ROM Organization of Microcontroller 8051 | ROM Memory of 8051 | 8051 Memory Organization

Summary

This video lecture delves into the ROM organization of the 8051 microcontroller, explaining its internal 4KB ROM and the capacity to interface with an additional 64KB of external ROM. It clarifies the Harvard architecture, distinguishing between non-volatile program memory (ROM) and volatile data memory (RAM), essential for various embedded applications. The video also discusses how to utilize the EA^ bar pin for selecting between internal and external ROM, emphasizing the flexibility of memory management in the 8051 microcontroller.

Takeaways

• 😀 The 8051 microcontroller has a built-in 4 KB ROM and can interface with an additional 64 KB of external ROM.
• 🔍 The 8051 microcontroller features 128 bytes of internal RAM and can interface with up to 64 KB of external RAM.
• 🏛️ The 8051 follows the Harvard architecture, which means it has separate memory spaces for program and data.
• 📝 Program memory in ROM is non-volatile and fixed, while data memory in RAM is volatile and can change based on the application.
• 🔑 The EA/VPP pin determines the use of internal ROM; setting it to logic one indicates the use of the internal 4 KB ROM.
• 📍 The internal ROM has a fixed address range from 0x0000 to 0x0FFF in hexadecimal.
• 🌐 When using both internal and external ROM, the external ROM can be up to 64 KB and starts from address 0x1000 onwards.
• 🔄 The external ROM's address range can be determined by the programmer and can go up to 0xFFFF in hexadecimal.
• 🛠️ The 8051 is used in various embedded applications such as remote controls, microwave ovens, and washing machine timing controls.
• 📌 Fixed data like ASCII codes and seven-segment display data are stored in ROM because they are non-volatile and do not change.
• 🔄 Data that changes during program execution, such as temperature or time data, is stored in RAM as it is volatile.

Q & A

What is the ROM organization of the microcontroller 8051?

The microcontroller 8051 has an internal ROM of 4 KB and can interface externally with up to 64 KB of ROM.

What is the size of the internal RAM in the 8051 microcontroller?

The internal RAM of the 8051 microcontroller is 128 bytes in size.

How much external RAM can be interfaced with the 8051 microcontroller?

Up to 64 KB of external RAM can be interfaced with the 8051 microcontroller.

What is the Harvard architecture, as it relates to the 8051 microcontroller?

The Harvard architecture used by the 8051 microcontroller means it has separate program memory (ROM) and data memory (RAM), with program memory being non-volatile and data memory being volatile.

Why is the program memory in the 8051 considered non-volatile?

The program memory is non-volatile because the program instructions are fixed and do not change, unlike data which can vary with different applications and is stored in volatile RAM.

What is the significance of the EA/VPP pin in the context of the 8051 microcontroller's ROM usage?

The EA/VPP pin determines whether the 8051 microcontroller uses its internal ROM. When set to logic one (connected to VCC), it indicates the use of internal ROM. If set to zero, it signifies the use of only external ROM.

What happens when the EA/VPP pin is not connected to VCC in the 8051 microcontroller?

If the EA/VPP pin is not connected to VCC (set to zero), the 8051 microcontroller will not use its internal ROM and will rely solely on external ROM.

What is the default address range of the internal ROM in the 8051 microcontroller?

The default address range of the internal ROM in the 8051 microcontroller is from 0000h to 0FFFh.

Can the 8051 microcontroller use both internal and external ROMs simultaneously?

Yes, the 8051 microcontroller can use both internal and external ROMs, but the internal ROM must be enabled by setting the EA/VPP pin to logic one.

Why might a programmer choose to use only external ROM in the 8051 microcontroller?

A programmer might choose to use only external ROM if they require more memory than the internal 4 KB ROM provides, or if they need a specific size of ROM that is not available as a single IC, such as 60 KB.

What is the maximum size of external ROM that can be interfaced with the 8051 microcontroller?

The maximum size of external ROM that can be interfaced with the 8051 microcontroller is 64 KB.

