stm32f37x_iwdg.c File Reference

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

#include "stm32f37x_iwdg.h"

Macros
#define	KR_KEY_RELOAD   ((uint16_t)0xAAAA)
#define	KR_KEY_ENABLE   ((uint16_t)0xCCCC)

Functions
void	IWDG_WriteAccessCmd (uint16_t IWDG_WriteAccess)
	Enables or disables write access to IWDG_PR and IWDG_RLR registers. More...
void	IWDG_SetPrescaler (uint8_t IWDG_Prescaler)
	Sets IWDG Prescaler value. More...
void	IWDG_SetReload (uint16_t Reload)
	Sets IWDG Reload value. More...
void	IWDG_ReloadCounter (void)
	Reloads IWDG counter with value defined in the reload register (write access to IWDG_PR and IWDG_RLR registers disabled). More...
void	IWDG_SetWindowValue (uint16_t WindowValue)
	Sets the IWDG window value. More...
void	IWDG_Enable (void)
	Enables IWDG (write access to IWDG_PR and IWDG_RLR registers disabled). More...
FlagStatus	IWDG_GetFlagStatus (uint16_t IWDG_FLAG)
	Checks whether the specified IWDG flag is set or not. More...

Detailed Description

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

Author

MCD Application Team

Version

V1.0.0

Date

20-September-2012

• Prescaler and Counter configuration
• IWDG activation
• Flag management

*  
============================================================================== 
                        ##### IWDG features #####
============================================================================== 
  [..] The IWDG can be started by either software or hardware (configurable
       through option byte).
           
  [..] The IWDG is clocked by its own dedicated low-speed clock (LSI) and
       thus stays active even if the main clock fails.
       Once the IWDG is started, the LSI is forced ON and cannot be disabled
       (LSI cannot be disabled too), and the counter starts counting down from 
       the reset value of 0xFFF. When it reaches the end of count value (0x000)
       a system reset is generated.
       The IWDG counter should be reloaded at regular intervals to prevent
       an MCU reset.
                           
  [..] The IWDG is implemented in the VDD voltage domain that is still functional
       in STOP and STANDBY mode (IWDG reset can wake-up from STANDBY).
            
  [..] IWDGRST flag in RCC_CSR register can be used to inform when a IWDG
       reset occurs.
            
  [..] Min-max timeout value @40KHz (LSI): ~0.1ms / ~28.3s
       The IWDG timeout may vary due to LSI frequency dispersion. STM32F37x
       devices provide the capability to measure the LSI frequency (LSI clock
       should be seleted as RTC clock which is internally connected to TIM14 CH1
       input capture). The measured value can be used to have an IWDG timeout with
       an acceptable accuracy. 
       For more information, please refer to the STM32F37x Reference manual.
          
                        ##### How to use this driver ##### 
============================================================================== 
  [..] This driver allows to use IWDG peripheral with either window option enabled
       or disabled. To do so follow one of the two procedures below.
  (#) Window option is enabled:    
      (++) Start the IWDG using IWDG_Enable() function, when the IWDG is used
           in software mode (no need to enable the LSI, it will be enabled
           by hardware).        
      (++) Enable write access to IWDG_PR and IWDG_RLR registers using
           IWDG_WriteAccessCmd(IWDG_WriteAccess_Enable) function.
      (++) Configure the IWDG prescaler using IWDG_SetPrescaler() function.
      (++) Configure the IWDG counter value using IWDG_SetReload() function.
           This value will be loaded in the IWDG counter each time the counter
           is reloaded, then the IWDG will start counting down from this value.
      (++) Wait for the IWDG registers to be updated using IWDG_GetFlagStatus() function.
      (++) Configure the IWDG refresh window using IWDG_SetWindowValue() function.

  (#) Window option is disabled:    
      (++) Enable write access to IWDG_PR and IWDG_RLR registers using
           IWDG_WriteAccessCmd(IWDG_WriteAccess_Enable) function.
      (++) Configure the IWDG prescaler using IWDG_SetPrescaler() function.
      (++) Configure the IWDG counter value using IWDG_SetReload() function.
           This value will be loaded in the IWDG counter each time the counter
           is reloaded, then the IWDG will start counting down from this value.
      (++) Wait for the IWDG registers to be updated using IWDG_GetFlagStatus() function.
      (++) reload the IWDG counter at regular intervals during normal operation 
           to prevent an MCU reset, using IWDG_ReloadCounter() function.
      (++) Start the IWDG using IWDG_Enable() function, when the IWDG is used
           in software mode (no need to enable the LSI, it will be enabled
           by hardware).

Attention

© 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:

   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.