A

Seminar REPORT

ON

(8051 Microcontroller)

Academic Session 2013-14

Submitted in partial fulfillment of the requirements of the degree of

BACHELOR OF TECHNOLOGY

In

ELECTRONICS & COMMUNICATION ENGINEERING

Submitted to: Submitted by:

Mr. Ansh singh Prof. R. K. SINGH Mannu sharma

Seminar Coordinator Head of Department

DEPARTMENT OF ELECTRONICS AND COMMUNICATION ENGINEERING

RAJASTHAN TECHNICAL UNIVERSITY, KOTA

2010-2014

ACKNOWLEDGEMENT

I would like to thanks almighty god for giving me luck & faith in my abilities to complete this. I

would like to express my deep sense of gratitude to my teachers for extending me the

opportunity for this and providing all the necessary resources and expertise for this purpose.

I would like to convey my deepest gratitude to (Seminar guide) for sparing his valuable

time for me to discuss and clarify issue connected with this Seminar report.

Mannu sharma

TABLE OF CONTENTS

Chapter 1: 8051 MICRONTROLLER…………………………….1

1.1 Introduction……………………………………………..……..…1

1.2 MCU 8051 standards……………………………………..…..…...1

Chapter 2: BLOCK DIAGRAM OF 8051………………..2-3

Chapter 3: PIN DIAGRAM OF 8051……………......…..4-5

Chapter 4: PORTS OF MCU 8051……………………………6-9

Chapter 5: MEMORY OF MCU 8051…………….…………….…..10-14

CONCLUSION...………………………………………...15

REFERENCES...………………………………………...16

CHAPTER-1

8051 MICROCONTROLLER

1.1 INTRODUCTION

The 8051 Microcontroller was designed in 1980’s by Intel. Its foundation was on Harvard Architecture and was developed principally for bringing into play in Embedded Systems. At first it was created by means of NMOS technology but as NMOS technology needs more power to function therefore Intel re-intended Microcontroller 8051 employing CMOS technology and a new edition came into existence with a letter ‘C’ in the title name, for illustration: 80C51. These most modern Microcontrollers need fewer amount of power to function in comparison to their forerunners.

There are two buses in 8051 Microcontroller one for program and other for data. As a result, it has two storage rooms for both program and data of 64K by 8 size. The microcontroller comprise of 8 bit accumulator & 8 bit processing unit. It also consists of 8 bit B register as majorly functioning blocks. It also has a number of other 8 bit and 16 bit registers.

For internal functioning & processing Microcontroller 8051 comes with integrated built-in RAM. This is prime memory and is employed for storing temporary data. It is unpredictable memory i.e. its data can get be lost when the power supply to the Microcontroller switched OFF.

1.2 MICROCONTROLLER 8051 STANDARDS:

4 Kb of ROM is not much at all. 128b of RAM (including SFRs) satisfies the user's basic needs. 4 ports having in total of 32 input/output lines are in most cases sufficient to make all

necessary connections to peripheral environment.

The whole configuration is obviously thought of as to satisfy the needs of most programmers working on development of automation devices. One of its advantages is that nothing is missing and nothing is too much. In other words, it is created exactly in accordance to the average user‘s taste and needs. Another advantages are RAM organization, the operation of Central Processor Unit (CPU) and ports which completely use all recourses and enable further upgrade.

CHAPTER-2

BLOCK DIAGRAM OF 8051

Block Diagram of 8051 Microcontroller:

Microcontroller 8051 block diagram is shown below. Let’s have a closer look at each & every fraction or block of this design:

8051 Microcontroller Block Diagram Explanation:

Block Diagram of 8051 Microcontroller

CPU (Central Processor Unit):

As you may be familiar that Central Processor Unit or CPU is the mind of any processing machine. It scrutinizes and manages all processes that are carried out in the Microcontroller. User has no power over the functioning of CPU. It interprets program printed in storage space (ROM) and carries out all of them and do the projected duty.

Interrupts:

As the heading put forward, Interrupt is a sub-routine call that reads the Microcontroller’s key function or job and helps it to perform some other program which is extra important at that point of time. The characteristic of Interrupt is extremely constructive as it aids in emergency cases. Interrupts provides us a method to postpone or delay the current process, carry out a sub-routine task and then all over again restart standard program implementation.

