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Chapter 1

INTRODUCTION

A toll road or tollway is a privately or publicly built road for which a driver pays

a toll (fee) for use. Structures for which tolls are charged include toll bridges and toll

tunnels. Non-toll roads are financed using other sources of revenue, most typically

fuel tax or general tax funds. The building or facility in which a toll is collected may be

called a toll booth, toll plaza, toll station, toll bar or toll gate. This building is usually

found on either side of a bridge and at exits.

Tolls have been placed on roads at various times in history, often to generate

funds for repayment of toll revenue bonds used to financed constructions and

operations. Toll roads are at least 2700 years old, as tolls had to be paid by

travelers. Many European roads were originally constructed as toll roads in order to

recoup the costs of construction. Three systems of toll roads then exist: open (with

mainline barriers); closed (with entry/exits tolls) and electronic toll collection (no toll

booth, only electronic toll collection gantries at entrances and exits).

Modern toll roads uses either or combination of the three systems. Electronic

toll collection is considered to be the newest technology system of today or the RFID

(Radio-frequency Identification) technology. The electronic system determines

whether the passing car is enrolled in the program, alerts enforcers if not. The

accounts of registered cars are debited automatically without stopping or even

1



opening a window. The system uses a radio transponder mounted in the vehicle to

deduct toll fees from a prepaid account as it passes through the barrier.

The electronic system is convenient in such a way that it lessens the delay in

toll collection but just recently, the Philippines did not approved the approach and

was questioned by the law due to direct implementations without prior notice. The

new technology was quite expensive and needed to be studied well. According to

some feedbacks, computer glitch can result in delays several miles long. Besides,

not all commuters have credit cards that are required in the system. Finally, the last

concern would be regarding privacy matters. Due to the usage of radio frequency

signals, the commuters can be possibly trace which most citizens does not agree

upon.

Considering some of the factors and drawbacks of the latest technology in

the tollway system, the proponents still wishes to create a system that would be

beneficial and would still lessen the errors and will not require a large amount of

personnel. These concerns led the proponents to design a much simpler and

effective tollway system that would somehow be convenient for all types of masses

that could be easily afforded and adapted.

2



BACKGROUND OF THE PROJECT

Economic Feasibility

Table 1.Costing of Materials

3

Item Price

PIC168F84A

Motor

Casing

Hook up wire / Telephone wire

Soldering lead

Coin slot

Relay

Switch

Capacitor, Resistor

Hi-end led

UPSLDR

Phototransistor

Lock

PBC Pipe

Transistor

BA6218

Misc.

1200.00

300.00

5000.00

400.00

200.00

1300.00

280.00

250.00

150.00

70.00

1800.0030.00

200.00

200.00

155.00

270.00

175.00

500.00

TOTAL Php 8,000.00



Technical Feasibility

The System needs the following materials

a.) Sensor

b.) Motor

c.) PIC1f684A

d.) PCB

e.) Toy car/truck

f.) Other Electronics Materials

g.) All of these materials are available and can purchased locally.

Rate of investment

Estimated Cost for Rental per month = Php 300.00

Estimated Power Consumed per month = Php 400.00

Maintenance every 1 month= Php 500.00

Coin Amount = amount of present toll fee = 70 Php for light vehicles

Php 3, 600.00 – rental a year

Php 2,000.00 - maintenance a year

+ Php 4800.00 – power consumed a year

Php 8000.00– total cost

Total Initial Investment (1 year) = Php 18,400

Assume that the number maximum of cars drove through the express way per day

is 20,000 vehicles.

