A Six week training and project report on

8051 Microcontroller and Embedded Systems

Submitted in the partial fulfillment for the award of the degree of the

BACHELOR OF TECHNOLOGY

In

ELECTRONICS AND COMMUNICATION ENGINEERING

By

AVINASH KUMAR (11004645)

DEPARTMENT OF ELECTRONICS AND COMMUNICATION ENGINEERING

Lovely Professional University Jalandhar – Delhi G. T Road (NH-1)

Phagwara, Punjab, 144402, India

2013

1

ACKNOWLEDGEMENT

It was highly educative and interactive to take training at Lovely professional university,

Phagwara, Punjab.

A person technically lacks without having practical knowledge but here it was a good chance for

learning and practicing new things to update our self. In a fully equipped environment and well

experienced trainers, it was a qualitative program for being known with engineering

requirements. Trainers guided me very well and updated me with all the valuable information

regarding my course and latest technology.

I am highly thankful to the respected Training and Placement Officer and respected Head of

Department of Electronics and Communication Department Mr. Mayank Gupta for allowing

me to join Lovely Professional University and motivating me to do the right things.

I would also like to thanks Mr. Dusyant Singh ,Mr. Bharat Sanchlecha and Mr. Swapnil

Bhargav for their precious guidance in field of microcontrollers and interfacing circuits and

devices and also sorting out our problems.

I would also like to thank my parents and my friends who encouraged me all the time while I

was taking my projects and training in order to complete it successfully.

2

3

CANDIDATE/S DECLARATION

I hereby certify that the work, which is being presented in the Training report entitled Embedded System, in partial fulfillment of the requirement for the award of the Degree of Bachelor of Technology submitted to the institution is an authentic record of my own work carried out during the period 03 June,2013 to 12 July,2013 under the supervision of Mr. Dusyant Singh ,Mr. Bharat Sanchlecha , Mr.Swapnil Bhargav. I also cited the reference about the texts/figures/tables from where they have been taken.

Date: Signature of the Candidate

This is to certify that the above statement made by the candidate is correct to the best of my /our knowledge.

Date: Signature Supervisor

OBJECTIVE OF TRAINING/PROJECT

Main objectives and goal of this training are as follows:-

4

To enhance my skills in Embedded System Design using 8051 microcontroller.

To have a practical approach to Digital and Analog electronics. To implement theoretical knowledge in practical world example using

hardware and software like Kiel and proteus. To prepare an individual project in embedded system.

TABLE OF CONTENTS

Chapter 1- Institute Profile 9

Chapter 2- Introduction to embedded systems 10-11

Chapter 3-Characteristics of Embedded Systems 11

Chapter 4- Processors in Embedded System 11-13

4.1 Microcontroller vs. Microprocessor

4.2 Microcontroller Families

Chapter 5-8051 microcontroller 13-16

5.1 AT 89C51

5.2 Pin Diagram of AT89C51

5.3 Pin Description of 8051

Chapter 6- Architecture of 8051 microcontroller 17-19

6.1 Block Diagram of 8051

6.2 Memory and Registers

6.2.1 SFRs

6.2.2 DPTR

Chapter 7-8051 Assembly Language Programming 19-37

5

7.1 How to Program an 8051 microcontroller

7.2 Instruction Set of 80517.2.1 Addressing Modes

7.2.2 Instruction Types7.3 Flags and PSW (Program Status Word) Register in 8051

7.4 Instructions that affects Flags

7.5 I/O PROGRAMMING

7.6 TIMERS AND COUNTERS

7.7 Serial Port Communication in 8051 microcontroller

7.8 INTERUPTS

Chapter 8- Interfacing Devices 37-44

8.1 LED INTERFACING 8.2 SEVEN SEGMENT INTERFACING 8.3 LCD INTERFACING 8.4 INTERFACING MOTOR WITH 8051

Chapter 9- Project Report 44-49

9.1 DESCRIPTION

9.2 COMPONENTS

9.3 CIRCUIT DIAGRAM

9.4 SOURCE CODE

Chapter 10 –References 50

TABLE OF FIGURES

Figure 5.1 - Pin Diagram of 8051 Microcontroller

Figure 6.1- Block Diagram of 8051 microcontroller

Figure 6.2- Register Bank Architecture

6

Figure 6.3- Register Bank Selection

Figure7.1-RAM Memory Location

Figure 7.2: Program Status Word

Figure 7.3: Port 0

Figure 7.4: Tmer Register

Figure 7.5:TMOD Register

Figure 7.6:TCON RegisterFigure 7.7: Serial And Parallel Communication

Figure 7.8: SCON Register

Figure 7.9:Intrupts in 8051

Figure 7.10: Interrupt Enable Register

Figure 8.1: LED Interfacing

Figure 8.2: Typical Seven Segment

Figure 8.3: Seven Segment Interfacing

Figure 8.4: DC Motor Interfacing

Figure 9.1:Stepper Motor

Figure 9.2: Transistor BC547

Figure 9.3: AT89C51 microcontroller

7

LIST OF TABLES

Table 4.1: Difference between Microcontroller and Microprocessor

Table 7.1: Addressing Modes

Table 7.2:Arithematic Operatons

Table 7.3: Logical OperationsTable 7.4: Data Transfer OperationsTable 7.5: Bitwise OperationsTable 7.6: Branching OperationsTable 7.7:Instructions Effecting FlagsTable 7.8:Dual Functionality of Port 3Table 8.1: Command to LCD Instruction Register

8

Chapter 1

Institute Profile

Lovely Professional University (LPU) is a private semi-residential university created under the state government private university act. LPU claims to be the largest private university in India in terms of number of students on a single campus and is situated on 600+ acres of green area on NH-1 at the entry of Jalandhar city.]The university has more than 25,000 students from 26 states and 16 countries. It is recognized by UGC under Section 2(f) of UGC Act 1956.

