1

TECHNICAL TRAINING REPORT at

CETPA INFOTECH AND

PVT.LTD.

C-24, Sector 2, Near Nirula‟s Hotel, Noida-201301

Submitted in partial fulfillment of the requirement of the award

of degree in

BACHELOR OF TECHNOLOGY

(Electronics and Instrumentation Engineering)

from

Amrapali Institute of Technology and Sciences, Haldwani (Affiliated to Uttarakhand Technical University, Dehradun)

Submitted to: Submitted by:

(Signature) (Signature) Mr. pramod morya Deepak Chand Seminar Incharge Department of EIE Department of EIE Roll No.:10030106008

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ACKNOWLEDGEMENT

Many lives and destinies are destroyed due to the lack of proper guidance, direction and opportunity. It is in this respect I feel that I am in a much better position today due to continuous process of motivation and focus provided by the CETPA team during my 6 weeks training here at CETPA INFOTECH PVT.LTD.

The process of completion of this training project was a tedious job and required careful guidance at all stages. I would like to extend my special thanks and heart-felt gratitude to Mr. Raj Kumar Goyal for supervising. The supervision and support that he gave truly helped the progression and smoothness of the summer training program. The co-operation is much indeed appreciated. It is also my duty to extend my sincere thanks to the highly experienced central planning team comprising of Miss Ruchi , Mr. Vikas Kalra for helping me and providing proper guidance. A big contribution and hard work from them during the six week is very great indeed. All projects during the program would be nothing without the enthusiasm and support from all of them. Besides, this summer training program makes me realized the value of working together as a team and as a new experience in working environment, which challenges us every minute. I take great pleasure in presenting this work, which was assigned to me during my industrial training.

Last but not the least, I am also highly thankful to Mr. Mudit Gupta (Seminar Incharge), Mrs. Pramod Kr Morya (Head of Department, Electronics and Instrumentation) for providing me the opportunity to complete the training project.

DEEPAK CHAND B.Tech 4th year (EIE)

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Table of Contents

1. INTRODUCTION TO EMBEDDED SYSTEM

1.1 Reprogramming system……………………………………………………….06

1.2 Embedded system……………………………………………………………..07

1.3 Learning to embedded system………………………………………………...07

1.4 Difference between microprocessor and micro-controller……………………07

2. 8051 MICROCONTROLLER ARCHITECTURE

2.1 AT89C51……………………………………………………………………..08

2.2 Pin configuration……………………………………………………………...08

2.3 pin description………………………………………………………………...09

3. PROGRAMMING THE AT89C51

3.1 Features………………………………………………………………………12

3.2 Description…………………………………………………………………...12

3.3 Pin diagram…………………………………………………………………..13

3.4 Special function register……………………………………………………..13

3.5 Data memory………………………………………………………………...14

3.6 Timer 2 Registers…………………………………………………………....14

3.7 Interrupt register…………………………………………………………......14

4. PROGRAM STATUS WORD

4.1 The Instruction set…………………………………………………………...16

4.2 Program status word…………………………………………………………16

4.3 Addressing mode…………………………………………………………….17

5. 8051 INSTRUCTION SET

6. INTERFACING 16*2 LCD WITH 8051

6.1 16*2 LCD module…………………………………………………………….21

6.2 16*2 LCD module commands………………………………………………...23

6.3 Lcd initialization……………………………………………………………....23

6.4 Sending data to LCD………………………………………………………….23

6.5 circuit Diagram……………………………………………………………......24

6.3 program……………………………………………………………………......26

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7. INTERFACING SEVEN SEGMENT

7.1 Display to 8051……………………………………………………………….27

7.2 Digit drive pattern…………………………………………………………….27

7.3 Program…………………………………………………………………….....30

8. INTERFACING DC MOTOR WITH 8051

8.1 L293 motor driver……………………………………………………………..31

8.2 Bi-directional DC motor using 8051………………………………………….32

8.3 Program……………………………………………………………………….33

9. INTERFACING HEX KEYPAD WITH 8051

9.1 Hex keypad……………………………………………………………………34

9.2 Interfacing hex keypad………………………………………………………..35

9.3 Program……………………………………………………………………….36

10 CONCLUSION……………………………………………………………….40

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Introduction To Embedded system

In the daily life we use lots of electronics devices like Calculators, Computers, Automatic

Washing Machines, and Mobile phones etc. The common things in all these devices is that they

all contain Microprocessor (Brain in the Electronic System). So they all are Microprocessor

Based system. Actually Microprocessor based system are divided into two categories:

1.1 Reprogrammable System

These are the general purpose systems. We can run programs of different type of

language program like C, C++, Java, visual Basic etc. Even we can listen the music, watching

the movies, surfing internet, sending mails etc. That is, these systems can be reprogrammed from

the user‟s side of view and they are general purpose type. Example of the systems are Personal

Computers, Laptops, and Workstations etc.

Microprocessor based system

Reprogrammable Embedded

System

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1.2 Embedded Systems

These are not general purpose systems but these systems are specially designed

for specific applications .The Examples of Embedded System are Robots, Calculator, Digital

Weighing Machines, PCO Machine, Metro Rails without Drives etc. In such a way we can say

that Embedded system are microprocessor based electronic system which are designed for the

specific task only

1.3 Learning Embedded System

The study of Embedded system means we want to get the knowledge so that we

can design the electronic system in such a way that it will increase intelligence in the system. We

would able to think Programming of the system in assembly and can burn Flash Memories.

