scrolling message display - project report - nov 15, 2011

7/29/2019 Scrolling Message Display - Project Report - Nov 15, 2011

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Chapter 1: INTRODUCTION

Human beings require some information for every sort of work. The information may

be visual or audible or as the case may be. Generally, written or visual information is

much more convenient than the other counterparts. In the present world, there is a lot

of information which needs to be displayed. May it be your laptop screen, a bank, an

airport, your cell phone, or any other public place; the required information is to be

presented in a suitable manner. The devices which are used for the purpose are called

display devices. A display device is an output device for presentation of information

in visual form. When the input information is supplied as an electrical signal, the

display is called an electronic display. Some of the very common applications for

electronic visual displays are television sets, computer monitors or cell phones. There

are a variety of electronic displays available in the market. Some displays can show

only digits or alphanumeric characters. They are called segment displays, because

they are composed of several segments that switch on and off to give appearance of

desired glyph. The segments are usually single LEDs or liquid crystals. They are

mostly used in digital watches and pocket calculators etc. These may be seven-

segment, fourteen-segment or sixteen-segment displays. Two dimensional displays

that cover a full area (usually a rectangle) are also called video displays, since it's the

main modality of presenting video. They are generally seen in television sets,

computer monitors etc. The technologies behind these devices are LEDs, LCDs,

TFTs, electroluminescent displays, plasma display panels, OLEDs, carbon nanotubes,

nano-crystal displays etc.

The display technology presented in the text uses a LED matrix for the purpose. An

LED matrix is a collection of LEDs arranged in the form of a matrix. It consists of

LEDs with their cathodes joined in the rows and the anodes joined in the rows (or vice

versa). The different characters can be produced on the matrix by switching on the

corresponding LEDs and switching off the rest. It is sometimes also called as a Dot-

Matrix. They can be used easily to represent characters, numerals and special

symbols. The model presented here uses these LED matrices to display a running text

(from right to left). These devices can be easily seen in banks, railway stations,

airports, sign boards, buses etc.


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Chapter 2: INTEL 8051 MICROCONTROLLER

2.1 INTRODUCTION

Intel Corporation introduced an 8-bit microcontroller called MCS-51 in 1981. This

microcontroller had 128 bytes of RAM, 4K bytes of on chip ROM, two timers, one

serial port, and four ports, all on a single chip. The 8051 is an 8 bit processor,

meaning that the CPU can work on only 8 bit data at a time. Data larger than 8 bits is

broken into 8 bit pieces and then processed by CPU. It has four I/O 8 bit wide ports.

The Intel MCS-51 is a Harvard architecture single chip microcontroller series which

was developed by Intel in 1981 for use in embedded systems. Intel's original versions

were popular in the 1980s and early 1990s, but has today largely been superseded by a

vast range of faster and/or functionally enhanced 8051-compatible devices

manufactured by more than 20 independent manufacturers including Atmel, Infineon

Technologies (formerly Siemens AG), Maxim Integrated Products (via its Dallas

Semiconductors subsidiary), NXP (formerly Philips Semiconductor), ST

Microelectronics, Silicon Laboratories, Texas Instruments and CypressSemiconductor.

Intel's original MCS-51 family was developed using NMOS technology, but later

versions, identified by a letter C in their name (e.g., 80C51) used CMOS technology

and were less power-hungry than their NMOS predecessors. This made them more

suitable for battery-powered devices.

Figure 2.1 A 8051 Microcontroller


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2.2 FEATURES OF 8051

o 8-bit data buso 16-bit address buso 32 general purpose registers each of 8 bitso ROM4K byteso RAM128 byteso 2 Timers (16-bit)o Four 8-bit portso 16-bit Program Counter

2.3 BLOCK DIAGRAM OF 8051

Interrupt

Control

CPU

Oscillator

On-Chip ROMfor Program

Code

On-Chip

RAM

Timer/Counter

Timer 1

Timer 0

Serial PortI/O PortsBus Control

External

Interrupts

RxD TxDP0 P1 P2P3

Figure 2.2 Block Diagram of 8051


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2.4 INTERNAL ARCHITECTURE OF 8051

The 8051 family is one of the most common microcontroller architectures used

worldwide. 8051 based microcontrollers are offered in hundreds of variants from

many different silicon manufacturers. The 8051 is based on an 8-bit CISC core with

Harvard architecture. It's an 8-bit CPU, optimized for control applications with

extensive Boolean processing (single-bit logic capabilities), 64K program and data

memory address space and various on-chip peripherals. The 8051 microcontroller

family offers developers a wide variety of high-integration and cost-effective

solutions for virtually every basic embedded control application. From traffic control

equipment to input devices and computer networking products, 8051 microcontrollers

deliver high performance together with a choice of configurations and options

matched to the special needs of each application. Whether it's low power operation,

higher frequency performance, expanded on-chip RAM, or an application-specific

requirement, there's a version of the 8051 microcontroller that's right for the job.

Figure 2.3 Basic Internal Architecture of 8051

PORT

1

PORT

2

PORT

0

PORT

31

Timers, Counters,

Interrupts, Serial Ports,

SFRs

CPU

RAM EEPROM


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2.5 MEMORY ORGANISATION IN 8051

The 8051 microcontroller has three general types of memory. They are On-Chip

memory, External code memory and External RAM. On-Chip Memory refers to any

memory (Code, RAM, or other) that physically exists on the microcontroller itself.

External Code Memory is code (or program) memory that resides off-chip. This is

often in the form of an external EPROM. External RAM is random access memory

that resides off-chip. This is often in the form of standard static RAM or flash RAM.

Figure 2.4 Memory Organisation Block Diagram of 8051

2.5.1 On-Chip Memory

The 8051s on-chip memory consists of 256 bytes. It is of generally two types viz.

internal RAM and Special Function Registers Memory (SFRs).The first 128 bytes

constitute the internal RAM. This Internal RAM is found on-chip on the 8051 so it is

the fastest RAM available, and it is also the most flexible in terms of reading, writing,

and modifying its contents. Internal RAM is volatile, so when the 8051 is reset this

memory is cleared. The internal RAM is sub-divided as Register Banks (00H to 1FH),

Bit addressable RAM (20H to 2FH), General Purpose RAM (30H to 7FH). Special

8051 Chip

Internal

RAM

Special

Function

Registers

Internal Code

Memory

(Optional)

External Code

Memory

External

RAM


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Function Registers (SFRs) are areas of memory that control specific functionality of

the 8051 processor. All addresses above 80h are assigned to SFRs. Another SFR

allows a program to read or write to the 8051s serial port. Other SFRs allow the user

to set the serial baud rate, control and access timers, and configure the 8051s interrupt

system. The memory space above 80H (80H to FFH) is allocated totally to SFRs.

2.5.2 External Code Memory

It is code (or program) memory that resides off-chip. This is often in the form of an

external EPROM. Code memory is the memory that holds the actual 8051 program

that is to be run. This memory is limited to 64K and comes in many shapes and sizes.

2.5.3 External RAM

It is a RAM memory that resides off-chip. This is often in the form of standard static

RAM or flash RAM. External RAM is any random access memory which is found

off-chip. Since the memory is off-chip it is not as flexible in terms of accessing, and is

also slower. External RAM loses in speed and flexibility it gains in quantity, While

Internal RAM is limited to 128 bytes, the 8051 supports External RAM up to 64K.

