Interrupts in 8085 microprocessor | Types of Interrupts in Computer Organization

Summary

This educational video introduces the concept of interrupts in computing, explaining how they are signals that temporarily halt a process to address a higher priority task. It distinguishes between hardware and software interrupts, using examples like keyboard presses and system calls. The script also covers interrupt priority levels, types such as vectored and non-vectored, and the difference between maskable and non-maskable interrupts. Aimed at students, the video simplifies a complex topic for better understanding and exam preparation.

Takeaways

• 📌 An interrupt is a signal that temporarily halts the normal flow of a process to allow the system to attend to a higher priority task.
• 🛠️ Interrupts can be generated by hardware, such as a keyboard press or a system overheating, or by software, like a system call to open a file.
• 🔌 The 8085 microprocessor example illustrates how hardware interrupts can be triggered through specific pins like TRAP, RST, and INTR.
• 💡 Software interrupts are often used for system calls, where the program execution is paused to perform an operation like file handling.
• 🔄 The priority of interrupts is crucial; software interrupts typically have higher priority than hardware interrupts.
• 🔄‍️‍ The 8085 microprocessor assigns different levels of priority to various interrupts, with TRAP having the highest and INTR the lowest.
• 🔄‍️‍ Handling interrupts involves two methods: daisy chaining and parallel interrupt handling, which are explained in a separate video.
• 📍 Vectored interrupts direct the processor to a fixed address to execute a specific service routine, while non-vectored interrupts do not have a fixed address.
• 🚫 Maskable interrupts can be ignored or postponed by the processor if a higher priority task is running, unlike non-maskable interrupts which must be immediately addressed.
• 🔥 Non-maskable interrupts are critical and cannot be ignored, such as a system overheating that requires immediate action to prevent damage.
• 📝 Understanding the concepts of interrupts, their types, and their handling is essential for competitive exams, interviews, and academic assessments.

Q & A

What does the term 'interrupt' mean in the context of computer science?

In computer science, an 'interrupt' refers to the process of stopping a currently running process to deal with a high-priority task or signal, and then returning to the original process once the task is completed.

How does an interrupt differ from a normal process execution?

An interrupt differs from normal process execution by preempting the current process to handle a high-priority task. This is done to ensure that critical issues or signals are addressed promptly.

What is a service routine in the context of interrupts?

A service routine is a specific program or set of instructions that the processor runs to handle an interrupt. It is designed to address the cause of the interrupt and then return control to the interrupted process.

What are the two primary ways in which interrupts can be generated?

Interrupts can be generated either by hardware or software. Hardware interrupts are caused by external devices, while software interrupts are generated by specific instructions within a program.

Can you provide an example of a hardware interrupt?

An example of a hardware interrupt is pressing a key on a keyboard or moving the mouse, which signals the processor to respond to the input.

What is the significance of the pins TRAP, RST, and INTR in the 8085 microprocessor?

In the 8085 microprocessor, pins like TRAP, RST (7.5, 6.5, 5.5), and INTR are used to signal hardware interrupts. These pins allow the processor to recognize and respond to external hardware events.

How does a software interrupt differ from a hardware interrupt?

A software interrupt is generated by specific instructions within a program, such as system calls or I/O operations, whereas a hardware interrupt is triggered by external hardware devices or system conditions.

What is the priority difference between hardware and software interrupts?

Software interrupts generally have a higher priority than hardware interrupts. This means that software interrupts are often handled before hardware interrupts.

What is the difference between vectored and non-vectored interrupts?

Vectored interrupts have a fixed address where the processor jumps to handle the interrupt, while non-vectored interrupts do not have a fixed address and the processor must determine the handling location at runtime.

What are maskable and non-maskable interrupts, and how do they differ?

Maskable interrupts can be temporarily ignored by the processor if a higher priority task is being handled, while non-maskable interrupts must be immediately addressed and cannot be ignored.

Why is it important to understand the concept of interrupts for competitive exams and college/university exams?

Understanding interrupts is important for exams as it is a fundamental concept in computer science that covers process management, interrupt handling, and system design, which are often tested in theoretical and practical examinations.