The Micro-controller 8051 can be assembled in such a manner that it momentarily stops or break the core program at the happening of interrupt. When sub-routine task is finished then the implementation of core program initiates automatically as usual. There are 5 interrupt supplies in 8051 Microcontroller, two out of five are peripheral interrupts, two are timer interrupts and one is serial port interrupt.

Memory:

Micro-controller needs a program which is a set of commands. This program enlightens Microcontroller to perform precise tasks. These programs need a storage space on which they can be accumulated and interpret by Microcontroller to act upon any specific process. The memory which is brought into play to accumulate the program of Microcontroller is recognized as Program memory or code memory. In common language it’s also known as Read Only Memory or ROM.

Micro-controller also needs a memory to amass data or operands for the short term. The storage space which is employed to momentarily data storage for functioning is acknowledged as Data Memory and we employ Random Access Memory or RAM for this principle reason. Microcontroller 8051 contains code memory or program memory 4K so that is has 4KB Rom and it also comprise of data memory (RAM) of 128 bytes.

Bus:

Fundamentally Bus is a group of wires which functions as a communication canal or mean for the transfer Data. These buses comprise of 8, 16 or more cables. As a result, a bus can bear 8 bits, 16 bits all together. There are two types of buses:

1. Address Bus: Microcontroller 8051 consists of 16 bit address bus. It is brought into play to address memory positions. It is also utilized to transmit the address from Central Processing Unit to Memory.

2. Data Bus: Microcontroller 8051 comprise of 8 bits data bus. It is employed to cart data.

Oscillator:

As we all make out that Microcontroller is a digital circuit piece of equipment, thus it needs timer for its function. For this function, Microcontroller 8051 consists of an on-chip oscillator which toils as a time source for CPU (Central Processing Unit). As the productivity thumps of oscillator are steady as a result, it facilitates harmonized employment of all pieces of 8051 Microcontroller. Input/output Port: As we are acquainted with that Microcontroller is employed in embedded systems to manage the functions of devices. Thus to gather it to other machinery, gadgets or peripherals we need I/O (input/output) interfacing ports in Micro-controller. For this function Micro-controller 8051 consists of 4 input/output ports to unite it to other peripherals.Timers/Counters: Micro-controller 8051 is incorporated with two 16 bit counters & timers. The counters are separated into 8 bit registers. The timers are utilized for measuring the intervals, to find out pulse width etc.

CHAPTER-3

PIN DIAGRAM OF 8051

Explanation on 8051 Pin Diagram:

8051 Microcontroller Pin Diagram

For explaining the pin diagram and pin configuration of microcontroller 8051, we are taking into deliberation a 40 pin Dual inline package (DIP). Now let’s study through pin configuration in brief:-

Pins 1 – 8:- recognized as Port 1. Different from other ports, this port doesn’t provide any other purpose. Port 1 is a domestically pulled up, quasi bi directional Input/output port.

Pin 9:- As made clear previously RESET pin is utilized to set the micro-controller 8051 to its primary values, whereas the micro-controller is functioning or at the early beginning of application. The RESET pin has to be set elevated for two machine rotations.

Pins 10 – 17:- recognized as Port 3. This port also supplies a number of other functions such as timer input, interrupts, serial communication indicators TxD & RxD, control indicators for outside memory interfacing WR & RD, etc. This is a domestic pull up port with quasi bi directional port within.

Pins 18 and 19:- These are employed for interfacing an outer crystal to give system clock.

Pin 20:- Titled as Vss – it symbolizes ground (0 V) association.

Pins- 21-28:- recognized as Port 2 (P 2.0 – P 2.7) – other than serving as Input/output port, senior order address bus indicators are multiplexed with this quasi bi directional port.

Pin- 29:- Program Store Enable or PSEN is employed to interpret sign from outer program memory.

Pin-30:- External Access or EA input is employed to permit or prohibit outer memory interfacing. If there is no outer memory need, this pin is dragged high by linking it to Vcc.

Pin-31:- Aka Address Latch Enable or ALE is brought into play to de-multiplex the address data indication of port 0 (for outer memory interfacing). Two ALE throbs are obtainable for every machine rotation.

