WWDG HAL module driver. This file provides firmware functions to manage the following functionalities of the Window Watchdog (WWDG) peripheral: + Initialization and Configuration functions + IO operation functions.
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#include "stm32f4xx_hal.h"
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Detailed Description
WWDG HAL module driver. This file provides firmware functions to manage the following functionalities of the Window Watchdog (WWDG) peripheral: + Initialization and Configuration functions + IO operation functions.
- Author:
- MCD Application Team
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##### WWDG Specific features #####
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Once enabled the WWDG generates a system reset on expiry of a programmed
time period, unless the program refreshes the counter (T[6;0] downcounter)
before reaching 0x3F value (i.e. a reset is generated when the counter
value rolls down 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.
(+) If required by application, an Early Wakeup Interrupt can be triggered
in order to be warned before WWDG expiration. The Early Wakeup Interrupt
(EWI) can be used if specific safety operations or data logging must
be performed before the actual reset is generated. When the downcounter
reaches 0x40, interrupt occurs. This mechanism requires WWDG interrupt
line to be enabled in NVIC. Once enabled, EWI interrupt 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 clock (Hz) = PCLK1 / (4096 * Prescaler)
(+) WWDG timeout (mS) = 1000 * (T[5;0] + 1) / WWDG clock (Hz)
where T[5;0] are the lowest 6 bits of Counter.
(+) WWDG Counter refresh is allowed between the following limits :
(++) min time (mS) = 1000 * (Counter - Window) / WWDG clock
(++) max time (mS) = 1000 * (Counter - 0x40) / WWDG clock
(+) Typical values:
(++) Counter min (T[5;0] = 0x00) at 42MHz (PCLK1) with zero prescaler:
max timeout before reset: approximately 97.52µs
(++) Counter max (T[5;0] = 0x3F) at 42MHz (PCLK1) with prescaler
dividing by 8:
max timeout before reset: approximately 49.93ms
##### How to use this driver #####
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*** Common driver usage ***
===========================
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(+) Enable WWDG APB1 clock using __HAL_RCC_WWDG_CLK_ENABLE().
(+) Configure the WWDG prescaler, refresh window value, counter value and early
interrupt status using HAL_WWDG_Init() function. This will automatically
enable WWDG and start its downcounter. Time reference can be taken from
function exit. Care must be taken to provide a counter value
greater than 0x40 to prevent generation of immediate reset.
(+) If the Early Wakeup Interrupt (EWI) feature is enabled, an interrupt is
generated when the counter reaches 0x40. When HAL_WWDG_IRQHandler is
triggered by the interrupt service routine, flag will be automatically
cleared and HAL_WWDG_WakeupCallback user callback will be executed. User
can add his own code by customization of callback HAL_WWDG_WakeupCallback.
(+) Then the application program must refresh the WWDG counter at regular
intervals during normal operation to prevent an MCU reset, using
HAL_WWDG_Refresh() function. This operation must occur only when
the counter is lower than the refresh window value already programmed.
*** Callback registration ***
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The compilation define USE_HAL_WWDG_REGISTER_CALLBACKS when set to 1 allows
the user to configure dynamically the driver callbacks. Use Functions
HAL_WWDG_RegisterCallback() to register a user callback.
(+) Function HAL_WWDG_RegisterCallback() allows to register following
callbacks:
(++) EwiCallback : callback for Early WakeUp Interrupt.
(++) MspInitCallback : WWDG MspInit.
This function takes as parameters the HAL peripheral handle, the Callback ID
and a pointer to the user callback function.
(+) Use function HAL_WWDG_UnRegisterCallback() to reset a callback to
the default weak (surcharged) function. HAL_WWDG_UnRegisterCallback()
takes as parameters the HAL peripheral handle and the Callback ID.
This function allows to reset following callbacks:
(++) EwiCallback : callback for Early WakeUp Interrupt.
(++) MspInitCallback : WWDG MspInit.
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When calling HAL_WWDG_Init function, callbacks are reset to the
corresponding legacy weak (surcharged) functions:
HAL_WWDG_EarlyWakeupCallback() and HAL_WWDG_MspInit() only if they have
not been registered before.
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When compilation define USE_HAL_WWDG_REGISTER_CALLBACKS is set to 0 or
not defined, the callback registering feature is not available
and weak (surcharged) callbacks are used.
*** WWDG HAL driver macros list ***
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Below the list of available macros in WWDG HAL driver.
(+) __HAL_WWDG_ENABLE: Enable the WWDG peripheral
(+) __HAL_WWDG_GET_FLAG: Get the selected WWDG's flag status
(+) __HAL_WWDG_CLEAR_FLAG: Clear the WWDG's pending flags
(+) __HAL_WWDG_ENABLE_IT: Enable the WWDG early wakeup interrupt
- Attention:
© Copyright (c) 2016 STMicroelectronics. All rights reserved.
This software component is licensed by ST under BSD 3-Clause license, the "License"; You may not use this file except in compliance with the License. You may obtain a copy of the License at: opensource.org/licenses/BSD-3-Clause
Definition in file stm32f4xx_hal_wwdg.c.
