introduction to micro controller

8/2/2019 Introduction to Micro Controller

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While this drama was going on, hobbyists and professionals, also split in two groups and

protected by anonymity, were working hard on their projects. Then, someone suddenly put a

question: Why should not we make a universal component? A cheap, universal integrated

circuit that could be programmed and used in any field of electronics, device or wherever

needed? Technology has been developed enough as well as the market. Why not? So it

happened, body and spirit were united and the first integrated circuit was designed and called

the MICROCONTROLLER

1.1 What are microcontrollers and what are they used for?

Like all good things, this powerful component is basically very simple. It is made by mixing

tested and high- quality "ingredients" (components) as per following receipt:

1. The simplest computer processor is used as the "brain" of the future system.2. Depending on the taste of the manufacturer, a bit of memory, a few A/D converters,

timers, input/output lines etc. are added

3. All that is placed in some of the standard packages.4. A simple software able to control it all and which everyone can easily learn about has

been developed.

On the basis of these rules, numerous types of microcontrollers were designed and they quickly

became man's invisible companion. Their incredible simplicity and flexibility conquered us a

long time ago and if you try to invent something about them, you should know that you are

probably late, someone before you has either done it or at least has tried to do it.

The following things have had a crucial influence on development and success of the

microcontrollers:

Powerful and carefully chosen electronics embedded in the microcontrollers canindependetly or via input/output devices (switches, push buttons, sensors, LCD


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displays, relays etc.), control various processes and devices such as industrial

automation, electric current, temperature, engine performance etc.

Very low prices enable them to be embedded in such devices in which, until recent timeit was not worthwhile to embed anything. Thanks to that, the world is overwhelmed

today with cheap automatic devices and various smart appliances.

Prior knowledge is hardly needed for programming. It is sufficient to have a PC(software in use is not demanding at all and is easy to learn) and a simple device

(called the programmer) used for loading raedy-to-use programs into the

microcontroller.

So, if you are infected with a virus called electronics, there is nothing left for you to do but to

learn how to use and control its power.

How does the microcontroller operate?

Even though there is a large number of different types of microcontrollers and even more

programs created for their use only, all of them have many things in common. Thus, if you

learn to handle one of them you will be able to handle them all. A typical scenario on the basis

of which it all functions is as follows:

1. Power supply is turned off and everything is stillthe program is loaded into themicrocontroller, nothing indicates what is about to come

2. Power supply is turned on and everything starts to happen at high speed! The controllogic unit keeps everything under control. It disables all other circuits except quartz

crystal to operate. While the preparations are in progress, the first milliseconds go by

3. Power supply voltage reaches its maximum and oscillator frequency becomes stable.SFRs are being filled with bits reflecting the state of all circuits within the

microcontroller. All pins are configured as inputs. The overall electronics starts opera

in rhythm with pulse sequence. From now on the time is measured in micro and

nanoseconds.

4. Program Counter is set to zero. Instruction from that address is sent to instruction decwhich recognizes it, after which it is executed with immediate effect.


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5. The value of the Program Counter is incremented by 1 and the whole process isrepeated...several million times per second.

1.2 What is what in the microcontroller?

As you can see, all the operations within the microcontroller are performed at high speed and

quite simply, but the microcontroller itself would not be so useful if there are not special

circuits which make it complete. In continuation, we are going to call your attention to them.

Read Only Memory (ROM)

Read Only Memory (ROM) is a type of memory used to permanently save the program being

executed. The size of the program that can be written depends on the size of this memory.

ROM can be built in the microcontroller or added as an external chip, which depends on the

type of the microcontroller. Both options have some disadvantages. If ROM is added as an


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external chip, the microcontroller is cheaper and the program can be considerably longer. At

the same time, a number of available pins is reduced as the microcontroller uses its own

input/output ports for connection to the chip. The internal ROM is usually smaller and more

expensive, but leaves more pins available for connecting to peripheral environment. The size of

ROM ranges from 512B to 64KB.