4



Estimated profit (1 day) = 20,000

X 70 Php

1,400,000/day

Estimated profit(1 month) = Php 42,000,000/month

Estimated profit(1 year )= Php 504,0000,000 /year

Initial Net Present Value (NPV) = Total Cost PV of future CF’s – Initial

Investment

= Php 504,000,000– Php 18400

Initial NPV of the Investment in the project after 1 year using the system= Php

503,981,600

In manual operation

Estimated profit (1 year )= Php 504,0000,000 /year

Number of workers in one lane toll station= 2 (person)

Estimated salary of worker per month = 8000

Php 500.00 - maintenance a month without automated system

Estimated profit in manual operation (1 year ) = 504,064,500

Final NPV = Php 504,064,500 - Php 503,981,600

Final NPV= 82,900

Therefore, the rate of investment for this project is almost a year to recover the

initial cost.

5



Statement of the Problem

The proponents aim to design a Tollway System that helps answer the

following questions:

1. Does a tollway lessen the error in manual operation?

2. Does a huge number of personnel in tollway station add to the booming

expenses of the tollway system owners/government?

3. Does a tollway system enable, businessman, owners/government save

money and investment on the maintenance?

Objectives of the Project

The general objective of this project is to design a tollway. It specifically aims

to:

1. Create a design on tollway system for tollway owner that is easy to

manage and will lessen error in manual operation.

2. Design a tollway system that will not require a huge number of personnel

to pay for maintenance operation.

3. Design a tollway system that will save time and money for tollway owners.

6



Significance of the Study

The project design focuses on the development of the Automated Tollway

System. It is conceptualized to address the problem in accessibility and convenience

of tollway system services.

The project system will be used for business. It works similarly on other coin-

slot machines or services such as vending machines, video games and many others.

Scope and Limitation

The System has the following features:

1. The system consists of a coin slot that is allotted for the 1 token.

2. The gate in the entrance will open if the sensor detects a vehicle.

3. When the sensor detects that a car already entered the gate, the entrance

gate will close.

4. The gate at the back will open if a coin is dropped in the coin slot.

5. Then the back gate will close again if the sensor detects that the vehicle had

already passed.

6. The system has a weighing scale that determines the weight of vehicles.

7. The system has a power backup in case of power interruptions.

7



The System has the following limitations:

1. The entire system is electrically operated.

2. The slot can only accept one token that has a corresponding value.

3. The system can only accommodate one vehicle at a time.

4. The power backup will last for maximum of one hour only.

5. The token can only be purchased to certified outlets and official distributors

such as gasoline stations, department stores and many more.

8

* Create a design

on tollway system

for tollway owner

that is easy to

manage and

lessen error in

manual operation.

* Design a tollwaysystem that will notrequire a hugenumber of

personnel to payfor maintenanceo eration.



The schematic diagram shown below explains how the project is being made

possible.

Figure.1 Conceptual Framework

9

* Does a tollwaylessen the error inmanual operation?

* Does a huge

number of personnel in

tollway station add

to the booming

expenses of the

tollway system

owners/governmen

t?

* Does a tollwaysystem enable,

businessman,owners/government save money andinvestment on themaintenance?

Problem Process Output

Develop and

Implement a

Tollway system .

es gn a o waysystem that willsave time andmoney for tollwayowners.



Definition of Terms

Tollway - is a privately or publicly built road for which a driver pays a toll (a fee) for

use.

Automation - the use of control systems (such as numerical control, programmable

logic control, and other industrial control systems), in concert with other applications

of information technology (such as computer-aided technologies [CAD, CAM, CAx]),

to control industrial machinery and processes, reducing the need for human

intervention.

Machine - any mechanical or electrical device that transmits or modifies energy to

perform or assist in the performance of tasks. It normally requires an input as a

trigger, transmits the modified energy to an output, which performs the desired task

alternative to the more complex dot-matrix displays.

Switch- an electrical component that can break an electrical circuit, interrupting the

current or diverting it from one conductor to another.

Direct current or DC motor - converts electrical energy into mechanical energy.

PIC16F84A - an 8-bit microcontroller of RISC (Reduced Instruction Set Computer)

architecture. It uses a total number of 35 instructions. It has a total of 18 pins and is

mostly found in a DIP18 type of case.

