initiate hardware interrupts in 8085 microprocessor

List the type of signals that have to be applied to initiate hardware interrupts in 8085.

It has three pins for interrupts; NMI, IRQ and FIRQ. A low level on any of these pins will cause an interrupt. The machine state will then be stacked and the routine entered. The appropriate routine address is found in a table of interrupt vectors. Two locations are dedicated to each Interrupt pin, in which are loaded the two bytes of the interrupt routine address.

An order of priority is imposed - the interrupts at the top of the list set the flag bits of the other interrupts to stop them interrupting during the interrupt service routine. The former values of these bits are restored when the flag register is pulled off the stack on return from the interrupt. Further interrupts are then free to occur thereafter.