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 Indirect Addressing Mode
Unlock Audio Lesson
Today, let's explore direct and indirect addressing modes. First, can anyone explain what we mean by indirect addressing mode?
Is it where the instruction points to a memory location that contains another address?
Exactly! In indirect addressing, the operand is not provided directly but is located in a memory address specified by another location. Can anyone summarize the first few stages involved in executing an instruction like `LOAD R1, M` where `M` is an indirect address?
First, we fetch the instruction, then load `M` into the memory address register?
Great! Remember, this implies you need to access the memory to get the operand indirectly via another address. How do we ensure we have the right operand?
We have to read the value that is stored at `M`, then use that value to fetch the actual operand.
Correct! That's two accesses. This is a classic example of the complexity involved in indirect addressing. To remember: **I for Indirect equals I for Intermediary!**
Register Indirect Addressing Mode
Unlock Audio Lesson
Now, let's move on to the register indirect addressing mode. How does it differ from the indirect addressing mode we just discussed?
In register indirect, the operand address is stored in a register instead of memory, right?
Spot on! This means we can access the operand more quickly. Can someone outline the major steps when using register indirect addressing?
You load the address from the register to the memory address register directly. It skips fetching from memory, making it faster!
Exactly! Fewer steps result in quicker access times. Who can summarize the advantages of using register indirect over memory indirect modes?
It decreases the number of memory accesses, reducing overall execution time.
Perfect! Remember, fewer accesses mean faster execution. Use the mnemonic **RI is Rapid Indirect!** to recall this.
Comparing Addressing Modes
Unlock Audio Lesson
Let’s compare the efficiency of different addressing modes. What did we conclude about indirect and register indirect modes?
Register indirect is generally faster because it requires fewer steps.
And the indirect mode involves more stages since it needs to fetch the address first.
Right! It’s crucial to understand when to use each mode. Can anyone think of a scenario where indirect addressing might be beneficial?
It could be useful in dynamic data structures like linked lists, where addresses can change.
Correct! Indirection allows for flexibility. Always remember, ***Use what works best for your application!***
Introduction & Overview
Read a summary of the section's main ideas. Choose from Basic, Medium, or Detailed.
Quick Overview
Standard
In this section, we explore complex addressing modes such as the indirect mode and register indirect mode. These modes allow a processor to access operands either directly via memory or through registers, influencing the instruction fetch process and control signals necessary for execution.
Detailed
Different Addressing Modes
This section discusses various addressing modes essential in computer architecture, with a focus on the indirect mode and register indirect mode. The indirect addressing mode allows the operand to be located by first fetching the address from a memory location specified by the instruction. The section breaks down the steps involved in executing an instruction like LOAD R1, M, where M can represent a memory address that needs to be accessed indirectly. During this process, multiple stages involve fetching the instruction, accessing the memory where M resides, and finally retrieving the operand stored at that address.
It also describes the register indirect mode where the address of the operand is stored directly in a register rather than in memory, streamlining the data access process. Both modes illustrate the complexity and importance of control signals and steps that determine how processors fetch and utilize data. This understanding is crucial for designing efficient systems capable of executing various instructions effectively. Furthermore, the efficiency of different addressing modes is discussed, showing that register indirect generally requires fewer steps than memory indirect modes.
Youtube Videos
Audio Book
Dive deep into the subject with an immersive audiobook experience.
Indirect Addressing Mode Overview
Unlock Audio Book
Signup and Enroll to the course for listening the Audio Book
Now, we will go to the another mode, which is more complex in nature which is the indirect mode. By indirect mode already we mean that whenever it’s the indirect mode of M; that means, we say this is the memory here is M, at the address of M here there may be some addresses called x is some content over here, then again you have to look at the content in x and basically this is your operand.
Detailed Explanation
The indirect addressing mode is a method where the operand's address is not contained directly within the instruction itself. Instead, the instruction specifies a memory location (let's call it M), which holds another memory address (let's refer to this new address as x). To find the actual operand, the CPU first retrieves the address x from M, then goes to memory location x to get the operand needed for further processing.
Examples & Analogies
Think of it like looking for a book in a library. The first step is to check the catalog (M), which gives you the location of another shelf (x). You then go to that shelf to find the specific book (the operand) you need for your research.
Instruction Fetching Stages
Unlock Audio Book
Signup and Enroll to the course for listening the Audio Book
So, if you now look at basically your first 3 stages. So, first 3 stages; as I already were discussing like PC out MAR and this is control stage basically are only for fetching the instruction.
Detailed Explanation
The initial stages of executing an instruction in the indirect mode involve three main steps: 1) The Program Counter (PC) outputs the address of the next instruction, 2) This address is stored in the Memory Address Register (MAR), and 3) A control signal is issued to begin fetching the instruction from memory. These stages are crucial because they ensure the CPU knows which instruction to execute next.
Examples & Analogies
Imagine a waiter in a restaurant taking down customer orders. The waiter (PC) notes down the order (address of the instruction) on a notepad (MAR) and then goes to the kitchen to get that specific dish (fetching the instruction).
Loading Operand from Indirect Mode
Unlock Audio Book
Signup and Enroll to the course for listening the Audio Book
Next one is what I have to do. So, this is the instruction load R into memory from indirect memory location.
Detailed Explanation
Once we have the instruction loaded, it indicates that we need to load data into a register (R) from the indirect memory location associated with M. In essence, the CPU will access memory, retrieve the address indicated by M, and then use that address to fetch the actual value that needs to be loaded into the register.
