Professional Courses
Industry-relevant training in Business, Technology, and Design to help professionals and graduates upskill for real-world careers.
Categories
Interactive Games
Fun, engaging games to boost memory, math fluency, typing speed, and English skills—perfect for learners of all ages.
Typing
Memory
Math
English Adventures
Knowledge
Enroll to start learning
You’ve not yet enrolled in this course. Please enroll for free to listen to audio lessons, classroom podcasts and take practice test.
Interactive Audio Lesson
Listen to a student-teacher conversation explaining the topic in a relatable way.
Understanding Programmed I/O
Unlock Audio Lesson
Today, we're going to discuss programmed I/O. Can anyone tell me what programmed I/O means?
Is it when the CPU directly controls the I/O operations?
Exactly! In programmed I/O, the CPU actively checks the status of an I/O device by polling it. This means the CPU waits for the device to be ready before performing data transfer, which can waste valuable CPU time.
What happens while the CPU is waiting?
Great question! While it's polling, the CPU is unable to perform other tasks, which means efficiency can be reduced.
So, how does the CPU know when the device is ready?
The CPU checks a status bit. If it's set to 1, the device is ready for data transfer.
Can you give us a simple example of this?
Sure! Think of it like waiting for a bus. You keep checking the bus schedule—if it says 'Bus is here,' you get on. Polling is like checking that schedule repeatedly until the bus arrives.
So to summarize, programmed I/O involves the CPU polling for device readiness, which can waste time if not managed correctly.
I/O Addressing Schemes
Unlock Audio Lesson
Now, let’s delve into how we address I/O devices. Can someone tell me why we need to address them?
So we can identify which device we're working with?
Exactly! Just like each house has a unique address, each device requires a unique identifier. This lets the CPU communicate effectively with multiple devices.
What are the main schemes for addressing, then?
There are two primary schemes: memory-mapped I/O and isolated I/O. Memory-mapped I/O uses the same address space for both memory and I/O, whereas isolated I/O has separate spaces.
What’s the advantage of each?
In memory-mapped I/O, you can use the same assembly instructions for both memory and I/O, making it simpler. Isolated I/O, however, allows for many more devices without address conflicts.
So more devices can be connected with isolated I/O?
Yes, that’s right! For example, isolated I/O could support 64k devices when using a 16-bit address bus, whereas memory-mapped might reserve only a few addresses for I/O.
To recap, addressing schemes like memory-mapped and isolated I/O are crucial for managing device communication. They determine how efficiently we can connect multiple devices.
Control Commands in I/O Operations
Unlock Audio Lesson
Next, let's talk about the control commands we need for I/O operations. Why do we need to issue commands?
To control what the I/O device does?
Correct! Commands like read, write, and status check help manage I/O devices effectively. Can anyone give me an example of a control command?
How about the command to read data from a device?
Exactly! The 'read' command allows us to retrieve data from an input device, while 'write' sends data to an output device.
What happens if we don't check the status of a device before commands?
Excellent question! If we attempt to use a device that's not ready, we might get incorrect data or encounter errors. That's why status checks are essential.
Are there different categories of control commands?
Yes! We have controlling commands, test commands, and read/write commands. Each serves a specific purpose in device management.
To summarize, control commands are critical for ensuring devices are managed correctly, involving reading, writing, and checking status.
Introduction & Overview
Read a summary of the section's main ideas. Choose from Basic, Medium, or Detailed.
Quick Overview
Standard
The section details how I/O devices communicate with a CPU using programmed I/O techniques, emphasizing the inefficiencies of polling. It contrasts memory-mapped I/O, which shares address space with memory, and isolated I/O, which has separate address spaces for memory and I/O devices.
Detailed
Detailed Summary of Mapping I/O Devices
This section elucidates the process of mapping I/O devices to the CPU, showcasing how data transfer can occur efficiently. The key concept here is programmed I/O, where the CPU actively waits and checks (polls) the status of I/O devices, leading to potential wastage of CPU resources. The steps involved in programmed I/O include the CPU initiating an I/O operation and monitoring the status of devices via a status bit.
