What is an Interrupts and its types in microprocessor ?

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answered Aug 21, 2021 by Kanishk01 (44.9k points)
selected Sep 23, 2021 by Harshal01

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INTERRUPT:-

An interrupt is an external event which informs the CPU that a device needs service.

Normally Program can be interrupt by three ways

(a) By External device

(b) By a special instruction In the program

(c) By the occurrence of some condition.

HARDWARE INTERRUPT:-

An interrupt caused by an external signal is referred as a hardware interrupt.

SOFTWARE INTERRUPT:-

Conditional interrupts or interrupts caused by special instructions are called software interrupt.

(i) TYPE-0 INTERRUPT:-

The divided by zero interrupt (type-0) automatically interrupt the 8086 when a divide error occurs.
The interrupt will occur if the quotient resulting from a division instruction or an IDIV (Integer Division) instruction is too large to fit in the destination register.

(ii) TYPE-1 INTERRUPT:-

The single step interrupt will be enabled only if trap flag (TF) bit is set (=1).

The TF bit can be SET/RESET by software.
Single step control is used for debugging in assembly language in executing a sequence of instruction.
In this mode the processor executes one instruction and then stops.
TRAP flag cannot be set directly .This is done by pushing on the stack ,changes are made and then they are popped.

(iii) TYPE-2 INTERRUPT:-

The non maskable interrupt is initialized through the 8086 NMI pin.
This is used for vital system function such as power failures or external emergency shutdown procedures.
The NMI is edge triggered on a low to high transition .The activation of this pin causes a type-2 interrupt.
NMI has higher priority than the maskable interrupt request pin (INTRA)

(iv)TYPE-3 INTERRUPT:-

Type-3 interrupt or break point is a very special single byte software interrupt.
The type-3 interrupt is produced by execution of the unit INT-3 instruction.
The main use of the type-3 interrupt is to implement a break point function in a system or used debugging software.
In type-3 interrupt the system executes the instruction up to the break point and then goes to the breakpoint procedure unlike the single step feature, which stop executing about each instructions.

(v) TYPE-4 INTERRUPT:-

The interrupt on overflow is a type -4 interrupt and occurs when the flag is set and INTO instruction executed.
The 8086 of will be set if the signed result or arithmetic operation on two signed number is too large to represented in the destination result or memory location.