So we have to select the microprocessor for which we have to study. Actually

we have to work on microcontroller, its assembly language and interfacing of different input

output devices.

1.4 Difference between Microprocessor and Microcontroller:-

Microprocessor

1) CPU is stand-alone, RAM,

ROM, I/O, timer are separate

2) Designer can decide on the

amount of ROM, RAM and I/O

ports.

3) expansive

4) versatility

5) general-purpose

Microcontroller

1) CPU, RAM, ROM, I/O and

timer are all on a single chip

2) fix amount of on-chip ROM,

RAM, I/O ports

3) for applications in which cost,

power and space are critical

4) single-purpose

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8051 Microcontroller Architecture

2.1 AT89C51

The AT89C51 is a low-power, high-performance CMOS 8-bit microcomputer with 4K

Bytes of Flash programmable and erasable read only memory (PEROM). The device

Is manufactured using Atmel‟s high-density nonvolatile memory technology and is

Compatible with the industry-standard MCS-51 instruction set and pin out. The on-chip

Flash allows the program memory to be reprogrammed in-system or by a conventional

Nonvolatile memory programmer. By combining a versatile 8-bit CPU with Flash

On a monolithic chip, the Atmel AT89C51 is a powerful microcomputer which provides

A highly-flexible and cost-effective solution to many embedded control applications.

2.2 Pin Configuration

The AT89C51 provides the following standard features: 4K bytes of Flash, 128 bytes of RAM,

32 I/O lines, two 16-bit timer/counters, a five vector two-level interrupt architecture,

A full duplex serial port, on-chip oscillator and clock circuitry. In addition, the AT89C51 is

designed with static logic for operation down to zero frequency and supports two software

selectable power saving modes. The Idle Mode stops the CPU while allowing the RAM,

timer/counters, serial port and interrupt system to continue functioning. The Power-down Mode

saves the RAM contents but freezes the oscillator disabling all other chip functions until the next

hardware reset.

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2.3 Pin Description

VCC

Supply voltage.

GND

Ground.

Port 0

Port 0 is an 8-bit open-drain bi-directional I/O port. As an output port, each pin can sink eight

TTL inputs. When is are written to port 0 pins, the pins can be used as high impedance inputs.

Port 0 may also be configured to be the multiplexed low order

Address/data bus during accesses to external program and data memory. In this mode P0 has

internal pull-ups. Port 0 also receives the code bytes during Flash programming,

and outputs the code bytes during program verification. External pull-ups are required during

program verification.

Port 1

Port 1 is an 8-bit bi-directional I/O port with internal pull-ups. The Port 1 output buffers can

sink/source four TTL inputs. When 1s are written to Port 1 pins they are pulled high by the

internal pull-ups and can be used as inputs. As inputs, Port 1 pins that are externally being pulled

low will source current (IIL) because of the internal pull-ups. Port 1 also receives the low-order

address bytes during Flash programming and verification.

Port 2

Port 2 is an 8-bit bi-directional I/O port with internal pull-ups. The Port 2 output buffers can

sink/source four TTL inputs. When 1s are written to Port 2 pins they are pulled high by the

internal pull-ups and can be used as inputs. As inputs, Port 2 pins that are externally being pulled

low will source current (IIL) because of the internal pull-ups. Port 2 emits the high-order address

byte during fetches from external program memory and during accesses to external data memory

that use 16-bit addresses (MOVX @ DPTR). In this application, it uses strong internal pull-ups

when emitting 1s. During accesses to external data memory that use 8-bit addresses (MOVX @

RI), Port 2 emits the contents of the P2 Special Function Register. Port 2 also receives the high-

order address bits and some control signals during Flash programming and verification.

Port 3

Port 3 is an 8-bit bi-directional I/O port with internal pull-ups. The Port 3 output buffers can

sink/source four TTL inputs. When 1s are written to Port 3 pins they are pulled high by the

internal pull-ups and can be used as inputs. As inputs, Port 3 pins that are externally being pulled

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low will source current (IIL) because of the pull-ups. Port 3 also serves the functions of various

special features of the AT89C51 as listed below: Port 3 also receives some control signals for

Flash programming and verification.

RST

Reset input. A high on this pin for two machine cycles while the oscillator is running resets the

device .

ALE/PROG

Address Latch Enable output pulse for latching the low byte of the address during accesses to

external memory. This pin is also the program pulse input (PROG) during Flash programming.

In normal operation ALE is emitted at a constant rate of 1/6

The oscillator frequency, and may be used for external timing or clocking purposes. Note,

however, that one ALE

Pulse is skipped during each access to external Data Memory. If desired, ALE operation can be

disabled by setting bit 0 of SFR location 8EH. With the bit set, ALE is active only during a

MOVX or MOVC instruction. Otherwise, the pin is weakly pulled high. Setting the ALE-disable

bit has no effect if the microcontroller is in external execution mode.

PSEN

Program Store Enable is the read strobe to external program memory. When the AT89C51 is

executing code from external program memory, PSEN is activated twice each machine cycle,

except that two PSEN activations are skipped during each access to external data memory.

EA/VPP

External Access Enable. EA must be strapped to GND in order to enable the device to fetch code

from external program memory locations starting at 0000H up to FFFFH. Note, however, that if

lock bit 1 is programmed, EA will be internally latched on reset. EA should be strapped to VCC

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for internal program executions. This pin also receives the 12-volt programming enable voltage

(VPP) during Flash programming, for parts that require 12-volt VPP.