The Lovely Faculty of Technology and Sciences was ranked 2 on the CSR-GHRDC Engineering Colleges Survey 2011. It was ranked 29. Lovely Professional University was declared as the Best ICT Enabled University of the Year by the Ministry of Communications and IT, Government of India

Occasion was the 7th e-INDIA Awards at Gandhinagar, Gujarat, India Award conferred on Lovely Professional University for having 'the Best University

Management System' The e-INDIA award is the India's largest ICT event.

SiliconIndia.com’ ranked Lovely Professional University among top 4 Best private Universities of India.

‘SiliconIndia.com’ is India’s largest professional News and Media Company. LPU got a "Punjab Gaurav Award" in the First Annual Corporate Summit 2012

organized by All India Technical and Management Association (AITMA).Excellency Hon'ble Governor Punjab Sh. Shivraj Patil bestowed 'Punjab Gaurav Award' upon LPU Chancellor.

LPU stared training on Embedded System by best of its Embedded system faculty member of university.

9

Students were selected by an online Examination conducted by University itself on basics of Microprocessor 8085, Microcontroller 8051, Digital Electronics, Analog and Liner IC’s.

Top 50 students were selected among third year students of ECE department.

Chapter 2

Introduction to Embedded Systems

An embedded system is a special-purpose system in which the computer is completely encapsulated by the device it controls. Unlike a general-purpose computer, such as a personal computer, an embedded system performs pre-defined tasks, usually with very specific requirements. Since the system is dedicated to a specific task, design engineers can optimize it, reducing the size and cost of the product. Embedded systems are often mass-produced, so the cost savings may be multiplied by millions of items.

Handheld computers or PDAs are generally considered embedded devices because of the nature of their hardware design, even though they are more expandable in software terms. This line of definition continues to blur as devices expand.

Physically, embedded systems range from portable devices such as digital watches and MP3 players, to large stationary installations like traffic lights, factory controllers. Complexity varies from low, with a single microcontroller chip, to very high with multiple units, peripheralsand networks mounted inside a large chassis or enclosure.

Embedded systems contain processing cores that are either microcontrollers or digital signal processors (DSP). The key characteristic, however, is being dedicated to handle a particular task. Since the embedded system is dedicated to specific tasks, design engineers can optimize it to reduce the size and cost of the product and increase the reliability and performance. Some embedded systems are mass-produced, benefiting from economies of scale.

Robotics and automation are a part of embedded systems itself. Robot development and automation needs study of embedded systems.

Examples of Embedded System are

I. automatic teller machines (ATMs)II. avionics, such as inertial guidance systems, flight control hardware/software and

other integrated systems in aircraft and missilesIII. cellular telephones and telephone switchesIV. computer equipment such as routers and printersV. engine controllers and antilock brake controllers for automobiles

10

VI. home automation products, like thermostats, air conditioners, sprinklers, and security monitoring systems

VII. handheld calculatorsVIII. household appliances, including microwave ovens, washing machines, television sets

IX. medical equipmentX. handheld computers

XI. videogame consoles

Chapter 3

Characteristics of Embedded Systems

1. Embedded systems are designed to do some specific task, rather than be a general-purpose computer for multiple tasks. Some also have real-time performance constraints that must be met, for reasons such as safety and usability; others may have low or no performance requirements, allowing the system hardware to be simplified to reduce costs.

2. The program instructions written for embedded systems are referred to as firmware, and are stored in read-only memory or Flash memory chips. They run with limited computer hardware resources: little memory, small or non-existent keyboard or screen.

3. Many embedded systems consist of small, computerized parts within a larger device that serves a more general purpose. For example- a line follower autonomous robot which follows a specific path and moves accordingly to the path.

4. The embedded systems are special purpose computer systems designed to perform only the specific purposes. For Example- a system designed to display numbers cannot be used to operate motors.

5. Embedded systems range from no user interface at all — dedicated only to one task — to complex graphical user interfaces that resemble modern computer desktop operating systems. Simple embedded devices use buttons, LEDs, graphic or character LCDs (for example popular HD44780 LCD) with a simple menu system.

Chapter 4

Processors in Embedded Systems

Embedded processors can be broken into two broad categories. Ordinary microprocessors (μP) use separate integrated circuits for memory and peripherals. Microcontrollers (μC) have many more peripherals on chip, reducing power consumption, size and cost. In contrast to the personal

11

computer market, many different basic CPU architectures are used, since software is custom-developed for an application and is not a commodity product installed by the end user. RISC as well as non-RISC processors are found. Word lengths vary from 4-bit to 64-bits and beyond, although the most typical remain 8/16-bit.

4.1 Microcontrollers and Microprocessors

Microcontrollers Microprocessors1. A Microcontroller (sometimes abbreviated µC, uC or MCU) is a small computer on a single integrated circuit containing a processor core, memory, and programmable input/output peripherals.

1. A Microprocessor is an IC which has only the CPU inside them i.e. only the processing powers such as Intel’s Pentium 1,2,3,4, core 2 duo, i3, i5 etc.

