Friday, 7 December 2012

Interrupts in 8085 Microprocessor

First of all i want to discuss that what is Interrupt???????

Interrupt is a mechanism by which an I/O or an instruction can suspend the normal execution of processor and get itself serviced. Generally, a particular task is assigned to that interrupt signal. In the microprocessor based system the interrupts are used for data transfer between the peripheral  devices and the microprocessor. The processor will check the interrupts always at the 2nd T-state of last machine cycle.

Interrupt Service Routine(ISR):-A small program or a routine that when executed services
 the corresponding interrupting source is called as an ISR.

Maskable/Non-Maskable Interrupt:-An interrupt that can be disabled by writing some instruction is known as Maskable Interrupt otherwise it is called Non-Maskable Interrupt.

There are two types of interrupts used in 8085 Microprocessor:

1.Hardware Interrupts
2.Software Interrupts

There are 6 pins available in 8085 for interrupt:

RST 7.5

Execution of Interrupts:-
When there is an interrupt requests to the Microprocessor then after accepting the interrupts Microprocessor send the INTA (active low) signal to the peripheral. The vectored address of particular interrupt is stored in program counter. The processor executes an interrupt service routine (ISR) addressed in program counter.