Token coin - a piece of metal or other composition used as a substitute for currency;

includes subway tokens.

10

http://en.wikipedia.org/wiki/Road

http://en.wikipedia.org/wiki/Control_system

http://en.wikipedia.org/wiki/Numerical_control

http://en.wikipedia.org/wiki/Programmable_logic_controller


http://en.wikipedia.org/wiki/Industrial_control_systems

http://en.wikipedia.org/wiki/Information_technology

http://en.wikipedia.org/wiki/Computer-aided_technologies

http://en.wikipedia.org/wiki/Industry

http://en.wikipedia.org/wiki/Machinery

http://en.wikipedia.org/wiki/Industrial_process

http://www.wordiq.com/definition/Energy

http://en.wikipedia.org/wiki/Dot-matrix

http://en.wikipedia.org/wiki/Electrical_component

http://en.wikipedia.org/wiki/Electrical_circuit

http://en.wikipedia.org/wiki/Electric_current

http://en.wikipedia.org/wiki/Token_coin

http://en.wikipedia.org/wiki/Road

http://en.wikipedia.org/wiki/Control_system

http://en.wikipedia.org/wiki/Numerical_control



http://en.wikipedia.org/wiki/Industrial_control_systems

http://en.wikipedia.org/wiki/Information_technology

http://en.wikipedia.org/wiki/Computer-aided_technologies

http://en.wikipedia.org/wiki/Industry

http://en.wikipedia.org/wiki/Machinery

http://en.wikipedia.org/wiki/Industrial_process

http://www.wordiq.com/definition/Energy

http://en.wikipedia.org/wiki/Dot-matrix

http://en.wikipedia.org/wiki/Electrical_component

http://en.wikipedia.org/wiki/Electrical_circuit


http://en.wikipedia.org/wiki/Token_coin



Resistor - a two-terminal electronic component that produces a voltage across its

terminals that is proportional to the electric current through it in accordance with

Ohm's law.

Capacitor or condenser - a passive electronic component consisting of a pair of

conductors separated by a dielectric.

Light-emitting diode (LED) - an electronic light source.

Radio-frequency identification (RFID) - is the use of an object applied to or

incorporated into a product, animal, or person for the purpose of identification and

tracking using radio waves.

Microcontroller - A single chip that contains the processor (the CPU), non-volatile

memory for the program (ROM or flash), volatile memory for input and output (RAM),

a clock and an I/O control unit.

11

http://en.wikipedia.org/wiki/Terminal_(electronics)

http://en.wikipedia.org/wiki/Electronic_component

http://en.wikipedia.org/wiki/Voltage

http://en.wikipedia.org/wiki/Proportionality_(mathematics)#Direct_proportion


http://en.wikipedia.org/wiki/Ohm's_law

http://en.wikipedia.org/wiki/Passivity_(engineering)


http://en.wikipedia.org/wiki/Electrical_conductor

http://en.wikipedia.org/wiki/Dielectric

http://en.wikipedia.org/wiki/Electronics

http://en.wikipedia.org/wiki/Terminal_(electronics)


http://en.wikipedia.org/wiki/Voltage

http://en.wikipedia.org/wiki/Proportionality_(mathematics)#Direct_proportion


http://en.wikipedia.org/wiki/Ohm's_law

http://en.wikipedia.org/wiki/Passivity_(engineering)


http://en.wikipedia.org/wiki/Electrical_conductor

http://en.wikipedia.org/wiki/Dielectric

http://en.wikipedia.org/wiki/Electronics



Chapter II

REVIEW OF RELATED LITERATURES AND STUDIES

Review of Related Literatures

A toll road (or tollway, turnpike, pike, toll highway or an express toll route) is a

privately or publicly built road for which a driver pays a toll (a fee) for use. Structures

for which tolls are charged include toll bridges and toll tunnels. Non-toll roads are

financed using other sources of revenue, most typically fuel tax or general tax funds.

