text: /**
    ******************************************************************************
    * @file    stm32f4xx_wwdg.c
    * @author  MCD Application Team
    * @version V1.6.1
    * @date    21-October-2015
    * @brief   This file provides firmware functions to manage the following 
    *          functionalities of the Window watchdog (WWDG) peripheral:           
    *           + Prescaler, Refresh window and Counter configuration
    *           + WWDG activation
    *           + Interrupts and flags management
    *             
   @verbatim    
   ===============================================================================
                             ##### WWDG features #####
   ===============================================================================
      [..]                                      
          Once enabled the WWDG generates a system reset on expiry of a programmed
          time period, unless the program refreshes the counter (downcounter) 
          before to reach 0x3F value (i.e. a reset is generated when the counter
          value rolls over from 0x40 to 0x3F). 
          An MCU reset is also generated if the counter value is refreshed
          before the counter has reached the refresh window value. This 
          implies that the counter must be refreshed in a limited window.
                
          Once enabled the WWDG cannot be disabled except by a system reset.
            
          WWDGRST flag in RCC_CSR register can be used to inform when a WWDG
          reset occurs.
               
          The WWDG counter input clock is derived from the APB clock divided 
          by a programmable prescaler.
                  
          WWDG counter clock = PCLK1 / Prescaler
          WWDG timeout = (WWDG counter clock) * (counter value)
                         
          Min-max timeout value @42 MHz(PCLK1): ~97.5 us / ~49.9 ms
                               
                        ##### How to use this driver #####
   ===============================================================================
      [..]
        (#) Enable WWDG clock using RCC_APB1PeriphClockCmd(RCC_APB1Periph_WWDG, ENABLE) function
                
        (#) Configure the WWDG prescaler using WWDG_SetPrescaler() function
                               
        (#) Configure the WWDG refresh window using WWDG_SetWindowValue() function
                
        (#) Set the WWDG counter value and start it using WWDG_Enable() function.
            When the WWDG is enabled the counter value should be configured to 
            a value greater than 0x40 to prevent generating an immediate reset.     
                
        (#) Optionally you can enable the Early wakeup interrupt which is 
            generated when the counter reach 0x40.
            Once enabled this interrupt cannot be disabled except by a system reset.
                    
        (#) Then the application program must refresh the WWDG counter at regular
            intervals during normal operation to prevent an MCU reset, using
            WWDG_SetCounter() function. This operation must occur only when
            the counter value is lower than the refresh window value, 
            programmed using WWDG_SetWindowValue().         
    
      @endverbatim
    ******************************************************************************
    * @attention
    *
    * <h2><center>&copy; COPYRIGHT 2015 STMicroelectronics</center></h2>
    *
    * 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.
    *
    ******************************************************************************
    */
  
  /* Includes ------------------------------------------------------------------*/
  #include "stm32f4xx_wwdg.h"
  #include "stm32f4xx_rcc.h"
  
  /** @addtogroup STM32F4xx_StdPeriph_Driver
    * @{
    */
  
  /** @defgroup WWDG 
    * @brief WWDG driver modules
    * @{
    */
  
  /* Private typedef -----------------------------------------------------------*/
  /* Private define ------------------------------------------------------------*/
  
  /* ----------- WWDG registers bit address in the alias region ----------- */
  #define WWDG_OFFSET       (WWDG_BASE - PERIPH_BASE)
  /* Alias word address of EWI bit */
  #define CFR_OFFSET        (WWDG_OFFSET + 0x04)
  #define EWI_BitNumber     0x09
  #define CFR_EWI_BB        (PERIPH_BB_BASE + (CFR_OFFSET * 32) + (EWI_BitNumber * 4))
  
  /* --------------------- WWDG registers bit mask ------------------------ */
  /* CFR register bit mask */
  #define CFR_WDGTB_MASK    ((uint32_t)0xFFFFFE7F)
  #define CFR_W_MASK        ((uint32_t)0xFFFFFF80)
  #define BIT_MASK          ((uint8_t)0x7F)
  
  /* Private macro -------------------------------------------------------------*/
  /* Private variables ---------------------------------------------------------*/
  /* Private function prototypes -----------------------------------------------*/
  /* Private functions ---------------------------------------------------------*/
  
  /** @defgroup WWDG_Private_Functions
    * @{
    */
  
  /** @defgroup WWDG_Group1 Prescaler, Refresh window and Counter configuration functions
   *  @brief   Prescaler, Refresh window and Counter configuration functions 
   *
  @verbatim   
   ===============================================================================
      ##### Prescaler, Refresh window and Counter configuration functions #####
   ===============================================================================  
  
  @endverbatim
    * @{
    */
  
  /**
    * @brief  Deinitializes the WWDG peripheral registers to their default reset values.
    * @param  None
    * @retval None
    */
  void WWDG_DeInit(void)
  {
    RCC_APB1PeriphResetCmd(RCC_APB1Periph_WWDG, ENABLE);
    RCC_APB1PeriphResetCmd(RCC_APB1Periph_WWDG, DISABLE);
  }
  