Pins 32-39: recognized as Port 0 (P0.0 to P0.7) – other than serving as Input/output port, low order data & address bus signals are multiplexed with this port (to provide the use of outer memory interfacing). This pin is a bi directional Input/output port (the single one in microcontroller 8051) and outer pull up resistors are necessary to utilize this port as Input/output.

Pin-40: termed as Vcc is the chief power supply. By and large it is +5V DC.

8051 Microcontroller Applications:

The microcontroller 8051 has been in application in a large amount of machines, principally because it is simple to incorporate in a project or to assemble a machine around it. The following are the key spots of spotlight:

1. Energy Management: Competent measuring device systems aid in calculating energy consumption in domestic and industrialized applications. These meter systems are prepared competent by integrating microcontrollers.

2. Touch screens: A high degree of microcontroller suppliers integrate touch sensing abilities in their designs. Transportable devices such as media players, gaming devices & cell phones are some illustrations of micro-controller integrated with touch sensing screens.

3. Automobiles: The microcontroller 8051 discovers broad recognition in supplying automobile solutions. They are extensively utilized in hybrid motor vehicles to control engine variations. In addition, works such as cruise power and anti-brake mechanism has created it more capable with the amalgamation of micro-controllers.

4. Medical Devices: Handy medicinal gadgets such as glucose & blood pressure monitors bring into play micro-controllers, to put on view the measurements, as a result, offering higher dependability in giving correct medical results.

5. Medical Devices: Handy medicinal gadgets such as glucose & blood pressure monitors bring into play micro-controllers, to put on view the measurements, as a result, offering higher dependability in giving correct medical results.

CHAPTER-4

PORTS OF MCU 8051

2.3 Input/Output Ports (I/O Ports)

All 8051 microcontrollers have 4 I/O ports each comprising 8 bits which can be configured as inputs or outputs. Accordingly, in total of 32 input/output pins enabling the microcontroller to be connected to peripheral devices are available for use.

Pin configuration, i.e. whether it is to be configured as an input (1) or an output (0), depends on its logic state. In order to configure a microcontroller pin as an output, it is necessary to apply a logic zero (0) to appropriate I/O port bit. In this case, voltage level on appropriate pin will be 0.

Similarly, in order to configure a microcontroller pin as an input, it is necessary to apply a logic one (1) to appropriate port. In this case, voltage level on appropriate pin will be 5V (as is the case with any TTL input). This may seem confusing but don't loose your patience. It all becomes clear after studying simple electronic circuits connected to an I/O pin.

Input/Output (I/O) pinFigure above illustrates a simplified schematic of all circuits within the microcontroler connected to one of its pins. It refers to all the pins except those of the P0 port which do not have pull-up resistors built-in.

Output pinA logic zero (0) is applied to a bit of the P register. The output FE transistor is turned on, thus connecting the appropriate pin to ground.

Input pinA logic one (1) is applied to a bit of the P register. The output FE transistor is turned off and the appropriate pin remains connected to the power supply voltage over a pull-up resistor of high resistance.

Logic state (voltage) of any pin can be changed or read at any moment. A logic zero (0) and logic one (1) are not equal. A logic one (0) represents a short circuit to ground. Such a pin acts as an output.

A logic one (1) is “loosely” connected to the power supply voltage over a resistor of high resistance. Since this voltage can be easily “reduced” by an external signal, such a pin acts as an input.

Port 0

The P0 port is characterized by two functions. If external memory is used then the lower address byte (addresses A0-A7) is applied on it. Otherwise, all bits of this port are configured as inputs/outputs.

The other function is expressed when it is configured as an output. Unlike other ports consisting of pins with built-in pull-up resistor connected by its end to 5 V power supply, pins of this port have this resistor left out. This apparently small difference has its consequences:

If any pin of this port is configured as an input then it acts as if it “floats”. Such an input has unlimited input resistance and indetermined potential.

When the pin is configured as an output, it acts as an “open drain”. By applying logic 0 to a port bit, the appropriate pin will be connected to ground (0V). By applying logic 1, the external output will keep on “floating”. In order to apply logic 1 (5V) on this output pin, it is necessary to built in an external pull-up resistor.

Only in case P0 is used for addressing external memory, the microcontroller will provide internal power supply source in order to supply its pins with logic one. There is no need to add external pull-up resistors.