The building or facility in which a toll is collected may be called a toll booth, toll plaza,

toll station, toll bar or toll gate. This building is usually found on either side of a bridge

and at exits.

Three systems of toll roads exist: open (with mainline barrier toll

plazas); closed (with entry/exit tolls) and all-electronic toll collection (no toll booths,

only electronic toll collection gantries at entrances and exits, or at strategic locations

on the mainline of the road).

On an open toll system, all vehicles stop at various locations along the

highway to pay a toll. While this may save money from the lack of need to construct

tolls at every exit, it can cause traffic congestion, and drivers may be able to avoid

tolls (shunpike) by exiting and re-entering the highway.

12



With a closed system, vehicles collect a ticket when entering the highway. In

some cases, the ticket displays the toll to be paid on exit. Upon exit, the driver must

pay the amount listed for the given exit. Should the ticket be lost, a driver must

typically pay the maximum amount possible for travel on that highway. Short toll

roads with no intermediate entries or exits may have only one toll plaza at one end,

with motorists traveling in either direction paying a flat fee either when they enter or

when they exit the toll road. In a variant of the closed toll system, mainline barriers

are present at the two endpoints of the toll road, and each interchange has a ramp

toll that is paid upon exit or entry. In this case, a motorist pays a flat fee at the ramp

toll and another flat fee at the end of the toll road; no ticket is necessary.

In an all-electronic system (such as that used on Highway 407 in the

Canadian province of Ontario and the Fort Bend Westpark Tollway in the U.S. state

of Texas), no cash toll collection takes place, tolls are usually collected with the use

of a transponder mounted on the windshield of each vehicle, which is linked to a

customer account which is debited for each use of the toll road. On some roads,

such as Highway 407, automobiles and light trucks without transponders are

permitted to use the road (though trucks with a gross vehicle weight over 5,000

kilograms must have a transponder)[1] - a bill for the toll due is then sent to the

registered owner of the vehicle by mail; by contrast, the Fort Bend Westpark Tollway

requires all vehicles to be equipped with a transponder

Modern toll roads often use a combination of the three, with various entry and

exit tolls supplemented by occasional mainline tolls.

13



Some toll roads charge a toll in only one direction, such as where the M4 in

Great Britain crosses the River Severn on either of the two Severn Bridges. On these

bridges, it is free to travel from Wales into England, but a toll must be paid on the

return journey. This is only practical where the detour to avoid the toll is very large –

in this case about 40 miles.

Toll payments may be made in cash, by credit card, by pre-paid card, or by

an electronic toll collection system. In some European countries, payment is made

using stickers which are affixed to the windscreen. Some toll booths are automated.

Tolls may vary according to the distance traveled, the building and maintenance

costs of the motorway, and the type of vehicle.

Tolls have been placed on roads at various times in history, often to generate

funds for repayment of toll revenue bonds used to finance constructions and/or

operation

Toll roads are at least 2700 years old, as tolls had to be paid by travellers

using the Susa–Babylon highway under the regime of Ashurbanipal, who reigned in

the seventh century BC.[3] Aristotle and Pliny refer to tolls in Arabia and other parts

of Asia. In India, before the 4th century BC, the Arthasastra notes the use of tolls.

Germanic tribes charged tolls to travellers across mountain passes. Tolls were used

in the Holy Roman Empire in the 14th century and 15th century.

A 14th century example (though not for a road) is Castle Loevestein in the

Netherlands, which was built at a strategic point where 2 rivers meet, and charged

tolls on boats sailing along the river.

14



Many modern European roads were originally constructed as toll roads in

order to recoup the costs of construction. In 14th century England, some of the most

heavily used roads were repaired with money raised from tolls by pavage grants.

