Interrupts in Computer System Architecture

1. PRESENTATION
ON
INTERRUPTS

2. INTERRUPTS
It is an unexpected hardware initiated subroutine call or
jump that temporarily suspends the running of the
current program.
Interrupt is a process where an external device can get
the attention of the microprocessor.
Initiation of I/O operation.
Completion of I/O operation.
An interrupt may be either:
Edge Sensitive
Level Sensitive

3. CATEGORIES OF INTERRUPTS
Maskable Interrupts.
Non-Maskable Interrupts.
Vectored Interrupts.
Non-Vectored Interrupts.

4. TYPES OF INTERRUPTS
External Interrupt.
Internal Interrupt.
Software Interrupt.
Hardware Interrupt.

5. USES OF INTERRUPTS
Input/Output data transfers for peripheral
devices.
Emergency situations like power down.
Input signals to be used for timing purposes.
Event driven programs.
Real time response applications and in
multitasking system.

6. INTERRUPT CONTROLLED I/O TRANSFERS
It is an asynchronous mechanism.
Each device is connected to an interrupt line.
When it needs service, it asserts the interrupt
line to request the processors attention.
The status of being executed must first be saved
& it will be saved on stack
If one or more device is connected to the
interrupt line, the processor ends to know which
device service routine it should branch to.
The identification of the device requesting
service can be done in either hardware or
software or a combination of both.

7. INTERRUPT CONTROLLED I/O TRANSFERS
Software Determination of the Requesting Device.
Enable Interrupts.
Request an Interrupt.
Servicing the Interrupt.
Returning to main program.
Interrupt Latency & Interrupt Response Time.
Interrupt Latency.
Interrupt Response Time.

8. INTERRUPT CYCLE
In this cycle, CPU has to check for an interrupt
each time an instruction is executed.
The interrupt enable flip-flop IEN can be set &
cleared with two instructions namely ION & IOF.
ION: Interrupts Enable On.
IOF: Interrupts Enable Off.
When IEN=0, Flag can’t interrupt computer.
When IEN=1,Flag can interrupt computer.