DEPARTMENT OF ELECTRONIC SCIENCE NEW PRINCE SHRI BHAVANI ARTS AND SCIENCE COLLEGE MEDAVAKKAM, CHENNAI- 600 100 UNIVERSITY OF MADRAS

A PROJECT “ELECTRONIC VOTING MACHINE” –BY MICROPROCESSOR 8085 Submitted in partial fulfillment of the requirements for the award Of the bachelor’s degree in the discipline of

ELECTRONIC SCIENCE

BY K.ARUN SHANKAR REG.NO: S603640

Under the guidance of

NEW PRINCE SHRI BHAVANI ARTS AND SCIENCE COLLEGE MARCH 2009

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BONAFIDE CERTIFICATE

This is certify that the project report titled

“ELECTRONIC VOTING MACHINE” BY MICROPROCESSOR 8085

Is a bonafide record of work done by

K. ARUN SHANKAR REG.NO.s603640

OF ELECTRONIC SCIENCE DEPARTMENT

NEW PRINCE SHRI BHAVANI ARTS AND SCIENCE COLLEGE

Patel road, medavakkam, Chennai – 6

In partial fulfillment of the requirements for the award

Of the Bachelor’s degree in the discipline of

Electronic science during the year 2006-2009.

Mrs. . Mrs.D.Beula.m.sc., m.phil., Guide Head of the DepartmentDepartment of electronics Department of electronics Science Science

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INTRODUCTION TO ELECTRONIC VOTING MACHINE

Digital integrated chips as if microprocessor

provides a broader base for only computers but also to many

applications of communications and, industrial automation and so

on. One such gadget is the voting machine, which is dealt in this

project. Microprocessor based voting machines the election process

simple and highly reliable.

EVM’s manufactured in 1989-90 were used for the first time in

legislative assemblies held in 1998.

VARIOUS FORM OF EVM

A electronic voting machine that consist of

two units

The control unit is with the presiding officer who can start the

election,

end the election or suspend the election temporarily if there

is any

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confusion etc.

The balloting unit is placed inside the voting

compartment.

Instead of issuing a ballot paper, the polling officer in charge

of the control unit will press the button on the balloting unit

against the

candidate and symbol of his choice.

Ballot, in modern usage , a sheet of paper used

in voting, usually in an electoral system that allows the voter to

make choices secretly. The term may also designate the method and

act of voting secretly by means of a mechanical device.

Used in elections in all democratic countries,

the ballot method protects voters from coercion and reprisal in the

exercise of their vote. Wherever the practice of deciding questions

by free vote has prevailed, some form of secret voting has always

been found necessary.

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The ballot box unit is designed in such a way that

it very closely resembles the existing ballot paper. The electoral

codes and names of the candidates are printed and pasted on the

box itself. The only difference is that the desired candidate is

selected by pressing a switch.

After polling the vote, a led is lighted up

confirming the voter that the machine his read his choice.

As we stated earlier we cannot

easily cheat

Microprocessor to favor any candidate. This voting machine is a

straightforward one.

In this, microprocessors based voting machine project, we have

eliminated invalid votes. We use microprocessors for fast actions for

example, the keyboard (i.e.) the valid keys are enabled for a voter

to cast his vote and can be disabled within few microseconds after

casting vote.

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Thus can avoid a voter casting vote for two

candidates. The microprocessors based voting machine also uses

the microprocessors to display the current votes polled done by the

microprocessors simultaneously controlling the whole procedure of

elections.

To store the results and the individual votes

acquired can be stored in the memory of the microprocessors itself.

Another important fact is we cannot read the individual votes during

the election time but only after End of election key is pressed by the

presiding officer the election results can be read. This is yet another

important feature of this machine.

The software developed for this machine has

been done with sufficient and necessary came that if two or more

people have got same number of votes then also the microprocessor

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displays their names or code and also their maximum votes, but it is

our duty to select the candidate.

The stamp used in the present voting system is

replaced by a switch “ON”…by pressing the vote switch and then

the machine records the voter’s choice in the memory of the

microprocessors.

At the end of the day the results are retrieved

by operating a END OF ELECTION switch. The biggest advantage of

the electronic machine is that the results are available immediately

at the end of voting period.