Outlines

00:00

🛠️ Introduction to Interrupts and Their Types

The video script begins with an introduction to the concept of interrupts in computer science, emphasizing their importance in competitive exams and academic curricula. The presenter defines an interrupt as a mechanism where an ongoing process is momentarily halted to attend to another process, which could be either hardware or software-generated. The script introduces the idea of an 'interrupt service routine', which is the procedure executed to handle the interrupt before resuming the original process. It also touches on the generation of interrupts through hardware, such as keyboard presses or system overheating, and software, like system calls to open a file. The 8085 microprocessor is used as an example to explain hardware interrupts via specific pins, while software interrupts are illustrated with system calls and the use of specific instructions or hexadecimal codes.

05:01

🔧 Understanding Software Interrupts and Interrupt Prioritization

This paragraph delves deeper into software interrupts, explaining how they are generated through programming instructions and system calls, which require the processor to interact with input/output devices. The script clarifies the difference between software and hardware interrupts, noting that software interrupts have a higher priority. It also introduces the concept of prioritization within software interrupts, using the 8085 microprocessor as an example to illustrate the hierarchy of interrupt priorities, with 'trap' having the highest and 'INTR' the lowest. The paragraph further explains the methods of handling multiple interrupts, such as daisy chaining and parallel interrupt handling, and introduces the concepts of vectored and non-vectored interrupts, where vectored interrupts have a fixed address to execute instructions upon occurrence, while non-vectored do not. The script concludes with the distinction between maskable and non-maskable interrupts, with maskable interrupts being ignorable under certain conditions and non-maskable interrupts requiring immediate attention.

Keywords

💡Interrupt

An interrupt is a signal sent to the processor that temporarily halts the current process to allow a higher priority task to be executed. In the video, it is described as a mechanism to stop a running process and switch to another process that requires immediate attention, which can be either hardware or software-based. The concept is central to the video's theme of understanding how interrupts work in computing systems.

💡Process

A process in computing is an instance of a running program. The script mentions that an interrupt can occur while a process is running, causing the processor to stop the current process and attend to the interrupt. This is crucial for handling events that require immediate attention, such as hardware signals or software requests.

💡Service Routine

A service routine is a specific piece of code that is executed in response to an interrupt. The script explains that once an interrupt occurs, the processor will run the service routine associated with that interrupt to handle the event. This is a key concept in the video as it illustrates how interrupts are managed within a system.

💡Hardware Interrupt

A hardware interrupt is generated by a peripheral device or hardware component, such as a keyboard press or a mouse click, as mentioned in the script. These interrupts are typically used to respond to external events or conditions that require the system's immediate attention.

💡Software Interrupt

A software interrupt is generated by a program or software instruction, as opposed to hardware. The script provides an example of opening a file, which requires the processor to switch from the current task to access the file in secondary memory. This type of interrupt is used to invoke system services or handle specific software events.

💡Priority

Priority in the context of interrupts refers to the level of importance assigned to different interrupts. The script explains that software interrupts have a higher priority than hardware interrupts, meaning they are more likely to be handled first by the processor. This concept is essential for understanding how interrupts are prioritized and managed.

💡8085 Microprocessor

The 8085 microprocessor is used as an example in the script to illustrate how hardware interrupts are managed in a specific architecture. It has specific pins for different types of interrupts, such as TRAP, RST, and INTR, which are used to handle various hardware events. This example helps to contextualize the concept of interrupts within a real-world computing system.

💡Daisy Chaining

Daisy chaining is a method of connecting multiple devices in a linear, sequential manner, as mentioned in the script. In the context of interrupts, it refers to a technique where multiple interrupt sources are connected in a chain, allowing the processor to handle them in a specific order. This is an important concept for understanding how multiple interrupts are managed in a system.

💡Vector Interrupt

A vector interrupt is a type of interrupt that directs the processor to a specific memory address to execute a predefined service routine, as explained in the script. This is in contrast to non-vectored interrupts, which do not have a fixed address. The concept is important for understanding how interrupts are handled and routed in a system.

