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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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.
(+) 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) @80 MHz(PCLK1) with zero prescaler:
max timeout before reset: ~51.2 µs
(++) Counter max (T[5;0] = 0x3F) @80 MHz(PCLK1) with prescaler dividing by 128:
max timeout before reset: ~26.22 ms
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##### How to use this driver #####
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*** Common driver usage ***
===========================
(+) Enable WWDG APB1 clock using __HAL_RCC_WWDG_CLK_ENABLE().
(+) Set the WWDG prescaler, refresh window and counter value
using HAL_WWDG_Init() function.
(+) Start the WWDG using HAL_WWDG_Start() 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 (EWI) which is
generated when the counter reaches 0x40, and then start the WWDG using
HAL_WWDG_Start_IT(). At EWI HAL_WWDG_WakeupCallback is executed and user can
add his own code by customization of callback HAL_WWDG_WakeupCallback.
Once enabled, EWI 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
HAL_WWDG_Refresh() function. This operation must occur only when
the counter is lower than the refresh window value already programmed.
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*** Callback registration ***
=============================
The compilation define USE_HAL_WWDG_REGISTER_CALLBACKS when set to 1 allows
the user to configure dynamically the driver callbacks. Use Functions
@ref HAL_WWDG_RegisterCallback() to register a user callback.
(+) Function @ref 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 @ref HAL_WWDG_UnRegisterCallback() to reset a callback to
the default weak (surcharged) function. @ref 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.
When calling @ref HAL_WWDG_Init function, callbacks are reset to the
corresponding legacy weak (surcharged) functions:
@ref HAL_WWDG_EarlyWakeupCallback() and HAL_WWDG_MspInit() only if they have
not been registered before.
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 most used 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:
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Definition in file stm32l4xx_hal_wwdg.c.
