121
Chapter 6 EIT: Exceptions, Interrupts and Traps
1.Overview
Chapter 6 EIT: Exceptions, Interrupts and Traps
1. Overview
EIT means that some events interrupt current program to execute other programs. EIT stands for Exception,
Interrupt and Trap.
• Exception is
the event which is generated in association with active context. It is returned to the instruction which triggered the
exception.
• Interrupt is
the event which is generated regardless of active context. Interrupt is triggered by hardware.
• Trap is
the event which is generated in association with active context. Some trap is specified by program such as system call.
It is returned to the instruction following the instruction which triggered the trap.
2. Features
• Supports multiple interrupts.
• Level mask function for interrupt (User can use 15 level.)
• Trap instruction (INT)
• EIT for emulator trigger (hardware/software)
3. EIT Trigger
• Reset
• User interrupt (peripheral function and external interrupt)
• Delayed interrupt
• Undefined-instruction exception
• Trap instruction (INT)
• Trap instruction (INTE)
• Step trace trap
• Coprocessor absent trap
• Coprocessor error trap
• CPU supervisor mode
• Memory protection violation
4. Return from EIT
To return from EIT, use RETI instruction.
