Figure 6.6: Return from interrupt

Return from Interrupt :

• Interrupt service routine starts at location X and the return instruction is in location X + L.


• After fetching the return instruction, the value of program counter becomes X + L + 1.


• While returning to user's program, processor must restore the earlier values.


• From control stack, it restores the value of program counter and the general registers.


• Accordingly it sets the value of the top of the stack and accordingly stack pointer is updated.


• Now the processor starts execution of the user's program (interrupted program) from memory location N + 1.

The data changes of memory and registers during return from and interrupt is shown in the Figure 6.6.