Identify the Incorrect Configuration
- Analyze the firmware code to determine where the interrupt vector table is defined. This is typically located in a separate source or header file.
- Verify the format and syntax to ensure the entries correspond to the correct interrupt service routines (ISRs). Look for mismatches between vectors and their intended handlers.
- Use a debugger to check the current state of the vector table in memory. Incorrect addresses or misplaced vectors often cause system instability or unexpected behaviors.
Consult the Hardware Manual
- Review the microcontroller's or processor's data sheet to understand the expected structure and size of the interrupt vector table. Each architecture has specific requirements that must be adhered to.
- Confirm that the correct base address is used for the vector table. Incorrect base addresses can lead to the execution of unintended code segments.
Correct Vector Table Definition
- Modify the vector table entries to align with documented specifications. Below is an example of how an interrupt vector table could be structured in C:
void (* const interrupt_vector_table[])(void) = {
[0] = Reset_Handler,
[1] = NMI_Handler,
[2] = HardFault_Handler,
// Add other interrupt vectors as per your specific architecture
};
- Ensure each vector points to the correct ISR functions. Implement or update handlers as necessary to ensure they perform desired actions.
Implement Vector Table Relocation
- If your firmware requires relocating the vector table (common in systems supporting bootloaders), ensure this is done correctly in startup code or bootloader.
- Set the vector table offset register (VTOR) or equivalent register to point to the new vector table location, as shown in the code snippet below:
#define VTOR_ADDRESS 0x08000000 // Example address
SCB->VTOR = VTOR_ADDRESS;
- Ensure the new location is properly initialized and accessible at runtime.
Test the Configuration
- Thoroughly test the interrupt vectors using application-specific test cases. Simulate different interrupt scenarios to confirm handlers execute as expected.
- Use a debugger to step through interrupt routines and monitor vector table accesses to ensure correctness across all conditions.
Optimize and Document Your Work
- Once verified, optimize the vector table and interrupt service routines for performance and memory usage, applying any processor-specific configurations that enhance efficiency.
- Document the configuration, explaining the setup and any assumptions made, to aid future development and troubleshooting processes.
// Example Documentation Comment
/*
* Interrupt Vector Table
* - Base address: 0x08000000
* - Handlers: Reset, NMI, HardFault, etc.
* - Modifications: VTOR updated in bootloader
*/