In this important that is one is machine

software. It has been designed in such a way that multiple voting is

not possible. Once the key is enabled, only that one vote can be

cast. After that casting one, within few microprocessor the ballot

box is disabled. This is achieved by microprocessor software.

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Therefore, this microprocessor software is

applicable for all the electronic device of interfacing of voting

machine.

These software programs are achieved by

own electronic engineer which is to make this device, for only to

given the machine by using software application of programs.

These software programs are written in the

microprocessors of 8085 integrated chips.

Therefore these indicates that the , within all

the software programs can had the operating system by controlling

module, balloting module, and these are done by interfacing within

peripheral

device are such as explained.

Thus all the digital device which is having the

basic property that contain the application of microprocessor and

some peripherals device and some interfacing chips are to be used

although these devices is the basic processor.

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The microprocessors 8085 is a programmed

integrated device that has computing and decision making

capability similar to that of the CPU of a computer. The

microprocessors communications and operates in the binary

numbers 0 and 1 called BITS. Therefore the binary instructions are

given abbreviated names called MNEMONICS, which form the

assembly languages for a given microprocessor .IC 8255 is a widely

used programmable , parallel I/O device. It can be programmed to

transfer data under various conditions , for simple I/O and interrupt

I/O.

VARIOUS UNITS OF EVM

CONTROL UNIT

BALLOTING UNIT

KEYBOARD UNIT

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CONTROL UNIT

As the name implies that it is used for

controlling the whole voting machine. That is control module, which

are used for controlling the microprocessor by some software

programs which are implemented. When these control module,

which are controlling by the control officer of presiding in election

committee.

During this controlling, there may be some

important contributes that is, control module which is used for the

election committee through the presiding officer.

When the control officer is set to work for

identifying the candidate by some clarification of the government.

After checking the people is set to put the vote for desired

nominees during the election.

When sometimes ,there may be some

malpractices is done during election, the control module that is

control officer is set to controlling the whole election is set to

suspend that is stop the election.

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After this the problem was solved, then the

election is start as such regularly, by this control module , some

kinds of machine is used for safer and more compatibility of

machine. The control module has five important switches, which

controls the electronic voting machine with their corresponding to

identify the button is pressed when the LED is glowing for desire

switches.

The control module has five important control

switches, which controls the whole voting machine with their

corresponding LED’s. The function of each key is explained below.

CLEAR KEY

The clear key is used to identify the accumulator and

goes into the accumulator. When the code is enter into the

microprocessors clear the memory content specified by the address

of voting machine.

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START KEY

The start key are used to start the election, by after

the clear key is pressed, its clear the memory location to start key is

pressed.

SUSPEND KEY

The suspend key are used after during the election

system is set suspend (or) paused in such a time by control officer.

VOTER KEY

After checking the control officer of voters, this key

is pressed, whether the voter is valid is set to put a vote. And when

is key is press it indicate the voter is a bonafide voter.

END KEY

When these key are used, that is election comes to

an end, That is key is pressed all the input and output process are

send to an end Moreover, these, by control module.

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BALLOTING UNIT

Ballot box unit are designed in such a way

that, it is closely resembles that and existing a ballot paper.

Electoral codes and names of he candidates are selected by

pressing a switch.

After polling the votes are identify by led is

glowing up and conforming the votes that the machine has read his

choice. Therefore, these ballot box units consist of number of

candidate, which are take an part of election member. There may be

have a candidate switch and led are used for candidate to identify

by people.

These led are used for identified, whether

the vote are put to the correct member by people. In addition, the

candidates switch and are connected by software programs by the

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microprocessors of 8085 IC. That is, when the switch is pressed the

candidate led is glowing.

Although, when these balloting unit consist

of some kind of memory by using microprocessors of 8085

integrated IC.

When people are get to ready to put the

vote for desired candidate for its voter then the microprocessor is

ready to keen the vote, that is memory is ready to catch the signal

and storing the date.

Balloting unit is presiding connected with

the control module which are interfacing through the electronic

lines, therefore control module is set to work for controlling the

date should presiding in electronic device.

KEYBOARD UNIT

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Keyboard module contains seven keys with

eight LED’s. when the valid voter key is pressed the ENABLE LED

glows indicating that the keys are enabled and the voter can cast

(i.e.)., a particular candidate key is pressed the contents of the

corresponding memory location of the candidate gets incremented

by one. Immediately the LED of that corresponding candidate glows

along with a buzzer denoting that the vote has been entered.

