_PIN (PC.13) by pressing Key push-button,
   the RTC backup data registers are reset and the Tamper interrupt is generated. 
   The corresponding ISR then checks whether the RTC Backup data registers are cleared.
   If yes LED1 turns on, otherwise LED1 toggles with a period of 1s.

@par Directory contents 

  - RTC/RTC_Tamper/Inc/stm32f1xx_it.h          Interrupt handlers header file
  - RTC/RTC_Tamper/Inc/main.h                  Header for main.c module
  - RTC/RTC_Tamper/Inc/stm32_assert.h          Template file to include assert_failed function
  - RTC/RTC_Tamper/Src/stm32f1xx_it.c          Interrupt handlers
  - RTC/RTC_Tamper/Src/main.c                  Main program
  - RTC/RTC_Tamper/Src/system_stm32f1xx.c      STM32f1xx system source file


@par Hardware and Software environment

  - This example runs on STM32F103xB devices.
    
  - This example has been tested with STM32F103RB-Nucleo board and can be
    easily tailored to any other supported device and development board.

@par How to use it ? 

In order to make the program work, you must do the following :
 - Open your preferred toolchain
 - Rebuild all files and load your image into target memory
 - Run the example

 * <h3><center>&copy; COPYRIGHT STMicroelectronics</center></h3>
 */