Port 1

P1 is a true I/O port, because it doesn't have any alternative functions as is the case with P0, but can be cofigured as general I/O only. It has a pull-up resistor built-in and is completely compatible with TTL circuits.

Port 2

P2 acts similarly to P0 when external memory is used. Pins of this port occupy addresses intended for external memory chip. This time it is about the higher address byte with addresses A8-A15. When no memory is added, this port can be used as a general input/output port showing features similar to P1.

Port 3

All port pins can be used as general I/O, but they also have an alternative function. In order to use these alternative functions, a logic one (1) must be applied to appropriate bit of the P3 register. In tems of hardware, this port is similar to P0, with the difference that its pins have a pull-up resistor built-in.

Pin's Current limitations

When configured as outputs (logic zero (0)), single port pins can receive a current of 10mA. If all 8 bits of a port are active, a total current must be limited to 15mA (port P0: 26mA). If all ports (32 bits) are active, total maximum current must be limited to 71mA. When these pins are configured as inputs (logic 1), built-in pull-up resistors provide very weak current, but strong enough to activate up to 4 TTL inputs of LS series.

CHAPTER-5

MEMORY IN 8051

2.4 Memory Organization

The 8051 has two types of memory and these are Program Memory and Data Memory. Program Memory (ROM) is used to permanently save the program being executed, while Data Memory (RAM) is used for temporarily storing data and intermediate results created and used during the operation of the microcontroller. Depending on the model in use (we are still talking about the

8051 microcontroller family in general) at most a few Kb of ROM and 128 or 256 bytes of RAM is used. However…

All 8051 microcontrollers have a 16-bit addressing bus and are capable of addressing 64 kb memory. It is neither a mistake nor a big ambition of engineers who were working on basic core development. It is a matter of smart memory organization which makes these microcontrollers a real “programmers’ goody“.

Program Memory

The first models of the 8051 microcontroller family did not have internal program memory. It was added as an external separate chip. These models are recognizable by their label beginning with 803 (for example 8031 or 8032). All later models have a few Kbyte ROM embedded. Even though such an amount of memory is sufficient for writing most of the programs, there are situations when it is necessary to use additional memory as well. A typical example are so called lookup tables. They are used in cases when equations describing some processes are too complicated or when there is no time for solving them. In such cases all necessary estimates and approximates are executed in advance and the final results are put in the tables (similar to logarithmic tables).

How does the microcontroller handle external memory depends on the EA pin logic state:

EA=0 In this case, the microcontroller completely ignores internal program memory and executes only the program stored in external memory.

EA=1 In this case, the microcontroller executes first the program from built-in ROM, then the program stored in external memory.

In both cases, P0 and P2 are not available for use since being used for data and address transmission. Besides, the ALE and PSEN pins are also used.

Data Memory

As already mentioned, Data Memory is used for temporarily storing data and intermediate results created and used during the operation of the microcontroller. Besides, RAM memory built in the 8051 family includes many registers such as hardware counters and timers, input/output ports, serial data buffers etc. The previous models had 256 RAM locations, while for the later models this number was incremented by additional 128 registers. However, the first 256 memory locations (addresses 0-FFh) are the heart of memory common to all the models belonging to the 8051 family. Locations available to the user occupy memory space with addresses 0-7Fh, i.e. first 128 registers. This part of RAM is divided in several blocks.

The first block consists of 4 banks each including 8 registers denoted by R0-R7. Prior to accessing any of these registers, it is necessary to select the bank containing it. The next memory block (address 20h-2Fh) is bit- addressable, which means that each bit has its own address (0-7Fh). Since there are 16 such registers, this block contains in total of 128 bits with separate addresses (address of bit 0 of the 20h byte is 0, while address of bit 7 of the 2Fh byte is 7Fh). The third group of registers occupy addresses 2Fh-7Fh, i.e. 80 locations, and does not have any special functions or features.

Additional RAM

In order to satisfy the programmers’ constant hunger for Data Memory, the manufacturers decided to embed an additional memory block of 128 locations into the latest versions of the 8051 microcontrollers. However, it’s not as simple as it seems to be… The problem is that electronics performing addressing has 1 byte (8 bits) on disposal and is capable of reaching only the first 256 locations, therefore. In order to keep already existing 8-bit architecture and compatibility with other existing models a small trick was done.