OUTPUT OF PORTS B and PORT C

The output of ports B and ports C are connected to a buffer IC

74LS244. the LED’s and the buzzer to indicate which key is pressed

etc., One output is used to control, (i.e.), enable or disable the

keyboard.

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PROGRAMMABLE PERIPHERAL DEVICE

8255

Intel 8255 is a programmable peripheral interface (PPI), also known

as a programmable interface adapter (PIA). It is a 40 pin IC. The

8255 is a widely used programmable, parallel I/O device that can be

used with almost any microprocessor.

It can be programmed to transfer data under various

conditions, for simple I/O and interrupt I/O. The 8255 has 24 I/O pins

that can be grouped primarily in two 8 bit parallel ports A&B, with

remaining eight bits as port C. The eight bits of port C can be used

as,

Two 4-bit ports namely port C upper (CU) and port C

lower (CL). Each port can be programmed as in input port or an

output port.

The functions of these ports are defined by writing a

control word in the control word in the control register.

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All the functions of 8255, are classified according to

two modes,

The bit set/reset (BSR) mode

I/O mode

The BSR mode is used to set or reset the bits in ports C.

The I/O mode is further divided into 3 modes, are mode 0, mode 1, mode 2.

In mode 0, all the ports function as simple I/O ports.

In mode 1, is a handshake mode where by ports A or ports B uses

bits from

port C as handshake signals.

In mode 2, port A can be set up for bi – directional data transfer

using handshake signals from port C and port B can be set up either

in mode 0 or mode 1. Handshake signal are exchanged between the

MPU and Peripherals prior to data transfer.

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PIN CONFIGURATION OF 8255

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BLOCK DIAGRAM OF 8255

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8255- FUNCTIONAL DESCRIPTION

DATABUS BUFFER

This tri-state bidirectional 8-bit buffer is used to

interface the 8255 to the system data bus. Data is transmitted or

received by the buffer upon execution of I/P Or O/P instruction by

the CPU control words and status information are also transmitted

through the data bus buffer.

READ/WRITE CONTROL LOGIC

The function of this block is managing all the

internal and external transfers of both data and control status

words. It accept inputs from the CPU address and control busses

and in turn, issues command to both of control groups.

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RD(Read) :

It is a active low control signal, which enables the

read operation. When the signal is low , the MPU reads from a

selected I/O ports of the 8255A.

WR(Write) :

It is an active low signal. Which enables a write

operation.

CS(Chip select):

It is an active low signal, which enables the

communication between the 8255A chip and the microprocessors.

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A0 and A1:

A0 and A1 are device select signals. These are

generally connected to MPU address lines A0 and A1 respectively.

And these address lines are used to select one of the ports or a

control register which is used to initialize the ports that are given

below.

A

1

A

0

RD W

R

C

S

INPUT OPERATION

(READ)

0 0 0 1 0 Port AData bus

0 1 0 1 0 Port B Data bus

1 0 0 1 0 Port C Data bus

1 1 0 1 0 Control word Data

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bus

D0 – D7:

These are the data input /output lines for the device.

All information read from and written to the 8255 occurs via these 8

data lines.

RESET:

The 8255 is placed into its reset state if this input line

is a logical 1. all peripheral orts are set t the input mode.

PA0 – PA7,PB0 –PB7, PC0 – PC7

These signal lines are used as 8- bit I/O ports.

They can be connected to the peripheral devices. The 8255 has

three 8 bit I/O ports and each one can be connected to the physical

lines of an external devices. These lines are labeled PA0-PB7 and

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PC0-PC7. The groups of the signals are divided into three different

I/O ports labeled port A (PA), port B (PB), port C(PC).

Two control groups, labeled group A control and

group B control define how the three I/O ports operate. There are

several different operating modes for the 8255 and these modes

must be defined by the CPU writing programming or control words

to the device 8255. The line group of port C consists of two 4 bit

ports. One of the four bit groups is associated with group A control

and the other 4 bit group with group B device signals. The upper 4

bits of port C are associated with A control while the lower 4 bits

are associated with group B control.