Random Access Memory (RAM)

Random Access Memory (RAM) is a type of memory used for temporary storing data and

intermediate results created and used during the operation of the microcontrollers. The content

of this memory is cleared once the power supply is off. For example, if the program performes

an addition, it is necessary to have a register standing for what in everyday life is called the

sum . For that purpose, one of the registers in RAM is called the "sum" and used for storing

results of addition. The size of RAM goes up to a few KBs.

Electrically Erasable Programmable ROM (EEPROM)

The EEPROM is a special type of memory not contained in all microcontrollers. Its contents

may be changed during program execution (similar to RAM ), but remains permanently saved

even after the loss of power (similar to ROM). It is often used to store values, created and used

during operation (such as calibration values, codes, values to count up to etc.), which must be

saved after turning the power supply off. A disadvantage of this memory is that the process of

programming is relatively slow. It is measured in milliseconds.


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Central Processor Unit (CPU)

As its name suggests, this is a unit which monitors and controls all processes within the

microcontroller and the user cannot affect its work. It consists of several smaller subunits, of

which the most important are:

Instruction decoder is a part of the electronics which recognizes program instructionsand runs other circuits on the basis of that. The abilities of this circuit are expressed inthe "instruction set" which is different for each microcontroller family.

Arithmetical Logical Unit (ALU) performs all mathematical and logical operationsupon data.


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Accumulator is an SFR closely related to the operation of ALU. It is a kind of workingdesk used for storing all data upon which some operations should be executed

(addition, shift etc.). It also stores the results ready for use in further processing. One of

the SFRs, called the Status Register, is closely related to the accumulator, showing at

any given time the "status" of a number stored in the accumulator (the number is

greater or less than zero etc.).

A bit is just a word invented to confuse novices at electronics. Joking aside, this wordin practice indicates whether the voltage is present on a conductor or not. If it is

present, the approprite pin is set to logic one (1), i.e. the bits value is 1. Otherwise, if

the voltage is 0 V, the appropriate pin is cleared (0), i.e. the bits value is 0. It is more

complicated in theory where a bit is referred to as a binary digit, but even in this case,

its value can be either 0 or 1.

Input/output ports (I/O Ports)

In order to make the microcontroller useful, it is necessary to connect it to peripheral devices.

Each microcontroller has one or more registers (called a port) connected to the microcontroller

pins.


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Oscillator

Even pulses generated by the oscillator enable harmonic and synchronous operation of all

circuits within the microcontroller. It is usually configured as to use quartz-crystal or ceramics

resonator for frequency stabilization. It can also operate without elements for frequency

stabilization (like RC oscillator). It is important to say that program instructions are not

executed at the rate imposed by the oscillator itself, but several times slower. It happens

because each instruction is executed in several steps. For some microcontrollers, the same

number of cycles is needed to execute any instruction, while it's different for othermicrocontrollers. Accordingly, if the system uses quartz crystal with a frequency of 20MHz,

the execution time of an instruction is not expected 50nS, but 200, 400 or even 800 nS,

depending on the type of the microcontroller!

Power Supply Circuit

There are two things worth attention concerning the microcontroller power supply circuit:

Brown out is a potentially dangerous state which occurs at the moment the microcontroller is

being turned off or when power supply voltage drops to the lowest level due to electric noise.

As the microcontroller consists of several circuits which have different operating voltage

levels, this can cause its out of control performance. In order to prevent it, the microcontroller

usually has a circuit for brown out reset built-in. This circuit immediately resets the whole

electronics when the voltage level drops below the lower limit.

Reset pin is usually referred to as Master Clear Reset (MCLR

) and serves for external reset ofthe microcontroller by applying logic zero (0) or one (1) depending on the type of the

microcontroller. In case the brown out is not built in the microcontroller, a simple external

circuit for brown out reset can be connected to this pin.


