Interrupt Signals

There are five  interrupt  signals in 8085 microprocessor.  These  signals  are used to inter rut the  current  program  under  execution and  transfer the execution to a predefined interrupt service routine (ISR)  stored at location  reserved for the  corresponding  interrupt signal. These  interrupt signals have a  predefined  priority. If more than  one interrupt signals  goes high  simultaneously  the interrupt  has higher  priority will be  given  first response. Followings  are various  interrupts defined  priority wise.

TRAP  it is a no maskable interrupt  which  cannot  be disabled  and has highest priority.

RST 7.5  RST 6.5 RST 5.5 These are maskable vectored interrupt called restart interrupts. Priority order  of these  interrupts is RST 7.5 RST 6.5 and then RST  5.5 .

INIR called  interrupt request it is a general  purpose non vectored interrupt. It  has lowest priority  among all  above interrupts. It  requires an external hardware to transfer the execution to one  of the eight  possible  locations.

Other  than  these  input  interrupt signals  one more  signal  is related to interrupts  defined below.

INTA it is  called  interrupt  acknowledge signal. It is an  active low output  signals. In  goes low  when  microprocessor receives high  INIR  signals.

All these  interrupts  will discussed in detail in chapter 8.