Exceptions, Interrupts, & Vector Table

• Exceptions

  • processor sets PC to specific memory address

    • Address is within a special range called vector table

    • Entries in Vector Table are instructions that branch to specific routines for handling particular interrupts/exceptions

  • 0x00000000 is reserved for vector table

    • some processors allow higher address 0xffff0000

    • Linux and windows use this higher address

• Each vector table entry contains a form of branch instruction pointing to specific routine

  • reset vector: location of first instruction executed by processor when power is applied.

    • branches to initialized code

  • undefined instruction vector: used when processor cannot decode an instruction

  • software interrupt vector: called when an SWI instruction is executed

    • often used to invoke an OS routine

  • prefetch abort vector: used when processor attempts to fetch instruction from address w/o correct access permissions

    • abort occurs in decode stage

  • data abort vector: when instruction attempts to access data memory w/o correct access permission

  • Interrupt request vector: external hardware causes interrupt

  • Fast interrupt request vector: same as above, but requiring faster response time