Describe Real and protected mode:
Operation of Real mode interrupt: When microprocessor completes executing the current instruction, it concludes 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 or more of these interrupt conditions are present, following sequence of events takes place:
1. Contents of the flag register are pushed onto the stack
2. Both the interrupt (IF) and trap (TF) 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 the subsequent instruction executes at the interrupt service procedure addressed by the vector.