2. Microcontrollers are designed to perform specific tasks. Specific means applications where the relationship of input and output is defined. Depending on the input, some processing needs to be done and output is delivered. For example, keyboards, mouse, washing machine, digicam, pen drive, remote, microwave, cars, bikes, telephone, mobiles, watches, etc.

2. Microprocessor find applications where tasks are unspecific like developing software, games, websites, photo editing, creating documents etc.

3. Since the applications are very specific, they need small resources like RAM, ROM, I/O ports etc. and hence can be embedded on a single chip.

3. In such cases the relationship between input and output is not defined. They need high amount of resources like RAM, ROM, I/O ports etc. So needs external RAM, ROM and Memory.

4. The microcontrollers operate from a few MHz to 30 to 50 MHz

4. Themicroprocessor operates above 1GHz as they perform complex tasks.

5.The microcontroller is designed for embedded applications. Microcontrollers are used in automatically controlled products and devices, such as automobile engine control systems, implantable medical devices, remote controls, office machines, appliances, power tools, toys and other embedded systems.

5.The microprocessors are used in personal computers or other general purpose applications such as for laptops and heavy applications where complexity is more and memory requirements are high.

Table 4.1: Difference Between Microcontroller and Microprocessor

So microcontrollers are more preferred over microprocessors for embedded applications because of the simplicity in design and cheaper availability. The system design using microcontroller cost much cheaper than the microprocessors design because memory, RAM, and ROM is built-in in a microcontroller as compared to microprocessor in which external memory and RAM and ROM are to interfaced with it.

12

4.2 Microcontroller Families

8051- These microcontrollers are old but still trendy and most of the companies fabricate these microcontrollers. The older types of 8051 have 12 clocks per instruction that make it sluggish whereas the recent 8051 have 6 clocks per instruction. The 8051 microcontroller does not have an in built memory bus and A/D converters. In 1980, Intel fabricated the single chip microcontroller 8051 with Harvard architecture.

 

PIC- Programmable Interface Controller is usually referred as PIC. They are slightly older than 8051 microcontrollers but excel cause of their small low pin count devices. They perform well and are affordable.  The Microchip technology fabricated the single chip microcontroller PIC with Harvard architecture. The programming part is very tedious and hence it is not recommended for beginners.

 

AVR (Advanced Version RISC) - In 1996, Atmel fabricated this single chip microcontroller with a modified Harvard Architecture. This chip is loaded with C- compiler, Free IDE and many more features. This microcontroller is a bit difficult for the starters to handle.

Chapter 5

8051 Microcontroller

The most commonly used microcontroller is 8051 families’ AT89C51 microcontroller which is produced by Atmel. It is widely used in most of the application for having an advantage of simple programming and low cost.

5.1 AT89C51

AT89C51 is an 8-bit, 40 pin microcontroller that belongs to Atmel's 8051 family. ATMEL 89C51 has 4KB of Flash programmable and erasable read only memory (PEROM) and 128 bytes of RAM. It can be erased and program to a maximum of 1000 times.

In 40 pin AT89C51, there are four ports designated as P1, P2, P3 and P0. All these ports are 8-bit bi-directional ports, i.e., they can be used as both input and output ports. Except P0 which needs external pull-ups, rest of the ports have internal pull-ups. When 1s are written to these port pins,

13

they are pulled high by the internal pull-ups and can be used as inputs. These ports are also bit addressable and so their bits can also be accessed individually.

5.1.1 Salient Features of AT89C51-

4K Bytes of In-System Reprogrammable Flash Memory Fully Static Operation: 0 Hz to 24 MHz Three-level Program Memory Lock 28 x 8-bit Internal RAM 32 Programmable I/O Lines Two 16-bit Timer/Counters Six Interrupt Sources Programmable Serial Channel Low-power Idle and Power-down Modes 40-pin DIP

5.1.2 Pin Diagram of AT89C51

14

Figure 5.1: Pin Diagram of 8051 microcontroller

5.1.3 Pin Description of AT89C51

Pins 1-8 (Port 1) - Each of these pins can be configured as an input or an output.

Pin 9 (Reset) - A logic one on this pin disables the microcontroller and clears the contents of most registers. In other words, the positive voltage on this pin resets the microcontroller. By applying logic zero to this pin, the program starts execution from the beginning.

15

Pins 10- 17 (Port 3) -Similar to port 1, each of these pins can serve as general input or output. Besides, all of them have alternative functions:

Pin 10 (RXD) - Serial asynchronous communication input or Serial synchronous communication output.

Pin 11(TXD) - Serial asynchronous communication output or Serial synchronous communication clock output.

Pin 12 (INT 0) - Interrupt 0 input.Pin 13(INT 1) - Interrupt 1 input.Pin 14(T0) - Counter 0 clock input.Pin 15(T1) - Counter 1 clock input.Pin 16(WR) -Write to external (additional) RAM.Pin 17 (RD) -Read from external RAM.Pin 18 and 19(X1, X2) - Internal oscillator input and output. A quartz crystal which specifies operating frequency is usually connected to these pins. Instead of it, miniature ceramics resonators can also be used for frequency stability. Later versions of microcontrollers operate at a frequency of 0 Hz up to over 50 Hz.Pin 20 (GND) - Ground. Used to provide earth to microcontroller circuit.Pin 21-28 (Port 2) - If there is no intention to use external memory then these port pins are configured as general inputs/outputs. In case external memory is used, the higher address byte, i.e. addresses A8-A15 will appear on this port. Even though memory with capacity of 64Kb is not used, which means that not all eight port bits are used for its addressing, the rest of them are not available as inputs/outputs.Pin 29 (PSEN) - If external ROM is used for storing program then a logic zero (0) appears on it every time the microcontroller reads a byte from memory.Pin 30 (ALE) - Prior to reading from external memory, the microcontroller puts the lower address byte (A0-A7) on P0 and activates the ALE output. After receiving signal from the ALE pin, the external register memorizes the state of P0 and uses it as a memory chip address. Immediately after that, the ALU pin is returned its previous logic state and P0 is now used as a Data Bus. As seen, port data multiplexing is performed by means of only one additional (and cheap) integrated circuit. In other words, this port is used for both data and address transmission.Pin 31 (EA) - By applying logic zero to this pin, P2 and P3 are used for data and address transmission with no regard to whether there is internal memory or not. It means that even there is a program written to the microcontroller, it will not be executed. Instead, the program written to external ROM will be executed. By applying logic one to the EA pin, the microcontroller will use both memories, first internal then external (if exists).