Turnpike trusts were established in England from 1706 onwards, and were ultimately

responsible for the maintenance and improvement of most main roads in England

and Wales, until they were gradually abolished from the 1870s. Most trusts improved

existing roads, but some new ones, usually only short stretches of road, were also

built. Thomas Telford's Holyhead road (now the A5 road) is exceptional as a

particularly long new road, built in the early 19th century with many toll booths along

its length. See also Toll roads in the United Kingdom.

One of the first U.S. toll roads, the Long Island Motor Parkway (which opened

on October 10, 1908) was built by William Kissam Vanderbilt II, the great-grandson

of Cornelius Vanderbilt. The road was closed in 1938 when it was taken over by the

state of New York in lieu of back taxes

Toll roads are found in many countries. The way they are funded and

operated may differ from country to country. Some of these toll roads are privately

owned and operated. Others are owned by the government. Some of the

government-owned toll roads are privately operated.

Some toll roads are managed under such systems as the Build-Operate-

Transfer (BOT) system. Private companies build the roads and are given a limited

franchise. Ownership is transferred to the government when the franchise expires.

Throughout the world, this type of arrangement is prevalent in Australia, India, South

15



Korea, Japan, Philippines, and Canada. The (BOT) system is a fairly new concept

that is gaining ground in the United States, with Arkansas, California, Delaware,

Florida, Illinois, Indiana, Mississippi[6], Texas, and Virginia already building and

operating toll roads under this scheme. Pennsylvania, Massachusetts, New Jersey,

and Tennessee are also considering the BOT methodology for future highway

projects.

The more traditional means of managing toll roads in the United States is

through semi-autonomous public authorities. New York, Massachusetts, New

Hampshire, New Jersey, Maryland, Ohio, Pennsylvania, Kansas, Oklahoma, and

West Virginia manage their toll roads in this manner. While most of the toll roads in

California, Delaware, Florida, Texas, and Virginia are operating under the BOT

arrangement, a few of the older toll roads in these states are still operated by public

authorities.

Review of Related Studies

An adaptation of military "identification friend or foe" or RFID technology,

called electronic toll collection, is lessening the delay incurred in toll collection. The

electronic system determines whether a passing car is enrolled in the program, alerts

enforcers if it is not. The accounts of registered cars are debited automatically

without stopping or even opening a window. Currently, DSRC is used as a wireless

protocol. Other systems are based on GPRS/GSM and GPS technology. Such a

16



system (for trucks only) in Germany launched successfully[citation needed] in

January 2005 and by the end of its first year of operation will have charged tolls for

around 22 billion driven kilometres. One of the advantages of GPS-based systems is

their ability to adapt easily and quickly to changes in charge parameters (road

classes, vehicle types, emission levels, time slots, etc.). Another advantage is the

systems' ability to support other value-added services on the same technology

platform. These services might include fleet and vehicle engine management

systems, emergency response services, pay-as-you-drive insurance services and

navigation capabilities.

The first major deployment of an RFID electronic toll collection system in the

United States was on the Dallas North Tollway in 1989 by Amtech (see TollTag). The

Amtech RFID technology used on the Dallas North Tollway was originally developed

at Sandia Labs for use in tagging and tracking livestock. In the same year, the

Telepass active transponder RFID system was introduced across Italy.

Highway 407 in the province of Ontario, Canada has no toll booths, and

instead reads a transponder mounted on the windshields of each vehicle using the

road (the rear license plates of vehicles lacking a transponder are photographed

when they enter and exit the highway). This made the highway the first all-automated

highway in the world. A bill is mailed monthly for usage of the 407. Lower charges

are levied on frequent 407 users who carry electronic transponders in their vehicles.

The approach has not been without controversy.

17



Chapter III

METHODOLOGY

This chapter presents the methods and the procedures used in the project.

The topics included here were the method used, locale of the study, the instrument

used in making the project.

Method Used

The project used laboratory experimental research to test the functionality of

the automated tollway using a coin sensor.

Locale of the Study

The project was conducted at University of Southern Mindanao, started on

December 2009 until March 2010

Project Instrument

The project design was tested using the hardware and software simulation.