PORT SELECTION 0 and PORT SELECTION 1

These input signals in conjunction with the RD and WR

inputs, control the selection of one of the three ports or the control

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word registers. They are normally connected to the least significant

bits of the address bus A0 and A1.

PORTS A, B and C

The 8255 contains three 8 bits ports (A, B and C) all can

be configured in a wide variety of functional characteristics by the

system software but each has its own special features to further

enhance the power and flexibility of the 8255.

PORT A

Port A contains are eight bit data output latch/buffer and

eight bit data input latch.

PORT B

Port B contains one eight-bit data input/output

latch/buffer and one 8 bit data input buffer.

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PORT C

Port c contains one eight-bit data latch/buffer and one

eight bit data input buffer (no latch for input). This port can be

divided into two four bit ports under the mode control. Each four bit

port contains a four bit latch and it can be used for the control

signals outputs and status signals inputs is conjunction with port A

and port B.

MODE SLECTION

There are three basic modes of operation that can be

selected by the system software. They are as follows :

MODE 0 - Basic input / output

MODE 1 - Strobe input/ output

MODE 2 - Bi-directional bus

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When the reset input goes high all the ports will be set

to the input mode. After the reset, the 8255 can remain in the input

mode with no additional initialization required.

During the execution of the system program of any of

the other modes may be selected using a single output instruction.

This allows a single 8255 to service a variety of peripheral devices

with a simple software maintenance routine.

The functions of 8255 are classified according to two modes:

BIT SET/RESET MODE (BSR MODE):

When D7 bit in control word is zero, 8255 is in BSR mode each

mode in port C alone can be set or rest.

I/O MODE:

In I/O Mode, the chip operates under Mode 0, Mode 1 and Mode

2.

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Mode 0:

Ports A and B operate as either inputs or outputs and

Ports C is divided into two 4-bit groups either of which can be

operated as inputs or outputs. The disadvantage of this mode is

that it does not have handshake or interrupt capability.

Mode 1:

Same as Mode 0 but Port C is used handshaking and

control. This mode is also known as strobe input/output mode.

The mode 1 has input control signals such as STB and IBF.

STB(Strobe Input)

It is an active low signal generated by a peripheral

device to indicate that it has transmitted a byte of

data.

IBF(Input Buffer Full)

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It is a high acknowledge signal by the 8255A to

indicate that the input latch has received that data

byte.

INTR(Interrupt Request)

It is an active high output signal used to interrupt

the microprocessors.

INTE(Interrupt Enable)

This is an internal flip-flop used to enable or

disable the generation.

The mode 1 has output signals such as :

OBF(Output Buffer full)

It is an active low output signal generated,

when the microprocessors writes into the output latch of the 8255A.

ACK(Acknowledge)

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It is an active low input signal from a

peripherals device that must output a low when the peripherals

device receives data from the ports of 8255A.

INTR(Interrupt request)

This is an output signal and it is set by the

raising edge of the ACK signal. This signal is used to interrupt the

MPU to request the next data byte for output. The INTR is set when

OBF, ACK and INTE are all one and reset by the falling edge of WR.

INTE(Interrupt enable)

This is an internal flip-flop to a port and needs

to be set to generate the INTR signal. The Two flip-flops INTEA and

INTEB are controlled by bits PC6 and PC2, through the BSR mode.

PC4,5:

These two lines can be set up either as input

or output.

PORT A as INPUT PORT:

When port A acts as an input port, port C bits

PC3, PC4 and PC5 acts as handshake signals. When port B acts as

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input port, port C bits PC0, PC1 and PC2 act as handshake signals.

The remaining port C bits PC6 and PC7 can be used as input or

output ports.

In Mode1, if port A is configured as an input

port, PC4 bit receives a strobe(STB) signal from an input device and

PC5 bit sends out an input buffer full signal(IBF). The input device

places 8 bits of data as PA0 and PA7 of the input latch. This makes

the IBF signal to determine whether data is available for input the

microprocessor.

PORT A as OUTPUT PORT:

In mode 1, when port A is configured as an output port,

port C bits PC3, PC6 and PC7, act as handshake signals. The

microprocessor writes data to port A and port A outputs data to an

output device. When port A receives data, a signal called output

buffer full(OBF) is reset to logic ‘0’. The output device monitors

OBF to determine when data is available. After accepting the data,

the output device sends an active low acknowledgement

signal(ACK) to the 8255 and this clears OBF. Now the

microprocessor can send the next data.