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2.Explanation of Block Diagram:

As u can see in the diagram, the circuit consist Microcontroller, Timer Circuit, Relay,

EEPROM, 7 Segment Display and bell.

Microcontroller:The microcontroller is used for the synchronization of the whole circuit. The keypad is

attached to the microcontroller, the data input in saved on the EEPROM memory. The

controller also converts the clock time in the 7 segment display.

Timer Circuit:The timer circuit used a crystal, to keep track of the time.

EEPROM:The EEPROM is used to save the time, when the time stored in the memory is equal

time in the timer circuit the relay in switched on.

7 Segment Display:The 7 Segment display is used to display the time from the timer circuit.

Bell:When the time stored in memory and the timer circuit matches, the relay is switched on,

which the starts the bell.


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Block Diagram:


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3.The CircuitryThe Project takes over the task of ringing of the bell in colleges or in automatically so labour

work is reduced. The manual switching of the bell is replaced by a inbuilt real time clock

(DS1307) which track over the real time. The clock also has a 3V battery so if there is a power

failure the clock will not loose track of time. The four 7-segments displays the time on the

clock. There is a numeric keypad which is connected to the microcontroller which will take the

input of setting the timer at what particular time the bell should ring. When the inputted time

equals to the time on the clock present, then the Relay for the Bell is switched on.

The Bell Ringing time can be edited at any time, so that it can be used at normal class timings

as well as exam times. The Microcontroller AT89S8252 is used to control all the Functions, it

get the time through the keypad and store it in its Memory.

Clock Circuit DS1307:The PIC16F88 has a built in oscillator for a 32 kHz watch crystal a DS1307 is easier to

use on a bread board. This is because you can control the layout of the circuit more

easily. The RTC also makes the software easier as it takes care of all calendar functions;

accounting for leap years etc. The DS1307 (RTC) Real Time Clock IC is an 8 pin

device using an I2C interface.

EEPROM:


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EEPROM stands for Electrically Erasable Programmable Read-Only Memory and is a

type of non-volatile memory used in computers and other electronic devices to store

small amounts of data that must be saved when power is removed, e.g., calibration

tables or device configuration.

Microcontroller AT89S8252:o 8K Bytes of In-System Reprogrammable Downloadable Flash Memoryo 2K Bytes EEPROM, Fully Static Operation: 0 Hz to 24 MHzo 4V to 6V Operating Rangeo Three-level Program Memory Locko 256 x 8-bit Internal RAM, 32 Programmable I/O Lineso Three 16-bit Timer/Counterso Nine Interrupt Sourceso Programmable UART Serial Channel, SPI Serial Interfaceo Low-power Idle and Power-down Modeso Interrupt Recovery from Power-downo Programmable Watchdog Timer, Dual Data Pointer, Power-off Flag


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3.1. Table 4: Component List :-Part Value Quantity

Resistor 330E 510k 4

2.2k 5

56k 1

Capacitor 33pF 2

1uF 1

1uF Radial 1

Diode 1N5711 1

Transistor BC547 4

Keypad 1

7 Segment Display 4

Crystal 12Mhz 1

32.768Khz 1

Battery 3V 1

Bell 1


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Circuit Diagram:


