Microprocessor Study Notes

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


There are 6 pins available in 8085 for interrupt:
TRAP
RST 7.5
RST6.5
RST5.5
INTR
INTA


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.

There are two types of interrupts used in 8085 Microprocessor:
Hardware Interrupts
Software Interrupts


Software Interrupts A software interrupts is a particular instructions that can be inserted into the desired location in the rpogram. There are eight Software interrupts in 8085 Microprocessor. From RST0 to RST7.
RST0
RST1
RST2
RST3
RST4
RST5
RST6
RST7