Target board and electronics component were used in hardware. Proteus

applications were used in software

18



APPENDICES

19



APPENDIX A. SYSTEM FLOW CHART

Yes

No

Yes

Yes

Yes No

No No

no

No

Yes

20

start

Is

incomin

g

vehicle?

Open 1ST gate

Vehicl

e

passe

d?

Is

vehicl

e

heavy

?

Close 1ST gate

Enable

weighing

Coin slot 1

Is coin

dropp

ed? ??

?

Coin slot 2

Is coin

dropp

ed? ?

A B



RB0=

1?

RB3=

=1?

APPENDIX B. PROGRAM FLOWCHART

Legend:

No

21

Open 2nd gate

Vehiclepassed in

2nd gate?

close 2nd gate Disable WS

start

call main

b’00000001’

A

A

B



RB4=

=?

RB2=

=1?

RB0=

1?

No

Yes

No

Yes

No

APPENDIX B.1 PROGRAM FLOW CHART

Legend:

\

No No

22

0x00

b’00000001’

b’00000010’

Call delay

B

start

call main

b’00000100’



RB2=

=1?

RB3=

=1?

RB1=

=1?

No

Yes

No

Yes yes

No

APPENDIX B.2 PROGRAM FLOW CHART

23

0x00

b’00000100’

b’00000010’

Porta,

b’00000100’

A

RB5==

1?

b’0000101

’b’0000011

0’



RB6==

1?

RB6==1?

No No

Yes

Yes

No

Yes

Yes

APPENDIX E PROGRAM CODE (PIC 1)

;**********************************************************************

; This file is a basic code template for assembly code generation *

24

RB0==

1?

b’10000000’

0x00

Portb,

b’0111111’

B

RB1==

1?

b’10000000’

0x00

Portb,

b’0111111’

B



; on the PIC16F84A. This file contains the basic code *

; building blocks to build upon. *

; *

; Refer to the MPASM User's Guide for additional information on *

; features of the assembler (Document DS33014). *

; *

; Refer to the respective PIC data sheet for additional *

; information on the instruction set. *

; *

;**********************************************************************

; *

; Filename: xxx.asm *

; Date: *

; File Version: *

; *

; Author: *

; Company: *

; *

; *

;**********************************************************************

; *

; Files Required: P16F84A.INC *

; *

;**********************************************************************

; *

25



; Notes: *

; *

;**********************************************************************

list p=16F84A ; list directive to define processor

#include <p16F84A.inc> ; processor specific variable definitions

__CONFIG _CP_OFF & _WDT_OFF & _PWRTE_ON & _RC_OSC

; '__CONFIG' directive is used to embed configuration data within .asm file.

; The lables following the directive are located in the respective .inc file.

; See respective data sheet for additional information on configuration word.

;***** VARIABLE DEFINITIONS

w_temp EQU 0x0C ; variable used for context saving

status_temp EQU 0x0D ; variable used for context saving

porta equ 0x05

portb equ 0x06

mcount equ 0x0c

ncount equ 0x0d

;**********************************************************************

26



ORG 0x000 ; processor reset vector

goto main ; go to beginning of program

ORG 0x004 ; interrupt vector location

movwf w_temp ; save off current W register contents

movf STATUS,w ; move status register into W register

movwf status_temp ; save off contents of STATUS register

; isr code can go here or be located as a call subroutine elsewhere

movf status_temp,w ; retrieve copy of STATUS register

movwf STATUS ; restore pre-isr STATUS register contents

swapf w_temp,f

swapf w_temp,w ; restore pre-isr W register contents

retfie ; return from interrupt

main

movlw 0x00

tris porta

movlw b'01111111'

27



tris portb

clrf porta

bcf portb,7

start

sense_1

btfss portb,2

goto sense_1

movlw b'00000001'

movwf porta

snap_up1

btfss portb,3

goto snap_up1

movlw 0x00

movwf porta

passed_?