XTAL1

Input to the inverting oscillator amplifier and input to the internal clock operating circuit.

XTAL2

Output from the inverting oscillator amplifier.

Oscillator Characters

XTAL1 and XTAL2 are the input and output, respectively, of an inverting amplifier which can

be configured for use as an on-chip oscillator, as shown in Figure 1. Either a quartz crystal or

ceramic resonator may be used. To drive the device from an external clock source, XTAL2

should be left unconnected while XTAL1 is driven as shown in Figure 2. There are no

requirements on the duty cycle of the external clock signal, since the input to the internal

clocking circuitry is through a divide-by-two flip-flop, but minimum and maximum voltage high

and low time specifications must be observed.

Idle Mode

In idle mode, the CPU puts itself to sleep while all the on chip peripherals remain active. The

mode is invoked by software. The content of the on-chip RAM and all the special functions

registers remain unchanged during this mode. The idle mode can be terminated by any enabled

interrupt or by a hardware reset. It should be noted that when idle is terminated by a hard ware

reset, the device normally resumes program execution, from where it left off, up to two machine

cycles before the internal reset algorithm takes control. On-chip hardware inhibits access to

internal RAM in this event, but access to the port pins is not inhibited. To eliminate the

possibility of an unexpected write to a port pin when Idle is terminated by reset, the instruction

following the one that invokes Idle should not be one that writes to a port pin or to external

Memory.

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Programming the AT89C51

AT89C52:

3.1 Features • Compatible with MCS-51™ Products

• 8K Bytes of In-System Reprogrammable Flash Memory

• Endurance: 1,000 Write/Erase Cycles

• Fully Static Operation: 0 Hz to 24 MHz

• Three-level Program Memory Lock

• 256 x 8-bit Internal RAM

• 32 Programmable I/O Lines

• Three 16-bit Timer/Counters

• Eight Interrupt Sources

• Programmable Serial Channel

• Low-power Idle and Power-down Modes

3.2 Description

The AT89C52 is a low-power, high-performance CMOS 8-bit microcomputer with 8K bytes of

Flash programmable and erasable read only memory (PEROM). The device is manufactured

using Atmel‟s high-density nonvolatile memory technology and is compatible with the industry-

standard 80C51 and 80C52 instruction set and pin out. The on-chip Flash allows the program

memory to be reprogrammed in-system or by a conventional nonvolatile memory programmer.

By combining a versatile 8-bit CPU with Flash on a monolithic chip, the Atmel AT89C52 is a

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powerful microcomputer which provides a highly-flexible and cost-effective solution to many

embedded control applications.

3.3 Pin Diagram

The AT89C52 provides the following standard features

8K bytes of Flash, 256 bytes of RAM, 32 I/O lines, three 16-bit timer/counters, a six-vector two-

level interrupt architecture, a full-duplex serial port, on-chip oscillator, and clock circuitry. In

addition, the AT89C52 is designed with static logic for operation down to zero frequency and

supports two software selectable power saving modes. The Idle Mode stops the CPU while

allowing the RAM, timer/counters, serial port, and interrupt system to continue functioning. The

Power-down mode saves the RAM contents but freezes the oscillator, disabling all other chip

functions until the next hardware reset.

3.4 Special Function Registers A map of the on-chip memory area called the Special Function Register (SFR) space. Note that

not all of the addresses are occupied, and unoccupied addresses may not be implemented on the

chip. Read accesses to these addresses will in general return random data, and write accesses will

have an indeterminate effect. User software should not write 1s to these unlisted locations, since

they may be used in future products to invoke.

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3.5 Data Memory The AT89C52 implements 256 bytes of on-chip RAM. The upper 128 bytes occupy a parallel

address space to the Special Function Registers. That means the upper 128 bytes have the same

addresses as the SFR space but are physically separate from SFR space. When an instruction

accesses an internal location above address 7FH, the address mode used in the instruction

specifies whether the CPU accesses the upper 128 bytes of RAM or the SFR space. Instructions

that use direct addressing access SFR space. New features. In that case, the reset or inactive

values of the new bits will always be 0.

3.6 Timer 2 Registers Control and status bits are contained in registers T2CON and for Timer 2. The register pair

(RCAP2H, RCAP2L) are the Capture/Reload registers for Timer 2 in 16-bit capture mode or 16-

bit auto-reload mode.

3.7 Interrupt Registers The individual interrupt enable bits are in the IE register. Two priorities can be set for each of the

six interrupt sources in the IP register‟s. Specifies whether the CPU accesses the upper 128 bytes

of RAM or the SFR space. Instructions that use direct addressing access SFR space. For

example, the following direct addressing instruction accesses the SFR at location 0A0H (which

is P2). Instructions that use indirect addressing access the upper 128 bytes of RAM. For example,

the following indirect addressing instruction, where R0 contains 0A0H, accesses the data byte at

address 0A0H, rather than P2 (whose address is 0A0H).

MOV @R0, #data

Note that stack operations are examples of indirect addressing, so the upper 128 bytes of data

RAM are available as stack space.

Timer 0 and 1

Timer 0 and Timer 1 in the AT89C52 operate the same way as Timer 0 and Timer 1 in the

AT89C51.

