Microcontroller

                       Microcontroller is a small computer which contains a CPU ,ROM,RAM,timer ,counters etc, in a single chip.It fetches the instructions from rom and performs tasks according to the instruction .
8051 is a 40 pin ic which contains a 4kb rom ,128 bytes of ram and two 16 bit timers/counters in a singhle chip.it has 4 ports port0,1,2,3.

                                           8051 Microcontroller:
Features of 8051:

• 80c51 is a microcontroller of 80 family with c series.
• It has 4k rom for storing the code and 128 bytes of ram for
• storing temporary data.
• It contains two timers and counters which are 16 bit wide.
• It has UART to receive and transmit data serialy.
• It consists a 16 bit addrss bus and 8 bit data bus for interfacing
• with external memory.
• 3 internal and 2 external interrupts.
• 32 general purpose registers.
• 16 bit program counter and data pointer.

Pin description of 8051:

Port 0(pin 32 to 39):

Port 0 serves as input output port. When 1 is written to pins of port 0
it serves as input ,when 0 is written it serves as output.
It is also designated as mutiplexed data and lower order(A0-A7) order
bus. When 8051 is connected to external memory it is used as data
and address bus.

Port 1(pin 1 to 8):
Pins from 1 to 8 are designated for port 1.It is a input output port
same as port 0
.
Port 2(pin 21 to 28):
It is also a input output port like port 0 and 1. When 8051 is connected
to external memory this port provides as higher order address bus(A8-
A15).

Port 3(pin10 to Pin 17):
It is also a input output port.Each pin of port 3 is used for special
functions which are listed below.
                 Pin no.        function
                  3.0               Rxd
                  3.1               Txd
                  3.2               -Int0
                  3.3                 -Int1
                  3.4               T0
                  3.5               T1
                  3.6              -WR
                  3.7              -RD

Note: “-“ repersents the active low signal.

VCC(Pin no.40):
This pin is connected to +5 V power supply.

GND(Pin no. 20):
This pin is connected to ground .

RST(Pin no. 9):
This pin is used to reset the MC.


XTAL1 & XTAL2(Pin no.18,19):
This pin is connected to crystal oscillator.Ceramic disc capacitors are
used as resonator.

-EA/VPP(Pin no. 31):
This pin is used to access the external memory.When 8051 is
connected to external memory this pin is grounded.When this pin is
connected to vcc 8051 fetches the code from internal memory.
This pin is also used to supply the power during flash programing.

ALE/PROG(Pin no30):
(Address Latch Enable)
This pin is sused when 8051 is connected to external memory.This pin
is high when address is present on Port0.Tis pin used to demultiplex
the address and data present on Port0.

-PSEN(Pin no. 39):
(Program Strobe Enable)
This pin is connected to external memory to enable the output of
memory.




Contact information:
khalsa.mps61@gmail.com
manpreetsinghakali@yahoo.in

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