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Mode 2:

Port A is bi-directional(both input and output) and Port

C is handshaking. Port B is not used. Port A uses five signals from

port C as Handshake signals for data transfer. The remaining three

signals from port C can be used either as simple I/O or as handshake

for port B.

CONTROL WORD

8255 is initialized by writing a control word in the

control register. The contents of control register is called control

word. This specifies an I/O function for each port.

Bit D7 of the control register I/O function or BIT

SET/RESET function, as classified in the following fig 1. if bit D7 =1,

bits D6-D0 determined I/O functions in various modes as shown in

fig. if bit D7=0, port C operates in the BIT SET/RESET mode. The BSR

control word does not affect the functions of port A and port B.

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There are three steps are needed to communicate

with peripherals through the 8255a. They are,

The address of PORT A, B and C of the control

register according the chip select logic and

address lines A0 and A1.

Writing a control word in the control register.

Writing an I/O instruction to communicate with

peripherals through port A,B and C.

MODE 0 : SIMPLE INPUT PORT OR OUTPUT PORT

In mode 0, port A and port B are used as two simple 8-

bit I/O ports and port C as two 4- bit I/O ports without handshake

facility. The 4-bits of port (Cl) lower and 4- bit of port(Cu) upper can

be individually initialized to act as import port or output port. The

I/O features in mode 0 are as follows:

o Output are latched.

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o Input are not latched.

o Ports do not have handshake or

interrupt capability.

PORT ADDRESSES

PORT A : DC

PORT B : DD

PORT C : DE

CONTROL REGISTER : DF

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VOTING MACHINE ARCHITECTURE

In this chapter let us consider the hardware

description of the system. The block diagram of the hardware part is

as shown in the fig. in general the control keys and the ballot keys

are connected to a encoder which converts each key into a

particular code. This binary information is sent through a buffer

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where it is amplified in current amplification and fed into the port of

a microprocessor.

In the similar way the output of the microprocessors

is sent to a buffer through the port. The output information is again

amplified and sent to drive the systems like LED etc. let us see each

section of the hardware in detail.

OCTAL TO BINARY : ( IC 74148)

When a particular key is pressed then that key is

grounded. To convert the key pressed into a particular binary code

we use IC 74148. this is an “octal to binary Encoder” we can have 8

key is as inputs. If any one of the key is grounded then there will be

equivalent binary output. It has active low inputs and active low

outputs. The chip is enabled when EI is taken low.

This chip is a higher order priority encoder , (i.e.) if

two key is pressed simultaneously then the chip will take the input

value which has higher order compared with order. It will give low

outputs from 0 to 8 values.

PIN DIAGRAM OF IC 74148

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Various function of this pin out configuration

Chip is given in tables

EI I N P U T S OUT PUT ACT IVE LOW

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S BIN ARY O/P

0 1 2 3 4 5 6 7 8 GS ED C B A

1 X X X X X X X X X 1 1 1 1 1

0 0 1 1 1 1 1 1 1 1 0 1 1 1 1

0 X 0 1 1 1 1 1 1 1 0 1 1 1 0

0 X X 0 1 1 1 1 1 1 0 1 1 0 1

0 X X X 0 1 1 1 1 1 0 1 1 0 0

0 X X X X 0 1 1 1 1 0 1 0 1 1

0 X X X X X 0 1 1 1 0 1 0 1 0

0 X X X X X X 0 1 1 0 1 0 0 1

0 X X X X X X X 0 1 0 1 0 0 0

0 X X X X X X X X 0 0 1 0 0 0

0 1 1 1 1 1 1 1 1 1 1 0 1 1 1

In our project we need to convert as OCTAL key into

BINARY data. This is efficiently done by IC 74148.

Also in the keyboard module, the chip enable pin EI is

controlled by the software programmed. (i.e.), that is connected to

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the output port of the microprocessors when any key is pressed,

immediately the microprocessors senses the key pressed and sends

signals to disable the IC 74148. Thus second time voting are

prevented.

The seven candidate keys are connected with the

three bits of port A and five control keys are encoded with the

other three bits of port A using this encoder.