Outlines

00:00

📚 Introduction to Microcontroller 8051 ROM Organization

This paragraph introduces the topic of the video lecture series on the microcontroller 8051, focusing on its ROM organization. It explains that the 8051 microcontroller has an internal ROM of 4 KB, with the capability to interface externally with up to 64 KB of ROM. The speaker emphasizes the importance of understanding the memory organization within the 8051 and outlines the basic categories of memory: internal ROM, external ROM, internal RAM, and external RAM. The paragraph also introduces the Harvard architecture of the 8051, distinguishing between non-volatile program memory (ROM) and volatile data memory (RAM), and gives examples of applications where the 8051 is used, such as in remote controls and microwave ovens, to illustrate the concept of fixed programs and changing data.

05:01

🔍 Deep Dive into 8051 ROM Architecture and External Memory Interfacing

The second paragraph delves deeper into the ROM architecture of the 8051 microcontroller, explaining how to interface with external memory and the role of the EA/VPP pin in determining whether to use internal ROM. It details the default address range for internal ROM and how to extend this with external ROM, which can go up to 64 KB. The paragraph clarifies the use of the EA/VPP pin: setting it to logic one indicates the use of internal ROM, while setting it to zero signifies reliance solely on external ROM. It also addresses the practicality of ROM sizes available in the market, explaining why one might choose to use both internal and external ROMs, and the flexibility this provides in designing embedded systems with the 8051 microcontroller. The speaker invites any students with questions to post them in the comment box for further clarification.

Keywords

💡Microcontroller 8051

The Microcontroller 8051, often referred to simply as '8051', is a widely used 8-bit microcontroller developed by Intel in the late 1970s. It is the central theme of the video, as the script discusses its ROM organization. The 8051 is known for its Harvard architecture, which separates program memory (ROM) and data memory (RAM), allowing for efficient execution of embedded systems applications.

💡ROM Organization

ROM Organization refers to the structure and layout of Read-Only Memory within a microcontroller. In the context of the 8051, it is the internal and external memory configuration that the video script explains. The 8051 has 4 KB of internal ROM, with the capability to interface with an additional 64 KB of external ROM, which is crucial for expanding the microcontroller's program storage capacity.

💡Internal ROM

Internal ROM is the built-in, non-volatile memory found within the 8051 microcontroller, which stores the microcontroller's firmware or program code. The script mentions that the 8051 has 4 KB of internal ROM, which is fixed and does not change, serving as the primary storage for the microcontroller's instructions.

💡External ROM

External ROM is memory that can be added to the 8051 microcontroller beyond its internal capacity. The video script explains that up to 64 KB of external ROM can be interfaced with the 8051, allowing for larger programs to be stored and executed. This is particularly useful for more complex embedded applications.

💡Internal RAM

Internal RAM refers to the volatile memory within the 8051 microcontroller that is used for temporary data storage. The script specifies that the 8051 has 128 bytes of internal RAM, which is essential for holding data that changes during program execution, such as variables and intermediate results.

💡External RAM

External RAM is additional memory that can be interfaced with the 8051 microcontroller to supplement its internal RAM. The video script mentions that up to 64 KB of external RAM can be connected to the 8051, providing more space for data storage in applications that require handling large amounts of data.

💡Harvard Architecture

The Harvard architecture is a computer architecture that uses separate memory spaces for instructions and data, allowing them to be accessed simultaneously. The video script explains that the 8051 microcontroller follows this architecture, which means it has separate program memory (ROM) and data memory (RAM), enhancing its efficiency in embedded systems.

💡EA/VPP Pin

The EA/VPP pin is a crucial pin on the 8051 microcontroller that determines the use of the internal ROM. The script explains that setting this pin to a logic high (1) enables the use of the internal ROM, while setting it to a logic low (0) indicates that only external ROM will be used, effectively discarding the internal ROM.

💡Non-Volatile Memory

Non-volatile memory is a type of memory that retains data even when power is not supplied. In the context of the 8051, the internal ROM is non-volatile, meaning the program code stored in it remains intact even when the microcontroller is powered off, as mentioned in the script.

