Question

List all the software interrupts of Intel 8085.

Answer 1

Software interrupt of Intel 8085:

• The normal operation of a microprocessor can be interrupted by special instruction. Such an interrupt is called a Software interrupt.
• 8085 provides 8 user-defined software interrupts RST 0 to RST 7 where RST means the restart.
• These interrupts are vectored interrupts and when these interrupts are called the control is transferred to the memory location as shown below:

Interrupt	Mnemonics	Call Location (Hex)
RST RST RST RST RST RST RST RST	0 1 2 3 4 5 6 7	0000H 0008H 0010H 0018H 0020H 0028H 0030H 0038H

• Software interrupts are not used to handle asynchronous events. They are used to call software routines like a single step, breakpoint etc.
• These interrupts are requested by executing interrupt instructions. They can also be requested due to arithmetic errors.
• After execution of these interrupts, the program counter is incremented. The microprocessor does not execute any interrupt acknowledge cycle. The microprocessor executes normal instruction cycle.
• These interrupts cannot be ignored or masked. They have more priority than any hardware interrupt.
• They are not used to interface peripherals. That means, they don’t improve the throughput of the system. They are used in program debugging