NVIC (Nested Vectored Interrupt Controller) in ARM Architecture - Practice Problems & Coding Challenges

Challenge - 5 Problems

🧠 Conceptual

intermediate

Understanding NVIC Priority Grouping

What does the priority grouping in NVIC control?

A It controls how many bits are used for pre-emption priority and how many for subpriority.

B It sets the total number of interrupts the NVIC can handle.

C It determines the clock speed of the NVIC module.

D It enables or disables the nested interrupt feature.

💡 Hint

Think about how NVIC decides which interrupt is more important when multiple occur.

Priority grouping splits the priority bits into pre-emption priority and subpriority bits. Pre-emption priority decides if an interrupt can interrupt another, while subpriority decides order when priorities are equal.

📋 Factual

intermediate

NVIC Interrupt Enable Registers

Which NVIC register is used to enable a specific interrupt?

A NVIC_STIR (Software Trigger Interrupt Register)

B NVIC_ICER (Interrupt Clear-Enable Register)

C NVIC_IPR (Interrupt Priority Register)

D NVIC_ISER (Interrupt Set-Enable Register)

💡 Hint

Look for the register that sets bits to enable interrupts.

The NVIC_ISER register is used to enable interrupts by setting bits corresponding to interrupt numbers.

🔍 Analysis

advanced

NVIC Behavior on Nested Interrupts

Given two interrupts with different pre-emption priorities, what happens when both occur simultaneously?

A The interrupt with lower pre-emption priority executes first.

B Both interrupts execute simultaneously in parallel.

C The interrupt with higher pre-emption priority executes first and can pre-empt the other.

D The NVIC disables both interrupts to avoid conflict.

💡 Hint

Consider how NVIC prioritizes interrupts based on priority levels.

NVIC uses pre-emption priority to decide which interrupt can interrupt another. The higher priority interrupt runs first and can pre-empt the lower priority one.

❓ Comparison

advanced

Difference Between NVIC and Traditional Interrupt Controllers

Which feature distinguishes the NVIC from traditional interrupt controllers?

A NVIC does not support interrupt masking or disabling.

B NVIC supports dynamic priority levels and nested interrupts with hardware support.

C NVIC requires software to manually save and restore context for interrupts.

D NVIC can only handle one interrupt at a time without nesting.

💡 Hint

Think about how NVIC improves interrupt handling efficiency.

NVIC provides hardware support for nested interrupts and flexible priority levels, allowing interrupts to pre-empt others efficiently.

❓ Reasoning

expert

Effect of Incorrect Priority Configuration in NVIC

If all interrupts are configured with the same pre-emption priority but different subpriorities, what is the effect on interrupt handling?

A No interrupt can pre-empt another; subpriority only decides order when interrupts are pending simultaneously.

B Interrupts with higher subpriority will pre-empt those with lower subpriority.

C NVIC will treat all interrupts as having different pre-emption priorities ignoring subpriority.

D NVIC disables all interrupts due to priority conflict.

💡 Hint

Recall the role of pre-emption priority versus subpriority in NVIC.

When pre-emption priorities are equal, no interrupt can pre-empt another. Subpriority only affects the order of pending interrupts but not pre-emption.