2.6 PIN DESCRIPTION OF 8051

I/O Ports: There are four ports P0, P1, P2 and P3 each use 8 pins, making them 8-bit

ports. All the ports upon reset are configured as output, ready to be used as output

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

Port 0 occupies a total of 8 pins (pins 32-39) .It can be used for input or output. Touse the pins of port 0 as both input and output ports, each pin must be connected

externally to a 10K ohm pull-up resistor. This is due to the fact that P2 is an open

drain. Open drain is a term used for MOS chips in the same way that open collector is

used for TTL chips. Port 0 is also designated as AD0-AD7, allowing it to be used for

both address and data. When connecting an 8051 to an external memory, port 0

provides both address and data. The 8051 multiplexes address and data through port 0

to save pins. ALE pin indicates if P2 has address or data. When ALE = 0, it provides


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data D0-D7, but when ALE =1 it has address and data with the help of a 74LS37

latch.

Figure 2.5 Pin Diagram of Intel 8051

Port 1 occupies a total of 8 pins (pins 1 - 8). It can be used as input or output. In

contrast to port 0, this port does not need any pull-up resistors since it already has

pull-up resistors internally. Upon reset, Port 1 is configured as an output port.

Port 2 occupies a total of 8 pins (pins 21 - 28). It can be used as input or output. Just

like P1, P2 does not need any pull-up resistors since it already has pull-up resistors

internally. Upon reset, Port 2 is configured as an output port. As shown in pin


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configuration 8051, port 2 is also designed as A8-A15, indicating the dual function.

While Port 0 provides the lower 8 bits via A0-A7, it is the job of Port 2 to provide bits

A8-A15 of the address.

Figure 2.6 External pull-up resistors connected at Port 0

Port 3 occupies a total of 8 pins (pins 1017). It can be used as input or output port.

P3 does not need any pull-up resistors, the same as P1 and P2 did not. Although port 3

is configured as an output port upon reset, it has the additional function of providing

some extremely important signals such as interrupts.P3.0 and P3.1 are used for the

Reception and Transmission of serial communication signals. P3.2 and P3.3 are set

aside for external interrupts. P3.4 and P3.5 are used for timers 0 and 1. Finally P3.6

and P3.7 are used to provide the write (WR) and read (RD) signals of external

memories.

ALE/PROG: Address Latch Enable is an 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.


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Table 2.1: Special functions of Port 3 pins

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

the 8051 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: It stands for 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 for internal program

executions. This pin also receives the 12-volt programming enable voltage (VPP)

during flash programming when 12-volt programming is selected.

XTAL1: Input to the inverting oscillator amplifier and input to the internal clock

operating circuit.

XTAL2: This pin is for output from the inverting oscillator amplifier.

GND and VCC: These two pins are the power pins of the 8051 microcontroller. Pin

20 (GND) is to be connected to the ground terminal and pin 40 (VCC) is to be

provided with DC voltage supply.

RST: This stands for reset. This pin is employed to store back the initial condition of

the microcontroller. Pin 9 is used for this reset purpose.

Port Pin IC Pin Number Alternate Functions

P3.0 10 RxD (Serial Input Port)

P3.1 11 TxD (Serial Output Port)

P3.2 12 Int0 (External Interrupt 0)

P3.3 13 Int1 (External Interrupt 1)

P3.4 14 T0 (Timer 0 External input)

P3.5 15 T1 (Timer 1 External Input)

P3.6 16 WR (External Data Memory Write Strobe)

P3.7 17 RD (External Data Memory Read Strobe)


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Chapter 3: SPECIAL FUNCTION REGISTERS OF 8051

3.1 Introduction to SFRs

The SFR registers are located within the internal memory in the address range 80H to

FFH. 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. Each SFR

has a very specific function. Each one has an address (within the range 80H to FFH)

and a name which reflects the purpose of the SFR. Out of the 128 bytes allocated to

the SFRs, only 21 SFRs have been defined in the standard 8051 architecture and the

rest of space is unspecified. Some of the SFRs are bit addressable. SFRs are addressed

just like internal RAM locations. The SFRs are set to their specified values when the

system is being reset. Each SFR has a predefined value which is assigned to it after

the system is reset.

3.2 A (ACCUMULATOR) REGISTER

This is a general-purpose register used for storing intermediate results obtained during

any operation. Prior to executing an instruction upon any number or operand, it is

necessary to store it in the accumulator first. All results obtained from arithmetical

operations performed by the ALU are stored in the accumulator. Data to be moved

from one register to another must go through the accumulator. In other words, the

accumulator register is the most commonly used register and it is impossible to

imagine a microcontroller without it. More than half instructions used by the 8051

microcontroller use somehow the accumulator.

D7 (MSB) D6 D5 D4 D3 D2 D1 D0 (LSB)

Figure 3.1 Bit Pattern of Accumulator Register


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Table 3.1: SFR Map of AT89C52

Special Function Registers

F8H - - - - - - - - FFH

F0H B* - - - - - - - F7H

E8H - - - - - - - - EFH

E0H A* - - - - - - - E7H

D8H - - - - - - - - DFH

D0H PSW* - - - - - - - D7H

C8H - - - - - - - - CFH

C0H - - - - - - - - C7H

B8H IP* - - - - - - - BFH

B0H P3* - - - - - - - B7H

A8H IE* - - - - - - - AFH

A0H P2* - - - - - - - A7H

98H SCON* SBUF - - - - - - 9FH

90H P1* - - - - - - - 97H

88H TCON* TMOD TL0 TL1 TH0 TH1 - - 8FH

80H P0* SP DPL DPH - - - PCON 87H

Note: * indicates the SFRs which are Bit-Addressable


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3.3 B REGISTER

Multiplication and division can be performed only upon numbers stored in the A and

B registers. All other instructions in the program can use this register as a spare

accumulator. It is important to note that during the process of writing a program, each

register is called by its name so that their exact addresses are not of importance for the

user. During compilation, their names will be automatically replaced by appropriate

addresses.

3.4 PSW REGISTER

This is Program Status Word. It is one of the most important SFRs. It contains several

status bits that reflect the current state of the CPU. Besides, this register contains

Carry bit, Auxiliary Carry, two register bank select bits, Overflow flag, parity bit and

user-definable status flag.

CY AC F0 RS1 RS0 OV - P

Figure 3.2 Bit Pattern of PSW register

P (Parity Bit): If a number stored in the accumulator is even then this bit will be

automatically set to 1, otherwise it will be cleared (0). It is mainly used during data

transmit and receive via serial communication.

Bit 1: This bit is intended to be used in the future versions of microcontrollers.

OV: Overflow occurs when the result of an arithmetical operation is larger than 255

and cannot be stored in one register. Overflow condition causes the OV bit to be set to

1; otherwise it will be cleared.

RS0, RS1: These are register bank select bits. These two bits are used to select one of

four register banks of RAM. By setting and clearing these bits, registers R0-R7 are

stored in one of four banks of RAM.


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Table 3.2: Combinations of RS1 and RS0 for register bank selection

RS1 RS0 Space in RAM

0 0 Bank0 (00H - 07H)

0 1 Bank1 (08H0FH)

1 0 Bank2 (10H-17H)

1 1 Bank3 (18H1FH)

F0: This is Flag 0 and is a general-purpose bit available for use.

AC: Auxiliary Carry Flag is used for BCD operations only.

CY: Carry Flag is the auxiliary bit used for all arithmetical operations and shift

instructions.

