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component details
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Component Details :

AT89C51 or 89C51 microcontroller

J:\final\AT89C51   89C51_files\AT89C51.jpg

AT89C51 is an 8-bit microcontroller and belongs to Atmel's 8051 family. AT89C51 has 4KB of Flash programmable and erasable read only memory (PEROM) and 128 bytes of RAM. It can be erased and program to a maximum of 1000 times.
In 40 pin AT89C51, there are four ports designated as P1, P2, P3 and P0. All these ports are 8-bit bi-directional ports, i.e., they can be used as both input and output ports. Except P0 which needs external pull-ups, rest of the ports have internal pull-ups. When 1s are written to these port pins, they are pulled high by the internal pull-ups and can be used as inputs. These ports are also bit addressable and so their bits can also be accessed individually.
Port P0 and P2 are also used to provide low byte and high byte addresses, respectively, when connected to an external memory. Port 3 has multiplexed pins for special functions like serial communication, hardware interrupts, timer inputs and read/write operation from external memory. AT89C51 has an inbuilt UART for serial communication. It can be programmed to operate at different baud rates. Including two timer & hardware interrupts, it has a total of six interrupts.

Block Diagram of AT89c51:

Microcontroller Block Diagram.JPG

Pin Description of AT89c51: 

 Pin No

 Function

 Name

1

8 bit input/output port (P1) pins

P1.0

2

P1.1

3

P1.2

4

P1.3

5

P1.4

6

P1.5

7

P1.6

8

P1.7

9

Reset pin; Active high

Reset

10

Input (receiver) for serial communication

RxD

8 bit input/output port (P3) pins

P3.0

11

Output (transmitter) for serial communication

TxD

P3.1

12

External interrupt 1

Int0

P3.2

13

External interrupt 2

Int1

P3.3

14

Timer1 external input

T0

P3.4

15

Timer2 external input

T1

P3.5

16

Write to external data memory

Write

P3.6

17

Read from external data memory

Read

P3.7

18

Quartz crystal oscillator (up to 24 MHz)

Crystal 2

19

Crystal 1

20

Ground (0V)

Ground

21

Program store enable; Read from external program memory

 P2.0/ A8

22

 P2.1/ A9

23

 P2.2/ A10

24

 P2.3/ A11

25

 P2.4/ A12

26

 P2.5/ A13

27

 P2.6/ A14

28

 P2.7/ A15

29

 

PSEN

30

Address Latch Enable

ALE

Program pulse input during Flash programming

Prog

31

External Access Enable;  Vcc for internal program executions

EA

Programming enable voltage; 12V (during Flash programming)

Vpp

32

8 bit input/output port (P0) pins

 

Low-order address bits when interfacing with external memory

 

 P0.7/ AD7

33

 P0.6/ AD6

34

 P0.5/ AD5

35

 P0.4/ AD4

36

 P0.3/ AD3

37

 P0.2/ AD2

38

 P0.1/ AD1

39

 P0.0/ AD0

40

Supply voltage; 5V (up to 6.6V)

Vcc

 

 

 

   

 

16x2 LCD

J:\final\LCD (2).jpg

 

LCD (Liquid Crystal Display) screen is an electronic display module and find a wide range of applications. A 16x2 LCD display is very basic module and is very commonly used in various devices and circuits. These modules are preferred over seven segments and other multi segment...

4x3 Keypad

keypad

At the lowest level, keyboards are organized in a matrix of rows and columns. The CPU accesses both rows and column through ports; therefore, with two 8-bit ports, an 8*8 matrix of keys can be connected to a microprocessor. When a key pressed, a row and column make a connect; otherwise, there is no connection between row and column. In IBM PC keyboards, a single microcontroller (consisting of microprocessor, RAM and EPROM, and several ports all on a single chip) takes care of software and hardware interfacing of keyboard. In such systems it is the function of programs stored in the EPROM of microcontroller to scan the keys continuously, identify which one has been activated, and present it to the motherboard. In this section we look at the mechanism by which the 8051 scans and identifies the key.

Preset

J:\final\Preset.jpg

A preset is a three legged electronic component which can be made to offer varying resistance in a circuit. The resistance is varied by adjusting the rotary control over it. The adjustment can be done by using a small screw driver or a similar tool. The resistance does not vary linearly but rather varies in exponential or logarithm...

Voltage Regulator (LM 7805)

d505ede7a85e4ba33d2953b60db763f1

A voltage regulator is an electrical regulator designed to automatically maintain a constant voltage level. A voltage regulator may be a simple "feed-forward" design or may include negative feedback control loops. It may use an electromechanical mechanism, or electronic components. Depending on the design, it may be used to regulate one or more AC or DC voltages.

Electronic voltage regulators are found in devices such as computer power supplies where they stabilize the DC voltages used by the processor and other elements. In automobile alternators and central power station generator plants, voltage regulators control the output of the plant. In an electric power distribution system, voltage regulators may be installed at a substation or along distribution lines so that all customers receive steady voltage independent of how much power is drawn from the line.

Crystal Oscillator

2mhz

A crystal oscillator is an electronic oscillator circuit that uses the mechanical resonance of a vibrating crystal of piezoelectric material to create an electrical signal with a very precise frequency. This frequency is commonly used to keep track of time (as in quartz wristwatches), to provide a stable clock signal for digital integrated circuits, and to stabilize frequencies for radio transmitters and receivers. The most common type of piezoelectric resonator used is the quartz crystal, so oscillator circuits designed around them became known as "crystal oscillators."