💡Maskable and Non-Maskable Interrupts

Maskable and non-maskable interrupts differentiate the level of urgency an interrupt holds. Maskable interrupts can be ignored or postponed if the processor is handling a higher priority task, while non-maskable interrupts must be dealt with immediately. The script uses the analogy of a fire in a building to illustrate the concept of non-maskable interrupts, emphasizing their immediate importance.

Highlights

Introduction to the concept of interrupts and their importance in competitive exams.

A simple definition of an interrupt as stopping one process to run another.

Interrupts can be generated by both hardware and software.

Explanation of service routines to handle interrupts.

Hardware interrupts are generated by peripheral devices like keyboards or system overheating.

Software interrupts are generated through programming instructions.

Technical examples of hardware interrupts using the 8085 microprocessor.

Software interrupts are often used for system calls like opening a file.

Interrupts have different priorities, with software interrupts having higher priority than hardware.

The concept of vectored and non-vectored interrupts, with fixed and non-fixed addresses.

Distinguishing between maskable and non-maskable interrupts based on their urgency.

High-priority interrupts are typically non-maskable, while low-priority interrupts can be maskable.

The importance of understanding interrupts for competitive exams and interviews.

Discussion on daisy chaining and parallel interrupt handling methods.

The significance of the 'trap' instruction in non-maskable interrupts.

Practical examples to illustrate the concepts of maskable and non-maskable interrupts.

Transcripts

(INTRO)

Dear students, welcome to Quits measures

In today's video I am going to explain

What is interrupt and what are the various types of interrupt

So see this topic is very simple

But this topic is very important in your competitive exams

In college and university exams

So I will explain it very easily with examples

So guys like the video quickly and subscribe the channel

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Then you can get it subscribed from other devices