The section also addresses the addressing schemes necessary for identifying I/O devices. Two primary methods for mapping I/O devices are presented: Memory-mapped I/O and Isolated I/O. In memory-mapped I/O, both memory and I/O devices share the same address space, allowing I/O operations to be treated similarly to memory operations. Conversely, isolated I/O uses distinct address spaces for memory and I/O devices, requiring additional control signals to differentiate between them. This fundamental understanding of I/O mapping aids in grasping how CPUs manage communication with peripherals.
Youtube Videos
Audio Book
Dive deep into the subject with an immersive audiobook experience.
Understanding Programmed I/O
Unlock Audio Book
Signup and Enroll to the course for listening the Audio Book
So, basically it is a sensing of status, then using the read write command, then transferring of data; this is the way that we are going to do, but here what is the problem that we have first? CPU needs to wait and poll, it is checking it continuously. So, it cannot do any other work. So, there is a wastage of CPU time.
Detailed Explanation
In programmed I/O, the CPU constantly checks the status of an I/O device to see if it's ready for data transfer. This continuous monitoring is termed polling. The downside is that while the CPU waits for the device to be ready, it cannot perform other tasks, leading to inefficient use of CPU resources.
Examples & Analogies
Imagine a waiter at a restaurant who stands by a customer's table waiting for them to finish their meal before taking the plates away. While the waiter is waiting, they cannot attend to other tables, which leads to delays and inefficient service.
Steps in Programmed I/O Operation
Unlock Audio Book
Signup and Enroll to the course for listening the Audio Book
So, basically this is now programmed I/O details now you just see these are the simple steps; first one CPU requests to I/O operation that in processor we have shown it, I/O module performs operation, then by looking into the state of the devices I/O module sets the status bit, CPU checks status bits periodically.
Detailed Explanation
The programmed I/O process consists of several key steps: 1. The CPU requests an I/O operation. 2. The I/O module responds and performs the necessary operation. 3. The I/O module checks the status of the device and updates a status bit. 4. The CPU periodically checks this status bit to determine if the operation can proceed.
Examples & Analogies
Think of it like a delivery service where the truck driver (CPU) requests packages to be delivered. The warehouse (I/O module) prepares the packages and sets a 'ready' sign when packages are ready. The driver keeps checking on the status until the 'ready' sign is displayed, allowing him to proceed with his deliveries.
Addressing I/O Devices
Unlock Audio Book
Signup and Enroll to the course for listening the Audio Book
So, first the issues for that I/O command is like that how to identify the module. So that means, we have to have device address so this is the one point how we are going to give the addresses of the I/O devices.
Detailed Explanation
Each I/O device must have a unique address within the computer system to allow the CPU to communicate with it effectively. This addressing scheme is similar to memory addressing, where each memory location has a specific address.
Examples & Analogies
Consider a postal system where every house has a unique address. Just like the postal service uses these addresses to deliver mail accurately, a computer uses unique addresses to send data to the correct I/O devices.
Control Commands for I/O Operations
Unlock Audio Book
Signup and Enroll to the course for listening the Audio Book
So, basically some control commands we have to issue just to initiate the process like that already have explained. If we want to print something in the printer we should send some control signal to the printer to initiate it.
Detailed Explanation
To manage I/O operations, several control commands are necessary, such as initiating a print job or reading data from a disk. These commands work to set the device in the correct state, ensuring it is ready for the intended operation.
Examples & Analogies
Before a movie starts, the director (CPU) sends commands to the actors (I/O devices) to get into position and prepare. Only once everyone is ready does the movie begin, similar to how control commands prepare a device for a task.
I/O Mapping Techniques
Unlock Audio Book
Signup and Enroll to the course for listening the Audio Book
So, in that particular case we are having two different ways of doing it. One is your memory mapped I/O and second one is your isolated I/O.
Detailed Explanation
When mapping I/O devices, there are two primary techniques: memory-mapped I/O, where devices share the same address space as memory, and isolated I/O, where devices have a separate address space. Memory-mapped I/O allows for simpler control using the same instructions as memory access, whereas isolated I/O requires distinct commands.
