ARM_Advanced_Exceptions_Interrupts_Extensions.pptx

ARM basic fundamntals

1. ARM Exceptions, Interrupts, and Core Extensions Detailed Explanation with Multiple Slides per Topic

2. Overview of Exceptions in ARM • Exceptions are events that interrupt normal execution. • Can be caused by software, hardware, or external signals. • ARM handles exceptions using vector table entries. • Examples include Reset, Undefined Instructions, and Data Abort.

3. Types of Exceptions 1. **Reset** – Occurs on processor startup or reset signal. 2. **Undefined Instruction** – Triggered when an unknown instruction is executed. 3. **Software Interrupt (SWI)** – Used for OS calls and system services. 4. **Prefetch Abort** – When instruction fetch fails due to memory issues. 5. **Data Abort** – Occurs when an invalid memory access happens.

4. Exception Handling Process 1. Processor saves CPSR into SPSR of the mode handling the exception. 2. The processor switches to the relevant mode (e.g., Abort mode). 3. Execution jumps to the corresponding address in the vector table. 4. Exception handler executes necessary routines. 5. The handler restores CPSR and resumes normal execution.

5. Exception Flow Diagram • Shows how ARM transitions between modes when exceptions occur. • Includes how CPSR is saved and execution branches to exception handlers. [Insert Figure Here]

6. Software Interrupt (SWI) in Detail • SWI is a special instruction used to invoke system calls. • Used to switch from user mode to supervisor mode. • Common in OS kernels and embedded system calls. • The processor jumps to the SWI vector in the vector table.

7. Overview of Interrupts in ARM • Interrupts allow external devices to signal the processor. • ARM supports two main types of interrupts: - **IRQ (Interrupt Request):** General-purpose interrupt. - **FIQ (Fast Interrupt Request):** Higher priority, faster response.

8. ARM Vector Table • The vector table is a memory-mapped table at address 0x00000000. • Contains branch instructions pointing to exception handlers. • Entries in the vector table: - Reset (0x00), Undefined Instruction (0x04), SWI (0x08), - Prefetch Abort (0x0C), Data Abort (0x10), IRQ (0x18), FIQ (0x1C).

9. FIQ vs IRQ – Key Differences • **FIQ (Fast Interrupt Request):** - Higher priority than IRQ. - Uses banked registers for faster execution. - Typically used for real-time applications like motor control. • **IRQ (Interrupt Request):** - Standard interrupt with lower priority. - Saves context and switches to interrupt mode.

10. Nested Interrupt Handling • ARM supports **nested interrupts**, where a higher priority interrupt can preempt a lower one. • The interrupt handler must save the CPSR before enabling other interrupts. • Used in real-time systems to ensure high-priority tasks run first.

11. Core Extensions in ARM • ARM cores include hardware extensions to improve performance and efficiency. • Three major core extensions: - Cache & Tightly Coupled Memory (TCM) - Memory Management (MMU, MPU) - Coprocessor Interface.

12. Cache and Tightly Coupled Memory (TCM) • Cache stores frequently accessed data to speed up execution. • ARM processors may have **separate instruction and data caches** (Harvard architecture). • TCM is a high-speed SRAM used for real-time tasks requiring predictable memory access.

13. • Diagram comparing cache-based and TCM-based architectures. • Shows how memory access latency is reduced .

14. Memory Management – MMU & MPU • **Memory Protection Unit (MPU):** - Defines memory regions with access permissions. - Used in embedded systems with simple memory maps. • **Memory Management Unit (MMU):** - Provides virtual memory mapping. - Supports multitasking operating systems (Linux, Android).

15. Coprocessors in ARM • ARM supports coprocessors to enhance specific functionalities. • Example: Vector Floating Point (VFP) coprocessor for floating-point arithmetic. • Coprocessor 15 (CP15) controls cache, MMU, and system configuration.