Interrupts

 Software Interrupts:-

Software interrupt are a type of interrupts that can be put at any location in the program.
There are eight software interrupts i.e. RST0 to RST7.
 These instructions transfer s the program control from the main program to subroutine program and after completing the subroutine program the control returns back to the main program

Vector Address these interrupts are calculated by the below given formula:-
 Vector Address = Interrupt Number * 8
e.g;
 RST1:        vector address=1*8    =  08
 RST2:        vector address=2*8    =  16
 RST3:        vector address=3*8    =  24

Interrupt	Vector Address
RST0	0000H
RST1	0008H
RST2	0010H
RST3	0018H
RST4	0020H
RST5	0028H
RST6	0030H
RST7	0038H

       

 Hardware Interrupt:-
 
          8085 has five hardware interrupt signals that can be used to interrupt program execution.these signals are
            (1)TRAP
            (2)RST 7.5
            (3)RST 6.5
            (4)RST 5.5
            (5)INTR/INTA
      

TRAP (PIN 6):

    Trap is highest priority, nonmaskable interrupt, when trap is received microprocessor starts the program execution from location (4.5*8) =0024H. this is why it is also called as vectored interrupt.

RST 7.5, 6.5, 5.5 (PIN 7,8,9):
     These are restart interrupts or vectored interrupt. these are maskable interrupt and has lower priority than TRAP, among these RST 7.5 has the highest priority and RST 5.5 having the lowest.

INTR (PIN 10):
    Interrupt request - this signal is used as a general purpose interrupt.it has lowest priority and is a maskable interrupt.

INTA (PIN 11):
     This is interrupt acknowledgement signal sent by the processor when INTR is recognized. This is active low signal.