Procedure
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Understanding Memory Maps
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Today, we are going to learn about memory maps. A memory map is essential for understanding how our microprocessor interfaces with memory. Can anyone tell me how many unique memory locations the 8085 can address?
Is it 65,536 locations because it has a 16-bit address bus?
Exactly! That's 64 KB of address space. Now, when we design our memory map, we need to assign address ranges to each memory chip connected to the microprocessor.
What kind of chips are we using in this experiment?
We'll be using a 2KB ROM and a 4KB RAM. Can you calculate how many address lines we'll need for each?
For ROM, we need 11 address lines because log2(2048) is 11. And for RAM, we need 12 because log2(4096) is 12.
Perfect! Now, let's explore how to create a memory map! The ROM will start at 0000H. What would be its ending address?
The ending address should be 07FFH!
Correct! And the RAM will start from 2000H. What's its ending address?
The ending address for RAM would be 2FFFH!
Great teamwork! So, ultimately, we created a memory map that correctly allocates our memory space. It'll be crucial for the next steps.
In summary, we learned how to calculate memory requirements and address lines using the exponent log base 2. Remember to use those calculations to create a proper memory map for any future projects!
Address Decoding Fundamentals
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Continuing from our last discussion, letβs talk about address decoding. Why do you think it's essential when interfacing multiple memory chips?
To make sure only one chip responds to a given address, right?
Exactly! Since our memory chips canβt respond to the full 16-bit address from the 8085, we use higher-order address lines to generate unique Chip Select signals. Who can give me an example of such a signal?
Like the overlineCS signal for ROM and RAM?
Correct! To achieve this, we use logic gates or decoder ICs. Do you remember the logic gate we can use for our ROM decoding from last time?
A 5-input NOR gate, right? We connect the higher address lines to it.
Well done! Now what about RAM decoding?
We can use a 4-input AND gate with some inverted signals.
Exactly! Address decoding is a crucial step to ensure our microprocessor efficiently communicates with the right memory. Can anyone summarize why it's vital?
It's vital to prevent address conflicts and to enable smooth memory operations!
Great summary! Address decoding is a fundamental concept that we must apply thoroughly when designing circuits with the 8085 microprocessor.
Executing Assembly Programs
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Let's shift gears and talk about the practical execution of assembly language programs. What is one of the operations we need to perform?
We need to write data to RAM at a specific address!
Correct! Weβll be writing the value 55H at address 2050H. Who can summarize a sample assembly code snippet that achieves this?
We start by loading the address into the HL register, then move the data into the accumulator and store it into memory.
Exactly! What about reading data from memory?
We load the address, then move the data from memory into the accumulator and then copy that to a register.
So, in reading, we need to ensure that the source memory location contains valid data, right? Now, what do you think is the best way to verify that our programs work correctly after execution?
We could use Examine Memory and check if the values are as expected after each operation.
Exactly! Itβs very important to verify our programs. In summary, weβve learned the need to correctly form our assembly instructions and the verification process afterward to ensure successful memory operations.
Introduction & Overview
Read summaries of the section's main ideas at different levels of detail.
Quick Overview
Standard
In this section, the procedure for conducting experiment No. 2 on memory interfacing with the 8085 microprocessor is detailed. Key components include designing a memory map, implementing address decoding for memory chips, and executing assembly language programs for memory operations. The experiment emphasizes understanding memory types, address lines, and practical application through a hands-on approach using the trainer kit.
Detailed
Detailed Summary
The Procedure section describes the hands-on experiment designed to interface memory with the 8085 microprocessor. The aim is to explore fundamental principles of memory mapping, address decoding, and conducting read/write operations with RAM and read operations with ROM.
Steps Overview
- Memory Configuration: The experiment starts with defining the memory configuration, specifying the sizes of both ROM and RAM.
- Address Lines: Calculation of address lines required for each chip based on their size is discussed, leading to understanding the memory map's layout.
- Memory Mapping: This part involves creating a memory map table showing the address range for ROM and RAM, essential for system architecture clarity.
