What happens when interrupt is pending?
A pending interrupt is simply an interrupt that has occurred, is enabled, but hasn’t made it through the interrupt prioritization process to have its handler executed. Interrupts wait for many things: instruction completion, other interrupts, periods where interrupts are disabled…
Which bit will show pending status of interrupt?
The interrupt-pending status is accessible via the Interrupt Set Pending (NVIC->ISPR[n]) and Interrupt Clear Pending (NVIC->ICPR[n]) registers. Similar to the interrupt-enable registers, the pending status controls, if there are more than 32 external interrupt inputs, will contain more than one register.
Which instructions used to check for pending interrupts?
CPU: The CPU checks for pending interrupts at the beginning of an instruction. It answers the highest-priority interrupt, which has a higher priority than that given in the interrupt priority register. 2.
What do you mean by instruction cycle and interrupt cycle?
Interrupt Cycle: An instruction cycle (sometimes called fetch-and-execute cycle, fetch-decode-execute cycle, or FDX) is the basic operation cycle of a computer. This cycle is repeated continuously by the central processing unit (CPU), from bootupto when the computer is shut down.
When to clear the interrupt flag in Cortex-M3 NVIC?
Your memory access is using the data port (and waits for the APB bus cycle to finish), while the instruction port keeps fetching more code which gets executed. The ISR return might execute before the data bus access has completed, so NVIC thinks that the (still) active IRQ was a new one.
What does the status pending mean in NVIC?
An interrupt can have the status pending though it is not active. Clear Interrupt Target State. Clears the interrupt target field in the non-secure NVIC when in secure state. External interrupt number. Value cannot be negative.
How to enable or disable interrupts in NVIC?
The NVIC has the following registers to enable/disable interrupts (one bit for each vector number): NVIC_ISER: Interrupt Set Enable Register to enable an interrupt source NVIC_ICER: Interrupt Clear Enable Register to disable an interrupt source NVIC_ISPR: Interrupt Set Pending Register to raise an interrupt
Is the Cortex M NMI interrupt a custom event?
It is custom IC and custom external event which triggers generic Cortex M NMI interrupt and can be a specific case to IC but is there any limitation for NMI like “you can not clear NMI pending flag and you have to reset it bla bla”? The NMI is acting just like any other interrupt here.