Timer 2

Timer 2 is a 16-bit Timer/Counter that can operate as either a timer or an event counter. The type

of operation is selected by bit C/T2 in the SFR T2CON. Timer 2 has three operating modes:

capture, auto-reload (up or down counting), and baud rate generator. The modes are selected by

bits in T2CON. Timer 2 consists of two 8-bit registers, TH2 and TL2. In the Timer function, the

TL2 register is incremented every machine cycle. Since a machine cycle consists of 12 oscillator

periods, the count rate is 1/12 of the oscillator frequency.

In the Counter function, the register is incremented in response to a 1-to-0 transition at its

corresponding external input pin, T2. In this function, the external input is sampled during S5P2

of every machine cycle. When the samples show a high in one cycle and a low in the next cycle,

the count is incremented. The new count value appears in the register during S3P1 of the cycle

following the one in which the transition was detected. Since two machine cycles (24 oscillator

periods) are required to recognize a 1-to-0 transition, the maximum count rate is 1/24 of the

oscillator frequency. To ensure that a given level is sampled at least once before it changes, the

level should be held for at least one full machine cycle.

Capture Mode

In the capture mode, two options are selected by bit EXEN2 in T2CON. If EXEN2 = 0, Timer 2

is a 16-bit timer or counter which upon overflow sets bit TF2 in T2CON. This bit can then be

15

used to generate an interrupt. If EXEN2 = 1, Timer 2 performs the same operation, but a 1- to-0

transition at external input T2EX also causes the current value in TH2 and TL2 to be captured

into CAP2H and RCAP2L, respectively. In addition, the transition at T2EX causes bit EXF2 in

T2CON to be set. The EXF2 bit, like TF2, can generate an interrupt.

Auto-reload (Up or Down Counter)

Timer 2 can be programmed to count up or down when configured in its 16-bit auto-reload

mode. This feature is invoked by the DCEN (Down Counter Enable) bit located in the SFR

T2MOD. Upon reset, the DCEN bit is set to 0 so that timer 2 will default to count up. When

DCEN is set, Timer 2 can count up or down, depending on the value of the T2EX pin.

Interrupts

The AT89C52 has a total of six interrupt vectors: two external interrupts (INT0 and INT1), three

timer interrupts (Timers 0, 1, and 2), and the serial port interrupt. Each of these interrupt sources

can be individually enabled or disabled by setting or clearing a bit in Special Function Register

IE. IE also contains a global disable bit, EA, which disables all interrupts at once. Note that bit

position IE.6 is unimplemented. In the AT89C51, bit position IE.5 is also unimplemented. User

software should not write 1s to these bit positions, since they may be used in future AT89

products. Timer 2 interrupt is generated by the logical OR of bits TF2 and EXF2 in register

T2CON. Neither of these flags is cleared by hardware when the service routine is vectored to. In

fact, the service routine may have to determine whether it was TF2 or EXF2 that generated the

interrupt, and that bit will have to be cleared in software. The Timer 0 and Timer 1 flags, TF0

and TF1, are set at S5P2 of the cycle in which the timers overflow. The values are then polled by

the circuitry in the next cycle. However, the Timer 2 flag, TF2, is set at S2P2 and is polled in the

same cycle in which the timer overflows.

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Programming Status Word

4.1 The Instruction Set All members of the Atmel microcontroller family execute the same instruction set. This

instruction set is optimized for 8- bit control applications and it provides a variety of fast

addressing modes for accessing the internal RAM to facilitate byte operations on small data

structures. The instruction set provides extensive support for 1-bit variables as a separate data

type, allowing direct bit manipulation in control and logic systems that require Boolean

processing. The following overview of the instruction set gives a brief description of how certain

instructions can be used.

4.2 Program Status Word The Program Status Word (PSW) contains status bits that reflect the current state of the CPU.

The PSW, shown in Figure 11, resides in SFR space. The PSW contains the Carry bit, the

Auxiliary Carry (for BCD operations), the two register bank select bits, the Overflow flag, a

Parity bit, and two user-definable status flags. The Carry bit, in addition to serving as a Carry bit

in arithmetic operations, also serves as the “Accumulator” for a number of Boolean operations.

The bits RS0 and RS1 select one of the four register banks shown in Figure 8. A number of

instructions refer to these RAM locations as R0 through R7. The status of the RS0 and RS1 bits

at execution time determines which of the four banks is selected. The Parity bit reflects the

number of 1s in the Accumulator: P=1 if the Accumulator contains an odd number of 1s, and

P=0 if the Accumulator contains an even number of 1s. Thus, the number of 1s in the

Accumulator plus P is always even. Two bits in the PSW are uncommitted and can be used as

general purpose status flags.

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4.3 Addressing Modes The addressing modes in the Flash microcontroller instruction set are as follows.

Direct Addressing In direct addressing, the operand is specified by an 8-bit address field in the instruction. Only

internal data RAM and SFRs can be directly addressed.

Indirect Addressing In indirect addressing, the instruction specifies a register that contains the address of the operand.

Both internal and external RAM can be indirectly addressed. The address register for 8-bit

addresses can be either the Stack Pointer or R0 or R1 of the selected register bank. The address

register for 16-bit addresses can be only the 16-bit data pointer register, DPTR.

