STM32F37 Standard Peripheral bibliotheek  1.0
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stm32f37x_wwdg.c File Reference

This file provides firmware functions to manage the following functionalities of the Window watchdog (WWDG) peripheral: More...

#include "stm32f37x_wwdg.h"
#include "stm32f37x_rcc.h"


#define CFR_OFFSET   (WWDG_OFFSET + 0x04)
#define EWI_BitNumber   0x09
#define CFR_EWI_BB   (PERIPH_BB_BASE + (CFR_OFFSET * 32) + (EWI_BitNumber * 4))
#define CFR_WDGTB_MASK   ((uint32_t)0xFFFFFE7F)
#define CFR_W_MASK   ((uint32_t)0xFFFFFF80)
#define BIT_MASK   ((uint8_t)0x7F)


void WWDG_DeInit (void)
 Deinitializes the WWDG peripheral registers to their default reset values. More...
void WWDG_SetPrescaler (uint32_t WWDG_Prescaler)
 Sets the WWDG Prescaler. More...
void WWDG_SetWindowValue (uint8_t WindowValue)
 Sets the WWDG window value. More...
void WWDG_EnableIT (void)
 Enables the WWDG Early Wakeup interrupt(EWI). More...
void WWDG_SetCounter (uint8_t Counter)
 Sets the WWDG counter value. More...
void WWDG_Enable (uint8_t Counter)
 Enables WWDG and load the counter value. More...
FlagStatus WWDG_GetFlagStatus (void)
 Checks whether the Early Wakeup interrupt flag is set or not. More...
void WWDG_ClearFlag (void)
 Clears Early Wakeup interrupt flag. More...

Detailed Description

This file provides firmware functions to manage the following functionalities of the Window watchdog (WWDG) peripheral:

MCD Application Team
  • Prescaler, Refresh window and Counter configuration
  • WWDG activation
  • Interrupts and flags management
                         ##### 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 @36MHz (PCLK1): ~114us / ~58.3ms.

                     ##### How to use this driver ##### 
      (#) Enable WWDG clock using RCC_APB1PeriphClockCmd(RCC_APB1Periph_WWDG, ENABLE)
      (#) 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().


© COPYRIGHT 2012 STMicroelectronics

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