- Interrupt is a process where an external device can get the attention of the microprocessor. The process starts from the I/O device. An interrupt is considered to be an emergency signal that may be serviced. The Microprocessor may respond to it as soon as possible.
- When the Microprocessor receives an interrupt signal, it suspends the currently executing program and jumps to an Interrupt Service Routine (ISR) to respond to the incoming interrupt. Each interrupt will most probably have its own ISR.
- Responding to an interrupt may be immediate or delayed depending on whether the interrupt is maskable or non-maskable and whether interrupts are being masked or not. There are two ways of redirecting the execution to the ISR depending on whether the interrupt is vectored or non-vectored.
The examples of vector interrupt are RST 7.5, RST 6.5, RST 5.5, TRAP.
Non-Vector Interrupt: In this type of interrupt, Processor cannot know the address of Interrupt. It should give externally. In the device will have to send the address of interrupt service routine to processor for performing Interrupt.
The example of Non-vector interrupt is INTR.
- When a device interrupts, it actually wants the MP to give a service which is equivalent to asking the MP to call a subroutine. This subroutine is called ISR (Interrupt Service Routine).
Software Interrupt: It is an instruction based Interrupt which is completely controlled by software. That means programmer can use this instruction to execute interrupt in main program.
There are eight software interrupts available in 8085 microprocessor. See the example with their hex code and vector address.
Hardware Interrupt: As name suggests it is interrupt which can get the interrupt request in hardware pin of microprocessor 8085. There are mainly six dedicated pins available for interrupt purpose.
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