Partner Link

Cheap Mobile Phones
- Cheap Mobile Phones - Best Mobile Phone Deals, Laptops, Sat Nav Devices, Cordless Phones, Internet Phones, Broadband Internet Deals from leading retailers of UK. Choose Products and Compare Prices for best deals.


Mobile Phones
- Offers mobile phones on contract, pay as you go, sim free deals with free gifts. We compare latest phone deals from leading retailers of UK.

. ||

Custom logo design
Get your company a logo design. Professional logo designs by expert logo designers. Call 0208 133 2514 for custom logo design packages.


Top Site

Flyer Printing Flyer Printing – Print your flyers on latest design. We offer cheap flyer printing services in all over UK. Full color flyer printing & art work in your own budget. Order for online flyer printing from your home.
Mobile Broadband Deals  Mobile Broadband - Buy Mobile Broadband Deals, Best Mobile Internet Offers With Free Line Rental, USB Modem and Cheapest Network Connection Offers from 3 Mobile in UK
Mobile Upgrades Upgrade Mobile Phone Deals – upgrade your mobile phones from o2, orange, virgin, vodafone, t-mobile and all Manufacturers Nokia, Samsung, Sony Ericsson, LG ,Blackberry and Motorola. Mobile Broadband Deals Mobile Broadband - Buy Mobile Broadband Deals, Best Mobile Internet Offers With Free Line Rental, USB Modem and Cheapest Network Connection Offers from 3 Mobile in UK.

Interrupt Driven I/O

The main disadvantage of programmed I/O as can be noticed is that the CPU is busy waiting for an I/O opportunity and as a result remain tied up for that I/O operation. This disadvantage can be overcome by means of interrupt driven I/O. In Programmed I/O CPU itself checks for an I/O opportunity but in case of interrupt driven I/O the I/O controller interrupts the execution of CPU when ever and I/O operation is required for the computation of the required I/O operation. This way the CPU can perform other computation and interrupted to perform and interrupt service routine only when an I/O operation is required, which is quite an optimal technique.

DMA driven I/O

In case data is needed to transferred from main memory to I/O port this can be done using CPU which will consume 2 bus cycles for a single word, one bus cycle from memory to CPU and other from CPU to I/O port in case of output and the vice versa in case of input. In case no computation on data is required CPU can be bypassed and another device DMA (direct memory access) controller can be used. Its possible to transfer a data word directly from memory to CPU and vice versa in a single bus cycle using the DMA, this technique is definitely faster.

We shall start our discussion with the study of interrupt and the techniques used to program them. We will discuss other methods of I/O as required.
What are interrupts?
Literally to interrupt means to break the continuity of some on going task. When we talk of computer interrupt we mean exactly the same in terms of the processor. When an interrupt occurs the continuity of the processor is broken and the execution branches to an interrupt service routine. This interrupt service routine is a set of instruction carried out by the CPU to perform or initiate an I/O operation generally. When the routine is over the execution of the CPU returns to the point of interruption and continues with the on going process.

Interrupts can be of two types

  1. Hardware interrupts
  2. Software interrupts
Only difference between them is the method by which they are invoked. Software interrupts are invoked by means of some software instruction or statement and hardware interrupt is invoked by means of some hardware controller generally.

Interrupt Mechanism

Interrupts are quite similar to procedures or function because it is also another form temporary execution transfer, but there some differences as well. Note that when procedures are invoked by there names which represents their addresses is specified whereas in case of interrupts their number is specified. This number can be any 8 bit value which certainly is not its address. So the first question is what is the significance of this number? Another thing should also be noticed that procedures are part of the program but the interrupts invoked in the program are no where declared in the program. So the next question is where do these interrupts reside in memory and if they reside in memory then what would be the address of the interrupt?
Firstly lets see where do interrupts reside. Interrupts certainly reside somewhere in memory, the interrupts supported by the operating system resides in kernel which you already know is the core part of the operating system. In case of DOS the kernel is io.sys which loads in memory at boot time and in case of windows the kernel is kernel32.dll or kernel.dll. these files contain most of the I/O routines and are loaded as required. The interrupts supported by the ROM BIOS are loaded in ROM part of the main memory which usually starts at the address F000:0000H. Moreover it is possible that some device drivers have been installed these device drivers may provide some I/O routines so when the system boots these I/O routines get memory resident at interrupt service routines. So these are the three possibilities.
Secondly a program at compile time does not know the exact address where the interrupt service routine will be residing in memory so the loader cannot assign addresses for interrupt invocations. When a device driver loads in memory it places the address of the services provided by itself in the interrupt vector table. Interrupt Vector Table (IVT) in short is a 1024 bytes sized table which can hold 256 far addresses as each far address occupies 4 bytes. So its possible to store the addresses of 256 interrupts hence there are a maximum of 256 interrupt in a standard PC. The interrupt number is used as an index into the table to get the address of the interrupt service routine.


javieth said...

I like to see a good illustration in the websides, even if the text isn´t good, i think the graphics have too much importance.I must to say this blog contain a great graphics and that´s what i´ve been looking for.Actually
costa rica investment opportunities
introduce wonderful graphics about different things.

ishfaq said...

thanks, i have visited so many sites for this topic but i dont find so descriptive and perfect answer for this particular topic. Again thanks to this site

Seo Firm said...

Thanks for showing up such fabulous information. I like this post, keep writing and give informative post...!

Anonymous said...

What an Awfully Written Article!!!

Anonymous said...

Everything is very open with a clear clarification of the challenges.
It was truly informative. Your website is extremely helpful.