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4.Code

INCLUDE reg_51.pdf

RB0 EQU 000H ; Select Register Bank 0

RB1 EQU 008H ; Select Register Bank 1 ...poke to PSW to use

;%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

; PORT DECLERATION

;%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

SDA EQU P1.1 ;SDA=PIN5

SCL EQU P1.0 ;SCL=PIN6

DS1307W EQU 0D0H ; SLAVE ADDRESS 1101 000 + 0 TO WRITE

DS1307R EQU 0D1H ; SLAVE ADDRESS 1101 000 + 1 TO READ

KEYS EQU P3

ROW1 EQU P3.1


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ROW2 EQU P3.2

ROW3 EQU P3.3

ROW4 EQU P3.4

COL1 EQU P3.5

COL2 EQU P3.6

COL3 EQU P3.7

DIS_A EQU P0.2

DIS_B EQU P0.3

DIS_C EQU P0.4

DIS_D EQU P0.6

DIS_E EQU P0.5

DIS_F EQU P0.1

DIS_G EQU P0.0

DIS1 EQU P0.7

DIS2 EQU P2.7

DIS3 EQU P2.6

DIS4 EQU P2.5

RELAY EQU P2.4


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WMCON DATA 96h ; watchdog and memory control register

EEMEN EQU 00001000b ; EEPROM access enable bit

EEMWE EQU 00010000b ; EEPROM write enable bit

WDTRST EQU 00000010b ; EEPROM RDY/BSY bit

DPS EQU 00000100b ; data pointer select bit

;%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

DSEG ; This is internal data memory

ORG 20H ; Bit adressable memory

FLAGS DATA 20H

LASTREAD BIT FLAGS.0

SQW BIT FLAGS.4

ACK BIT FLAGS.5

BUS_FLT BIT FLAGS.6

_2W_BUSY BIT FLAGS.7

CANCEL BIT FLAGS.1

CANCEL1 BIT FLAGS.2

ALARM BIT FLAGS.3

BITCNT DATA 21H

BYTECNT DATA 22H


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SECS DATA 24H ; ' SECONDS STORAGE RAM

MINS DATA 25H ; ' MINUTES ' '

HRS DATA 26H ; ' HOURS ' '

DAY DATA 27H ; ' DAY ' '

DATE1 DATA 28H ; ' DATE ' '

MONTH DATA 29H ; ' MONTH ' '

YEAR DATA 2AH ; ' YEAR ' '

CONTROL DATA 2BH ; FOR STORAGE OF CONTROL REGISTER WHEN READ.

ALM_HOUR DATA 2CH ; INTERNAL (ALARM HOURS) STORAGE.

ALM_MIN DATA 2DH ; INTERNAL (ALARM MINUTES) STORAGE.

ALM_CNTRL DATA 2EH ; INTERNAL STORAGE FOR ALARM (ON) TIME.

COUNT DATA 2FH

SPEED DATA 30H

VALUE_1 DATA 31H

VALUE_2 DATA 32H

VALUE_3 DATA 33H

VALUE_4 DATA 34H

NUMBER1 DATA 35H ;temp to store dialled number

KBELL DATA 36H

NUMB1 DATA 37H ;Temp Reg to store pressed Keys


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NUMB4 DATA 3AH ;Temp Reg to store pressed Keys

KEY DATA 3BH

TIM DATA 3CH

STACK DATA 3FH

;%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

; ***MACRO'S***

SCL_HIGH MACRO

SETB SCL ; SET SCL HIGH

JNB SCL,$ ; LOOP UNTIL STRONG 1 ON SCL

ENDM

;%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

CSEG AT 0 ; RESET VECTOR

;---------==========----------==========---------=========---------

; PROCESSOR INTERRUPT AND RESET VECTORS


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;---------==========----------==========---------=========---------

ORG 00H ; Reset

JMP MAIN

ORG 000BH ;Timer Interrupt0

JMP REFRESH

ORG 001BH ;Timer Interrupt1

JMP RELAY_TIMER

;---------==========----------==========---------=========---------

; Main routine. Program execution starts here.