16

Pin 32-39 (Port 0) - Similar to P2, if external memory is not used, these pins can be used as general inputs/outputs. Otherwise, P0 is configured as address output (A0-A7) when the ALE pin is driven high (1) or as data output (Data Bus) when the ALE pin is driven low (0).Pin 40 (Vcc) - +5V power supply.

Chapter 6

Architecture of 8051 Microcontroller

6.1 Block Diagram of 8051 Microcontroller

Figure 6.1: Block Diagram of 8051 microcontroller

Address bus-For a device (memory or I/O) to be recognized by the CPU, it must be assigned an address. The address assigned to a given device must be unique. The CPU puts the address on the address bus, and the decoding circuitry finds the device.

17

Data bus-The CPU either gets data from the device or sends data to it.

Control bus-Provides read or write signals to the device to indicate if the CPU is asking for information or sending it information.

6.2 Memory and Registers

The 8051 microcontroller has a total of 256 bytes of RAM in which 128 is visible or useraccessible and extra 128 is for special function registers.

The user accessible RAM is used for temporary data storage. The user accessible RAM is from the address range 00 to 7Fh.

From the user accessible RAM, 32 bytes of RAM is used for registers and rest for Stack operations. The 32 Bytes of RAM is divided into four register Banks i.e. Bank0, Bank 1, Bank 2, Bank3. Each of these banks have 8 Registers i.e. R0 to R7 each.

RAM locations from 0 to 7 are set aside for bank 0 of R0 – R7 where R0 is RAM location 0, R1 is RAM location 1, and R2 is location 2, and so on, until memory location 7, which belongs to R7 of bank 0. The second bank of registers R0 – R7 starts at RAM location 08 and goes to location 0FH. The third bank of R0 – R7 starts at memory location 10H and goes to location 17H. Finally, RAM locations 18H to 1FH are set aside for the fourth bank of R0 – R7.

Figure 6.2: Register Bank Architecture

Generally for normal operations, Register bank Bank0 is set by default. But we can switch to other banks by using PSW Commands.

18

Figure 6.3: Register Bank Selection

6.2.1 SFRs (Special Function Register) - These Registers are in extra 128 bytes of the memory. This part of memory is not user accessible and these registers are used for special purposes. These registers range from 80h to FFH. There are a total of only 21 SFRs in this range and all other addresses from 80h to FFH are invalid and there use can cause errors and not valuable results.

Some of the SFRs are TCON, SBUF, ACC, B, SCON, TMOD SP, P0, PSW, TL0, and TL1. These all the registers have some specific function that has to be performed after they are programmed.

(i) Bit Addressable SFR with byte addressSP – Stack printer – 81HDPTR – Data pointer 2 bytesDPL – Low byte – 82HDPH – High byte – 83HTMOD – Timer mode control – 89HTH0 – Timer 0 Higher order bytes – 8CHTL0 – Timer 0 Low order bytes – 8AHTH1 – Timer 1 High bytes = 80HTL1 – Timer 1 Low order byte = 86HSBUF – Serial data buffer = 99HPCON – Power control – 87H.

6.2.2 DPTR - Data Pointer in 8051 16 bit register; it is divided into two parts DPH and DPL. DPH for Higher order 8 bits, DPL for lower order 8 bits. DPTR, DPH, DPL these all are SFRs in 8051.

Chapter 7

8051 Assembly Language Programming

7.1 How to Program an 8051 microcontroller

19

[Label:] mnemonic [operands] [; comment]Mnemonics -Assembly level instructions are called mnemonic like MOV R5Operands -On which the operation is performed.

Example:

Loop: MOV R1, #25H ; transfer 25H into R1↑ ↑ ↑ ↑

The Two instructions which are used to start and terminate program are

ORG -This instruction indicate the origin of program,Example- ORG 3000H→ means program starts from 3000H location.→ this instruction hasn’t take any memory space. It is used to show the starting address of program.

END - This instruction show the END of program or it is used to terminate the program.

Example: ORG 0H ; start compiler from 0h addressAgain: MOV R5, # 25H ; transfer 25H to R5 ADD A, R5 ; Add the R5 with Accumulator SJMP Again ; jump to the location again END ; end the program.

7.2 Instruction Set of 8051 7.2.1 Addressing Modes

Addressing modes InstructionsRegister MOV A, B

Direct MOV 30H,A Indirect MOV A,@R0

Immediate MOV A,#80H Indexed MOVC A,@A+PC

Register Addressing Mode-The register addressing instruction involves information transfer between Registers. Example:

20

Table 7.1: Addressing Modes

MOV R0, AThe instruction transfers the accumulator content into the R0register. The register bank (Bank 0, 1, 2 or 3) must be specified prior to this instruction.In the Register Addressing mode, the instruction involves transfer of information between registers. The accumulator is referred to as the A register.

