STM32F4 Standard Peripheral bibliotheek  1.0
ST Microelectronics bibliotheek documentatie voor de STM32F4 Standard Peripheral Library
 All Data Structures Files Functions Variables Enumerations Enumerator Groups
stm32f4xx_wwdg.c File Reference

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

#include "stm32f4xx_wwdg.h"
#include "stm32f4xx_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 @42 MHz(PCLK1): ~97.5 us / ~49.9 ms
*          ===================================================================
*                                 How to use this driver
*          =================================================================== 
*          1. Enable WWDG clock using RCC_APB1PeriphClockCmd(RCC_APB1Periph_WWDG, ENABLE) function
*          2. Configure the WWDG prescaler using WWDG_SetPrescaler() function
*          3. Configure the WWDG refresh window using WWDG_SetWindowValue() function
*          4. 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.     
*          5. 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.
*          6. 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

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:

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.