3.5 DPTR

This is data pointer register. DPTR register is not a true one because it doesn't

physically exist. It consists of two separate registers: DPH and DPL. For this reason it

may be treated as a 16-bit register or as two independent 8-bit registers. Their 16 bits

are primarily used for external memory addressing. Besides, the DPTR register is

usually used for storing data and intermediate results.

D15 D8 D7 D0

Figure 3.3 Bit Pattern of Data Pointer Register (16 bits)

DPH DPL


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3.6 SP Register

This is stack pointer register. A value stored in the stack pointer points to the first free

stack address and permits stack availability. Stack pushes increment the value in the

stack pointer by 1. Likewise, stack pops decrement its value by 1. Upon any reset and

power-on, the value 7 (00000111) is stored in the Stack Pointer, which means that the

space of RAM reserved for the stack starts at this location. If another value is written

to this register, the entire stack is moved to the new memory location.

3.7 IE (Interrupt Enable) Register

This is also an 8-bit register and is used for enabling and disabling of the interrupts in

the microcontroller. The interrupts may be generated by timers (T1 and T0), external

interrupts or serial interrupts.

EA - ET2 ES ET1 EX1 ET0 EX0

Figure 3.4 Bit Pattern of Interrupt Enable (IE) Register

Table 3.3: Functions of various bits of IE register

Bit Name If Set If Reset

EA Enables all Interrupt Requests Disables all Interrupt Requests

ES Enables Serial Interrupt Disables Serial Interrupt

ET1 Enables Timer 1 Interrupt Disables Timer 1 Interrupt

EX1 Enables External Interrupt 1 Disables External Interrupt 1

ET0 Enables Timer 0 Interrupt Disables Timer 0 Interrupt

EX0 Enables External Interrupt 0 Disables External Interrupt 0


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3.8 IP (INTERRUPT PRIORITY) REGISTER

It is not possible to foreseen when an interrupt request will arrive. If several interrupts

are enabled, it may happen that while one of them is in progress, another one is

requested. In order that the microcontroller knows whether to continue operation or

meet a new interrupt request, there is a priority list instructing it what to do.

- - PT2 PS PT1 PX1 PT0 PX0

Figure 3.5 Bit Pattern of Interrupt Priority (IP) Register

The priority list offers 3 levels of interrupt priority i.e. Reset; the absolute master;

when a reset request arrives, everything is stopped and the microcontroller restarts.

Interrupt priority 1 can be disabled by Reset only. Interrupt priority 0 can be disabled

by both Reset and interrupt priority 1.

3.9 INPUT/OUTPUT REGISTERS

If neither external memory nor serial communication system are used then 4 ports

within total of 32 input/output pins are available for connection to peripheral

environment. Each bit within these ports affects the state and performance of

appropriate pin of the microcontroller. Thus, bit logic state is reflected on appropriate

pin as a voltage (0 or 5 V) and vice versa, voltage on a pin reflects the state of

appropriate port bit. If a bit is cleared, the appropriate pin will be configured as

output, while if it is set, the appropriate pin will be configured as input. Upon reset

and power-on, all port bits are set, which means that all appropriate pins will be

configured as inputs.

PX7 PX.6 PX.5 PX.4 PX.3 PX.2 PX.1 PX.0

Figure 3.6 Bit Pattern of Port (P0, P1, P2, P3) SFRs


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3.10 TIMERS AND COUNTERS

The microcontroller oscillator uses quartz crystal for its operation. As the frequency

of this oscillator is precisely defined and very stable, pulses it generates are always of

the same width, which makes them ideal for time measurement. In order to measure

time between two events it is sufficient to count up pulses coming from this oscillator.

That is exactly what the timer does. If the timer is properly programmed, the value

stored in its register will be incremented (or decremented) with each coming pulse.

3.10.1 Timers in 8051

The 8051 microcontroller has 2 timers/counters called T0 and T1. They can be used

for generating clock pulses to be used in serial communication, also called Baud Rate.

The timers T0 and T1 are both 16 bits wide. Each timer is accessed as two separate

registers of lower byte and higher byte. Both the timers (T1 and T0) use a common

register TMOD that control their operation and operating modes.

D15 D8 D7 D0

Figure 3.7 Timer 1/0

3.10.2 TMOD Register

The TMOD register selects the operational mode of the timers T0 and T1. As seen in

figure below, the low 4 bits (0 - 3) refer to the timer 0, while the high 4 bits (4 - 7)

refer to the timer 1. There are 4 operational modes and each of them is described

herein.

GATE1 C/T1 T1M1 T1MO GATE2 C/T0 T0M1 T0M0

Figure 3.8 Bit Pattern of TMOD Register

GATE1 enables and disables Timer 1 by means of a signal brought to the INT1 pin

(P3.3). For GATE1 set, Timer 1 operates only if the INT1 bit is set else, Timer 1operates regardless of the logic state of the INT1 bit. C/T1 selects pulses to be

TH 1/0 TL 1/0


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counted up by the timer/counter. If set, Timer counts pulses brought to the T1 pin

(P3.5), else Timer counts pulses from internal oscillator. GATE0 enables and disables

Timer 0 using a signal brought to the INT0 pin (P3.2). For GATE0 set, Timer 0

operates only if the INT0 bit is set, else Timer 0 operates regardless of the logic state

of the INT0 bit. C/T0 selects pulses to be counted up by the timer/counter 0. If set,

Timer counts pulses brought to the T0 pin (P3.4), else Timer counts pulses from

internal oscillator. The various modes of operation of these timers are as described in

the table below. The bits T1M1 and T1M0 select the operational mode for Timer 1

and the bits T0M1 and T0M) select the modes for Timer 0.

Table 3.4: Modes of operation of timers 1/0 defined in TMOD register

M1 M0 Mode of Operation

0 0 13 Bit Timer

0 1 16 Bit Timer

1 0 8 Bit Auto-Reload

1 1 Split Mode

Table 3.5: Reset Values of various SFRs:

SFR Reset Value SFR Reset value

B 00000000 TCON 00000000

A 00000000 TMOD 00000000

PSW 00000000 TL0 00000000

IP XX000000 TL1 00000000

P3 11111111 TH0 00000000

IE 0X000000 TH1 00000000

P2 11111111 P0 11111111

SCON 00000000 SP 00000111

SBUF XXXXXXXX DPL 00000000

P1 11111111 DPH 00000000


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Chapter 4: COMPONENTS DESCRIPTION

4.1 LED

A light-emitting diode (LED) is a semiconductor light source. They are used as

indicator lamps in many devices and are increasingly used for other lighting. Early

LEDs emitted low-intensity red light, but modern versions are available across the

visible, ultraviolet and infrared wavelengths, with very high brightness. When a light-

emitting diode is forwardbiased (switched on), electrons are able to recombine with

electron holes within the device, releasing energy in the form of photons. This effect

is called electroluminescence and the colourof the light (corresponding to the energy

of the photon) is determined by the energy gap of the semiconductor. LEDs are often

small in area (less than 1 mm2), and integrated optical components may be used to

shape its radiation pattern.

Figure 4.1 Electronic symbol of an LED

LEDs present many advantages over incandescent light sources including lower

energy consumption, longer lifetime, improved robustness, smaller size, and faster

switching. However, LEDs which are powerful enough for room lighting are

relatively expensive and require more precise current and heat management than

compact fluorescent lamp sources of comparable output.