Direct Addressing Mode- This mode allows you to specify the operand by giving its actual memory address (typically specified in hexadecimal format) or by giving its abbreviated name (e.g. P3).Used for SFR accessesExample:MOV A, P3 ; Transfer the contents of Port 3 to the accumulator

MOV A, 020H ; Transfer the contents of RAM location 20H to the accumulator.

Indirect Addressing Mode-In the Indirect Addressing mode, a register is used to hold the effective address of the operand. This register, which holds the address, is called the pointer register and is said to point to the operand.Only registers R0, R1 and DPTR can be used as pointer registers.R0 and R1 registers can hold an 8-bit address whereas DPTR can hold a 16-bit address.DPTR is useful in accessing operands which are in the external memory.

Examples:MOV @R0, A ; Store the content of accumulator into the memory location pointed to by the contents of register R0. R0 could have an 8-bit address, such as 60H.

MOVX A, @DPTR ; Transfer the contents from the memory location pointed to by DPTR into the accumulator. DPTR could have a 16-bit address, such as 1234H.

Immediate Addressing Mode-In the Immediate Constant Addressing mode, the source operand is an 8- or 16-bit constant value. This constant is specified in the instruction itself (rather than in a register or a memory location).The destination register should hold the same data size which is specified by the source operand.Examples:ADD A, #030H; Add 8-bit value of 30H to the accumulator register (which is an 8-bit register).

MOV DPTR, #0FE00H; Move 16-bit data constant FE00H into the 16-bit Data Pointer Register.

Indexed Addressing Mode- The Indexed addressing is useful when there is a need to retrieve data from a look-up table (LUT). A 16-bit register (data pointer) holds the base address and the accumulator holds an 8-bit displacement or index value. The sum of these two registers forms the effective address for a JMP or MOVC instruction.Example:

21

MOV A, #08H ; Offset from table start

MOV DPTR, #01F00H ; Table start address

MOVC A, @A+DPTR ; Gets target value from the table starts address + offset and puts it in A.

7.2.2 Instruction TypesThe 8051 instructions are divided into five functionalgroups:

Arithmetic operations Logical operations Data transfer operations Bitwise operations Branching operations

Arithmetic Instructions-This group of operators perform arithmetic operations. Arithmetic operations affect the flags, such as Carry Flag (CY), Overflow Flag (OV) etc., in the PSW register.The appropriate status bits in the PSW are set when specific conditions are met, which allows the user software to manage the different data formats (carry, overflow etc…)

Arithmetic Instructions of 8051 are shown as follows- [@ RI] implies contents of memory location pointed to by R0 or R1. Rn refers to registers R0-R7 of the currently selected register bank.

22

Table 7.2:Arithematic OperatonLogical Instructions-Logical instructions perform standard Boolean operations such as AND, OR, XOR, NOT (compliment). Other logical operations are clear accumulator, rotate accumulator left and right, and swap nibbles in accumulator.Examples:ANL A, #02H; Mask bit 1ORL TCON, A; TCON=TCON OR A

23

Table 7.3:Logical Operation

Data Transfer Instructions- Data transfer instructions can be used to transfer data between an internal RAM location and an SFR location without going through the accumulator.It is also possible to transfer data between the internal and external RAM by using indirect addressing. The upper 128 bytes of data RAM are accessed only by indirect addressing and the SFRs are accessed only by direct addressing.

Figure 7.1:RAM Memory Location

24

The following is the table for instructions for Data Transfer-

Table 7.4:Data Transfer Operations

Bitwise Instructions-The Boolean Variable operations include set, clear, as well as and, or and complement instructions. Also included are bit–level moves or conditional jump instructions. All bit accesses use direct addressing.

Examples:

SETB TR0 ; Start Timer0.

POLL: JNB TR0, POLL ; Wait until timer overflows.

25

The following table contains all the Boolean Variable Instructions of 8051 microcontroller.

Table 7.5:Bitwise Operations

Branching Instructions- Program branching instructions are used to control the flow of program execution. Some instructions provide decision making capabilities before transferring control to other parts of the program e.g. conditional and unconditional branches.

the following table contains all the branching instructions

26

Table 7.6: Branching Operations

7.3Flags and PSW (Program Status Word) Register in 8051 1. The program status word (PSW) register, also referred to as the flag register, is an 8 bit register. 2. Only 6 bits are used These four are CY (carry), AC (auxiliary carry), P (parity), and OV (overflow) they are called conditional flags, meaning that they indicate some conditions that resulted after an

27

instruction was execute.

3. The PSW3 and PSW4 are designed as RS0 and RS1, and are used to change the bank. The two unused bits are user-definable.

PSW 7 PSW 6 PSW 5 PSW 4 PSW 3 PSW 2 PSW 1 PSW 0

Figure 7.2: Program Status Word CY- PSW.7- Carry flag. AC- PSW.6- Auxiliary Carry flag. F0 (-----) PSW.5- Available to the user for general purpose RS1 PSW.4 - Register Bank selector bit 1. RS0 PSW.3 -Register Bank selector bit 0. OV PSW.2 -Overflow flag. F0 (-----) PSW.1- User definable bit. P PSW.0- Parity flag. Set/cleared by hardware each.

