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Default Apply Reset CPANEL

AT89C51 Microcontroller CP044 Image:

DataSheet: AT89C51.pdf

AT89C51 is an 8-bit microcontroller and belongs to Atmel's 8051 family. ATMEL 89C51 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 bidirectional 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 timers & hardware interrupts, it has a total of six interrupts.

Pin Diagram:

Pin Description:

Pin No

Function

Name

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40



P1.0 P1.1 P1.2 P1.3 P1.4 P1.5 P1.6 P1.7 Reset

8 bit input/output port (P1) pins

Reset pin; Active high Input (receiver) for serial RxD communication Output (transmitter) for serial TxD communication External interrupt 1 Int0 External interrupt 2 Int1 Timer1 external input T0 Timer2 external input T1 Write to external data memory Write Read from external data memory Read

P3.0 P3.1 8 bit input/output port (P3) pins

Quartz crystal oscillator (up to 24 MHz) Ground (0V)

8 bit input/output port (P2) pins / High-order address bits when interfacing with external memory

Program store enable; Read from external program memory Address Latch Enable Program pulse input during Flash programming External Access Enable; Vcc for internal program executions Programming enable voltage; 12V (during Flash programming)

8 bit input/output port (P0) pins Low-order address bits when interfacing with external memory

Supply voltage; 5V (up to 6.6V)

49459 reads

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P3.2 P3.3 P3.4 P3.5 P3.6 P3.7 Crystal 2 Crystal 1 Ground P2.0/ A8 P2.1/ A9 P2.2/ A10 P2.3/ A11 P2.4/ A12 P2.5/ A13 P2.6/ A14 P2.7/ A15 PSEN ALE Prog EA Vpp P0.7/ AD7 P0.6/ AD6 P0.5/ AD5 P0.4/ AD4 P0.3/ AD3 P0.2/ AD2 P0.1/ AD1 P0.0/ AD0 Vcc

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