What does it mean? It means that additional memory block shares the same addresses with locations intended for the SFRs (80h- FFh). In order to differentiate between these two physically separated memory spaces, different ways of addressing are used. The SFRs memory locations are accessed by direct addressing, while additional RAM memory locations are accessed by indirect addressing.

Memory expansion

In case memory (RAM or ROM) built in the microcontroller is not sufficient, it is possible to add two external memory chips with capacity of 64Kb each. P2 and P3 I/O ports are used for their addressing and data transmission.

From the user’s point of view, everything works quite simply when properly connected because most operations are performed by the microcontroller itself. The 8051 microcontroller has two pins for data read RD#(P3.7) and PSEN#. The first one is used for reading data from external data memory (RAM), while the other is used for reading data from external program memory (ROM). Both pins are active low. A typical example of memory expansion by adding RAM and ROM chips (Hardward architecture), is shown in figure above.

Even though additional memory is rarely used with the latest versions of the microcontrollers, we will describe in short what happens when memory chips are connected according to the previous schematic. The whole process described below is performed automatically.

When the program during execution encounters an instruction which resides in external memory (ROM), the microcontroller will activate its control output ALE and set the first 8 bits of address (A0-A7) on P0. IC circuit 74HCT573 passes the first 8 bits to memory address pins.

A signal on the ALE pin latches the IC circuit 74HCT573 and immediately afterwards 8 higher bits of address (A8-A15) appear on the port. In this way, a desired location of additional program memory is addressed. It is left over to read its content.

Port P0 pins are configured as inputs, the PSEN pin is activated and the microcontroller reads from memory chip.

Similar occurs when it is necessary to read location from external RAM. Addressing is performed in the same way, while read and write are performed via signals appearing on the control outputs RD (is short for read) or WR (is short for write).

Addressing

While operating, the processor processes data as per program instructions. Each instruction consists of two parts. One part describes WHAT should be done, while the other explains HOW to do it. The latter part can be a data (binary number) or the address at which the data is stored. Two ways of addressing are used for all 8051 microcontrollers depending on which part of memory should be accessed:

Direct Addressing

On direct addressing, the address of memory location containing data to be read is specified in instruction. The address may contain a number being changed during operation (variable). For example:

Since the address is only one byte in size (the largest number is 255), only the first 255 locations of RAM can be accessed this way. The first half of RAM is available for use, while another half is reserved for SFRs.

MOV A,33h; Means: move a number from address 33 hex. to accumulator

Indirect Addressing

On indirect addressing, a register containing the address of another register is specified in instruction. Data to be used in the program is stored in the letter register. For example:

Indirect addressing is only used for accessing RAM locations available for use (never for accessing SFRs). This is the only way of accessing all the latest versions of the microcontrollers with additional memory block (128 locations of RAM). Simply put, when the program encounters instruction including “@” sign and if the specified address is higher than 128 ( 7F hex.), the processor knows that indirect addressing is used and skips memory space reserved for SFRs.

MOV A,@R0; Means: Store the value from the register whose address is in the R0 register into accumulator

On indirect addressing, registers R0, R1 or Stack Pointer are used for specifying 8-bit addresses. Since only 8 bits are avilable, it is possible to access only registers of internal RAM this way (128 locations when speaking of previous models or 256 locations when speaking of latest models of microcontrollers). If an extra memory chip is added then the 16-bit DPTR Register (consisting of the registers DPTRL and DPTRH) is used for specifying address. In this way it is possible to access any location in the range of 64K.

CONCLUSION

In this paper I have tried to give an overview on Microcontroller 8051 system of

opcommunication. A high speed communication devices needs to be developed for

interconnecting the network of internet and computers. In many networks MCU 8051 is used

because it used as a verstile device in single chip..

I have learned about the ports, timers, memory of MCU.

Hence in the last I can say that MCU 8051 is an emerging device in spite nowadays not a

single internetworking application is impossible without such an easy source of electronics.

REFERENCES

Microcontroller details:

http://www.mikroe.com/chapters/view/65/chapter-2-8051-microcontroller-

architecture/

Introduction about MCU 8051 and timers

http://www.8051intel.com/documents/introduction/

http://www.embededelectronics.com

Fundamentals of Microcontroller

Genius publication