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8051 and 8051 Microcontroller

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Features of 8051
The main features of 8051 microcontroller are:
        i.            RAM – 128 Bytes (Data memory)
      ii.            ROM – 4Kbytes (ROM signify the on – chip program space)
    iii.            Serial Port – Using UART makes it simpler to interface for serial communication.
    iv.            Two 16 bit Timer/ Counter
      v.            Input/output Pins – 4 Ports of 8 bits each on a single chip.
    vi.            6 Interrupt Sources
 vii.            8 – bit ALU (Arithmetic Logic Unit)
viii.            Harvard Memory Architecture – It has 16 bit Address bus (each of RAM and ROM) and 8 bit Data Bus.
    ix.            8051 can execute 1 million one-cycle instructions per second with a clock frequency of 12MHz.
This microcontroller is also called as “System on a chip” because it has all the features on a single chip. The Block Diagram of 8051 Microcontroller is as shown in Figure 1.1
8051 Block Diagram, 8051 Architecture
Figure 1.1 Block Diagram of 8051 Microcontroller
Memory Architecture
The 4 discrete types of memory in 8051 are:
        i.            Internal RAM – This memory is located from address 0 to 0xff.  The memory locations from 0x00 to 0x7F are accessed directly. The bytes from 0x20 to 0x2F are bit-addressable. Loading R0 and R1 the memory location from 0x80 to 0xFF can easily accessed.
      ii.            Special Function Registers (SFR) – Located from address 0x80 to 0xFF of the memory location. The same instructions used for lower half of Internal RAM can be used to access SFR’s. The SFR’s are bit addressable too.
    iii.            Program Memory – This is read only memory which is located at address 0. With the help of 16 bit Special Function Register DPTR, this memory can also save the tables of constants.
    iv.            External Data Memory – Located at address 0. The Instruction MOVX (Move External) should be used to access the external data memory.


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I really love to read articles that have good information and ideas to share to each reader. I hope to read more from you guys and continue that good work that is really inspiring to us.

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It's very good fundamental about microcontroller..




thanks for giving a complete knowledge of 8051

 excellent site i wud like to contribute  i do have few codes

i wont to know about at89s52

it is advanced controller it has 3 intrupt. and progaram burning is easy in thise just download ace.isp softwear and se dia. in it



it is just like 80c51 , having a pin compatibility with 80c51, but having 8k on chip ROM and having 256 bytes RAM, 3 timers, 8 interrupt sources, one serial port, 32 I/O pins






could u please tell me abt proteus software......

 Nice info, though i would like to know where are interrupts used in the applications.

I have just read about it but haven't seen them in action in any of the books or applications.

Can you give some info on that? It'll be great help.

thankyou for for useful information 

 what software can I use for programming the 8051?




keil uv3 or uv4

thanks a lot for providing detail information about project

will you provide me program with assembly language on project LCD BASED ELECTRONIC VOTING MACHINE.

If so please email me the same at


Maraming salamat po.(Tagalog)


It means "thank you so much."


It fills me with great joy, it really be of great help for our project.

Thank you so much for nice information.

Thank you so much for nice information.


very usefull,explained briefly thanks

Thanks to Engineers Garage for giving students ample opportunity to learn from this website, indeed it is empowering the people with knowledge, i sincerely appreciate your good work.

Thanks and keep doing the good work

The information is very useful. Please provide more info on C programming 89C51 microcontroller focussing on headers , initialization , i/p and o/p configuring methods, interupt initialization,...etc. This will greatly help in starting a project.


 best site! 


hi very member of the excelent page.

I want somes examples simples about  all interrupt please.

thank for read me.

Thanks so much for this! This is exactly what I was looking for.

Existance this summery in front page allowes programmer newer to this 8051 MC, program without use of any other information.

Really awesome

 After reading these information one must say really awesome !!!!!!!

Than a Lot man

 I like this site...its very useful to make new projects! :)

this is the good site for the engeneers



 super website i got many details from this.

Hello, i'm new to this site, i've found it when i was searching in Google, Thanks for your post

Thank you is great job! am enjoying it...LONG LIVE SIR....

amazing site......... thanks for such very useful info.

Nice Information...

pls provide (how to program a 8051 chip with the help of C language)...... 

Hi !

I am working as Embedded Developer. I really find all the articles and tutorials very useful for the reference.

Thanks for your efforts for providing such valuable information.

I hope you will try to make this website more effective in future.

All the very best!!!



At Table 1.2, AT89C52 appears to have a typo at the RAM which should be 256 and not 128.

Just a 2 cent worth opinion. Nevertheless, great information.            

it's good information fundamental abaut microcontroller.

Thank for useful information about microcontroller 8051...It is clear and nice

Is there a burner for 8051 that can  be use to transfer the program to the 8051?

Wow... Great Analysis of providing an information in a better way... Nice to acquire... yes


Articles like this are an exalmpe of quick, helpful answers.

can any one help me to choose  software for burning code in AT89c51 and how to choose a burner

hi i am doing a project on ivrs based industrial controlled system. can you please sent me required circuit diagram alongwith source code written in c language


which compiler is used in 8051 microcontroller programming (KEIL oR OTHER) ?

thanks to Engineers Garage team it is very useful.


it's very very valuable information

I'm novice to micro controller field .I referred most of the articles,circuits and programs from Engineers Garage.It is an excellent guide for the learners like me.Thanks to your team.


Gr8 Effort :)

It is very helpful..

thank u

I'm extremely impressed with your writing skills as well as with the layout on your blog. Is this a paid theme or did you modify it yourself? Either way keep up the nice quality writing, it is rare to see a great blog like this one today.. wesdf

really i m impressed by the blog

thank u very much

please give me the information of 8051 micro controller

very nice site n it is very useful for the students...smiley

how i can download it?????


Thanks for giving such an nice experience to us.your way of presentation is superb.just add some 3diamensonal pictures of microcontroller which will understand about your ideas more easier

add some 3diamensional pictures of microcontrollr which will helpfull us to capture  your ideas more easily 

yes this site usu full to education

by:- Happy Kathrotiya




this is much good...

wah wah kadkina..........makhi



i am working in a company so don't have sufficient knowledge for this project.

I want full led board 12*12 matrix with led controller,drivers etc

and the other things is that i want to operate this led by remote control.


will it be possible to interface 8051 microcontroller?

just provide me

1. types of components that are used in my project.

2. cost of that components.

3. circuit diagram.

4. layout

5. specification of that project.

hii its a nice website it helps all the trainees in embedded......

can you please help me??

i want the program source code for the printing of ascii characters on lcd display in 8051 by using keil software


Nice effort and I appreciate it. 

I have included this on my blog as a reference tutorial so my readers can benefit from this. I also have started writing about the 8051 microcontroller as I simply love working on it.


thanks 4 good knowledge abt 8051

i want 8051 development board from where i can get that


very good info.. thank u..

I found this site really very useful and helpful .

But ,couldnt find appropriate software for programming.

Can anybody suggest me software for 8051 programming (Embedded C). 

I have tried the code using Keil but it generates the following error inspite of having license copy 




Regards ,





nice effort...............good site


A very useful site...nice...

very superb site


can u give post the flowchat of project of electronic voting machine usine using ic AT89c51 with

led display


really this is amazing but some of the details i'm expecting in PDF

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