💡Volatile Memory

Volatile memory is memory that loses its data when power is turned off. The script refers to the internal RAM of the 8051 as volatile, indicating that the data stored in it is temporary and will be lost if the power is not maintained.

💡Embedded Applications

Embedded applications are specialized computer programs designed for specific tasks within embedded systems. The video script provides examples of such applications, including remote controls, microwave ovens, and washing machine timing controls, which utilize the 8051 microcontroller for their operation.

Highlights

Introduction to the ROM organization of the microcontroller 8051.

The 8051 microcontroller has an internal ROM of 4 KB and supports interfacing with an external ROM of up to 64 KB.

Understanding the memory organization within the 8051 microcontroller is essential for students.

8051 has four different categories of memory: internal ROM, external ROM, internal RAM, and external RAM.

The 8051 microcontroller follows the Harvard architecture, separating program and data memory.

Program memory in ROM is non-volatile, while data memory in RAM is volatile.

The reason for the use of volatile data memory is the changing nature of data in various applications.

8051 is used in many embedded applications such as remote controls, microwave ovens, and washing machine timing controls.

Program stored in ROM is fixed and does not change, unlike data stored in RAM which may vary with application.

Fixed data such as ASCII codes and seven-segment display data is stored in ROM due to its non-volatile nature.

The EA/VPP pin configuration determines the use of internal ROM in the 8051 microcontroller.

When using only external ROM, the EA/VPP pin should be set to 0, and the external ROM can have a maximum size of 64 KB.

The internal ROM has a fixed address range from 0000h to FFFFh when EA/VPP is set to 1.

When interfacing external ROM, the address range can be decided by the programmer, starting from 1000h to FFFFh.

The flexibility of the 8051 microcontroller allows for the use of internal ROM, external ROM, or a combination of both.

The video offers to help clarify any confusion regarding ROM architecture in the 8051 microcontroller.