Light-emitting diodes are used in applications as diverse as replacements foraviation

lighting, automotive lighting (particularly brake lamps, turn signals and indicators) as

well as in traffic signals. LEDs have allowed new text, video displays, and sensors to

be developed, while their high switching rates are also useful in advanced

communications technology. Infrared LEDs are also used in the remote control units

of many commercial products including televisions, DVD players, and other domestic

appliances.
http://en.wikipedia.org/wiki/Semiconductorhttp://en.wikipedia.org/wiki/Lightinghttp://en.wikipedia.org/wiki/Visible_spectrumhttp://en.wikipedia.org/wiki/Ultraviolethttp://en.wikipedia.org/wiki/Infraredhttp://en.wikipedia.org/wiki/Semiconductor_diodehttp://en.wikipedia.org/wiki/Voltage_biashttp://en.wikipedia.org/wiki/Electronshttp://en.wikipedia.org/wiki/Carrier_generation_and_recombinationhttp://en.wikipedia.org/wiki/Electron_holehttp://en.wikipedia.org/wiki/Photonhttp://en.wikipedia.org/wiki/Electroluminescencehttp://en.wikipedia.org/wiki/Colorhttp://en.wikipedia.org/wiki/Energy_gaphttp://en.wikipedia.org/wiki/Led#Advantageshttp://en.wikipedia.org/wiki/Energy_conservationhttp://en.wikipedia.org/wiki/Energy_conservationhttp://en.wikipedia.org/wiki/Service_lifehttp://en.wikipedia.org/wiki/Thermal_management_of_high-power_LEDshttp://en.wikipedia.org/wiki/Fluorescent_lamphttp://en.wikipedia.org/wiki/Navigation_light#Aviation_navigation_lightshttp://en.wikipedia.org/wiki/Navigation_light#Aviation_navigation_lightshttp://en.wikipedia.org/wiki/Automotive_lighting#Light_emitting_diodes_.28LED.29http://en.wikipedia.org/wiki/LED#Indicators_and_signshttp://en.wikipedia.org/wiki/Traffic_signalhttp://en.wikipedia.org/wiki/Infraredhttp://en.wikipedia.org/wiki/Remote_controlhttp://en.wikipedia.org/wiki/Remote_controlhttp://en.wikipedia.org/wiki/Infraredhttp://en.wikipedia.org/wiki/Traffic_signalhttp://en.wikipedia.org/wiki/LED#Indicators_and_signshttp://en.wikipedia.org/wiki/Automotive_lighting#Light_emitting_diodes_.28LED.29http://en.wikipedia.org/wiki/Navigation_light#Aviation_navigation_lightshttp://en.wikipedia.org/wiki/Navigation_light#Aviation_navigation_lightshttp://en.wikipedia.org/wiki/Fluorescent_lamphttp://en.wikipedia.org/wiki/Thermal_management_of_high-power_LEDshttp://en.wikipedia.org/wiki/Service_lifehttp://en.wikipedia.org/wiki/Energy_conservationhttp://en.wikipedia.org/wiki/Energy_conservationhttp://en.wikipedia.org/wiki/Led#Advantageshttp://en.wikipedia.org/wiki/Energy_gaphttp://en.wikipedia.org/wiki/Colorhttp://en.wikipedia.org/wiki/Electroluminescencehttp://en.wikipedia.org/wiki/Photonhttp://en.wikipedia.org/wiki/Electron_holehttp://en.wikipedia.org/wiki/Carrier_generation_and_recombinationhttp://en.wikipedia.org/wiki/Electronshttp://en.wikipedia.org/wiki/Voltage_biashttp://en.wikipedia.org/wiki/Semiconductor_diodehttp://en.wikipedia.org/wiki/Infraredhttp://en.wikipedia.org/wiki/Ultraviolethttp://en.wikipedia.org/wiki/Visible_spectrumhttp://en.wikipedia.org/wiki/Lightinghttp://en.wikipedia.org/wiki/Semiconductor


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4.2 RESISTOR

A linear resistor is a linear, passive two-terminal electrical component that

implements electrical resistance as a circuit element. The current through a resistor is

in direct proportion to the voltage across the resistor's terminals. Thus, the ratio of the

voltage applied across a resistor's terminals to the intensity of current through the

circuit is called resistance. The commercially available resistors vary in their peak

power dissipation capability. The most common versions available are 0.25W, 0.5W,

1W and 2W.Resistors are common elements of electrical networks and electronic

circuits and are ubiquitous in most electronic equipment. Practical resistors can be

made of various compounds and films, as well as resistance wire (wire made of a

high-resistivity alloy, such as nickel-chrome). Resistors are also available in SIP

(Single Inline Package) forms, wherein a number of individual resistors are packed in

one case with their one terminal common and the other terminals as open.

Figure 4.2 General appearance of an electrical resistor

The resistors available in the market have coloured bands printed on them. The value

of a resistor can be easily calculated by using these bands. The colour of first band

indicates the first digit; second band indicates the second digit; third band indicates

the multiplier value and the fourth band indicates the tolerance value of the resistor.

The values for various colours are as shown in the table. For example, if the colour

bands are in the order yellow, violet, red and gold; it shows that the resistors value is

4.7 K with a tolerance value of 5%.

First Digit Second Digit

Multiplier

Tolerance


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Table 4.1: Resistance Colour Codes

Colour 1st

Digit 2nd

Digit Multiplier Tolerance

Black 0 0 10 -

Brown 1 1 10 -

Red 2 2 102 -

Orange 3 3 10 -

Yellow 4 4 10 -

Green 5 5 105 -

Blue 6 6 10 -

Violet 7 7 10 -

Grey 8 8 10 -

White 9 9 10 -

Gold - - 10- 5%

Silver - - 10- 10%

None - - - 20%

4.3 Capacitor

A capacitor is a passive two-terminal electrical component used to store energy in an

electric field. The forms of practical capacitors vary widely, but all contain at least

two electrical conductors separated by a dielectric. When there is a potential

difference (voltage) across the conductors, a static electric field develops across the

dielectric (insulator), causing positive charge to collect on one plate and negative

charge on the other plate. Energy is stored in the electrostatic field. Capacitors are

widely used in electronic circuits for blocking direct current while allowing

alternating current to pass, in filter networks, in the resonant circuits and for many

other purposes. An ideal capacitor is characterized by a constant value, capacitance,


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measured in farads. This is the ratio of the electric charge on each conductor to the

potential difference between them. Capacitors are of two types: Electrolytic

Capacitors and Non-electrolytic capacitors. Non-electrolytic capacitors may be

ceramic, paper, polystyrene, glass capacitors etc.

Figure 4.3 Typical shape (cylindrical) of an electrolytic capacitor

4.4 DIODE

In electronics, a diode is a type of two-terminal electronic component with a nonlinear

currentvoltage characteristic. A semiconductor diode is a crystalline piece of

semiconductor material connected to two electrical terminals. The most common

function of a diode is to allow an electric current to pass in one direction (called the

diode's forward direction), while blocking current in the opposite direction (thereverse direction). Thus, the diode can be thought of as an electronic version of a

check valve. This unidirectional behaviour is called rectification, and is used to

convert alternating current to direct current, and to extract modulation from radio

signals in radio receivers.

