Differentiate between protected and real modes of an Intel microprocessor
Operation of Real mode interrupt: When microprocessor completes executing the current instruction, it determines whether an interrupt is active by checking (1) instruction execution, (2) single -step (3) NMI (4) co-processor segment overrun (5) INTR and (6) INT instruction in the order presented. If one ormore of these interrupt conditions are present, following sequence of events takes place:
1. The contents of flag register are pushed onto the stack
2. Both the trap (TF) and interrupt (IF) flags are cleared. This disables INTR pin and trap or single-step feature.
3. Contents of the code segment register (CS) are pushed onto the stack.
4. Contents of the instruction pointer (IP) are pushed onto the stack.
5. The interrupt vector contents are fetched and then placed into both CS and IP so that next instruction executes at the interrupt service procedure addressed by the vector.