系统时钟：

The WWDG clock is prescaled from the APB clock and has a configurable time-window that
can be programmed to detect abnormally late or early application behavior.

/** @defgroup WWDG_Prescaler WWDG Prescaler* @{*/
#define WWDG_PRESCALER_1   0x00000000u     /*!< WWDG counter clock = (PCLK1/4096)/1 */
#define WWDG_PRESCALER_2   WWDG_CFR_WDGTB_0      /*!< WWDG counter clock = (PCLK1/4096)/2 */
#define WWDG_PRESCALER_4   WWDG_CFR_WDGTB_1     /*!< WWDG counter clock = (PCLK1/4096)/4 */
#define WWDG_PRESCALER_8  (WWDG_CFR_WDGTB_1 | WWDG_CFR_WDGTB_0)    /*!< WWDG counter clock = (PCLK1/4096)/8 */

寄存器配置

  hwwdg.Instance = WWDG;hwwdg.Init.Prescaler = WWDG_PRESCALER_1;hwwdg.Init.Window = 240;hwwdg.Init.Counter = 240;hwwdg.Init.EWIMode = WWDG_EWI_DISABLE;if (HAL_WWDG_Init(&hwwdg) != HAL_OK){Error_Handler();}

理论计算时间（1分频）
$$T=\frac{240\ast 4096}{8000000}\ast 1000=122.88ms$$

2分频时间为： 2*122.88 = 245.76ms

喂狗：

/*** @brief  Refresh the WWDG.* @param  hwwdg  pointer to a WWDG_HandleTypeDef structure that contains*                the configuration information for the specified WWDG module.* @retval HAL status*/
HAL_StatusTypeDef HAL_WWDG_Refresh(WWDG_HandleTypeDef *hwwdg)
{/* Write to WWDG CR the WWDG Counter value to refresh with */WRITE_REG(hwwdg->Instance->CR, (hwwdg->Init.Counter));/* Return function status */return HAL_OK;
}