7.4 Instructions that affects Flags

28

CY AC F0 RS1 RS0 OV --------- P

Instructions CY OV ACADD X X XADDC X X XSUBB X X XMUL 0 XDIV 0 XDA XRPC XPLC XSETB C 1CLR C 0CPL C XANL C, bit XANL C, /bit XORL C,/bit XORL C, bit XMOV C,bit XCJNE X

Table 7.7:Instructions Effecting Flags

7.5 I/O PROGRAMMING The four 8-bit I/O ports P0, P1, P2 and P3 each use 8 pins. All the ports upon RESET are configured as input, ready to be used as input ports.

When the first 0 is written to a port, it becomes an output.To reconfigure it as an input, a 1 must be sent to the port.PX=00H ; Makes Port X as Output portPX=FFH ; Makes Port X as input port

To use any of these ports as an input port, it must be programmed.

7.5.1 Port 0

It can be used for input or output; each pin must be connected externally to a 10K ohm pull-up resistor.

This is due to the fact that P0 is an open drain, unlike P1, P2, and P3. Open drain is a term used for MOS chips in the same way that open collector is used for

TTL chips.

Figure 7.3: Port 0

Port 0 is also designated as AD0-AD7, allowing it to be used for both address and data.

7.5.2 Port 1

Port 1 can be used as input or output. In contrast to port 0, this port does not need any pull-up resistors since it already has pull-

up resistors internally. Upon reset, port 1 is configured as an input port. To make port 1 an input port, it must be programmed as such by writing 1 to all its bits.

29

7.5.3 Port 2

Port 2 can be used as input or output. Just like P1, port 2 does not need any pull-up resistors since it already has pull-up

resistors internally. Upon reset, port 2 is configured as an input portP0.4. Port 2 is also designated as A8 – A15, indicating its dual function .Port 0 provides the

lower 8 bits via A0 – A7.

7.5.3 Port 3

Port 3 can be used as input or output. Port 3 does not need any pull-up resistors. Port 3 is configured as an input port upon reset; this is not the way it is most commonly

used. Port 3 has the additional function of providing some extremely important signals

Serial Communication

External Interrupts

Timers

Read/ Write Signals

Table 7.8:Dual Functionality of Port 3

7.6 TIMERS AND COUNTERS

7.6.1 TimersThe 8051 comes equipped with two timers, both of which may be controlled, set, read, and configured individually. The 8051 timers have three general functions:

30

P3 Function

Pin

P3.0 Rxd 10

P3.1 Txd 11

P3.2Int0

12

P3.3Int1

13

P3.4 T0 14

P3.5 T1 15

P3.6Wr

16

P3.7Rd

17

1) Keeping time and/or calculating the amount of time between events,

2) Counting the events themselves,

3) Generating baud rates for the serial port.

Both Timer 0 and Timer 1 are 16 bits wide.Since 8051 has an 8-bit architecture, each 16-bits timer is accessed as two separate registers of low byte and high byte.

One timer is TIMER0 and the other is TIMER1. The two timers share two SFRs (TMOD and TCON) which control the timers, and each timer also has two SFRs dedicated to itself (TH0/TL0 and TH1/TL1).The upper higher bits are TH0 and TH1 and the lower bits are TL0 AND TL1The TMOD and TCON are two control registers for the two timers.

Figure 7.4: Tmer Register

(i) TMOD Register

It is used to set the various timer operation mode.– TMOD is an 8-bit register where the lower 4 bits are set aside for timer 0 and the upper 4 bits are set aside for timer 1.

MSB LSB

31

Gate C/T M0 M1 GATE C/T M0 MI Timer 1 Timer 0

Figure 7.5:TMOD Register

GATE: To start and stop the timer GATE=1 _HW control: is enabled only while INTx pin is ‘1’and TRx control pin (in

TCON) is set. GATE=0 _SW control (used frequently)

C/T: Timer or counter selection C/T = 0 _Timer (input from internal system clock) the crystal (1/12) is used to trigger the

timer. C/T = 1 _Counter (input from Tx input pin)

M1 and M0: Mode selection for timer and counter Mode M1 M0

0 0 0 13-bit timer/counter mode 1 0 1 16-bit timer/counter mode 2 1 0 8-bit auto reload timer/counter mode 3 1 1 split timer/counter mode

(ii) TCON Register

TCON.7 TCON.6 TCON.5 TCON.4 TCON.3 TCON.2 TCON.1 TCON.0

TF1 TF0 TR1 TR0 IE1 IE0 IT1 IT0

Figure 7.6:TCON Register

TF1: Timer 1 overflows flag TF1=1: Timer/counter 1 overflows. TF1=0: processor vectors to the interrupt services.

TR1: Timer 1 run control bit TR1=1: turn Timer 1 ON TR1=0: turn Timer 1 OFF

IE1: External interrupt 1 edge flag IE1=1: external interrupt is detected. IE1=0: when interrupt is processed.

IT1: Interrupt 1 type control bit IT1=1: falling edge. IT1=0: low level triggered external interrupt.

Gate=0, SETB TR1 _Run Timer 1

32

SETB TR0 _Run Timer 0Gate=0, CLR TR1 _OFF Timer 1CLR TR0 _OFF Timer 0

Timer Mode 0 Mode 0: 13-bit Timer/counter mode 0000 ~ 1FFFH

Timer Mode 2Mode 2: 8-bit auto reload Timer/counter mode (00 ~ FFH). In auto reload, TH is loaded with the initial count and a copy of it is given to TL. This reloading leaves TH unchanged still holding a copy of original values. This mode has many applications, including setting the baud rate in serial communication.