btfsc portb,2

goto passed_?

call delay

call delay

call delay

call delay

movlw b'00000001'

movwf porta

snap_down1

btfss portb,4

28



goto snap_down1

movlw b'00000010'

movwf porta

call delay

call delay

call delay

call delay

call delay

call delay

size_?

btfss portb,5

goto light_scale

goto heavy_scale

light_scale

movlw b'00001010'

movwf porta

dropped_light?

btfss portb,0

goto dropped_light?

movlw b'10000000'

movwf portb

gate2_clossed?

btfss portb,6

goto gate2_clossed?

movlw 0x00

29



movwf porta

bcf portb,7

goto start

heavy_scale

movlw b'00000110'

movwf porta

dropped_heavy?

btfss portb,1

goto dropped_heavy?

movlw b'10000000'

movwf portb

gate2_clossed_?

btfss portb,6

goto gate2_clossed_?

movlw 0x00

movwf porta

bcf portb,7

goto start

delay

movlw 0xff

movwf mcount

loadan

movlw 0xff

30



movwf ncount

decn

decfsz ncount,f

goto decn

decfsz mcount,f

goto loadan

return

END

31



APPENDIX E.1 PROGRAM CODE (PIC 2)

;**********************************************************************

; This file is a basic code template for assembly code generation *

; on the PIC16F84A. This file contains the basic code *

; building blocks to build upon. *

; *

; Refer to the MPASM User's Guide for additional information on *

; features of the assembler (Document DS33014). *

; *

; Refer to the respective PIC data sheet for additional *

; information on the instruction set. *

; *

;**********************************************************************

; *

; Filename: xxx.asm *

; Date: *

; File Version: *

; *

; Author: *

; Company: *

; *

32



; *

;**********************************************************************

; *

; Files Required: P16F84A.INC *

; *

;**********************************************************************

; *

; Notes: *

; *

;**********************************************************************

list p=16F84A ; list directive to define processor

#include <p16F84A.inc> ; processor specific variable definitions

__CONFIG _CP_OFF & _WDT_OFF & _PWRTE_ON & _RC_OSC

; '__CONFIG' directive is used to embed configuration data within .asm file.

; The lables following the directive are located in the respective .inc file.

; See respective data sheet for additional information on configuration word.

;***** VARIABLE DEFINITIONS

w_temp EQU 0x0C ; variable used for context saving

status_temp EQU 0x0D ; variable used for context saving

33



porta equ 0x05

portb equ 0x06

mcount equ 0x0c

ncount equ 0x0d

;**********************************************************************

ORG 0x000 ; processor reset vector

goto main ; go to beginning of program

ORG 0x004 ; interrupt vector location

movwf w_temp ; save off current W register contents

movf STATUS,w ; move status register into W register

movwf status_temp ; save off contents of STATUS register

; isr code can go here or be located as a call subroutine elsewhere

movf status_temp,w ; retrieve copy of STATUS register

movwf STATUS ; restore pre-isr STATUS register contents

swapf w_temp,f

swapf w_temp,w ; restore pre-isr W register contents

retfie ; return from interrupt

34



main

movlw 0x00

tris porta

movlw 0xff

tris portb

clrf porta

bcf porta,2

start

pic_1

btfss portb,0

goto pic_1

movlw b'00000100'

movwf porta

snap_up2

btfss portb,2

goto snap_up2

movlw 0x00

movwf porta

sense_2

btfsc portb,1

goto sense_2

movlw b'00000100'

35



movwf porta

snap_down2

btfss portb,3

goto snap_down2

movlw b'00000010' ;send to pic1

movwf porta

bcf porta,2

movlw b'00000001'

movwf porta

call delay

call delay

call delay

goto main

delay

movlw 0xff

movwf mcount

loadan

movlw 0xff

movwf ncount

decn

decfsz ncount,f

goto decn

decfsz mcount,f

goto loadan

36

sample maam

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