Complete Memory Map Table
Interactive Audio Lesson
Listen to a student-teacher conversation explaining the topic in a relatable way.
Introduction to Memory Components
π Unlock Audio Lesson
Sign up and enroll to listen to this audio lesson
Today, we're going to explore the fundamentals of memory components in microprocessor systems, especially focusing on the 8085 microprocessor. Who can tell me the two primary types of memory we often encounter?
Is it ROM and RAM?
Exactly! ROM stands for Read-Only Memory, and RAM stands for Random Access Memory. Why do you think both are important in a microprocessor system?
ROM stores permanent instructions while RAM is for temporary data, right?
Correct! Great job, Student_2. Just remember, ROM retains data while powered, and RAM loses its data. Can anyone share an example of what is stored in ROM?
Boot programs or firmware!
Yes, well done! Now let's summarize: RAM is volatile memory used temporarily, while ROM is non-volatile and retains data permanently.
Understanding Memory Mapping
π Unlock Audio Lesson
Sign up and enroll to listen to this audio lesson
Next, we dive into memory mapping. Why is it crucial to create a memory map for our 8085 system?
To organize how memory is allocated and make sure there are no overlaps?
Exactly, Student_4! A well-designed memory map helps us avoid conflicts and ensures smooth operation. Can anyone tell me how many address lines we need for a 2KB ROM?
We need 11 address lines, right? Since log2(2048) equals 11.
Great! Yes, for a 2KB ROM, that's correct. Let's use the formula for address lines: Number of Address Lines = log2(N). Now, can anyone help me create a memory map using the given configurations?
If ROM starts at 0000H and ends at 07FFH, then the RAM could start at 2000H, right?
Exactly! And the RAM would then occupy the address range up to 2FFFH. Well done, everyone!
Address Decoding Logic
π Unlock Audio Lesson
Sign up and enroll to listen to this audio lesson
Now let's talk about address decoding. Who remembers why we need to decode addresses when interfacing different memory chips?
To ensure that only one memory chip communicates with the processor at a time?
We can use logic gates or decoder ICs to generate a Chip Select signal, right?
Absolutely right! We often use a NOR gate for ROM and a AND gate with some inverted signals for RAM to generate these CS signals. Keep that in mind!
Assembly Language Programming for Data Operations
π Unlock Audio Lesson
Sign up and enroll to listen to this audio lesson
Let's move into practical applications by writing assembly programs for memory operations. What is the first thing we'll do in our write program?
We initialize the address in register HL to the target memory location?
Exactly right! We'll use the 'LXI H' instruction for that. And then after we move our data into the accumulator, what instruction do we use to write it to RAM?
MOV M, A!
Great! After that, we can verify if the data has been correctly written. How would you do that?
I would use the 'Examine Memory' function on the trainer kit after executing the program.
Perfect! And remember, once we write data, we can read it back using 'MOV A, M.' Good job, everyone!
Verification of Memory Operations
π Unlock Audio Lesson
Sign up and enroll to listen to this audio lesson
As we wrap up, let's discuss how we verify our memory operations on the 8085 trainer kit. Why do you think verification is necessary?
To ensure that our programs are working correctly and the data is stored/ retrieved correctly!
If we entered incorrect machine code or forgot to initialize registers, right?
Correct! Those mistakes could lead to unexpected results. In summary, verifying each step helps ensure the integrity of our data operations.
Introduction & Overview
Read summaries of the section's main ideas at different levels of detail.
Quick Overview
Standard
The section covers the principles of memory interfacing with the 8085 microprocessor, detailing how to design a memory map, the importance of address buses and control signals, and practical applications including writing assembly language programs for reading and writing data from RAM and ROM. A complete memory map table organizes memory addresses, sizes, and decoding information.
Detailed
Complete Memory Map Table
This section covers the essential aspects of memory interfacing with the 8085 microprocessor. The 8085, with its 16-bit address bus, can access up to 64 KB of memory, which includes RAM and ROM. The primary goals detailed here involve:
- Memory Mapping: Understanding how memory is organized and the importance of memory maps, which visually or tabularly represent how memory space is allocated.
- Address Decoding: Since various memory chips require unique addresses, decoding plays a critical role to ensure proper communication between the processor and memory. This is illustrated through logic gates and dedicated decoder ICs.
- Programming: Execution of assembly language programs to demonstrate the effective use of RAM and ROM for storing and retrieving data.