;---------==========----------==========---------=========---------

MAIN:

MOV PSW,#RB0 ; Select register bank 0

MOV SP,STACK

CLR RELAY ;Switch OFF relay

MOV SPEED,#00H

MOV COUNT,#00H


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MOV KBELL,#00H

CLR ALARM

MOV VALUE_1,#15H

MOV VALUE_2,#15H

MOV VALUE_3,#15H

MOV VALUE_4,#15H

CLR DIS1

CLR DIS2

CLR DIS3

CLR DIS4

MOV TMOD,#01H ;enable timer0 for scanning

MOV TL0,#00H

MOV TH0,#0FDH

SETB ET0

SETB EA

SETB TR0 ;Start the Timer

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

; INITILIZE RTC

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

SETB SDA ; ENSURE SDA HIGH


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SCL_HIGH ; ENSURE SCL HIGH

CLR ACK ; CLEAR STATUS FLAGS

CLR BUS_FLT

CLR _2W_BUSY

CLR SQW

CALL OSC_CONTROL ;Initilize the RTC

ACALL SQW_CONTROL_1HZ

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

; CHECK FOR ENTER THE TIME

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

LCALL SEND_START ; SEND 2WIRE START CONDITION

MOV A,#DS1307W ; SEND DS1307 WRITE COMMAND

LCALL SEND_BYTE

MOV A,#08H ; SET POINTER TO REG 08H ON DS1307

LCALL SEND_BYTE

LCALL SEND_STOP ; SEND STOP CONDITION

LCALL SEND_START ; SEND START CONDITION

MOV A,#DS1307R ; SEND DS1307 READ COMMAND

LCALL SEND_BYTE

LCALL READ_BYTE ; READ A BYTE OF DATA

MOV R1,A


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LCALL SEND_STOP ; SEND 2WIRE STOP CONDITION

MOV NUMBER1,#01H

CJNE A,#0AAH,KEYBOARD1

AJMP START_PROGRAM

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

; KEYBOARD ROUTINE

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

KEYBOARD1:

MOV KBELL,#0FFH

KEYBOARD:

MOV KEY,#00H

SETB COL1

SETB COL2

SETB COL3

K11: CLR ROW1

CLR ROW2

CLR ROW3

CLR ROW4

MOV A,KEYS


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ANL A,#11100000B

CJNE A,#11100000B,K11 ;check till all keys released

K2: ACALL DEALAY ;call 20 msec delay

MOV A,KEYS ;see if any key is pressed

ANL A,#11100000B ;mask unused bits

CJNE A,#11100000B,OVER ;key pressed, await closure

SJMP K2

OVER: ACALL DEALAY

MOV A,KEYS

ANL A,#11100000B

CJNE A,#11100000B,OVER1

SJMP K2

OVER1: MOV A,KEYS

ORL A,#11111110B

MOV KEYS,A

CLR ROW1

MOV A,KEYS

ANL A,#11100000B

CJNE A,#11100000B,ROW_1

MOV A,KEYS

ORL A,#11111110B


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JC MAT1

MOV KEY,#01H

AJMP K1

MAT1: RLC A

JC MAT2

MOV KEY,#02H

AJMP K1

MAT2: RLC A

JC K1

MOV KEY,#03H

AJMP K1

ROW_2: RLC A

JC MAT3

MOV KEY,#04H

AJMP K1

MAT3: RLC A

JC MAT4

MOV KEY,#05H

AJMP K1

MAT4: RLC A


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JC K1

MOV KEY,#06H

AJMP K1

ROW_3: RLC A

JC MAT5

MOV KEY,#07H

AJMP K1

MAT5: RLC A

JC MAT6

MOV KEY,#08H

AJMP K1

MAT6: RLC A

JC K1

MOV KEY,#09H

AJMP K1

ROW_4: RLC A

JC MAT7

MOV KEY,#10H ;for *

AJMP K1


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MAT7: RLC A

JC MAT8

MOV KEY,#00H ;for 0

AJMP K1

MAT8: RLC A

JC K1

MOV KEY,#12H ;for =

K1:

