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To accommodate interrupts, an interrupt cycle is added to the instruction cycle, as shown in Figure 7. In the interrupt cycle, the processor checks to see if any interrupts have occurred, indicated by the presence of an interrupt signal. If no interrupts arc pending, the processor proceeds to the fetch cycle and fetches the next instruction of the current program. If an interrupt is pending, the processor does the following:

  • It suspends execution of the current program being executed and saves its context. This means saving the address of the next instruction to be executed (current contents of the program counter) and any other data relevant to the processor's current activity.
  • It sets the program counter to the starting address of an interrupt handler routine.

Figure 7: Instruction Cycle with Interrupts.

The processor now proceeds to the fetch cycle and fetches the first instruc­tion in the interrupt handler program, which will service the interrupt. The inter­rupt handler program is generally part of the operating system. Typically, this program determines the nature of the interrupt and performs whatever actions are needed. In the example we have been using, the handler determines which I/O module generated the interrupt, and may branch to a program that will write more data out to that I/O module. When the interrupt handler routine is com­pleted, the processor can resume execution of the user program at the point of interruption. Figure 8 shows a revised instruction cycle state diagram that includes interrupt cycle processing.

Figure 8: Instruction cycle state diagram with interrupt

Multiple interrupts

In some cases, multiple interrupts can occur. For example, a program may be receiving data from a communications line and printing results. The printer will generate an interrupt every lime that it completes a print operation. The communi­cation line controller will generate an interrupt every time a unit of data arrives. I he unit could either be a single character or a block, depending on the nature of the communications discipline. In any case, it is possible for a communications interrupt to occur while a printer interrupt is being processed. Two approaches can be taken to dealing with multiple interrupts:

  • Disabling interrupts while an interrupt is being processed.
  • Defining priorities for interrupts.

The first is to disable interrupts while an interrupt is being processed. A disabled interrupt sim­ply means that the processor can and will ignore that interrupt request signal. If an interrupt occurs during this time, it generally remains pending and will be cheeked by the processor after the processor has enabled interrupts. Thus, when a user pro­gram is executing and an interrupt occurs, interrupts are disabled immediately. After the interrupt handler routine completes, interrupts are enabled before re­suming the user program, and the processor checks to see if additional interrupts have occurred. This approach is nice and simple, as interrupts are handled in strict sequential order (Figure 2.10).

Questions & Answers

Do somebody tell me a best nano engineering book for beginners?
s. Reply
what is fullerene does it is used to make bukky balls
Devang Reply
are you nano engineer ?
what is the Synthesis, properties,and applications of carbon nano chemistry
Abhijith Reply
so some one know about replacing silicon atom with phosphorous in semiconductors device?
s. Reply
Yeah, it is a pain to say the least. You basically have to heat the substarte up to around 1000 degrees celcius then pass phosphene gas over top of it, which is explosive and toxic by the way, under very low pressure.
how to fabricate graphene ink ?
for screen printed electrodes ?
What is lattice structure?
s. Reply
of graphene you mean?
or in general
in general
Graphene has a hexagonal structure
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what is biological synthesis of nanoparticles
Sanket Reply
what's the easiest and fastest way to the synthesize AgNP?
Damian Reply
types of nano material
abeetha Reply
I start with an easy one. carbon nanotubes woven into a long filament like a string
many many of nanotubes
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what is the function of carbon nanotubes?
I'm interested in nanotube
what is nanomaterials​ and their applications of sensors.
Ramkumar Reply
what is nano technology
Sravani Reply
what is system testing?
preparation of nanomaterial
Victor Reply
Yes, Nanotechnology has a very fast field of applications and their is always something new to do with it...
Himanshu Reply
good afternoon madam
what is system testing
what is the application of nanotechnology?
In this morden time nanotechnology used in many field . 1-Electronics-manufacturad IC ,RAM,MRAM,solar panel etc 2-Helth and Medical-Nanomedicine,Drug Dilivery for cancer treatment etc 3- Atomobile -MEMS, Coating on car etc. and may other field for details you can check at Google
anybody can imagine what will be happen after 100 years from now in nano tech world
after 100 year this will be not nanotechnology maybe this technology name will be change . maybe aftet 100 year . we work on electron lable practically about its properties and behaviour by the different instruments
name doesn't matter , whatever it will be change... I'm taking about effect on circumstances of the microscopic world
how hard could it be to apply nanotechnology against viral infections such HIV or Ebola?
silver nanoparticles could handle the job?
not now but maybe in future only AgNP maybe any other nanomaterials
I'm interested in Nanotube
this technology will not going on for the long time , so I'm thinking about femtotechnology 10^-15
can nanotechnology change the direction of the face of the world
Prasenjit Reply
At high concentrations (>0.01 M), the relation between absorptivity coefficient and absorbance is no longer linear. This is due to the electrostatic interactions between the quantum dots in close proximity. If the concentration of the solution is high, another effect that is seen is the scattering of light from the large number of quantum dots. This assumption only works at low concentrations of the analyte. Presence of stray light.
Ali Reply
how did you get the value of 2000N.What calculations are needed to arrive at it
Smarajit Reply
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Source:  OpenStax, Computer architecture. OpenStax CNX. Jul 29, 2009 Download for free at http://cnx.org/content/col10761/1.1
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