Mode 2 Programming 8 bit - 00 ~FFH TH copy to TL Start SETB TR0, or TR1 TL increased FFH (OV monitoring) TH reloads to TL.

7.6.2 Counters

Counter is used to count input pulses.C/T=0: As Time, using 8051’s crystal as the source ofthe frequency.C/T=1: As counter, a pulse outside of the 8051 that increments the TH and TL register.When the C/T=1, the counter counts up as pulses are fed from Pins P3.4 (for counter 0) or P3.5 (for counter 1).

7.7Serial Port Communication in 8051 microcontrollerThe 8051 microcontroller transmits data serially as well as parallel communication is also done. For serial communication, the microcontroller comes with serial communication pin TXD and RXD. Normally TXD is used for transmitting serial data which is in SBUF register, RXD is used for receiving the serial data. SCON register is used for controlling the operation.The two registers used for controlling the communication are SCON and SBUF.

Serial Communication Parallel Communication

33

Figure 7.7:Serial And Parallel Comunication

Serial data communication uses two methods-

Synchronous method transfers a block of data at a time Asynchronous method transfers a single byte at a time

It is possible to write software to use either of these methods, but the programs can be tedious and longThere are special IC chips made by many manufacturers for serial communications

UART (universal asynchronous Receiver transmitter) USART (universal synchronous-asynchronous Receiver-transmitter)

The rate of data transfer in serial data communication is stated in bps (bits per second).Another widely used terminology for bps is baud rate.

7.7.1 SCON Register (8 Bit)

Figure 7.8: SCON RegisterRI (Receive Interrupt Flag)-Set by hardware on receiving. Must be cleared by software

TI (Transmit Interrupt Flag) -Set by hardware on transmitted, must clear by hardware

RB8 (Receive bit 8) Mode 2,3 : copy of bit 8 Mode 1 & SM2 clear : copy of stop bit

TB8 Transmit bit 8- The 9th data bit of mode 2, 3. Set or clear by software

34

REN Receive Enable- Set by software to enable reception, if is cleared reception will be blocked.

SM2 Serial Mode (bit 2) -Use in mode 2, 3 for multiprocessor communications.

SM1 & SM0 Serial Mode (bit 6 & 7)

Operating modes

Mode 0 8-bit shift register, f/12 1Mbit with 12 MHz Oscillator Frequency

Mode 1 8-bit UART, variable baud rateMode 2 9-bit UART, f/64 or f/32

187.5K and 375K with 12MHz Oscillator FrequencyMode 3 9-bit UART, variable baud rate.

7.7.2 SBUF

These are two separate data buffers for transmit and receive.The register SBUF is used to hold both the transmitter and receiver serial port data. To transmit the data, load SBUF register with data.

MOV SBUF, source When transmission is complete the TI bit will be set in the SCON register.

When a data frame is received the RI bit in SCON is set high.The received data may then be loaded from SBUF

MOV destination, SBUF Data reception is double buffered.

7.7.3 SMOD Addition bit to double baud speed.

7.8 INTERUPTS

An interrupt is an external or internal event that interrupts the microcontroller to inform it that a device needs its service.

The advantage of interrupts is that the microcontroller can serve many devices. Each device can get the attention of the microcontroller based on the assigned priority. The microcontroller can also ignore (mask) a device request for service.

7.8.1 Hardware and Software interruptThe interrupts in a controller can be either hardware or software. If the interrupts are generated by the controller’s inbuilt devices, like timer interrupts; or by the interfaced devices, they are

35

called the hardware interrupts. If the interrupts are generated by a piece of code, they are termed as software interrupts.

The 8051 controller has six hardware interrupts of which five are available to the programmer.

1. RESET Interrupt - This is also known as Power on Reset (POR). When the RESET interrupt is received, the controller restarts executing code from 0000H location. This is an interrupt which is not available to or, better to say, need not be available to the programmer.

 2. Timer interrupts - Each Timer is associated with a Timer interrupt. A timer interrupt notifies the microcontroller that the corresponding Timer has finished counting. Therefore these are two interrupts for the timers.

 3. External interrupts - There are two external interrupts EX0 and EX1 to serve external devices. Both these interrupts are active low. In AT89C51, P3.2 (INT0) and P3.3 (INT1) pins are available for external interrupts 0 and 1 respectively. An external interrupt notifies the microcontroller that an external device needs its service.

 4. Serial interrupt - This interrupt is used for serial communication. When enabled, it notifies the controller whether a byte has been received or transmitted.

Figure 7.9:Intrupts in 8051

The interrupts must be enabled by software in order for the microcontroller to respond to them.

Interrupt Enable Register- There is a register called IE (interrupt enable) that is responsible for enabling (unmasking) and disabling (masking) the interrupts.

36

IE.7 IE.6 IE.5 IE.4 IE.3 IE.2 IE.1 IE.0

EA -------- ET2 ES ET1 EX1 ET0 EX0

Figure 7.10: Interrupt Enable Register

To enable any of the interrupts, first the EA bit must be set to 1. After that the bits corresponding to the desired interrupts are enabled.

ET0, ET1 and ET2 bits are used to enable the Timer Interrupts 0, 1 and 2, respectively. In AT89C51, there are only two timers, so ET2 is not used.

EX0 and EX1 are used to enable the external interrupts 0 and 1. ES is used for serial interrupt.

EA bit acts as a lock bit. If any of the interrupt bits are enabled but EA bit is not set, the interrupt will not function. By default all the interrupts are in disabled mode.