Examples & Analogies
It's like having a multi-functional office where desks (memory) and filing cabinets (I/O devices) share the same room (memory-mapped I/O) versus having a separate room for filing cabinets (isolated I/O). The multi-functional setup allows for easier access, but the separate rooms provide organization.
Understanding Memory-Mapped I/O
Unlock Audio Book
Signup and Enroll to the course for listening the Audio Book
Now you consider that size of my address bus is your 16, then what is the memory capacity with my size of address bus is 16, you should know it now. Say, this is your 216, which is your 64k.
Detailed Explanation
In a memory-mapped I/O system with a 16-bit address bus, the maximum addressable memory space is 64KB. Some of this space is allocated to I/O devices. By reserving specific address ranges for devices, we can identify and communicate with them efficiently.
Examples & Analogies
Imagine a library where every book (memory) has a shelf with a specific label. If some shelves are reserved for magazines (I/O devices), it allows librarians to quickly locate either books or magazines in their respective areas.
Understanding Isolated I/O
Unlock Audio Book
Signup and Enroll to the course for listening the Audio Book
So, in case of isolated I/O the memory space and I/O space are different. So, now, if you consider the same example then what will happen? We are having 16 as size of address bus is 16.
Detailed Explanation
In isolated I/O systems, memory and I/O devices each have their own separate address space. This means that you can have a much larger number of I/O devices compared to a memory-mapped I/O configuration, but it requires separate instructions to interact with each device.
Examples & Analogies
Think of a restaurant that has a dining area (memory) and a separate kitchen (I/O). While both areas serve the restaurant, their operations are distinct; different staff manages orders in the kitchen compared to the dining area.
Control Signals in Isolated I/O
Unlock Audio Book
Signup and Enroll to the course for listening the Audio Book
Now how to identify whatever addresses that we have put in this particular address bus. It is an address of a memory location or it is an address of an I/O devices.
Detailed Explanation
To differentiate between memory and I/O addresses in an isolated I/O system, control signals are used. For example, a specific signal indicates if the current address corresponds to a memory location or an I/O device, ensuring correct data handling.
Examples & Analogies
Consider a remote control that can switch between different devices like the TV (memory) and the DVD player (I/O). The remote has buttons that tell it which device it should communicate with, much like a control signal directing the CPU in a computing environment.
Definitions & Key Concepts
Learn essential terms and foundational ideas that form the basis of the topic.
Key Concepts
-
Programmed I/O: A method where the CPU polls for device readiness before transferring data.
-
Memory-mapped I/O: I/O devices share the same address space as memory, allowing for simplified operations.
-
Isolated I/O: Uses a distinct address space for I/O devices, enabling greater device connections without conflict.
-
Control Commands: Commands issued by the CPU to interact with I/O devices, such as read and write.
Examples & Real-Life Applications
See how the concepts apply in real-world scenarios to understand their practical implications.
Examples
-
In programmed I/O, the CPU continuously checks a device's status until it is ready, simulating a 'waiting' process similar to checking for a bus arrival.
-
In memory-mapped I/O, a printer could be accessed using the same instructions as for memory, making it simpler to read and print data.
Memory Aids
Use mnemonics, acronyms, or visual cues to help remember key information more easily.
🎵 Rhymes Time
-
Polling for data can be a chore, waiting for devices to be ready, is what we often abhor!
📖 Fascinating Stories
-
Imagine a mailman checking every house on a block (polling) until someone waves from the porch, saying they have mail ready.
🧠 Other Memory Gems
-
PC: Polling Continuously for device readiness!
🎯 Super Acronyms
ISO for Isolated I/O
- 'Separate Operations.'
Flash Cards
Review key concepts with flashcards.
Glossary of Terms
Review the Definitions for terms.
-
Term: Programmed I/O
Definition:
A method where the CPU actively waits for an I/O device to be ready by polling its status.
-
Term: Memorymapped I/O
Definition:
A scheme where I/O devices share the same address space with memory, allowing similar operations on both.
-
Term: Isolated I/O
Definition:
A scheme where I/O devices have a separate address space distinct from memory.
-
Term: Control Commands
Definition:
Instructions involved in initiating, controlling, and fetching data from I/O devices.
-
Term: I/O Module
Definition:
A hardware component that manages communication between the CPU and peripherals.