MOV A,KBELL

CJNE A,#0FFH,KB_RET1

MOV A,KEY

CJNE A,#10H,CXCX0 ;Key to Erase last dislled NUMBER1

MOV KEY,#00H

MOV NUMBER1,#01H

MOV VALUE_1,#15H

MOV VALUE_2,#15H

MOV VALUE_3,#15H

MOV VALUE_4,#15H

AJMP KEYBOARD


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KB_RET1: JMP KB_RET

CXCX0: MOV A,NUMBER1

CJNE A,#01H,CXCX1

MOV A,KEY

CLR C

SUBB A,#03H ; Chk Key Pressed 0,1

JNC CXCX5

MOV A,KEY

INC NUMBER1

MOV NUMB1,KEY

MOV VALUE_1,KEY

AJMP KEYBOARD

CXCX1: CJNE A,#02H,CXCX2

MOV A,NUMB1

CJNE A,#02,JKJL

MOV A,KEY

CLR C

SUBB A,#04H ; Chk Key Pressed 0,1,2,3

JNC CXCX5

JKJL: MOV A,KEY


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CLR C

SUBB A,#10H ; Chk Key Pressed 0,1...8,9

JNC CXCX5

INC NUMBER1

MOV NUMB2,KEY

MOV VALUE_2,KEY

AJMP KEYBOARD


MOV A,KEY

CLR C

SUBB A,#06H ; Chk Key Pressed 0,1...,5

JNC CXCX5

INC NUMBER1

MOV NUMB3,KEY

MOV VALUE_3,KEY

AJMP KEYBOARD


MOV A,KEY

CLR C

SUBB A,#10H ; Chk Key Pressed 0,1,....,8,9

JNC CXCX5


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INC NUMBER1

MOV NUMB4,KEY

MOV VALUE_4,KEY

CXCX5: AJMP KEYBOARD


MOV A,KEY

CJNE A,#12H,CXCX5 ;Key to OK TIME

CALL FLASHING

MOV KBELL,#00H

MOV A,NUMB1

SWAP A

ORL A,NUMB2

MOV NUMB2,A

MOV A,NUMB3

SWAP A

ORL A,NUMB4

MOV NUMB4,A


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;(((((((((((((((((((((((((((((((((((((((((((((((((((((((((((((((((((((((((((((((

; STORE THE TIME TO RTC CHIP

;(((((((((((((((((((((((((((((((((((((((((((((((((((((((((((((((((((((((((((((((


MOV A,#DS1307W ; LOAD DS1307 WRITE COMMAND

LCALL SEND_BYTE ; SEND WRITE COMMAND

MOV A,#08H ; SET DS1307 DATA POINTER TO

BEGINNING

LCALL SEND_BYTE ; OF USER RAM 08H

MOV A,#0AAH ; WRITE BYTE TO ENTIRE RAM SPACE

LCALL SEND_BYTE

LCALL SEND_STOP ; SEND 2WIRE STOP CONTION


MOV A,#DS1307W ; LOAD DS1307 WRITE COMMAND

LCALL SEND_BYTE ; SEND WRITE COMMAND

MOV A,#01H ; SET DS1307 DATA POINTER TO

BEGINNING

MOV VALUE_2,NUMB2


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MOV VALUE_3,NUMB3

MOV VALUE_4,NUMB4

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

DELAY:

MOV R1,#0CCH

REP2: MOV R2,#0FFH

REP1: NOP

DJNZ R2,REP1

DJNZ R1,REP2

RET

END

5.Conclusion


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By this project, automatic bell we have studied that integrated circuits are of

immense use. It a microcontroller cam modified as per specifications.Thus, along with the advantages and disadvantages, etc

6.BIBLIOGRAPHY


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[1] 8051 Projectshttp://www.8051projects.info

[2] http://www.projectsof8051.com

[3] http://www.google.com
http://www.8051projects.info/http://www.8051projects.info/http://www.8051projects.info/http://www.projectsof8051.com/http://www.projectsof8051.com/http://www.google.com/http://www.google.com/http://www.google.com/http://www.projectsof8051.com/http://www.8051projects.info/

introduction to micro controller

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