In this ppt you will learn about the various memory and its types inside the computer. The ppt also describes an analogy for your better understanding. Hope it will be fun learning.

1. Lecture 1
MEMORY ORGANISATION IN EMBEDDED
SYSTEMS

2. Memory
1. Memory is an important component in an embedded system as it
stores all and any form of data depending upon its design
architecture.
2. For anyone to learn and have a deeper knowledge of the embedded
systems, it's important that one should first understand what the
memory of their hardware can actually offer or how one can design
the hardware for their application .
3. In data centers, they deal with Petabytes of memory. In personal
computers, they deal with mega->terabytes size of memory, But
when it comes to embedded systems ,it's usually from kiloBytes to
megaBytes of memory.
4. So, It is important that we understand,utilise and optimise this
small amount of memory efficiently in embedded systems.

3. Types of Memory
Lorem Ipsum
MEMORY
RAM - Volatile
memory
SRAM
DRAM
SDRAM
Register
PROM
EPROM
EEPROM
Flash
ROM - NonVolatile
memory
Volatile memory :
Loses data once the
power is turned off.
Non- volatile memory :
Retains data on losing
power.

4. Transformation of ROM
ROM is a non-volatile memory, meaning the data stored in ROM stays even after the power is
turned off, having said so ROM also has endurance issues that data cannot be written over and
over again, it has got limited number of write erase cycles before failure.
ROM PROM EEPROM
EPROM Flash
ROM and PROM are programmed only once by the manufacturer and remains unchanged.
EPROM are programmable multiple times and can be erased by exposing the memory to UV
(ultra-violet)light.
The next in the evolution comes the EEPROM and FLash which are electrically erasable and
programmable ROM but Flash comes with an endurance issue (10,000 - 1,00,000+ write erase
cycles)

5. RAM (Random access memory):
RAM is a volatile memory (Ram requires constant electrical power to store Data
and if the power is turned off then the data is erased.) and as the name suggests
allows access to any part of the memory given the address of that location.
1. In order for Data or program to run on a computer. First, It needs to be loaded into RAM.
2. So, RAM basically stores the data of your current running programs. For eg, if you have
opened your MS office document ,the MS word program will be copied to RAM and that’s
when we get the loading symbol in the front when the program gets copied in the background.
3. Once the program is loaded in the RAM, the CPU can now run the program and access the
data. The data that you keep feeding to your document will be saved to your RAM before you
SAVE it with the command File->Save As to your respective drive folder of ROM memory.
4. So, RAM is a very convenient type of memory to hold data that keeps changing continuously.
5. More space in RAM allows the user to use more applications simultaneously and efficiently.

6. Types Of RAM :
DRAM , SRAM, SDRAM
1. A DRAM uses a transistor - capacitor circuit to
hold a bit of data. Charged state is 1 bit and
discharged state is 0 bit.
2. While using capacitor, there may be leakage of
current in capacitor due to the little amount of
current that may be drawn by the adjacent
transistor or just due to the inner behaviour of the
capacitor itself.
3. So, the circuit needs to be refreshed with voltage
continuously and will not work without power.
4. The data transfer is slow compared to SRAM and
the cost is comparatively low.
SDRAM is a
synchronous DRAM
where the instructions are
synchronised with the
clock speed of the
microprocessor.

7. SRAM on the other hand works much faster than DRAM as it doesn’t have any
capacitor in its circuit and 2 cross coupled transistors i.e 4 transistors for storing
the charge and 2 transistors for access control. SRAM is much costlier and
works very fast.

8. Register memory
Registers are small memory that are present inside the processor itself. They
contain the data of operands and instructions of a program that CPU is
currently processing.
Since registers are inside the processor, the time required to fetch data is very
fast, but it cannot hold large data like RAM or ROM. It can hold only in bit
levels.
INTEL 8085 has popular 8-bit registers. ARM architecture has 32 bit registers.
Registers also hold the peripheral address in microcontroller.

9. So far, In the ppt we have learnt about the
volatile and non volatile memories of a
computer. To make the understanding
much better let us site an Analogy.
The core memory of a computer , ie the
ROM or HDD can be imagined to a library
, where numerous books on various topics
are stacked up neatly each one labelled.
The matrix of books arranged is the ROM.
The labels on each book can be imagined
as memory addresses of each byte.
Memory Analogy

10. And now consider yourself to be the CPU. Your
task is to look for data to prepare for a science
quiz. So, you have collected all the related
books and placed them on the table top, which
is the RAM. Now, More the table space, more
books can be accommodated. This helps in
fetching more data and saves time in going
back to the shelf searching for the book and
again coming back to the table.
This is analogous to having more RAM size,
when the program from the ROM is copied
entirely to the RAM , the processor need not go
back and forth to fetch data and instruction
from the ROM as everything is copied to RAM
and the execution is much faster.

11. When you start the process, you will start
reading the index of the book , memorize the
page number and go to the particular page
looking for information.
This is similar to saving the page number data
to the register memory and performing the next
task.
When you want to search the meaning of a
particular word. You memorize the word in
your head and take another book from the table
top to know the meaning of it.
This is similar to saving the address data in
register memory and looking for the data in that
address in RAM.
Once the work is complete, all the books on the
table will go back to the shelf and this is similar
to RAM data dissolving once the power is out.
And once you come out your memory will
eventually forget the trivial data of page number
and others. But some important data, like word-
meaning might stay in your head for a long time
then sync that to cache memory of the CPU.

12. Thank You
Hope you would have gained a good
knowledge about memory and a
overview of how it works inside the
computer