- Address Decoding Logic: Address decoding mechanisms are described, detailing how unique chip select signals are generated via logic gates or decoder ICs. This is critical for preventing multiple memory chips from responding to the same address.
- Memory Operations: It goes into detail on how to perform memory read/write operations by articulating the specific control signals involved and their operational flow in the 8085 microprocessor.
- Assembly Language Programming: The procedure concludes by guiding students to write assembly language programs for various operations, showcasing their understanding of the microprocessor's functionality along with verification through the trainer kit's features.
The knowledge gained from this section is foundational for developing skills in designing and troubleshooting microprocessor-based systems.
Audio Book
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Part A: Memory Map Design and Interfacing Schematic
Chapter 1 of 5
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Chapter Content
- Given Memory Configuration:
- ROM: 2 KB
- RAM: 4 KB
- Calculate Address Lines Required for Each Chip:
- ROM (2KB): 2048 bytes. Requires log_2(2048)=11 address lines (A0-A10).
- RAM (4KB): 4096 bytes. Requires log_2(4096)=12 address lines (A0-A11).
- Assign Memory Addresses and Create Memory Map:
- ROM: Starting address 0000H. Ending Address = 0000H + 2048 - 1 = 07FFH.
- Address Range: 0000H - 07FFH.
- RAM: Starting address 2000H. Ending Address = 2000H + 4096 - 1 = 2FFFH.
- Address Range: 2000H - 2FFFH.
Detailed Explanation
In this section, we design a memory map for the interfacing of 2KB ROM and 4KB RAM with the 8085 microprocessor. We first confirm the sizes of the RAM and ROM, then we calculate the address lines needed. ROM, with 2KB, requires 11 address lines since 2048 bytes corresponds to 2^11. RAM, with 4KB, needs 12 address lines for 4096 bytes since that's 2^12. Next, we designate memory addresses by assigning the ROM starting at 0000H and ending at 07FFH, with an address range from 0000H to 07FFH. We allocate the RAM to begin from 2000H to prevent overlap with any potential devices, ending at 2FFFH.
Examples & Analogies
Think of this as creating a filing cabinet for documents where each drawer can hold a certain number of files. Assigning address lines is like labeling each drawer to allow easy accessβif you have more files, you need more drawers. In our example, the ROM and RAM represent different types of files stored in specific drawers, helping us organize our documents efficiently.
Memory Map Table Completion
Chapter 2 of 5
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Chapter Content
- Complete Memory Map Table:
- Memory Device: ROM
- Size: 2KB
- Starting Address: 0000H
- Ending Address: 07FFH
- Address Lines Used for Chip Select: A0-A10
- Address Lines by Chip: A11, A12, A13, A14, A15 (all must be 0)
- Memory Device: RAM
- Size: 4KB
- Starting Address: 2000H
- Ending Address: 2FFFH
- Address Lines Used for Chip Select: A0-A11
- Address Lines by Chip: A12, A13, A14, A15 (A12=1, others=0)
Detailed Explanation
Next, we create a memory map table to provide a structured overview of how the memory is organized. For the ROM, we note its size (2KB), address range (0000H to 07FFH), and the address lines usedβspecifically, A0 through A10. For the RAM, it is 4KB and utilizes the address lines A0 through A11 for addressing, with extra conditions on higher lines to ensure proper selection.
Examples & Analogies
Continuing with the filing cabinet analogy, think of the memory map table as an inventory list that tells you what each drawer contains and how to access it. Each entry in the table helps a user quickly identify which drawer (memory block) to open and what files (data) can be found inside depending on their needs.
Chip Select Generation and Interfacing
Chapter 3 of 5
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Chapter Content
- Design Address Decoding Logic and Interfacing Schematic:
- Common Connections:
- 8085 A0-A10 to ROM A0-A10.
- 8085 A0-A11 to RAM A0-A11.
- 8085 D0-D7 to ROM D0-D7 and RAM D0-D7.