Register Instructions The register banks, which contain registers R0 through R7, can be accessed by instructions

whose codes carry a 3- bit register specification. Instructions that access the registers this way

make efficient use of code, since this mode eliminates an address byte. When the instruction is

executed, one of the eight registers in the selected bank is accessed. One of four banks is selected

at execution time by the two bank select bits in the PSW.

Register-Specific Instructions Some instructions are specific to a certain register. For example, some instructions always

operate on the Accumulator, so no address byte is needed to point to it. In these cases, the

opcode itself points to the correct register. Instructions that refer to the Accumulator as A

assemble as Accumulator-specific opcodes.

Indexed Addressing Program memory can only be accessed via indexed addressing. This addressing mode is intended

for reading look-up tables in program memory. A 16-bit base register (either DPTR or the

Program Counter) points to the base of the table, and the Accumulator is set up with the table

entry number. The address of the table entry in program memory is formed by adding the

Accumulator data to the base pointer. Another type of indexed addressing is used in the “case

Jump” instruction. In this case the dust ination address of a jump instruction is computed as the

sum of the base pointer and the Accumulator data.

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8051 INSTRUCTION SET

The instruction set is divided in to 5 categories. They are as follows:

1. Arithmetic instructions.

2. Logic instructions.

3. Data transfer instructions.

4. Boolean variable manipulation instruction.

5. Program and machine control instruction.

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Interfacing 16×2 LCD with 8051

LCD display is an inevitable part in almost all embedded projects and this article is about

interfacing 16×2 LCD with 8051 microcontroller. Many guys find it hard to interface LCD

module with the 8051 but the fact is that if you learn it properly, it‟s a very easy job and by

knowing it you can easily design embedded projects like digital voltmeter / ammeter, digital

clock, home automation displays, status indicator display, digital code locks, digital

speedometer/ odometer, display for music players etc. etc. Thoroughly going through this article

will make you able to display any text (including the extended characters) on any part of the

16×2 display screen. In order to understand the interfacing first you have to know about the 16×2

LCD module.

6.1 16×2 LCD module

16×2 LCD module is a very common type of LCD module that is used in 8051 based embedded

projects. It consists of 16 rows and 2 columns of 5×7 or 5×8 LCD dot matrices. The module

were are talking about here is type number JHD162A which is a very popular one. It is available

in a 16 pin package with back light, contrast adjustment function and each dot matrix has 5×8 dot

resolution. The pin numbers, their name and corresponding functions are shown in the table

below.

Pin No: Name Function

1 VSS This pin must be connected to the ground

2 VCC Positive supply voltage pin (5V DC)

3 VEE Contrast adjustment

4 RS Register selection

5 R/W Read or write

6 E Enable

7 DB0 Data

8 DB1 Data

9 DB2 Data

10 DB3 Data

11 DB4 Data

12 DB5 Data

13 DB6 Data

14 DB7 Data

15 LED+ Back light LED+

16 LED- Back light LED-

VEE pin is meant for adjusting the contrast of the LCD display and the contrast can be adjusted

by varying the voltage at this pin. This is done by connecting one end of a POT to the Vcc (5V),

22

other end to the Ground and connecting the center terminal (wiper) of of the POT to the VEE

pin. See the circuit diagram for better understanding.

The JHD162A has two built in registers namely data register and command register. Data

register is for placing the data to be displayed, and the command register is to place the

commands. The 16×2 LCD module has a set of commands each meant for doing a particular job

with the display. We will discuss in detail about the commands later. High logic at the RS pin

will select the data register and Low logic at the RS pin will select the command register. If we

make the RS pin high and the put a data in the 8 bit data line (DB0 to DB7), the LCD module

will recognize it as a data to be displayed. If we make RS pin low and put a data on the data line,

the module will recognize it as a command.

R/W pin is meant for selecting between read and write modes. High level at this pin enables read

mode and low level at this pin enables write mode.

E pin is for enabling the module. A high to low transition at this pin will enable the module.

DB0 to DB7 are the data pins. The data to be displayed and the command instructions are placed

on these pins.

LED+ is the anode of the back light LED and this pin must be connected to Vcc through a

suitable series current limiting resistor. LED- is the cathode of the back light LED and this pin

must be connected to ground.

6.2 16×2 LCD module commands

16×2 LCD module has a set of preset command instructions. Each command will make the

module to do a particular task. The commonly used commands and their function are given in the

table below.

Command Function

0F LCD ON, Cursor ON, Cursor blinking

ON

01 Clear screen

2 Return home

4 Decrement cursor

06 Increment cursor

E Display ON ,Cursor ON

80 Force cursor to the beginning of 1st line

C0 Force cursor to the beginning of 2nd

line

38 Use 2 lines and 5×7 matrix

83 Cursor line 1 position 3

3C Activate second line

0C3 Jump to second line, position3

OC1 Jump to second line, position1

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6.3 LCD initialization

The steps that has to be done for initializing the LCD display is given below and these steps are

common for almost all applications.

Send 38H to the 8 bit data line for initialization

Send 0FH for making LCD ON, cursor ON and cursor blinking ON.

Send 06H for incrementing cursor position.

Send 01H for clearing the display and return the cursor.

6.4Sending data to the LCD

The steps for sending data to the LCD module is given below. I have already said that the LCD

module has pins namely RS, R/W and E. It is the logic state of these pins that make the module

to determine whether a given data input is a command or data to be displayed.

Make R/W low.

Make RS=0 if data byte is a command and make RS=1 if the data byte is a data to be

displayed.

Place data byte on the data register.

