Is calling EXTI_GetITStatus() sometimes unnecessary?

[sima2]

Posted on February 13, 2018 at 16:02

I wonder if I can delete the call to EXTI_GetITStatus() in the following example code?

TheEXTI0_IRQHandler is not used for any other external interrupts. So thecall to

EXTI_GetITStatus() seems unnecessary?

/**
 * @brief ISR for EXTI0 detects a rising edge.
 *
 * This ISR is run when PE0 receives an rising edge. It will increment the counter variable.
 */
void EXTI0_IRQHandler(void)
{
 if (EXTI_GetITStatus(EXTI_Line0) != RESET) // Make sure it is an External interrupt line 0 interrupt 
 {
 counter++;
 EXTI_ClearITPendingBit(EXTI_Line0); // Clear the pending bit
 }
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#stm32

[Tesla DeLorean]

Posted on February 13, 2018 at 17:38

I would not delete it, and I'd move the counter++ the other side of the clearing code.

The CM3/4 have a pipeline/tail-chaining/write-buffer issue with clearing interrupt sources on off-core buses, due to extended latency of this completing. The interrupt can remain pending as you exit the IRQ handler, and then briefly re-enter, validation allows you to ignore this spurious entry. This is a long described hazard.

[sima2]

Posted on February 14, 2018 at 10:11

Just for curiosity. Do you have more information about this, some reference?

[Tesla DeLorean]

Posted on February 14, 2018 at 16:20

https://community.st.com/0D50X00009XkiGqSAJ

 

https://community.st.com/0D50X00009XkYyUSAV

 

https://community.st.com/0D50X00009XkZ4PSAV