What is the significance of the interrupt vector table (IVT) in MCUs?

Let%27s delve into the significance of the Interrupt Vector Table (IVT) in microcontrollers (MCUs):

1. What is the IVT?:
- The IVT is a critical data structure within an MCU.
- It contains memory addresses (vectors) that point to specific interrupt service routines (ISRs) or exception handlers.
- Each entry in the IVT corresponds to a specific interrupt or exception source.

2. Role of the IVT:
- Dispatching Interrupts:
- When an interrupt occurs (e.g., button press, timer overflow), the MCU consults the IVT.
- The IVT provides the address of the corresponding ISR.
- The MCU jumps to that address to execute the ISR.
- Exception Handling:
- Exceptions (such as divide-by-zero, memory access violations) also have entries in the IVT.
- The IVT directs the MCU to the appropriate exception handler.
- Priority and Order:
- The IVT determines the order in which interrupts are serviced.
- Higher-priority interrupts have lower vector numbers.
- The MCU services the highest-priority interrupt first.
- Customization:
- The IVT allows customization of interrupt handling.
- Developers can define their own ISRs and assign them to specific interrupt sources.

3. Vector Table Location:
- The IVT resides in a fixed location in memory.
- Its starting address is often set by the MCU manufacturer.
- Some MCUs allow relocation of the IVT to a different memory region.

4. Interrupt Prioritization:
- The IVT%27s order affects interrupt prioritization.
- Critical interrupts (e.g., system faults) have lower vector numbers.
- Peripheral-specific interrupts follow.

5. Efficient Dispatching:
- The IVT ensures efficient dispatching of interrupts.
- Without it, the MCU would need to scan flags or check conditions for each interrupt source.

6. Application Considerations:
- Custom Handlers:
- Developers can replace default ISRs with custom handlers.
- This allows tailored interrupt handling.
- Shared ISRs:
- Some MCUs share a single ISR for multiple interrupt sources.
- The IVT directs the MCU to the common ISR, which then identifies the specific source.

7. Security and Safety:
- The IVT plays a role in system security.
- Unauthorized modification of the IVT can disrupt normal operation.
- Secure bootloaders verify the integrity of the IVT during firmware updates.

In summary, the IVT is a crucial map that guides the MCU to the right code when handling interrupts and exceptions. It ensures efficient and reliable interrupt handling in embedded systems¹².

(1) 8-bit PIC® MCU Vectored Interrupts - Developer Help. https://developerhelp.microchip.com/xwiki/bin/view/products/mcu-mpu/8bit-pic/pic18/vectint/.
(2) . https://bing.com/search?q=interrupt+vector+table+(IVT)+in+MCUs+significance.
(3) What is Interrupt Vector Table? - Microcontrollers Lab. https://microcontrollerslab.com/what-is-interrupt-vector-table/.
(4) What is Interrupt Vector Table (IVT) - Beginners Guide - microdigisoft.com. https://microdigisoft.com/what-is-interrupt-vector-table-ivt/.
(5) undefined. https://ww1.microchip.com/downloads/en/AppNotes/90003162A.pdf.
(6) undefined. https://onlinedocs.microchip.com/oxy/GUID-BA964748-63AC-4D4B-AD5F-E96EAA995DF8-en-US-22/GUID-62FC3E7B-300F-4961-9F3E-68300C0CBDBF.html.

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