Figure 4.4 Electronic symbol and packaging of a diode

2200uF/

50V

Anode Cathode


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4.5 CRYSTAL

The crystal used in a typical 8051 system is of frequency 11.0592 Mega Hertz. For

8051 system, we have to use two non-electrolytic capacitor of value 30pF in

conjunction with the crystal as shown in the figure. Some of the salient features of

the crystal are as listed below:

o Output Frequency: 11.0592 MHzo Frequency Tolerance:30ppmo Load Capacitance:18pFo Frequency Stability: 0ppmo

Operating Temperature Range:-40C to +85Co Crystal Mounting Type:SMDo No. of Pins: 2o Accuracy:30ppmo Temperature Stability: 50ppm

Figure 4.5 Typical arrangement for oscillator circuitry in an 8051 system

4.6 LM7805

The LM78XX series of three terminal positive regulators are available in the TO-220

package and with several fixed output voltages, making them useful in a wide range

of applications.For ICs within the family, the xx is replaced with two digits, indicating

the output voltage (for example, the 7805 has a 5 volt output, while the 7812 produces

12 volts). Each type employs internal current limiting, thermal shut down and safe

C2

30pF

C1

30pF

XTAL2

XTAL1

GND


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operating area protection, making it essentially indestructible. If adequate heat sinking

is provided, they can deliver over 1A output current. Although designed primarily as

fixed voltage regulators, these devices can be used with external components to obtain

adjustable voltages and currents.

Table 4.2: List of various Fixed Voltage Regulator ICs

Positive Voltage Regulators Negative Voltage Regulators

IC Number Output IC Number Output

LM7805 5 Volts LM7905 -5 Volts





4.7 AT89C52 MICROCONTROLLER

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

8K bytes of flash programmable and erasable read only memory. The device is

manufactured using Atmels high-density non-volatile 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 non-volatile memory programmer. It is available in a variety ofpackaging case viz. Dual Inline Package (DIP) having 40 pins; Plastic Leaded Chip

Carrier (PLCC) having 44 pins; Thin Quad Flat Pack (TQFP) having 44 pins.

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, programmable serial channel,

three level program memory lock, and clock circuitry. By combining a versatile 8-bit

CPU with flash on a monolithic chip, the Atmel AT89C52 is a powerful


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

embedded control applications.

The first 128 bytes of the internal RAM is allocated to the special function registers as

in standard 8051. But the number of SFRs in AT89C52 is greater than in standard

8051 architecture. There are a total of 27 special function registers in AT89C52. The

additional six SFRs are T2CON, T2MOD, TL2, TH2, RCAP2L and RCAP2H.The

registers TL2 and TH2 comprise the Timer 2 whereas the registers T2MOD and

T2CON contain the control and the status bits for the timer 2. The register pair

(RCAP2H, RCAP2L)is the Capture/Reload register for timer 2 in 16-bit capture mode

or 16-bit auto-reload mode.

4.8 SHIFT REGISTER (74164)

In digital circuits, a shift register is a cascade of flip flops, sharing the same clock,

which has the output of any one but the last flip-flop connected to the "data" input of

the next one in the chain, resulting in a circuit that shifts by one position the one-

dimensional "bit array" stored in it, shifting in the data present at its input and shiftingout the last bit in the array, when enabled to do so by a transition of the clock input.

Shift registers can have both parallel and serial inputs and outputs. These are often

configured as serial-in parallel-out (SIPO) or as parallel-in serial-out (PISO). There

are also types that have both serial and parallel input and types with serial and parallel

output. There are also bi-directional shift registers which allow shifting in both

directions i.e. left to right or right to left. The serial input and last output of a shift

register can also be connected together to create a circular shift register. One of the

most common uses of a shift register is to convert between serial and parallel

interfaces. This is useful as many circuits work on groups of bits in parallel, but serial

interfaces are simpler to construct. Shift registers can be used as simple delay circuits.

The shift register used in the model is Motorolas SN74LS164N. It is a high speed 8

bit Serial-In Parallel-Out (SIPO) Shift Register. It is available as a 14 pin IC in DIP

(Dual Inline Package) case. Serial data is entered through a 2-Input AND gate

synchronous with the LOW to HIGH transition of the clock. The device features an


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asynchronous Master Reset which clears the register setting all outputs LOW

independent of the clock. It utilizes the schottky diode clamped process to achieve

high speeds and is fully compatible with all Motorola TTL products. The pin diagram

of the IC is as shown below.

Figure 4.6 Pin Diagram of SN74LS164N

The SN74LS164N is an edge-triggered 8-bit shift register with serial data entry and

an output from each of the eight stages. Data is entered serially through one of two

inputs (A or B); either of these inputs can be used as an active HIGH Enable for data

entry through the other input. An unused input must be tied HIGH, or both inputs

connected together. Each low-to-high transition on the clock (CP) input shifts data

one place to the right and enters into Q0 the logical AND of the two data inputs, that

existed before the rising clock edge. A LOW level on the Master Reset (MR) input

overrides all other inputs and clears the register asynchronously, forcing all Q outputs

to low state.

4.9 PRINTED CIRCUIT BOARD

4.9.1 Introduction

A printed circuit board, or PCB, is used to mechanically support and electricallyconnect electronic components using conductive pathways, tracks or signal traces

14 813 12 11 10 9

1 72 3 4 5 6

VCC Q7 Q6 Q5 Q4 #MR CP

A B Q0 Q1 Q2 Q3 GND


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etched from copper sheets laminated onto a non-conductive substrate. It is also

referred to as printed wiring board (PWB) or etched wiring board. Printed circuit

boards are used in virtually all but the simplest commercially produced electronic

devices.

Conducting layers are typically made of thin copper foil. Insulating layers dielectrics

are typically laminated together with epoxy resin prepeg. The board is typically

coated with a solder mask that is green in colour. Some of these dielectrics are poly-

tetra-fluoro-ethylene (Teflon), FR-1, FR-4, CEM-1 and CEM-3. Well known prepreg

materials used in the PCB industry are FR-2, FR-3, FR-4, FR-5, FR-6, G-10, CEM-1,

CEM-2, CEM-3, CEM-4, and CEM-5. The board with copper on it is called copper-

clad laminate. Copper foil thickness can be specified in ounces per square foot or

micrometres.

4.9.2 Printing Process

There are a number of sequential steps to print a circuit board which is briefly

explained as follows.

oCleaning: The copper clad board is washed in order to remove dirt, dust, oxidegrease or any particle impurities from its surface.

o Designing: The layout for the actual PCB is to be developed in dedicatedcomputer software. The layout takes care of all the dimensions of the

components and wiring.

o Printing: Once the layout has been developed in the software, take the print onthe butter paper using a laser printer. Then press the butter paper against the

copper board and hold it firmly. Then a hot iron is to be pressed over it a

number of times so that the pattern over the paper is completely transferred on

to the copper board.

o Etching: For etching of the plates take a utensil and wash it properly. Foretching, take water in the utensil, just enough to complete immerse the board.

Add 230 grams of ferric chloride carefully without splashing and place the

PCB inside the utensil. Place the plate in utensil with the copper side up such

that the copper side is completely immersed in solution. After sometime the


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copper side etches and the base material could not thus, the etching process is

completed.

o Drilling: When the PCB dries, drilling needs to be done. The holes should beexactly placed so that the component fix exactly in the holes without any

bending of leads. For the drilling of holes, place it on the proper position.

Always ensure that the copper lines passage near the holes.

o Washing: The paint of pattern is removed by rubbing it with rag to see theentire copper pattern. Now wash the PCB in water. The PCB is complete after

this step.

4.9.3 Advantages of PCBs:

o Reduced wiring error.o Easier component mounting.o Cost is less.o More reliable.o Reduced size and weight.


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CHAPTER 5: DETAILED DESCRIPTION OF THE PROJECT

5.1 POWER SUPPLY UNIT

Every electronic system requires a suitable power supply to perform its operation. If

the power supply is not available to the system, it is not going to work by any means.

