Exception entry and exit sequence in ARM Architecture - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is the first step in the ARM exception entry sequence?

The processor saves the current program status and the return address to a specific register or stack, then switches to the exception mode.

beginner

Why does the ARM processor switch modes during an exception?

Switching modes allows the processor to use a separate set of registers and handle the exception safely without corrupting the main program state.

beginner

What happens to the program counter (PC) during exception entry in ARM architecture?

The PC is set to the address of the exception handler, which is a predefined location where the processor jumps to handle the exception.

beginner

Describe the main purpose of the exception exit sequence in ARM processors.

The exception exit sequence restores the saved program status and return address, switches back to the original mode, and resumes normal program execution.

beginner

How does the ARM processor ensure the original program state is preserved during exceptions?

By saving the current program status and return address in special registers or stack before handling the exception, allowing full restoration after the exception is handled.

What does the ARM processor do immediately after detecting an exception?

A Ignores the exception

B Continues normal execution

C Resets the processor

D Saves the current state and switches to exception mode

When an exception occurs, the ARM processor saves the current state and switches to a special mode to handle the exception.

Where does the ARM processor jump to during exception entry?

A Exception handler address

B Start of the program

C Random memory location

D Stack pointer

The processor sets the program counter to the exception handler address to begin handling the exception.

Why does ARM use different modes during exceptions?

A To use separate registers and protect program state

B To speed up execution

C To save power

D To change instruction set

Different modes allow the processor to use separate registers, preventing corruption of the main program's data.

What is restored during the exception exit sequence?

A Only the stack pointer

B Program status and return address

C Only the program counter

D Nothing is restored

The processor restores the saved program status and return address to resume normal execution.

Which register typically holds the return address during an exception in ARM?

A Status Register (CPSR)

B Program Counter (PC)

C Link Register (LR)

D Stack Pointer (SP)

The Link Register (LR) stores the return address so the processor knows where to continue after the exception.

Explain the sequence of steps the ARM processor follows when an exception occurs.

Think about what must be saved and what changes to the processor state happen first.

Describe how the ARM processor returns to normal execution after handling an exception.

Focus on how the processor recovers the original state.