WWDG HAL module driver. This file provides firmware functions to manage the following functionalities of the Window Watchdog (WWDG) peripheral: + Initialization and de-initialization functions + IO operation functions + Peripheral State 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 de-initialization functions + IO operation functions + Peripheral State 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 (downcounter)
before reaching 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 clock (Hz) = PCLK1 / (4096 * Prescaler)
(+) WWDG timeout (mS) = 1000 * Counter / WWDG clock
(+) 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
(+) Min-max timeout value at 50 MHz(PCLK1): 81.9 us / 41.9 ms
(+) 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 the value 0x40, an EWI interrupt
is generated and the corresponding interrupt service routine (ISR) can
be used to trigger specific actions (such as communications or data
logging), before resetting the device.
In some applications, the EWI interrupt can be used to manage a software
system check and/or system recovery/graceful degradation, without
generating a WWDG reset. In this case, the corresponding interrupt
service routine (ISR) should reload the WWDG counter to avoid the WWDG
reset, then trigger the required actions.
Note:When the EWI interrupt cannot be served, e.g. due to a system lock
in a higher priority task, the WWDG reset will eventually be generated.
(+) Debug mode : When the microcontroller enters debug mode (core halted),
the WWDG counter either continues to work normally or stops, depending
on DBG_WWDG_STOP configuration bit in DBG module, accessible through
__HAL_DBGMCU_FREEZE_WWDG() and __HAL_DBGMCU_UNFREEZE_WWDG() macros
##### How to use this driver #####
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(+) Enable WWDG APB1 clock using __HAL_RCC_WWDG_CLK_ENABLE().
(+) Set the WWDG prescaler, refresh window, counter value and Early Wakeup
Interrupt mode using using HAL_WWDG_Init() function.
This enables WWDG peripheral and the downcounter starts downcounting
from given counter value.
Init function can be called again to modify all watchdog parameters,
however if EWI mode has been set once, it can't be clear until next
reset.
(+) 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 window value already programmed.
(+) if Early Wakeup Interrupt mode is enable an interrupt is generated when
the counter reaches 0x40. User can add his own code in weak function
HAL_WWDG_EarlyWakeupCallback().
*** WWDG HAL driver macros list ***
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Below the list of most used macros in WWDG HAL driver.
(+) __HAL_WWDG_GET_IT_SOURCE: Check the selected WWDG's interrupt source.
(+) __HAL_WWDG_GET_FLAG: Get the selected WWDG's flag status.
(+) __HAL_WWDG_CLEAR_FLAG: Clear the WWDG's pending flags.
- Attention:
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Definition in file stm32f4xx_hal_wwdg.c.
