S32K中的主题 S32K148 - interrupts disable/enable

S32K148 - interrupts disable/enable

jakub_mielczare — Wed, 29 Jul 2020 14:09:00 GMT

Hello,

Assume I have following code sequence:

1. disable_interrupts()

2. some code

3. disable_interrupts()

4. some code

5. enable_interrupts()

6. some code

7. enable_interrupts()

disable_interrupts() is done by __asm("cpsid i")

enable_interrupts() is done by __asm("cpsie i")

When will interrupts become enabled back in the above sequence, at 5. or at 7.? Does S32K148 keep track of nested "cpsid" and "cpsie"?

Kind regards,

Jakub

Re: S32K148 - interrupts disable/enable

Joey_van_Hummel — Wed, 29 Jul 2020 14:31:53 GMT

CPS Instructions in the ARMv7-M architecture directly influence PRIMASK and FAULTMASK registers. No nesting is performed.

Re: S32K148 - interrupts disable/enable

jakub_mielczare — Thu, 30 Jul 2020 13:52:55 GMT

Thank you.

Is it safe to call those instructions from ISR?

Re: S32K148 - interrupts disable/enable

Joey_van_Hummel — Thu, 30 Jul 2020 21:16:18 GMT

It's safe in the sense that the documentation doesn't state not to do it.

If you want to enable interrupt nesting, calling CPSIE inside the ISR (like you would on an S12X) is not the way to go, since PRIMASK and FAULTMASK are unchanged upon exception entry. It won't have any effect. You can make use of the priority levels. Higher priority exceptions can interrupt lower priority exceptions.

If you want to prevent interrupts from interrupting your ISR, you can safely call CPSID and then re-enable with CPSIE when you're done.