It is just like as we humans need energy (taken by food) to do our work, an electronic

system needs a power supply to perform its task. The specification of a power supply

depends on the power requirement of the system and this requirement is determined

by its rating of the system. The main components used in supply system are:

o Transformero Rectifiero Input Filtero Voltage Regulatoro Output Indication

5.1.1 Transformer

The main source of power supply is a transformer. Transformers convert AC

electricity from one voltage to another with little loss of power. Transformers work

only with AC. The input coil is called the primary coil and the output coil is called the

secondary coil. There is no electrical connection between the two coils; instead they

are linked by an alternating magnetic field created in the soft-iron core of the

transformer. The two lines in the middle of the circuit symbol represent the core.

Transformers are of two types: Step-Up and Step-Down. Step-up transformers

increase the applied voltage whereas step-down transformers reduce the applied

voltage. The ratio of the number of turns on each coil, called the turns ratio,

determines the ratio of the voltages. A step-down transformer has a large number of

turns on its primary coil which is connected to the high voltage mains supply, and a

small number of turns on its secondary coil to give a low output voltage. The

maximum output power of a power supply is dependent on maximum output power of

the transformer. We determine power from its current and voltage rating. e.g.: if there

is a transformer of 12V, 500mA then maximum power delivered by transformer is


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6Watt. It means we can drive a load from this transformer up to 6w. A step down

transformer is to be used in a power supply since we generally require either 5 volts or

12 volts for electronic systems.

Figure 5.1 Electrical Symbol of a Step-Down Transformer

5.1.2 Rectifier

It is a circuit arrangement which is used to convert AC to DC. Every electronic circuit

requires a rectifier circuit. Generally a bridge rectifier is employed in electronic

circuits in which four diodes are used.

Figure 5.2 Typical arrangement for a Bridge Rectifier

5.1.3 Input Filter

After rectification, we obtain DC power from AC; but it is a pulsating DC as it has

AC ripples in it. In order to reduce these ripples we use filters. To reduce low

frequency ripples we use electrolytic capacitors. The voltage rating of the capacitor

must be double from incoming DC supply.

Figure 5.3 Smoothed DC Output


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The process of removing ripples is also called as smoothing. Smoothing is performed

by a large value electrolytic capacitor (as mentioned above) connected across the DC

supply to act as a reservoir, supplying current to the output when the varying DC

voltage from the rectifier is falling. The capacitor charges quickly near the peak of the

varying DC, and then discharges as it supplies current to the output.

5.1.4 Voltage Regulator

Voltage regulator is a device which provides constant output voltage for a varying

input voltage. They are of two types:

o Fixed Voltage Regulatorso Adjustable Voltage Regulators

Fixed voltage regulators have a fixed value at the output terminal when a varying

input is applied. These can be 78XX or 79XX. The 78XX series represent positive

fixed voltage regulators and the 79XX series represent the negative fixed voltage

regulators. The last two digits represent the output voltage value. On the other hand,

adjustable voltage regulators provide the feature of adjusting their output voltage by

changing some external resistance values.

Figure 5.4 Circuit Symbol of a Regulator Figure 5.5 7805 Voltage Regulator

5.1.5 Output Indication

Generally an LED is used to indicate that the output voltage. The LED is connected

between the regulator output and the ground terminals. If the LED glows, it means

that the circuit is working.


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Figure 5.6 Block Diagram of a Power Supply

Figure 5.7 Circuit Diagram of a Power Supply

5.2 PRINTED CIRCUIT BOARD

The circuit boards for the model have been printed by using chemical etching process.

First of all, a layout of the LED matrix is made on the dedicated software program.

The layout of the matrix is as shown in figure. It consists of spaces for LEDs arrangedin the form of a rectangular matrix. Each character that will be formed on the matrix

will require certain number of rows and columns. The cathodes of all the LEDs are to

be connected together to ground terminal. Then the layout for the circuit board has

been prepared on the same software program. It is also shown in the figure below.

The chemical used for the etching purpose was ferric chloride powder (aqueous

solution). The copper clad board was printed with the layout printed on a butter paper

Transformer Bridge Rectifier Smoothing

Voltage Regulator

230 VoltAC

Regulated DC


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and then etched with ferric chloride. The tracks remained on to the board and the rest

of copper was removed due to etching process.

Figure 5.8 Layout for LED Matrix

Figure 5.9 Layout for Circuit Board

5.3 DISPLAY UNIT

The heart of the model is its display unit i.e. the LED Matrix. The information to be

shown is displayed on this matrix itself. Each character which is to be displayed can

be formed by glowing appropriate LEDs and turning off the rest. The size of the


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character can vary according to the design. The character size may be 7*5 or 8*5 or

8*8 and so on. Generally the matrix is made by connecting the cathodes in rows and

anodes in columns (or vice versa). In this model, a slightly different approach is

employed. All the cathodes have been made common and are connected to ground.

The anode terminals are left open and are to be connected to the signal pins.

Figure 5.10 Two 7*5 LED matrices placed together

Now the main problem in the display unit is how to make the characters on the

matrix. This is explained by the following figure. Suppose we have to print A on the

matrix as shown. Suppose the display is 8*5 and the anodes are connected in rows and

the cathodes are connected in columns. Now in order to make an LED glow, we have

to identify the corresponding row and column and then send a high signal to the anode

and a low signal to the cathode. This will make the LED forward bias, and the LED

will glow.

This was the case for a single LED. If we have to print an entire character; as in the

model; then we have to provide the suitable signals to the complete column at a one

time and then to the next column and so on. This process should be so fast that the eye


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cannot observe the flickering of the LEDs.Now for letter A, we will have to transmit

the signal at column 1 as 01111110 as shown; at second column as 00010001 ans

so on. So, the complete code for letter A would be 7EH,11H,11H,11H,7EH. The time

period for shifting of values from one column to another should be fast enough so as

to be notiiced by the eyes. Likewise letter A, all the other characters, numerals and

special symbols can be displayed on the matrix.

Figure 5.11 Formation of letter A on the Matrix

5.4 CIRCUIT DESCRIPTION

The microcontroller (AT89C52) has been provided the clock through a crystal

oscillator (frequency is 11.0592 MHz) and two 33pF capacitors. The reset circuitry

consists of a 10uF/25V capacitor and a 10K resistance. The pins P3.6 (16) and P3.7

(17) are used for providing clear to the controller and clock to the shift registersrespectively. Next is the Port 2. The pins of port 2 are directly connected to the inputs

of shift registers as shown in the figure. The clock input of the shift registers are

connected to pin P3.7 of the controller as it is providing the clock to the shift registers.

The outputs of the shift registers are connected to the anodes of the LEDs. The

cathodes of all the LEDs are common and connected to ground. Each shift register

controls an entire row and hence seven shift registers are required to display a single

character. This can be observed from the figure as well that seven shift registers have

been used for one character.


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5.5 CIRCUIT DIAGRAM

Figure 5.12 Basic Circuit Diagram of the model

5.6 OPERATING PROCEDURE

The operating principle of this circuit lies in the basic idea of shift registers. As some

serial data is given to the shift registers, with each incoming clock, the data is shifted

outwards. The data enters at the input pin of the register through the controller and

with each incoming clock, the serial data travels from QA to QH. Data is provided to

these registers through port 2 of the microcontroller.

As the data is available at the input of shift registers, this data is displayed on the LED

matrix in the first column at the next clock transition. Then at the next clock, new data

is available at the input while the previous data is shifted in each register and hence

displayed on the second column while the fresh data is displayed at the first column.