The section concludes with practical examples, including detailed memory maps for specific RAM and ROM configurations, identifying address lines required for each chip, and crafting procedures to verify memory operations.
Audio Book
Dive deep into the subject with an immersive audiobook experience.
Memory Configuration Overview
Chapter 1 of 6
π Unlock Audio Chapter
Sign up and enroll to access the full audio experience
Chapter Content
Given Memory Configuration:
- ROM: 2 KB
- RAM: 4 KB
Detailed Explanation
In this part of the memory map, we are specifying the types of memory components that are being used in the 8085 microprocessor setup. We have a Read-Only Memory (ROM) sized at 2 KB, which is primarily used for storing firmware or boot programs that are meant to be read only. Alongside, we have a Random Access Memory (RAM) of size 4 KB, which allows both reading from and writing to its memory locations, thus facilitating temporary data storage for active programs.
Examples & Analogies
Think of ROM as a library where the books are placed there and can be read by anyone, but no one can make changes to the text. RAM, on the other hand, is like a notebook where you can jot down notes and remove things as you please, giving you the flexibility to work with the information actively.
Address Lines Calculation
Chapter 2 of 6
π Unlock Audio Chapter
Sign up and enroll to access the full audio experience
Chapter Content
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).
Detailed Explanation
Here we are determining how many address lines are required to access all memory locations within each chip. For the ROM, we have a total storage of 2048 bytes (2 KB), which mathematically translates to needing 11 address lines to uniquely identify each byte (from A0 to A10). For the RAM, which holds 4096 bytes (4 KB), we need 12 address lines (from A0 to A11) to ensure every individual byte can be addressed. The calculation is based on the formula log base 2 of the number of bytes.
Examples & Analogies
Consider the address lines as street addresses in a city. Just like each street address allows you to find a specific house, the address lines let the microprocessor pinpoint a specific byte of data in memory. For example, a small town might only need a few address lines (like A0-A10) because it has fewer houses, while a big city with more houses needs more address lines (like A0-A11) to ensure everyone has a unique address.
Memory Map Assignments
Chapter 3 of 6
π Unlock Audio Chapter
Sign up and enroll to access the full audio experience
Chapter Content
Assign Memory Addresses and Create Memory Map:
- ROM: Assign starting address 0000H
- Ending Address = 0000H+2048β1=07FFH.
- Address Range: 0000Hβ07FFH.
- RAM: Assign starting address 2000H (leaving a gap for other potential devices/expansion).
- Ending Address = 2000H+4096β1=2FFFH.
- Address Range: 2000Hβ2FFFH.
Detailed Explanation
Now we are determining the actual memory address ranges for the ROM and RAM. The ROM starts at address 0000H and because it has a total size of 2 KB, it occupies memory addresses from 0000H to 07FFH. For the RAM, weβre starting at address 2000H, which is chosen to allow space for possible other devices in the future. The RAM addresses range from 2000H to 2FFFH. This layout is essential to prevent overlapping of address ranges, ensuring that each component can be accessed correctly without confusion.
Examples & Analogies
Imagine setting up an apartment complex with designated parking spaces. The ROM is like the parking spaces assigned to the first few apartments (0000H-07FFH), while the RAM has its spaces starting after a buffer zone (2000H-2FFFH) allowing enough room for additional cars or equipment. This system keeps everything organized and avoids any mix-ups about who parks where.
Memory Map Table Completion
Chapter 4 of 6
π Unlock Audio Chapter
Sign up and enroll to access the full audio experience
Chapter Content
Complete Memory Map Table:
| Memory Device | Memory Size | Starting Address | Ending Address | Address Lines Used | Address Lines by Chip (for Chip Select) |
|---------------|-------------|------------------|----------------|--------------------|---------------------------------------|
| ROM | 2KB | 0000H | 07FFH | A0-A10 | A11, A12, A13, A14, A15 (all must be 0) |
| RAM | 4KB | 2000H | 2FFFH | A0-A11 | A12=1, A13, A14, A15 (others=0) |
Detailed Explanation
This table summarises the memory map details for quick reference. It lists the memory devices (ROM and RAM), their respective sizes, assigned starting and ending addresses, and the specific address lines being utilized for chip selection. The ROM uses address lines A0 through A10 for selecting addresses, while A11, A12, A13, A14, and A15 are set to zero. This prevents the ROM from interfering with other memory devices. Similarly, for the RAM, we also designate address lines A0 through A11 and specifically use A12 as one of the select lines.