Pulse E from high to low.

Repeat above steps for sending another data.

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6.5 Circuit diagram

Interfacing 16x2 LCD module to 8051

The circuit diagram given above shows how to interface a 16×2 LCD module with AT89S1

microcontroller. Capacitor C3, resistor R3 and push button switch S1 forms the reset circuitry.

Ceramic capacitors C1, C2 and crystal X1 is related to the clock circuitry which produces the

system clock frequency. P1.0 to P1.7 pins of the microcontroller is connected to the DB0 to DB7

pins of the module respectively and through this route the data goes to the LCD module. P3.3,

P3.4 and P3.5 are connected to the E, R/W, RS pins of the microcontroller and through this route

the control signals are transferred to the LCD module. Resistor R1 limits the current through the

back light LED and so do the back light intensity. POT R2 is used for adjusting the contrast of

the display.

25

6.6 Program

MOV A,#38H // Use 2 lines and 5x7 matrix

ACALL CMND

MOV A,#0FH // LCD ON, cursor ON, cursor blinking ON

ACALL CMND

MOV A,#01H //Clear screen

ACALL CMND

MOV A,#06H //Increment cursor

ACALL CMND

MOV A,#82H //Cursor line one , position 2

ACALL CMND

MOV A,#3CH //Activate second line

ACALL CMND

MOV A,#49D

ACALL DISP

MOV A,#54D

ACALL DISP

MOV A,#88D

ACALL DISP

MOV A,#50D

ACALL DISP

MOV A,#32D

ACALL DISP

MOV A,#76D

ACALL DISP

MOV A,#67D

ACALL DISP

MOV A,#68D

ACALL DISP

MOV A, #0C1H //Jump to second line, position 1

ACALL CMND

MOV A,#67D

ACALL DISP

MOV A,#73D

ACALL DISP

MOV A,#82D

ACALL DISP

MOV A,#67D

ACALL DISP

MOV A,#85D

ACALL DISP

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MOV A,#73D

ACALL DISP

MOV A,#84D

ACALL DISP

MOV A,#83D

ACALL DISP

MOV A,#84D

ACALL DISP

MOV A,#79D

ACALL DISP

MOV A,#68D

ACALL DISP

MOV A,#65D

ACALL DISP

MOV A,#89D

ACALL DISP

HERE: SJMP HERE

CMND: MOV P1, A

CLR P3.5

CLR P3.4

SETB P3.3

CLR P3.3

ACALL DELY

RET;

DISP: MOV P1, A

SETB P3.5

CLR P3.4

SETB P3.3

CLR P3.3

ACALL DELY

RET;

DELY: CLR P3.3

CLR P3.5

SETB P3.4

MOV P1, #0FFh

SETB P3.3

MOV A, P1

JB ACC.7, DELY

CLR P3.3

CLR P3.4

END

27

Interfacing seven segment display to 8051

This article is about how to interface a seven segment LED display to an 8051 microcontroller. 7

segment LED display is very popular and it can display digits from 0 to 9 and quite a few

characters like A, b, C., H, E, e, F, n, o,t,u,y, etc. Knowledge about how to interface a seven

segment display to a micro controller is very essential in designing embedded systems. A seven

segment display consists of seven LEDs arranged in the form of a squares ’8′ slightly inclined to

the right and a single LED as the dot character. Different characters can be displayed by

selectively glowing the required LED segments. Seven segment displays are of two types,

common cathode and common anode. In common cathode type , the cathode of all LEDs are

tied together to a single terminal which is usually labeled as „com„ and the anode of all LEDs

are left alone as individual pins labeled as a, b, c, d, e, f, g & h (or dot) . In common anode type,

the anode of all LEDs are tied together as a single terminal and cathodes are left alone as

individual pins. The pin out scheme and picture of a typical 7 segment LED display is shown in

the image below.

7 segment LED display

7.1 Digit drive pattern

Digit drive pattern of a seven segment LED display is simply the different logic combinations of

its terminals‘ a’ to ‘h„ in order to display different digits and characters. The common digit

drive patterns (0 to 9) of a seven segment display are shown in the table below.

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Digit A b C d e f g

0 1 1 1 1 1 1 0

1 0 1 1 0 0 0 0

2 1 1 0 1 1 0 1

3 1 1 1 1 0 0 1

4 0 1 1 0 0 1 1

5 1 0 1 1 0 1 1

6 1 0 1 1 1 1 1

7 1 1 1 0 0 0 0

8 1 1 1 1 1 1 1

9 1 1 1 1 0 1 1

Interfacing seven segment display to 8051

29

The circuit diagram shown above is of an AT89S51 microcontroller based 0 to 9 counter which

has a 7 segment LED display interfaced to it in order to display the count. This simple circuit

illustrates two things. How to setup simple 0 to 9 up counter using 8051 and more importantly

how to interface a seven segment LED display to 8051 in order to display a particular result. The

common cathode seven segment display D1 is connected to the Port 1 of the microcontroller

(AT89S51) as shown in the circuit diagram. R3 to R10 are current limiting resistors. S3 is the

reset switch and R2, C3 forms a denouncing circuitry. C1, C2 and X1 are related to the clock

circuit. The software part of the project has to do the following tasks.

1. Form a 0 to 9 counter with a predetermined delay (around 1/2 second here).

2. Convert the current count into digit drive pattern.

3. Put the current digit drive pattern into a port for displaying.

All the above said tasks are accomplished by the program given below.