- 8085 overlineRD to ROM overlineOE and RAM overlineOE.
- 8085 overlineWR to RAM overlineWE (ROM does not have overlineWE).
Detailed Explanation
Finally, we design the address decoding logic necessary for the 8085 to correctly select between the ROM and RAM during operations. We connect the lower address lines directly to the corresponding pins on the memory chips. Control signals (like read and write signals) must also be routed properly to ensure that data flows correctly between the microprocessor and the memory devices.
Examples & Analogies
Imagine you have tellers at a bank that only serve specific types of transactions based on the kind of account. The address lines are akin to the signals that direct customers to the right teller, ensuring an orderly process. Without proper routing, people might end up at the wrong teller, just like data could go to the wrong memory chip.
Assembly Language Programs and Execution
Chapter 4 of 5
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Chapter Content
Part B: Assembly Language Programs and Execution
1. Program to Write Data to Memory (RAM)
- Aim: Store the data 55H at memory location 2050H.
- Assembly Code:
- ORG 0000H ; Program starts at 0000H (typical ROM location)
- LXI H, 2050H ; Load 16-bit address 2050H into HL
- MVI A, 55H ; Move immediate data 55H into Accumulator A
- MOV M, A ; Move content of Accumulator (A) to memory location (HL)
- HLT ; Halt processor
Detailed Explanation
In this part, we write an assembly program that demonstrates how to store data in the RAM. The program first sets the location where it will write the data, loads the value into the accumulator, and then writes it to the specified address. A simple halt command ends the program, signaling that the task is complete.
Examples & Analogies
Think of the assembly program as a delivery service. The delivery person (the program) has a specific address (2050H) and carries a package (the data 55H). The delivery (MOV M, A) is completed after arriving at the correct address, confirming the data was stored successfully.
Verification on 8085 Trainer Kit
Chapter 5 of 5
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Chapter Content
Part C: Verification on 8085 Trainer Kit
1. Power On the 8085 trainer kit.
2. Enter Machine Code: Using the kit's monitor program, navigate to the memory entry mode. Starting from address 0000H, enter the hexadecimal machine code for each program.
3. Verify Program Entry: Use the 'Examine Memory' function to confirm that all opcodes and operands have been entered correctly.
Detailed Explanation
Once the assembly language programs are complete, we need to load them into the 8085 trainer kit for execution. This requires entering the machine code correctly according to the specifications of the programs we've prepared. Finally, using the built-in examine function, we check that the machine code has been entered accurately to avoid any errors during execution.
Examples & Analogies
Consider this verification process like checking the ingredients before cooking a recipe. Just as you wouldn't want to realize halfway through that you've forgotten an important ingredient, verifying the machine code ensures that everything is in place before we hit 'start' on our program.
Key Concepts
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Memory Map: A visual representation of memory allocation.
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Address Decoding: Generating unique signals for memory chip selection.
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Assembly Language Programs: Instructions written to interact with memory.
Examples & Applications
Writing a value 55H to memory location 2050H.
Reading a value from memory location 2050H into register B.
Transferring a block of 5 bytes from one memory range to another.
Memory Aids
Interactive tools to help you remember key concepts
Rhymes
In memory maps, we do not miss, without their guide, we lose our bliss.
Stories
Once there was a busy post office (the microprocessor) where each letter (data) needs to go to its specific address (memory). Without the map, the mail could easily get lost!
Memory Tools
RAID: Read And Interface Decode for memory operations!
Acronyms
MACE for Memory Address Control Enable.
Flash Cards
Glossary
- Memory Map
A graphical representation that shows how memory addresses are allocated to different memory chips.
- Address Lines
Lines used in microprocessors for addressing memory locations.
- Chip Select (CS)
A signal used to select a specific memory chip for read/write operations.
- Address Decoding
The method of translating higher-order address lines to generate chip select signals for memory chips.
- Assembly Language
A low-level programming language that is closely related to machine code for programming microprocessors.
Reference links
Supplementary resources to enhance your learning experience.