Examples & Analogies
Consider this memory map table as a directory in a shopping mall. Just as you can find stores (memory devices) by looking at their exact locations (addresses), this table helps you locate how much space each store uses (size) and what entrance (address lines) to use to get to the right store without getting lost among other stores.
Chip Select Address Decoding
Chapter 5 of 6
π Unlock Audio Chapter
Sign up and enroll to access the full audio experience
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
In this step, we establish the connections required for memory interfacing between the 8085 microprocessor and the memory chips (ROM and RAM). The address lines from the processor need to connect to the address lines of the ROM and RAM correspondingly, facilitating direct communication. Similarly, the data lines from the microprocessor connect to those of the memory chips allowing the transfer of data. Control signals like read (overlineRD) and write (overlineWR) are connected similarly to manage data operations effectively.
Examples & Analogies
Think of this as wiring a sound system in a home theater. Just like you connect your audio receiver (8085) to various speakers (ROM and RAM), ensuring each wire goes to the correct spot to produce sound at the right time, these connections ensure data is precisely read from and written to memory at the appropriate times.
Chip Select Logic Generation
Chapter 6 of 6
π Unlock Audio Chapter
Sign up and enroll to access the full audio experience
Chapter Content
Chip Select (overlineCS) Generation:
- For ROM (0000Hβ07FFH): Requires A15=0, A14=0, A13=0, A12=0, A11=0.
- Decoding logic: Connect A11, A12, A13, A14, A15 to a 5-input NOR gate. The output of the NOR gate connects to the ROM's overlineCS.
- For RAM (2000Hβ2FFFH): Requires A15=0, A14=0, A13=0, A12=1.
- Decoding logic: Connect A15, A14, A13 (inverted) and A12 (direct) to a 4-input AND gate. The output of the AND gate connects to the RAM's overlineCS.
Detailed Explanation
To control which memory is accessed when a specific address is requested, we use logic gates to create Chip Select (overlineCS) signals. For the ROM, when the processor selects addresses from 0000H to 07FFH, it ensures higher address lines (A11 to A15) remain low (0). A NOR gate can provide this logic ensuring that the ROM is selected if all relevant lines are low. Conversely, for RAM, we require a high signal on line A12 while the others are low, which is generated using an AND gate by appropriately inverting some of the address lines.
Examples & Analogies
Imagine a light switch system in a house where specific switches control individual lights (memory). Just as flipping the switch down for all lights means they turn off (like the NOR gate logic for ROM), having one switch up and others down can turn on a specific light (like the AND gate logic for RAM). This ensures only the light (memory) connected to that switch is activated when needed.
Key Concepts
-
Address Bus: A 16-bit bus used by the 8085 to address up to 64KB of memory.
-
Data Bus: An 8-bit bidirectional bus that transfers data to and from memory.
-
Memory Map: A systematic arrangement showing the allocation of memory space for RAM, ROM, and I/O devices.
-
Address Decoding: The process of selecting a specific memory chip based on address input.
-
Control Signals: Signals used by the microprocessor to manage memory operations.
Examples & Applications
A memory map for an 8085 system with 2KB ROM starting at 0000H and 4KB RAM starting at 2000H.
A decoder circuit that uses an AND gate to generate chip select signals based on higher-order address lines.
Memory Aids
Interactive tools to help you remember key concepts
Rhymes
ROM is forever, RAM is fast, both work together for data to last.
Stories
Imagine a library where ROM is the reference section full of permanent books and RAM is the reading room where people work on temporary projects.
Memory Tools
Remember R.O.M for 'Read On Memory' and R.A.M for 'Random Access Memory.'
Acronyms
M.A.D
Memory Allocation and Decoding - for designing a memory map.
Flash Cards
Glossary
- Memory Map
A tabular or graphical representation of memory allocation in a microprocessor system.
- Address Decoder
Logic used to activate specific memory chips based on address lines.
- ROM
Read-Only Memory, non-volatile storage for firmware and applications.
- RAM
Random Access Memory, volatile storage used for temporary data during operation.
- 8085 Microprocessor
An 8-bit microprocessor with a 16-bit address bus capable of addressing 64KB of memory.
Reference links
Supplementary resources to enhance your learning experience.