Thank you for sharing!
Feel free to surf my web site :: Zachariah Savilla

Anonymous said...

I'm really loving the theme/design of your site. Do you ever run into any browser compatibility issues? A small number of my blog audience have complained about my site not operating correctly in Explorer but looks great in Firefox. Do you have any advice to help fix this problem?

Also visit my web-site ...

Anonymous said...

Thanks very nice blog!

Here is my weblog :: food supplements

Anonymous said...

Do you have any video of that? I'd love to find out some additional information.

Also visit my site ... freelance business
my web page > Http://Www.Ot.Ufc.Br/Mediawiki/Index.Php?Title=UsuáRio:Angelikam

Anonymous said...

This item of golf clothes is lightweight and can
therefore be easily stored in one of the many pockets found on the majority of today's golf bags. Are you the kind of man who prefers classic prep to unrefined, edgier looks. 'V' necks should be paired with a button down collared shirt, remembering to keep the shirt collar tucked in.

Here is my webpage; jual sweater

Anonymous said...

I have loaded your blog in 4 different browsers and I must say this blog loads a lot quicker then most.
Would you mind e-mailing me the name of your website hosting company?

My personal e-mail is: I will even sign up
through your own affiliate link if you would like. Kudos

My web blog - basic electrical circuit symbols

Anonymous said...

NLP behavioural modelling allows us to discovery how we think, feel and behave.
Your family members and friends should always remind you whenever they see your fingers in your mouth.
According to Web - Md males tend to bite their nails more than women.

my blog: How to stop biting your nails

Anonymous said...

When covering the area, it should be enough
to use a regular bandage. After all, they can be readily sourced from
the internet. Those with sensitive skin should not use it as it can irritate.

My web site: How to get rid Of warts

Anonymous said...

hey there and thank you for your information – I have certainly picked
up something new from right here. I did however expertise some technical points using
this web site, as I experienced to reload the site lots of times previous to I could get it to load properly.
I had been wondering if your hosting is OK?
Not that I'm complaining, but slow loading instances times will very frequently affect your placement in google and could damage your high-quality score if advertising and marketing with Adwords. Anyway I am adding this RSS to my email and can look out for a lot more of your respective fascinating content. Make sure you update this again soon.

Feel free to surf to my page: hip to waist ratio calculator

Anonymous said...

That is a good tip particularly to those new to the blogosphere.

Simple but very precise info… Thanks for sharing this one.
A must read article!

my homepage; registry cleaners

Anonymous said...

Adjustable dumbbells have came a long way and a large volume of
these regulate weights with no trouble.

Look into my site: D�noncer un abus

Anonymous said...

The Timeless edition is definitely the most popular and ranges in fat from
five to 45 kilos.

Stop by my web page: alternating dumbbell Curls

Anonymous said...

A calorie deficit is created by eating fewer calories than you melt away.

Also visit my site: dumbbell sets

Anonymous said...

If this comes in the sort of dwelling cleansing for an hour or power coaching on the gymnasium, the
outcome is that each workout keeps your muscle tissues solid, your heart potent, as
well as your physique in shape.

Also visit my website additional reading

Anonymous said...

My partner and I stumbled over here by a different web page
and thought I should check things out. I like what I see so i
am just following you. Look forward to looking into your web page yet again.

Here is my site: just click the next post

Anonymous said...

The other downside will be the simple fact that front-drive ellipticals demand a roller monitor within
their layout.

Here is my blog cheap bowflex selecttech 552 dumbbells

Anonymous said...

The pedals change smoothly so it's nevertheless quiet sufficient to hear the television without the want to convert the volume up.

Here is my web blog :: bowflex selecttech 552 adjustable dumbbells

Anonymous said...

Contrary to other gym treadmills you often find, this
a single adds a very purely natural step-like movement to the movement.

Here is my website ... your blog

Anonymous said...

Informative article, exactly what I needed.

Here is my webpage

Anonymous said...

When applying FES the muscle isn't consistently contracted. This is good as these exercises have been joined to backbone and back again ache.

Here is my web site flex mini coupon

Anonymous said...

It operates with all the Fluid Check procedure that is a unique top quality in Acumen in which it analyzes body style,
relative temperature at the same time because the environment's humidity, so it could alert the user of fluid loss in the course of training.

My web blog; best adjustable dumbbells

Anonymous said...

A person's legs are noted as among the far more noticed features in the body as well as leg press is an excellent approach to shapelier legs.

Feel free to visit my weblog :: select dumbbells

Anonymous said...

So you should not make checklist price the end-all decision maker
when selecting your new dumbbells.

Look into my web site - More Material

Anonymous said...

You are able to quickly swap resistance with the
energy rods by way of a variety of motions for a entire power
and aerobic exercise.

Also visit my web site: click through the up coming document

Anonymous said...

The Bowflex exercise and physical fitness device will come
using a 12 calendar year warranty, so you is not going to should purchase substitute

Visit my blog post :: adjustable dumbbell set

Anonymous said...

Other than the usual coronary heart level, you will discover programs
that may evaluate the gap protected, calories consumed, ordinary coronary heart level, hypertension, and
lots of far more.

my web site -

Anonymous said...

Pave your way to a more healthy you with no avoidable
paying out.

My site: used bowflex selecttech 552 dumbbells

Anonymous said...

Hello There. I found your blog using msn. This is a really well written article.
I will make sure to bookmark it and come back to read more of your useful info.

Thanks for the post. I will certainly return.

my blog post musicos artistas -

Post a Comment

Thanks for interest it