HEX INVERTER IC 7404

Since, IC 74148 is an active low output chip, we need

to use an inverter. IC 7404 in an Hex inverter. That is it has six NOT

gates with six inputs and six outputs.

We use this chip for inverting three outputs of IC

74148 from control module and three outputs of IC 74148 from

keyboard module. IC 7404 pin out configuration is as shown in the

fig, the outputs of Hex inverter is given to buffer as data input.

PIN CONFIGURATION OF IC 7404

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OCTAL BUFFER(LS 74244)

In octal buffer, there are two groups, which have

4 tri-state output buffers. The buffer is controlled by 2 active low

enabled lines (Pin no.1 and Pin no.19). These pins are connected

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which is called as an output enabled input pin (OE). It has 3 states,

logic 0, logic 1 and high impedance Z.

When OE is low (Logic 0), the device passes the

non-inverted data from an input to the Y output. When OE is high,

the outputs are in the high impedance state (i.e.). The output is

disconnected from the rest of the circuit.

PIN DIAGRAM OF 74LS244

EVM – CIRCUIT DIAGRAM

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SOFTWARE DEVELOPMENT

OF

ELECTRONIC VOTING MACHINE

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This chapter deals with the whole programming method

of electronic voting machine. The important aspect in the first part

of the software is to communicate with the peripherals devices. The

8085 microprocessors has two instructions for data transfer

between the processor and I/O device. The instruction IN inputs the

data from a input device such as LED dislplay. These are two byte

instructions with second byte specifying the address of the port

number of an I/O device. The 8085 executes the OUT instructions in

the three machine cycles and it taken ten 7T- states to complete the

execution.

This type of interfacing with the peripherals is called

POLLED or PROGRAMMED I/O transfer. In this case executing the IN

instruction the microprocessors waits till the input is given through

it wastes a lot of time in micro seconds , we are using this type of

I/O transfer for our project work.

This program checks for any key closure and executes the

operation each time. After executing the END of election key closure

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operation the software is written for collecting the number of votes

with the candidates code from particular memory locations.

The candidate codes are verified and the corresponding

memory locations are incremented.

The codes for the control module layout and ballot box layout is

given below:

CONTROL MODULE LED CODE:

LED CODES 8-BIT PATTERN

CLEAR LED (7F)H (0111 1111)H

START LED (BF)H (1011 1111)H

SUSPEND LED (DF)H (1101 1111)H

VALID VOTER LED (EF)H (1110 1111)H

END OF ELECTION LED (F7)H (1111 1011)H

CONTROL MODULE KEY CODE:

KEYS CODE 8-BIT PATTERN

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CLEAR (01)H (0000 0001)H

START (02)H (0000 0010)H

SUSPEND (03)H (0000 0011)H

VALID VOTER (04)H (0000 0100)H

END (05)H (0000 0101)H

BALLOT BOX LED CODES:

LEDS CODE 8-BIT PATTERN

CANDIDATE 1 (7F)H (0111 1111)H

CANDIDATE 2 (BF)H (1011 1111)H

CANDIDATE 3 (DF)H (1101 1111)H

CANDIDATE 4 (EF)H (1110 1111)H

CANDIDATE 5 (F7)H (1111 0111)H

CANDIDATE 6 (FB)H (1111 1011)H

CANDIDATE 7 (FD)H (1111 1101)H

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BALLOT BOX KEY CODES:

KEYS CODE 8-BIT PATTERN

CANDIDATE 1 (10)H (0001 0000)H

CANDIDATE 2 (20)H (0010 0000)H

CANDIDATE 3 (30)H (0011 0000)H

CANDIDATE 4 (40)H (0100 0000)H

CANDIDATE 5 (50)H (0101 0000)H

CANDIDATE 6 (60)H (0110 0000)H

CANDIDATE 7 (70)H (0111 0000)H

CONTROL WORD

D0 = 0 = PORT C1 = Output

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D1 = 0 = PORT B = Output

D2 = 0 = MODE SEL. = Mode 0

D3 = 0 = PORT CU = Output

D4 = 1 = PORT A = Input

D5 = 0 = MODE SEL. = Mode 0

D6 = 0

D7 = 1 = I/O MODE

D7 D6 D5 D4 D3 D2 D1 D0

1 0 0 1 0 0 0 0

CONTROL WORD - 90AH

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