/**
  @page WWDG_Example WWDG example
  
  @verbatim
  ******************** (C) COPYRIGHT 2013 STMicroelectronics *******************
  * @file    WWDG/WWDG_Example/readme.txt 
  * @author  MCD Application Team
  * @version V1.3.0
  * @date    13-November-2013
  * @brief   Description of the WWDG example.
  ******************************************************************************
  *
  * Licensed under MCD-ST Liberty SW License Agreement V2, (the "License");
  * You may not use this file except in compliance with the License.
  * You may obtain a copy of the License at:
  *
  *        http://www.st.com/software_license_agreement_liberty_v2
  *
  * 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.
  *
  ******************************************************************************
  @endverbatim

@par Example Description 

This example shows how to update at regular period the WWDG counter and how to
simulate a software fault generating an MCU WWDG reset on expiry of a programmed 
time period.

The WWDG timeout is set to 49.92 ms and the refresh window is set to 80. 
The WWDG counter is refreshed each 40ms in the main program infinite loop to 
prevent a WWDG reset.
LED2 is also toggled each 40 ms indicating that the program is running.

An EXTI Line is connected to a GPIO pin, and configured to generate an interrupt
on the rising edge of the signal.

The EXTI Line is used to simulate a software failure: once the EXTI Line event 
occurs by pressing the Key push-button, the corresponding interrupt is served.
In the ISR, a write to invalid address generates a Hardfault exception containing
an infinite loop and preventing to return to main program (the WWDG counter is 
not refreshed).
As a result, when the WWDG counter falls to 63, the WWDG reset occurs.

If the WWDG reset is generated, after the system resumes from reset, LED1 turns on.
If the EXTI Line event does not occur, the WWDG counter is indefinitely refreshed
in the main program infinite loop, and there is no WWDG reset. 


@par Directory contents
  
  - WWDG/WWDG_Example/system_stm32f4xx.c   STM32F4xx system clock configuration file
  - WWDG/WWDG_Example/stm32f4xx_conf.h     Library Configuration file
  - WWDG/WWDG_Example/stm32f4xx_it.c       Interrupt handlers
  - WWDG/WWDG_Example/stm32f4xx_it.h       Interrupt handlers header file
  - WWDG/WWDG_Example/main.c               Main program
  - WWDG/WWDG_Example/main.h               Main program header file
  
     
@par Hardware and Software environment 

  - This example runs on STM32F405xx/407xx, STM32F415xx/417xx, STM32F427xx/437xx and 
    STM32F429xx/439xx devices.
    
  - This example has been tested with STMicroelectronics STM324xG-EVAL (STM32F40xx/
    STM32F41xx Devices), STM32437I-EVAL (STM32F427xx/STM32F437xx Devices) and 
    STM324x9I-EVAL RevB (STM32F429xx/STM32F439xx Devices) evaluation boards and 
    can be easily tailored to any other supported device and development board.
                                 
  - STM324xG-EVAL/STM32437I-EVAL Set-up  
    - Use LED1 and LED2 leds connected respectively to PG.06 and PG.08 pins.
    - Use the KEY push-button connected to PG.15 pin (EXTI Line15).
    
  - STM324x9I-EVAL RevB Set-up
    - Use LED1 and LED2 connected respectively to PG.06 and PG.07 pins. 
    - Use the TAMPER/KEY push-button connected to PC.13 pin (EXTI Line13).    

     
@par How to use it ?

In order to make the program work, you must do the following:
 - Copy all source files from this example folder to the template folder under
   Project\STM32F4xx_StdPeriph_Templates
 - Open your preferred toolchain 
 - Select the project workspace related to the used device 
   - If "STM32F40_41xxx" is selected as default project Add the following files in the project source list:
     - Utilities\STM32_EVAL\STM3240_41_G_EVAL\stm324xg_eval.c
           
   - If "STM32F427_437xx" is selected as default project Add the following files in the project source list:
     - Utilities\STM32_EVAL\STM324x7I_EVAL\stm324x7i_eval.c
          
   - If "STM32F429_439xx" is selected as default project Add the following files in the project source list:
     - Utilities\STM32_EVAL\STM324x9I_EVAL\stm324x9i_eval.c
                 
 - Rebuild all files and load your image into target memory
 - Run the example
   
 * <h3><center>&copy; COPYRIGHT STMicroelectronics</center></h3>
 */