Transcripts

welcome to engineering funda family this

video is a part of microcontroller 8051

video lecture series and in this video

i'll be going to explain you

rom organization of microcontroller 8051

my dear students there are few basic

things that you should understand

see

the single chip of microcontroller 8051

that is having 4 kb of rom

but

here we can interface

externally 64 kb of rom

and whenever you interface external

memory

at that time there are few things that

you need to keep in your mind that is

what i'll be explaining you in this

video

but before that you should understand

how memory organization is there inside

microcontroller 8051 so all the basics

regarding memory that i'll be explaining

you in this video step by step so let us

see all those things one by one so here

my dear students

first of all you should understand that

8051

that is having four different categories

of memories

here

internal rom is there which is having

size of 4 kb with 8 0 5 1

as well as externally we can interface

64 kb of rom with 8051

and

8051 that is having internal ram of size

of 128 bytes

here my dear students externally we can

interface

64 kb of ram with 8051 so in total there

can be four different categories of

memories

these two memories internal memories

that is already there with eight zero

five one but as if programmer is having

need of some extra memory then

programmer can

interface external ram and rom with

eight zero five one

here few more things that you need to

understand like architecture of 8051

microcontroller

8051 microcontroller follows harvard

architecture howard architecture means

what howard architecture means here we

have separate program memory and

separate data memory

obviously program memory which will be

having instructions that we will be

having with rom it should be

non-volatile

while data memory that will be there

with ram that could be volatile

let me try to explain you why it is like

this the reason is

see whatever program that we have for

this microcontroller that should be

fixed right it will never change it will

just execute instructions one by one

but data may change so in various

applications you will be having

different data so you may need to change

the data with respect to execution of

program that's why

data will be volatile that will be

storing inside ram

let me explain you further how things

are there with eight zero five one so

when we talk about applications then you

should know eight zero one that we use

it with many embedded applications those

applications may be remote control it

may be there based on microwave own it

may be there with washing machine timing

control so likewise there are many

embedded applications which is

practically available with eight zero

five one microcontroller

here my dear students

when you use eight zero five one in

application at a time you should

understand few basic things like

whatever program that we store inside

memory that should be fixed right you

cannot change program so that will be

there inside rom

but data may change with respect to

application that will be temporarily

stored inside memory that's why it

should be there with ram

like for example

when you store temperature as a data

obviously data will change like for

example you are having

ac in which you are storing one program

so your program is based on

temperature should not exceeds to

25 degree celsius right that is what

your program

so that program will be there inside rom

but

temperature data that will change

as cooling is happening your temperature

will go down

right and it should not exit to 25

degree celsius so that data of

temperature that will there inside ram

so harvard architecture is used with

8051 in which

program will be stored inside rom

and data will be stored inside ram

here my dear students some fixed data

like ascii code

right like data of seven segment display

that we will be storing inside rom as it

should be non-volatile right it will be

fixed but the data which we use it in

program

like temperature data time data so those

data will be changing right so that's

why we will be storing that inside ram

so in short my dear students eight zero

five one that is based on howard

architecture it will be having ram as

well as rom rom will be used for program

ram will be used for data here

internal ram and rom is available

internal ram is having size of 128 byte

internal rom is having size of 4 kb but

as if programmer is having some high end

application then programmer can

interface external memory like ram and

rom and at max we can interface 64 kb of

rom and ram now i'll explain you how

rom architecture is there with eight

zero five one

so here my dear students when

only we use internal rom at that time

it should be very clear to you first of

all you will have to make

e a bar terminal is equals to 1.

see with 8 0 5 1 this pin is playing

essential rule it explains you whether

we use internal rom or not

as if you use internal rom then you'll

have to make sure this pin that should

be connected with vcc means it is logic

one whenever you make this pin is equals

to logic one you are using internal rom

here as if programmer is not interfacing

external memory then only internal rom

will be available and that address will

start from zero zero zero zero hex to 0

f f f hex

that is by default address of this

internal rom where programmer can store

their program

here few more cases are there like as a

programmer needs to have some extra

memory

then obviously programmer will be using

internal as well as external rom

and

in case of programmer is using internal

rom then ea bar that must be equals to

one what it indicates internal rom is

there with size of 4 kb and it will be

having address ranging from 0 0 0 0 hash

to 0 f f f hex means this address is

allocated with internal rom

now

here as programmer is having need of

some more memory external rom is

available right but at max you can have

64 kb means 60 kb of external rom can be

interfaced so from here onwards only you

can use addresses so next address after

this 0 f x that will be 1 0 0 0

hex right

here my dear students

after that it can go up to maximum

ffff hacks right so this will be the

available range for external rom

and here my dear students ea bar

explains whether we use internal rom or

not here sometimes

you may be having only external rom

so in that case you will have to keep ea

bar is equals to zero what it means

eight zero five one will not use

internal rom so in that case external

rom that can be having maximum size of

64 kb it will be starting from 0 0 0 0

hex to up

ffff hex

address right now few of my students who

have been asking me some questions like

they have been telling me sir

if you use only external rom then what

is the use of internal rom so obviously

here programmer is deciding this right

let me tell you one more thing like for

example when you have external rom only

at the time you are discarding internal

rom why the reason is my dear students

when you go in market you don't have

external rom with the size of 60 kb

right

either you

buy a rom with size of 32 kb

or you can buy a rom with the size of 64

kb

so you cannot have 60 kb of rom for that

you'll have to use multiple roms right

so here external rom that we are using

with 64 kb

or 32 kb you don't have facility of 60

kb of rom for that you have to use

multiple ics that is why

8051 is having this facility in which

you can have internal as well as

external as well as only external rom

facility but here remember when you keep

ea bar is equals to 1 your internal rom

will be there in use and it will be

having fixed address you cannot change

this address right

only thing is external rom that can be

having different address that can be

decided by programmer so this is how

structure is there in terms of rom i

hope it is clear to you still if any

confusion is there just post that in

comment box i'll be happy to help you

thank you so much for watching this

video