Disabling interrupts and clearing flags (TIM8 CC4) - Only working when interrupts are enabled?

[Tobe]

I have quite a complicated case, where a interrupt is beeing executed, allthough it has been disabled, and its flag beeing cleared. At the same time interrupts are disabled, and i put a few nops in between just to rule out any delay related issues. The disabling of the interrupt works, but there is just one afterwards that i cant get rid of.

For now i just would like to know, if anyone has any idea if the title can be answered with yes. (And if there is a explanation why that is)

I would have liked to try a minimal code, but its quite complicated and i am afraid the error can then not be reproduced. Timers are interconnected too.

[waclawek.jan]

If you disable the interrupt at the source (e.g. in TIMx_DIERx), it takes time until this gets propagated into NVIC.

There may be a strange effect with the interrupt "reappearing" in NVIC, if it was cleared too soon after disabling the interrupt source.

JW

[Tobe]

This is how i clear it:

CLEAR_BIT(TIM8->DIER, TIM_DIER_CC4IE);

30 NOP´s

TIM8->SR = ~TIM_SR_CC4IF;

30 NOP´s

other code

SET_BIT(TIM8->EGR, TIM_EGR_COMG); //should not matter here

delayMicros(2);

When i enable interrupts before the delay, the interrupt does not get fired again, if i enable interrupts after, it does get fired again. See the picture for timing illusatration:

• PC4 is the actual clearing (first 5 lines of code above).
  
• PB11 is the problem interrupt
• Pink lines show interrupt times
• PA12 is the interrupt, that (should) disables the problem interrupt
• Ignore the "IRQ Disabled" channel, as it has some issue and is not valid

[waclawek.jan]

There is no direct relationship between commutation event and CC4 event, so it can't be judged from this description without knowing your entire program.

JW