.

Instruction MOVC A,@A+PC is the instruction that produces the required digit drive pattern for

the display. Execution of this instruction will add the value in the accumulator A with the content

of the program counter (address of the next instruction) and will move the data present in the

resultant address to A. After this the program resumes from the line after MOVC A,@A+PC.

In the program, initial value in A is 00001001B. Execution of MOVC A,@A+PC will add

oooo1001B to the content in PC (address of next instruction). The result will be the address of

command DB 3FH (line15) and the data present in this address ie 3FH (digit drive pattern for 0)

gets moved into the accumulator. Moving this pattern in the accumulator to Port 1 will display 0

which is the first count.

At the next count, value in A will advance to 00001010 and after the execution of MOVC

A,@+PC ,the value in A will be 06H which is the digit drive pattern for 1 and this will display 1

which is the next count and this cycle gets repeated for subsequent counts.

The reason why accumulator is loaded with 00001001B (9 in decimal) initially is that the

instructions from line 9 to line 15 consumes 9 bytes in total.

The lines 15 to 24 in the program which starts with command DB can be called as a Look up

Table (LUT). Command DB is known as Define Byte – which defines a byte. This table defines

the digit drive patterns for 7 segment display as bytes (in hex format). MOVC operator fetches

the byte from this table based on the result of adding PC and contents in the accumulator.

Register B is used as a temporary storage of the initial value of the accumulator and the

subsequent increments made to accumulator to fetch each digit drive pattern one by one from the

look up table (LUT).

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7.2 Program

Org 0000h

back: jnb p1.0,seg0

jnb p1.1,seg1

jnb p1.2,seg2

jnb p1.3,seg3

jnb p1.4,seg4

jnb p1.5,seg5

jnb p1.6,seg6

jnb p1.7,seg7

sjmp back

seg0: mov p2,#0c0h

sjmp back

seg1: mov p2,#0F9h

sjmp back

seg2: mov p2,#0A4h

sjmp back

seg3: mov p2,#0B0h

sjmp back

seg4: mov p2,#099h

sjmp back

seg5: mov p2,#092h

sjmp back

seg6: mov p2,#082h

sjmp back

seg7: mov p2,#0F8h

sjmp back

ret

31

Interfacing DC motor to 8051

This article shows how to interface a DC motor to an 8051 microcontroller. 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. Most of the DC motors have power

requirements well out of the reach of a microcontroller and more over the voltage spikes

produced while reversing the direction of rotation could easily damage the microcontroller. So it

is not wise to connect a DC motor directly to the microcontroller. The perfect solution is to use a

motor driver circuit in between the microcontroller and the DC motor.

8.1 L293 motor driver

L293 is a dedicated quadruple Half H Bridge motor driver IC available in 16 pin package. To

know more about H Bridge, check this link. H bridge motor driver circuit. L293 has a current

capacity of 600mA/channel and has supply voltage range from 4.5 to 36V DC. They are fitted

with internal high speed clamp diodes for inductive spike protection. Other good features of

L293 are high noise immunity, internal ESD protection, thermal shutdown, separate input supply

for each channel etc. The pin out and truth table of an L293 motor driver is shown in the figure

below.

L293 pinout and function diagram

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8.2 Bi directional DC motor using 8051.

This project describes a bidirectional DC motor that changes its direction automatically after a

preset amount of time (around 1S). AT89S51 is the microcontroller used here and L293 forms

the motor driver. Circuit diagram is shown below.

Bi directional DC motor using 8051

In the circuit components R1, S1 and C3 forms a denouncing reset circuitry. C1, C2 and X1 are

related to the oscillator. Port pins P1.0 and P1.1 are connected to the corresponding input pins of

the L293 motor driver. The motor is connected across output pins 3 and 6 of the L293. The

software is so written that the logic combinations of P1.0 and P1.1 controls the direction of the

motor. Initially when power is switched ON, P1.0 will be high and P1.1 will be low. This

condition is maintained for a preset amount of time (around 1S) and for this time the motor will

be running in the clockwise direction (refer the function table of L293). Then the logic of P1.0

and P1.1 are swapped and this condition is also maintained for the same duration. This makes the

33

motor to run in the anti-clockwise direction for the same duration and the entire cycle is

repeated.

8.3 Program

ORG 00H // initial starting address

MAIN: MOV P1,#00000001B // motor runs clockwise

ACALL DELAY // calls the 1S DELAY

MOV P1,#00000010B // motor runs anti clockwise

ACALL DELAY // calls the 1S DELAY

SJMP MAIN // jumps to label MAIN for repaeting the cycle

DELAY: MOV R4, #0FH

WAIT1: MOV R3, #00H

WAIT2: MOV R2, #00H

WAIT3: DJNZ R2, WAIT3

DJNZ R3, WAIT2

DJNZ R4,WAIT1

RET

END

34

Interfacing hex keypad to 8051

This article is about interfacing a hex key pad to 8051 microcontroller. A clear knowledge on

interfacing hex key pad to 8051 is very essential while designing embedded system projects

which requires character or numeric input or both. For example projects like digital code lock,

numeric calculator etc. Before going to the interfacing in detail, let‟s have a look at the hex

keypad.

9.1 Hex keypad

Hex key pad is essentially a collection of 16 keys arranged in the form of a 4×4 matrix. Hex key

pad usually have keys representing numeric 0 to 9 and characters A to F. The simplified diagram

of a typical hex key pad is shown in the figure below.