  /**
    * @brief  Sets the WWDG Prescaler.
    * @param  WWDG_Prescaler: specifies the WWDG Prescaler.
    *   This parameter can be one of the following values:
    *     @arg WWDG_Prescaler_1: WWDG counter clock = (PCLK1/4096)/1
    *     @arg WWDG_Prescaler_2: WWDG counter clock = (PCLK1/4096)/2
    *     @arg WWDG_Prescaler_4: WWDG counter clock = (PCLK1/4096)/4
    *     @arg WWDG_Prescaler_8: WWDG counter clock = (PCLK1/4096)/8
    * @retval None
    */
  void WWDG_SetPrescaler(uint32_t WWDG_Prescaler)
  {
    uint32_t tmpreg = 0;
    /* Check the parameters */
    assert_param(IS_WWDG_PRESCALER(WWDG_Prescaler));
    /* Clear WDGTB[1:0] bits */
    tmpreg = WWDG->CFR & CFR_WDGTB_MASK;
    /* Set WDGTB[1:0] bits according to WWDG_Prescaler value */
    tmpreg |= WWDG_Prescaler;
    /* Store the new value */
    WWDG->CFR = tmpreg;
  }
  
  /**
    * @brief  Sets the WWDG window value.
    * @param  WindowValue: specifies the window value to be compared to the downcounter.
    *   This parameter value must be lower than 0x80.
    * @retval None
    */
  void WWDG_SetWindowValue(uint8_t WindowValue)
  {
    __IO uint32_t tmpreg = 0;
  
    /* Check the parameters */
    assert_param(IS_WWDG_WINDOW_VALUE(WindowValue));
    /* Clear W[6:0] bits */
  
    tmpreg = WWDG->CFR & CFR_W_MASK;
  
    /* Set W[6:0] bits according to WindowValue value */
    tmpreg |= WindowValue & (uint32_t) BIT_MASK;
  
    /* Store the new value */
    WWDG->CFR = tmpreg;
  }
  
  /**
    * @brief  Enables the WWDG Early Wakeup interrupt(EWI).
    * @note   Once enabled this interrupt cannot be disabled except by a system reset.
    * @param  None
    * @retval None
    */
  void WWDG_EnableIT(void)
  {
    *(__IO uint32_t *) CFR_EWI_BB = (uint32_t)ENABLE;
  }
  
  /**
    * @brief  Sets the WWDG counter value.
    * @param  Counter: specifies the watchdog counter value.
    *   This parameter must be a number between 0x40 and 0x7F (to prevent generating
    *   an immediate reset) 
    * @retval None
    */
  void WWDG_SetCounter(uint8_t Counter)
  {
    /* Check the parameters */
    assert_param(IS_WWDG_COUNTER(Counter));
    /* Write to T[6:0] bits to configure the counter value, no need to do
       a read-modify-write; writing a 0 to WDGA bit does nothing */
    WWDG->CR = Counter & BIT_MASK;
  }
  /**
    * @}
    */
  
  /** @defgroup WWDG_Group2 WWDG activation functions
   *  @brief   WWDG activation functions 
   *
  @verbatim   
   ===============================================================================
                      ##### WWDG activation function #####
   ===============================================================================  
  
  @endverbatim
    * @{
    */
  
  /**
    * @brief  Enables WWDG and load the counter value.                  
    * @param  Counter: specifies the watchdog counter value.
    *   This parameter must be a number between 0x40 and 0x7F (to prevent generating
    *   an immediate reset)
    * @retval None
    */
  void WWDG_Enable(uint8_t Counter)
  {
    /* Check the parameters */
    assert_param(IS_WWDG_COUNTER(Counter));
    WWDG->CR = WWDG_CR_WDGA | Counter;
  }
  /**
    * @}
    */
  
  /** @defgroup WWDG_Group3 Interrupts and flags management functions
   *  @brief   Interrupts and flags management functions 
   *
  @verbatim   
   ===============================================================================
              ##### Interrupts and flags management functions #####
   ===============================================================================  
  
  @endverbatim
    * @{
    */
  
  /**
    * @brief  Checks whether the Early Wakeup interrupt flag is set or not.
    * @param  None
    * @retval The new state of the Early Wakeup interrupt flag (SET or RESET)
    */
  FlagStatus WWDG_GetFlagStatus(void)
  {
    FlagStatus bitstatus = RESET;
      
    if ((WWDG->SR) != (uint32_t)RESET)
    {
      bitstatus = SET;
    }
    else
    {
      bitstatus = RESET;
    }
    return bitstatus;
  }
  
  /**
    * @brief  Clears Early Wakeup interrupt flag.
    * @param  None
    * @retval None
    */
  void WWDG_ClearFlag(void)
  {
    WWDG->SR = (uint32_t)RESET;
  }
  
  /**
    * @}
    */
  
  /**
    * @}
    */
  
  /**
    * @}
    */
  
  /**
    * @}
    */
  
  /************************ (C) COPYRIGHT STMicroelectronics *****END OF FILE****/
  