Chapter 8

INTERFACING DEVICES WITH 8051 MICROCONTROLLER

8.1 LED INTERFACING

Interfacing an LED with 8051 is easy. The I/O pins are used as output pins. When any of the bit is set to 1, the LED glows if LED n side is connected to ground and p side with bit. And if p side is connected to power and n side to bit, then on bit low, the LED glows.

Code- ORG 0000hloop: CLR P2.0 CALL DELAY SETB P2.0 CALL DELAY JMP loopdelay: mov R7,#100 djnz r7, $ Ret

37

Figure 8.1:Led Interfacing

8.2 SEVEN SEGMENT INTERFACING

A seven segment consists of eight LEDs which are aligned in a manner so as to display digits from 0 to 9 when proper combination of LED is switched on. Seven segment uses seven LED’s to display digits from 0 to 9 and the eighth LED is used for the dot. A typical seven segment looks like as shown in the figure below. 

38

Figure 8.2:Typical Seven Segment DisplayCode-

ORG 000H START: MOV DPTR,#300H MOV R0, #0AH LABEL: CLR A MOVC A,@A+DPTR MOV P1, A ACALL DELAY DJNZ R0,LABEL SJMP STARTDELAY: MOV R4, #05H WAIT1: MOV R3, #00HWAIT2: MOV R2, #00HWAIT3: DJNZ R2,WAIT3 DJNZ R3,WAIT2 DJNZ R4,WAIT1 RET ORG 300HMydata DB: 3FH,06H,5BH,4FH,66H,6DH,7DH,07H,7FH,6FH END

39

Figure 8.3:Seven Segment Interfacing

8.3 LCD INTERFACING

A 16x2 LCD means it can display 16 characters per line and there are 2 such lines. In this LCD each character is displayed in 5x7 pixel matrix. This LCD has two registers.

 1. Command/Instruction Register - stores the command instructions given to the LCD. A command is an instruction given to LCD to do a predefined task like initializing, clearing the screen, setting the cursor position, controlling display etc.

 2. Data Register - stores the data to be displayed on the LCD. The data is the ASCII value of the character to be displayed on the LCD.

Code-

40

Table 8.1: Command to LCD Instruction Register

41

Figure 8.4: LCD Interfacing

8.4 INTERFACING MOTOR WITH 8051

Interfacing DC motor to 8051 forms an essential part in designing embedded robotic projects. A well designed 8051-DC motor  system has essentially two parts. Firstly an 8051 with the required software to control the motor and secondly a suitable driver circuit.

L293D-L293 is a dedicated quadruple half H bridge motor driver IC available in 16 pin package. The L293 is designed to provide bidirectional drive currents of up to 1 A at voltagesfrom 4.5 V to 36 V.

42

 Figure 8.5: DC Motor Interfacing

Code- ORG 00H START: CLR P1.2 CLR P1.1 SETB P1.0 ACALL DELAY ;clockwise CLR P1.2 SETB P1.1 CLR P1.0 ;anticlockwise DELAY: MOV R4, #0FHWAIT1: MOV R3, #00HWAIT2: MOV R2, #00HWAIT3: DJNZ R2, WAIT3 DJNZ R3, WAIT2 DJNZ R4, WAIT1 RET END

43

Chapter 9 Project Description

CONTROLING A STEPPER MOTOR MOVEMENT USING BUTTONS9.1: Project Description: My project is basically controlling a single stepper motor in different movements using different buttons .It has to make choice according to buttons pressed, they send them in different subroutines in order to move differently.

9.2: Components:

9.2.1:- Stepper Motor :It is type which can be rotated in steps not contineousaly.

Figure 9.1: Stepper motor

9.2.2: Transistor BC547: BC547 is an NPN bi-polar junction transistor. A transistor, stands for transfer of resistance, is commonly used to amplify current.

44

Figure 9.2:BC547 Transistor

9.2.3: AT89C51 Microcontroller: AT89C51 is an 8-bit microcontroller and belongs to Atmel's 8051 family.

Figure 9.3: Microcontroller

9.3: Circuit Diagram:

45

9.4: Source Code:

#include<reg51.h>

sbit sw0=P1^0;

sbit sw1=P1^1;

sbit sw2=P1^2;

void Msdelay();

void main()

{

unsigned char ch;

label:ch=P1;

ch=ch&0x07;

switch(ch)

{

case 0:

{

P2 = 0xcc;

Msdelay();

P2 = 0x66;

Msdelay();

P2 = 0x33;

Msdelay();

P2 = 0x99;

Msdelay();

46

break;

}

case 1:

{

P2=0xcc;

Msdelay();

P2=0x66;

Msdelay();

break;

}

case 2:

{

P2=0xcc;

Msdelay();

break;

}

case 3:

{

P2=0x99;

Msdelay();

P2=0x33;

Msdelay();

P2=0x66;

Msdelay();

47

P2=0xcc;

Msdelay();

break;

}

}

goto label;

}

void Msdelay()

{

unsigned char i,j,k;

for(i=0;i<6;i++)

for(j=0;j<255;j++)

for(k=0;k<255;k++);

}

48

REFERENCES

I. The MAZIDI BOOKSII. ENGINEERSGARAGE.COM

III. WIKIPEDIA.ORGIV. ATMEL.COMV. DATASHEETS.COM

VI. CIRCUITSTODAY.COMVII. PDFs FROM VARIOUS SITES

VIII. GOOGLE.COM

49