Hex keypad

The hex keypad has 8 communication lines namely R1, R2, R3, R4, C1, C2, C3 and C4. R1 to

R4 represents the four rows and C1 to C4 represents the four columns. When a particular key is

pressed the corresponding row and column to which the terminals of the key are connected gets

shorted. For example if key 1 is pressed row R1 and column C1 gets shorted and so on. The

program identifies which key is pressed by a method known as column scanning. In this method

a particular row is kept low (other rows are kept high) and the columns are checked for low. If a

particular column is found low then that means that the key connected between that column and

the corresponding row (the row that is kept low) is been pressed. For example if row R1 is

initially kept low and column C1 is found low during scanning, that means key 1 is pressed.

35

9.2 Interfacing hex keypad

The circuit diagram for demonstrating interfacing hex keypad to 8051 is shown below. Like

previous 8051 projects, AT89S51 is the microcontroller used here. The circuit will display the

character/numeric pressed on a seven segment LED display. The circuit is very simple and it

uses only two ports of the microcontroller, one for the hex keypad and the other for the seven

segment LED display.

Interfacing hex keypad to 8051

The hex keypad is interfaced to port 1 and seven segment LED display is interfaced to port 0 of

the microcontroller. Resistors R1 to R8 limits the current through the corresponding segments of

the LED display. Capacitors C1, C2 and crystal X1 completes the clock circuitry for the

microcontroller. Capacitor C3, resistor R9 and push button switch S1 forms a debouncing reset

mechanism.

36

9.3 Program

ORG 00H

MOV DPTR, #LUT // moves starting address of LUT to DPTR

MOV A, #11111111B // loads A with all 1's

MOV P0, #00000000B // initializes P0 as output port

BACK:MOV P1, #11111111B // loads P1 with all 1's

CLR P1.0 // makes row 1 low

JB P1.4, NEXT1 // checks whether column 1 is low and jumps to NEXT1 if not

low

MOV A, #0D // loads a with 0D if column is low (that means key 1 is

pressed)

ACALL DISPLAY // calls DISPLAY subroutine

NEXT1: JB P1.5, NEXT2 // checks whether column 2 is low and so on...

MOV A, #1D

ACALL DISPLAY

NEXT2: JB P1.6, NEXT3

MOV A, #2D

ACALL DISPLAY

NEXT3:JB P1.7,NEXT4

MOV A, #3D

ACALL DISPLAY

NEXT4: SETB P1.0

CLR P1.1

37

JB P1.4, NEXT5

MOV A, #4D

ACALL DISPLAY

NEXT5:JB P1.5,NEXT6

MOV A, #5D

ACALL DISPLAY

NEXT6:JB P1.6,NEXT7

MOV A,#6D

ACALL DISPLAY

NEXT7: JB P1.7, NEXT8

MOV A,#7D

ACALL DISPLAY

NEXT8: SETB P1.1

CLR P1.2

JB P1.4,NEXT9

MOV A,#8D

ACALL DISPLAY

NEXT9:JB P1.5, NEXT10

MOV A,#9D

ACALL DISPLAY

NEXT10:JB P1.6,NEXT11

MOV A,#10D

ACALL DISPLAY

38

NEXT11: JB P1.7, NEXT12

MOV A,#11D

ACALL DISPLAY

NEXT12: SETB P1.2

CLR P1.3

JB P1.4, NEXT13

MOV A,#12D

ACALL DISPLAY

NEXT13: JB P1.5, NEXT14

MOV A, #13D

ACALL DISPLAY

NEXT14: JB P1.6, NEXT15

MOV A, #14D

ACALL DISPLAY

NEXT15: JB P1.7, BACK

MOV A, #15D

ACALL DISPLAY

LJMP BACK

DISPLAY: MOVC A,@A+DPTR // gets digit drive pattern for the current key from LUT

MOV P0, A // puts corresponding digit drive pattern into P0

RET

39

LUT: DB 01100000B // Look up table starts here

DB 11011010B

DB 11110010B

DB 11101110B

DB 01100110B

DB 10110110B

DB 10111110B

DB 00111110B

DB 11100000B

DB 11111110B

DB 11110110B

DB 10011100B

DB 10011110B

DB 11111100B

DB 10001110B

DB 01111010B

END

Firstly the program initializes port 0 as an output port by writing all 0′s to it and port 1 as an

input port by writing all 1′s to it. Then the program makes row 1 low by clearing P1.0 and scans

the columns one by one for low using JB instruction. If column C1 is found low, that means 1 is

pressed and accumulator is loaded by zero and DISPLAY subroutine is called. The display

subroutine adds the content in A with the starting address of LUT stored in DPTR and loads A

with the data to which the resultant address points (using instruction MOVC A, @A+DPTR).

The present data in A will be the digit drive pattern for the current key press and this pattern is

put to Port 0 for display. This way the program scans for each key one by one and puts it on the

display if it is found to be pressed.

40

CONCLUSION

The internal hardware configuration of 8051 register and control circuits have been examined at

the functional block diagram level the 8051 may be consider to be collection of RAM ,ROM, and

address registers that have some unique functions

Actually microprocessor is the subset and micro-controller is the super set. Micro-controller is

the complete on the single chip hence embedded system provide a medium through which we

can relate the micro-controller with the input and output devices