Examples & Analogies
Continuing with the book example, once the waiter knows the order includes a specific dish, he doesn't just put any random food on the plate (loading R). Instead, he goes back to the kitchen to fetch that specific dish (the value from the indirect location) which was already prepared.
Stages of Memory Access
Unlock Audio Book
Signup and Enroll to the course for listening the Audio Book
So, now the after executing the third instruction the third control step register instruction register IR is having the value of LOAD R, M. So, in the fourth stage what I am going to do I am going to take the value of M and I am going to feed it into the memory address register so that you can read the value of memory location M that is x in this example.
Detailed Explanation
When the instruction to load data into the register is ready, the Instruction Register (IR) reflects this command, which tells the CPU to take the stored address in M and prepare to fetch the data from that memory location. This value of M is loaded into the Memory Address Register (MAR), setting the stage for the actual memory access needed to retrieve the operand.
Examples & Analogies
This is similar to the waiter identifying the specific dish on the menu (LOAD R, M) and then going to the exact kitchen area (MAR) where that dish is stored (loading the address to fetch the operand).
Fetching the Actual Operand
Unlock Audio Book
Signup and Enroll to the course for listening the Audio Book
So, in stage 5 we have to wait till everything is ready. Once it is ready basically we know that the value of memory location M that is x in the example is now loaded into the memory data register.
Detailed Explanation
At this stage, after waiting for the memory fetch cycle to complete, the CPU ensures the value from the memory location indicated by M (x) is now available in the Memory Data Register (MDR). This is crucial as it prepares the operand to be moved to the designated register.
Examples & Analogies
Think of the waiter waiting for the chef to finish preparing the dish (fetching x). Once the dish is ready, it is placed on a serving tray (MDR) so the waiter can deliver it to the customer (load into R).
Memory Data to Register Transfer
Unlock Audio Book
Signup and Enroll to the course for listening the Audio Book
After you have to wait for some amount of time and then in this case now exactly you are going to have the operand which is present in the memory location x that the content we are assuming l for the time being will be taken from MDR it will be dump to register R.
Detailed Explanation
Once the operand is prepared and available in the Memory Data Register, the next step is to load this data into the designated register (R). This is done by transferring the value from the MDR into R, completing the process of loading the operand through the indirect addressing method.
Examples & Analogies
Finally, the waiter delivers the specific dish (l) from the tray (MDR) to the customer’s table (R). This completes the cycle of retrieving and delivering the requested item.
Comparing Indirect and Register Indirect Modes
Unlock Audio Book
Signup and Enroll to the course for listening the Audio Book
So, in the indirect mode we can get the values. So, now, again another mode we are taking which is called registering indirect in this case it was a memory indirect it is a register indirect.
Detailed Explanation
The discussion shifts to another addressing mode known as register indirect mode. Unlike indirect mode, where the address is stored in memory, in register indirect mode, the address of the operand is stored directly within a CPU register. This typically allows for faster access as there is one less memory fetch involved.
Examples & Analogies
If we return to our restaurant example, instead of fetching a dish from memory (the kitchen), the waiter now simply retrieves it from a platter (the register) already at the table. It’s quicker and more efficient.
Summary of Addressing Modes
Unlock Audio Book
Signup and Enroll to the course for listening the Audio Book
Depending on different type of addressing modes the sequence of control or the number of steps will all differ.
Detailed Explanation
Finally, the section wraps up by summarizing that different addressing modes, such as immediate, direct, indirect, and register indirect, each have their unique processes and steps involved. Understanding these differences is vital for optimizing instruction execution and understanding control signals within a CPU.
Examples & Analogies
It's like understanding various routes to reach a destination: some take longer and have more steps (indirect mode), while others are direct and quicker (register indirect mode). Knowing your options helps you to plan your journey effectively.
Definitions & Key Concepts
Learn essential terms and foundational ideas that form the basis of the topic.
Key Concepts
-
Indirect addressing involves accessing memory through an address stored in another memory location.
-
Register indirect addressing optimizes operand retrieval by using a register to store the address.
Examples & Real-Life Applications
See how the concepts apply in real-world scenarios to understand their practical implications.
Examples
-
For indirect addressing, if
Mcontains the addressx, the instructionsLOAD R1, Mfirst fetch the addressxfrom memoryM, then fetch the actual operand from addressx. -
In register indirect addressing, an instruction like
LOAD R1, R2means thatR2holds the address to the operand, making it faster to access.
Memory Aids
Use mnemonics, acronyms, or visual cues to help remember key information more easily.
🎵 Rhymes Time
-
Indirect accesses double the steps, through addresses it preps!
📖 Fascinating Stories
-
Imagine a librarian who doesn't know where the book is but holds a card with another librarian's address. That’s just like indirect addressing; it finds the book through a middleman!
🧠 Other Memory Gems
-
Remember IIR: Indirect address through Indirect Register for easier access!
🎯 Super Acronyms
Use **RI** for Register Indirect’s speed and ease!
Flash Cards
Review key concepts with flashcards.
Glossary of Terms
Review the Definitions for terms.
-
Term: Addressing Mode
Definition:
The technique used to specify the location of operands for instructions in computer programs.
-
Term: Indirect Addressing
Definition:
A method where the address of the operand is stored in a memory location that is designated by the instruction.
-
Term: Register Indirect Addressing
Definition:
A method of addressing where the operand address is contained within a register.