STM32 HAL Lib，Can not clear TIM SR register by use __HAL_TIM_CLEAR_FLAG？ - stm32

Question

The TIM SR register value always be 0x1F, And Can not use to clear the reg.
HAL Lib Always runs into time interrupt really fast, and Can not clear SR register.
How to fix the promble？
Cubemx set
NVIC
`
void TIM3_IRQHandler(void)
{
/* USER CODE BEGIN TIM3_IRQn 0 */
/* USER CODE END TIM3_IRQn 0 */
HAL_TIM_IRQHandler(&htim3);
/* USER CODE BEGIN TIM3_IRQn 1 */
/* USER CODE END TIM3_IRQn 1 */
}
`
`
void HAL_TIM_PeriodElapsedCallback(TIM_HandleTypeDef *htim)
{
if ( htim == &htim3){
__HAL_TIM_CLEAR_FLAG(&htim3,TIM_FLAG_UPDATE) ;
HAL_GPIO_TogglePin(GPIOC,GPIO_PIN_13) ;
}
}
`

Answer 1

I will base my explanation on STM32F746's TIM3. Timers across STM32 that share number are usually identical or very similar.
TIM3->SR has 0x1F? That's 5 flags set! TIM3 is a general purpose STM32 timer. These 5 flags mean you have counter interrupt and four capture/compare interrupt status flags set at the same time. Something weird is going on. Are you sure you're supposed to have those flags set? Well, if their interrupts are not enabled, it doesn't matter.
You can clear these flags in TIM3->SR by writing zero to the specific position you want to clear and 1 everywhere else. As per reference manual, this register ignores if you write 1. It doesn't set bits when you do that. It only resets when you write zero. So,
TIM3->SR = 0; //clear all interrupt flags
TIM3->SR = ~TIM_SR_UIF; //clear update interrupt flag only
This works because the bits in the reference manual are marked rc_w0 - read, clear by writing zero. If bits in your SR register work differently, you may have to clear them differently. For example, sometimes status register is read-only and you clear it via write to flag clear register. Check reference manual of your MCU.