Subscribers are very important

So let's start what is the concept of interrupt

So what is interrupt actually

Just 5 minutes, I will complete the video in 5 minutes

This is what the meaning of interrupt

Means already one thing is going on

Already one process is going on

But we are stopping that process in between

We are going on some other process

That is the meaning of interrupt

So this is a simple definition

Many definitions will be available

The simple definition is that already you are running a process

By stopping it, you run some other process

That is interrupt

So that second process can be a hardware

It can be a software

So it needs some attention

Kind of attention

So to give it attention, we will stop the running process

So you can show it like this

Means I have a process, I am already running it

The processor is already running it

While running what happened is that there was an interrupt

As soon as the interrupt came, I went to interrupt

Went to interrupt, means to say

Why was the interrupt occurred, from where it occurred

And what I have to do with it now

Obviously I have to fix it too

Whatever problem it is

So I have to fix it

So I will run its service routine

Means what is the meaning of service routine

That the program, means I have an interrupt occurred here

So what I have to do is service routine

I have to go to interrupt service routine

Whatever the program, whatever the interrupt

What I will do with it

I will handle it

By handling it, I will come back to my work

Means I will come back to that process

And resume it

This is the simple meaning of interrupt

So who generates interrupt

We have two ways to generate interrupt

Hardware and software

Means hardware can also generate

And we can also generate through software method

So what does hardware mean

If any hardware, means any peripheral device

Is generating, then that is hardware

Like you pressed something on the keyboard

So this is an example of hardware interrupt

You moved it on the mouse, clicked it

That is what the example of hardware interrupt is

Let's say you have a system

System is heated up

So what will it do when it is heated up

It will turn on the fan

That is what the example of hardware interrupt

You are working on the laptop

While working, let's say you or someone

By mistake, the switch off, switch on button

The power off button

Someone pressed it by mistake

So what happened in that case too

Interrupted

So all these are examples of hardware interrupts

And if we see it a little bit technically

So let's say if I

Give example of 8085 microprocessor

Because it is the most popular

If we talk about in our B Tech

So if we talk about 8085

So we get different pins in it

Like we get

There is a trap

RST 7.5 comes

RST 6.5 comes

RST 5.5 comes

Apart from this, INTR

So what are all these pins

On top of that, the 40 pin architecture

So on top of the 40 pin architecture

We have some pins

TRAP, RST 7.5, 6.5, 5.5

INTR

What are all these pins

On top of it

So whenever anything comes on top of these pins

When anything comes on top of these pins

So what is it in a way

This is an example of hardware interrupt

So anyone is generated by hardware

That is the simple meaning of hardware interrupt

Then comes software interrupt

So what does software interrupt mean

That you are generating an interrupt through a software

Rather than hardware

Like a simple example

You wrote a program

Let's say main

And inside that

There are many lines

You wrote a line in between

Open and file

Means what you did

You wrote in between

To open a particular file

to open a file

You have to go to that file

And where are the files by default

They are in secondary memory

So your processor is executing your work one by one

So what will happen in this case

We will tell the process

Who will get control

It will go to input output device

Means you have to go in between the running process

On secondary memory

There that particular file

Will have to be accessed

Because you have to open

And let's say there is a close, read, write

All that work is in a way

If I am writing system calls

Then all that is an example of software interrupts

And if we talk technically

Let's say 8085

Then all this is there

But normally if we talk

Then we have RST

From 0 to RST7

What are they

Software interrupts

So if you are using this directly

Otherwise sometimes we can write instructions in the program

In which if we write their hexadecimal code

If we write their hexadecimal code

Then what will happen

Then there will be an interrupt

That will be a software interrupt

So this is hardware, this is software

Write the second point in your notes

That software interrupt is having the higher priority

Than the hardware

So there is more priority than hardware

And if we talk about software interrupt

Like I have written here 8085

Then trap has the highest priority

Then 7.5

Then 6.5, then 5.5

And the lowest priority is

INTR, so trap has the highest priority

Because at one time

If it will handle one interrupt

Then who has to do it first

So that is based on its priority

And to handle this also

There are two methods, daisy chaining method

And one is for parallel interrupt

Means if you want to handle parallel

Or through daisy chaining, serial chaining

I have already made a video on that

And its link will be in the suggested video

In the description box

So sometimes questions come on that too

Then vector interrupt

What is the meaning of vector interrupt

Let's say we have

To go to a particular address

I said that we are already doing some work

Interrupt happened in between, so I will handle that interrupt

So what is the meaning of handling this interrupt

Processor will go to a particular address

Run the program, what is this to do

So what is the meaning of vector

The simple meaning of vector

That you have put a program

On a fixed address

As soon as the interrupt happened

You go to that address and there

Execute whatever instruction is written

And non-vectored means

That you have no fixed

Address

You will go to a particular location

not like a fixed location

And execute there

Vector has fixed address

Non-vectored address is not fixed

So like your RST

7.5, 6.5, 5.5, INTR

All of these

Are in a way vector interrupt

But trap is

Non-vectored interrupt

So these small points you should know

Then maskable

And non-maskable, this actually comes

That when the interrupt

Happened, so obviously we want

First of all, the processor leaves all the work

And handle that interrupt

But what is the difference between maskable and non-maskable

Maskable means

Which the processor can't ignore

And non-maskable means

Which we can ignore a little

Interrupt is there, I will see later

I am already doing a good work

A good priority work, so I will see the interrupt later

Like let's say

You are living in a building, there is a fire

So obviously what will happen in that case

In that case you want this thing

Not to be ignored, quickly

Some remedy or solution is found there

So that is your one way

Maskable interrupt

Like trap is your maskable interrupt

Means system got heat up

As soon as the heat up happens, you want the fan to run

So that it doesn't happen

Okay, no problem, I will see

After a while, no, it shouldn't happen

So maskable means

On which we can do

We can put a mask, what can we put in a way

We put a mask, means we hide it

And non-maskable means

On which we can't put a mask, means we can't hide it

Or we can't ignore it

Write this point

So what can we do with maskable

We can ignore it in a way

And we can't ignore non-maskable

trap comes in non-maskable

Means we can't ignore it

This one comes in a way

Maskable interrupt

Means you can do it in a simple way

That high priority interrupt

High priority, by default

Will be non-maskable, means we can't ignore it

Low priority interrupt

That can be a maskable

So these small points

for one marks, in your competitive exams

In interviews, you can ask

Or in your college university exams

can be asked

So this is your interrupt

In this way, you won't get anything outside

After this, your daisy chaining

Parallel

Complete that method also

So that your interrupt portion is completed

Thank you.