Likewise, a complete character can be displayed on the board in five clock cycles. In

this way, the data will be shifted from right to left and will appear as if it is moving

from left to right.


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5.7 PROJECT COST

Table 5.1: Cost of various components

S. No. PARTS AND COMPONENTS COST (IN RS.)

1. PCB 1200

2. SOLDERING IRON AND SOLDER WIRE 200

3. TRANSFORMER 100

4. LM7805 20

5. RESISTORS, CAPACITORS AND DIODES 60

6. LED 200

7. AT89C52 150

8. SN741LS164N 600

9. WIRES AND CONNECTORS 100

10. GENERAL PURPOSE PCB 70

11. OTHERS 500


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CONCLUSION AND FUTURE SCOPE

The concept of displaying a scrolling message on LED matrices has emerged as a

very great tool for conveying useful information at public places. May it be a bank, an

airport or a railway station, retail showrooms, cinema halls and hospitals etc. It can be

employed at every place where some information needs to be displayed. The message

is easy to read as it moves at a reasonable speed. Moreover the language to be

displayed on the board is not restricted to English only. The message can be displayed

in any language; the program needs to be written accordingly.

The present model is a static one, i.e. if a new message is to be displayed; the

programming needs to be changed. This model can be further extended for dynamic

messages i.e. the user just types the desired message using a standard QWERTY

keyboard and the message will be show on the display. This can be achieved by

interfacing a keyboard and an external flash memory unit (for storing the typed

message) with the microcontroller. The typed message will be first stored in the

memory and then the microcontroller will fetch the data from the memory itself.


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REFERENCES

Referred Books

1. Mohammed Ali Mazidi, The 8051 Microcontroller and Embedded SystemsUsing Assembly And C, 2ndEdition, Pearson Education, 2007

2. Robertl L. Boylestad, Loius Nashelsky, Electronic Devices and CircuitTheory, 9thEdition, Pearson Education, 2007

3. Owen Bishop, Electronics Circuits and Systems, 2nd Edition, Newnes, 20034. Paul Horowitz, Winfield Hill, The Art of Electronics, 2nd Edition, 20015. Loius E. Frenzel Jr., Crash Course in Electronics Technology, Howard W.

Sama & Company, 1

st

Edition, 1989.

Referred Websites

1. www.wikipedia.org2. www.mikroe.com3. www.alldatasheet.com4. www.hackaday.com


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APPENDIX (A)

SOURCE CODE

org 000

clr a

mov p3,a

mov p2,a

setb p3.6

main: mov p2,#00h

call tran

call delay44

call j

call s

call r

call w1

call gap

call e1

call gap

call l1

call gap

call c1

call gap


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call o1

call gap

call m1

call gap

call e1 //WELCOME

call gap

call gap

call t11

call gap

call o1 //TO

call gap

call gap

call m1

call gap

call dot

call gap

call m1

call gap

call dot

call gap //M M

CALL gap


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call e1

call gap

call n1

call gap

call g1

call gap

call i1

call gap

call n1

call gap

call e1

call gap

call e1

call gap

call r11

call gap

call i1

call gap

call n1

call gap

call g1


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call gap // ENGINEERING

call gap

call C1

call gap

call O1

call gap

call L1

call gap

call L1

call gap

call E1

call gap

call G1

call gap

call E1

call gap

call J

call s

call r

call gap

call gap


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call gap

call gap

call gap

call gap

call gap

call gap

jmp main

w1: clr a

mov a,#0ffh

mov p2,a

call tran

call delay44

mov a,#20h

mov p2,a

call tran

call delay44

mov a,#10h

mov p2,a

call tran

call delay44


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44

mov a,#20h

mov p2,a

call tran

call delay44

clr a

mov a,#0ffh

mov p2,a

call tran

call delay44

ret

H1: clr a

mov a,#0ffh

mov p2,a

call tran

call delay44

mov a,#08h

mov p2,a

call tran

call delay44

mov a,#08h

mov p2,a


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call tran

call delay44

mov a,#08h

mov p2,a

call tran

call delay44

clr a

mov a,#0ffh

mov p2,a

call tran

call delay44

ret

B1: clr a

mov a,#0ffh

mov p2,a

call tran

call delay44

mov a,#49h

mov p2,a

call tran

call delay44


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mov a,#49h

mov p2,a

call tran

call delay44

mov a,#49h

mov p2,a

call tran

call delay44

clr a

mov a,#36h

mov p2,a

call tran

call delay44

ret

e1: clr a

mov a,#0ffh

mov p2,a

call tran

call delay44

mov a,#49h

mov p2,a


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call tran

call delay44

mov a,#49h

mov p2,a

call tran

call delay44

mov a,#41h

mov p2,a

call tran

call delay44

ret

GAP: clr a

mov a,#70h

mov p2,a

call tran

call delay44

mov a,#70h

mov p2,a

call tran

call delay44

mov a,#70h


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mov p2,a

call tran

call delay44

ret

a1: clr a

mov a,#7eh

mov p2,a

call tran

call delay44

mov a,#11h

mov p2,a

call tran

call delay44

mov a,#11h

mov p2,a

call tran

call delay44

mov a,#11h

mov p2,a

call tran

call delay44


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clr a

mov a,#7eh

mov p2,a

call tran

call delay44

ret

l1: clr a

mov a,#0ffh

mov p2,a

call tran

call delay44

mov a,#40h

mov p2,a

call tran

call delay44

mov a,#40h

mov p2,a

call tran

call delay44

mov a,#40h

mov p2,a


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call tran

call delay44

ret

c1: clr a

mov a,#3eh

mov p2,a

call tran

call delay44

mov a,#41h

mov p2,a

call tran

call delay44

mov a,#41h

mov p2,a

call tran

call delay44

mov a,#41h

mov p2,a

call tran

call delay44

clr a


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mov a,#22h

mov p2,a

call tran

call delay44

ret

N1: clr a

mov a,#0FFh

mov p2,a

call tran

call delay44

mov a,#04h

mov p2,a

call tran

call delay44

mov a,#08h

mov p2,a

call tran

call delay44

mov a,#10h

mov p2,a

call tran


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call delay44

clr a

mov a,#0FFh

mov p2,a

call tran

call delay44

ret

I1: clr a

mov a,#41h

mov p2,a

call tran

call delay44

mov a,#41h

mov p2,a

call tran

call delay44

mov a,#0FFh

mov p2,a

call tran

call delay44

mov a,#41h


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mov p2,a

call tran

call delay44

clr a

mov a,#41h

mov p2,a

call tran

call delay44

ret

o1: clr a

mov a,#3eh

mov p2,a

call tran

call delay44

mov a,#41h

mov p2,a

call tran

call delay44

mov a,#41h

mov p2,a

call tran


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call delay44

mov a,#41h

mov p2,a

call tran

call delay44

clr a

mov a,#3eh

mov p2,a

call tran

call delay44

ret

m1: clr a

mov a,#0ffh

mov p2,a

call tran

call delay44

mov a,#02h

mov p2,a

call tran

call delay44

mov a,#04h


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mov p2,a

call tran

call delay44

mov a,#02h

mov p2,a

call tran

call delay44

clr a

mov a,#0ffh

mov p2,a

call tran

call delay44

ret

t11: clr a

mov a,#01h

mov p2,a

call tran

call delay44

mov a,#01h

mov p2,a

call tran


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call delay44

mov a,#0ffh

mov p2,a

call tran

call delay44

mov a,#01h

mov p2,a

call tran

call delay44

clr a

mov a,#01h

mov p2,a

call tran

call delay44

ret

s1: clr a

mov a,#26h

mov p2,a

call tran

call delay44

mov a,#49h


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mov p2,a

call tran

call delay44

mov a,#49h

mov p2,a

call tran

call delay44

mov a,#49h

mov p2,a

call tran

call delay44

clr a

mov a,#32h

mov p2,a

call tran

call delay44

ret

G1: clr a

mov a,#3Eh

mov p2,a

call tran


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call delay44

mov a,#41h

mov p2,a

call tran

call delay44

mov a,#51h

mov p2,a

call tran

call delay44

mov a,#51h

mov p2,a

call tran

call delay44

clr a

mov a,#32h

mov p2,a

call tran

call delay44

ret

d1: clr a

mov a,#0ffh


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mov p2,a

call tran

call delay44

mov a,#41h

mov p2,a

call tran

call delay44

mov a,#41h

mov p2,a

call tran

call delay44

mov a,#41h

mov p2,a

call tran

call delay44

clr a

mov a,#3eh

mov p2,a

call tran

call delay44

ret


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p11: clr a

mov a,#0ffh

mov p2,a

call tran

call delay44

mov a,#09h

mov p2,a

call tran

call delay44

mov a,#09h

mov p2,a

call tran

call delay44

mov a,#09h

mov p2,a

call tran

call delay44

clr a

mov a,#06h

mov p2,a

call tran


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call delay44

ret

R11: clr a

mov a,#0ffh

mov p2,a

call tran

call delay44

mov a,#09h

mov p2,a

call tran

call delay44

mov a,#19h

mov p2,a

call tran

call delay44

mov a,#29h

mov p2,a

call tran

call delay44

clr a

mov a,#46h


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mov p2,a

call tran

call delay44

ret

y1: clr a

mov a,#01h

mov p2,a

call tran

call delay44

mov a,#02h

mov p2,a

call tran

call delay44

mov a,#0fch

mov p2,a

call tran

call delay44

mov a,#02h

mov p2,a

call tran

call delay44


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clr a

mov a,#01h

mov p2,a

call tran

call delay44

ret

DOT: clr a

mov p2,a

call tran

call delay44

clr a

mov p2,a

call tran

call delay44

ret

J: mov p2,#08h

call tran

call delay44

mov p2,#14h

call tran

call delay44


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mov p2,#36h

call tran

call delay44

mov p2,#49h

call tran

call delay44

mov p2,#36h

call tran

call delay44

mov p2,#14h

call tran

call delay44

mov p2,#08h

call tran

call delay44

call gap

RET

s: mov p2,#79h

call tran

call delay44

mov p2,#09h


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call tran

call delay44

mov p2,#09h

call tran

call delay44

mov p2,#0ffh

call tran

call delay44

mov p2,#48h

call tran

call delay44

mov p2,#48h

call tran

call delay44

mov p2,#4fh

call tran

call delay44

call gap

RET

r: mov p2,#63h

call tran


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call delay44

mov p2,#55h

call tran

call delay44

mov p2,#2ah

call tran

call delay44

mov p2,#1ch

call tran

call delay44

mov p2,#2ah

call tran

call delay44

mov p2,#55h

call tran

call delay44

mov p2,#63h

call tran

call delay44

call gap

RET


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tran:

clr p3.7

clr p3.0

mov r3,#14

g: djnz r3,g

setb p3.7

setb p3.0

ret

delay44:

MOV R5,#0fH

INLO2:

MOV R0,#0F0H

INLO1:

MOV R1,#05H

DJNZ R1,$

DJNZ R0,INLO1

DJNZ R5,INLO2

RET

END


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APPENDIX (B)

CODES FOR CHARACTERS AND SYMBOLS

00H, 00H, 00H, 00H, 00H

! 00H, 00H, 5FH, 00H, 00H

" 04H, 02H, 05H, 02H, 01H

# 14H, 7FH, 14H, 7FH, 14H

$ 26H, 49H, 7FH, 49H, 32H

% 22H, 10H, 08H, 04H, 22H

& 00H, 36H, 49H, 36H, 28H

' 04H, 02H, 01H, 00H, 00H

< 08H, 14H, 22H, 41H, 00H

> 00H, 41H, 22H, 14H, 08H

* 2AH, 1CH, 08H, 1CH, 2AH

+ 08H, 08H, 3EH, 08H, 08H

, 00H, 58H, 38H, 00H, 00H

- 08H, 08H, 08H, 08H, 08H

. 40H, 00H, 00H, 00H, 00H

/ 20H, 10H, 08H, 04H, 02H

0 3EH, 41H, 41H, 41H, 3EH

: 00H, 00H, 22H, 00H, 00H

; 00H, 40H, 32H, 00H, 00H


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= 14H, 14H, 14H, 14H, 14H

? 06H, 01H, 51H, 09H, 06H

@ 3EH, 4DH, 53H, 1DH, 1EH

[ 7FH, 41H, 41H, 41H, 00H

\ 02H, 04H, 08H, 10H, 40H

] 00H, 41H, 41H, 41H, 7FH

^ 04H, 02H, 01H, 02H, 04H

_ 40H, 40H, 40H, 40H, 40H

` 01H, 02H, 04H, 00H, 00H

{ 77H, 49H, 41H, 41H, 00H

| 00H, 00H, 77H, 00H, 00H

} 00H, 41H, 41H, 49H, 77H

~ 04H, 02H, 04H, 02H, 00H

A 7CH, 12H, 11H, 12H, 7CH

B 7FH, 49H, 49H, 49H, 36H

C 3EH, 41H, 41H, 41H, 22H

D 7FH, 41H, 41H, 22H, 1CH

E 7FH, 49H, 49H, 49H, 41H

F 7FH, 09H, 09H, 09H, 01H

G 3EH, 41H, 49H, 49H, 7AH

H 7FH, 08H, 08H, 08H, 7FH


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I 00H, 41H, 7FH, 41H, 00H

J 20H, 40H, 41H, 3FH, 01H

K 7FH, 08H, 14H, 22H, 41H

L 7FH, 40H, 40H, 40H, 40H

M 7FH, 02H, 0CH, 02H, 7FH

N 7FH, 04H, 08H, 10H, 7FH

O 3EH, 41H, 41H, 41H, 3EH

P 7FH, 09H, 09H, 09H, 06H

Q 3EH, 41H, 51H, 21H, 5EH

R 7FH, 09H, 19H, 29H, 46H

S 46H, 49H, 49H, 49H, 31H

T 01H, 01H, 7FH, 01H, 01H

U 3FH, 40H, 40H, 40H, 3FH

V 1FH, 20H, 40H, 20H, 1FH

W 3FH, 40H, 30H, 40H, 3FH

X 63H, 14H, 08H, 14H, 63H

Y 07H, 08H, 70H, 08H, 07H

Z 61H, 51H, 49H, 45H, 43H

1 00H, 42H, 0FFH, 40H, 00H

2 42H, 61H, 51H, 49H, 46H

3 49H, 49H, 49H, 49H, 36H


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4 07H, 08H, 08H, 08H, 77H

5 4FH, 49H, 49H, 49H, 39H

6 3EH, 49H, 49H, 49H, 32H

7 41H, 21H, 11H, 09H, 07H

8 3EH, 49H, 49H, 49H, 3EH

9 06H, 09H, 09H, 09H, 7EH

scrolling message display - project report - nov 15, 2011

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