8051 Pin Diagram

8051 family members (e.g., 8751, 89C51, 89C52, DS89C4xO) come in different packages, such as DIP (dual in-line package), QFP (quad flat package), and LLC (leadless chip carrier),

They all have 40 pins that are dedicated to various functions such as I/O, RD, WR, address, data, and interrupts.However, since the vast majority of developers use the 40-pin chip.

 

Pins 1 – 8 (port 1):

• this all are Port 1.it doesn’t provide any other purpose.
• Port 1 is a domestically pulled up, quasi bi directional Input/output port.

Pin 9 (RESET):

• RESET pin is utilized to set the micro-controller 8051 to its primary values, whereas the micro-controller is functioning or at the early beginning of application.
• The RESET pin has to be set elevated for two machine rotations.

Pins 10 – 17(Port 3) 

• This port also supplies a number of other functions such as timer input, interrupts, serial communication indicators TxD & RxD, control indicators for outside memory interfacing WR & RD, etc. 
• This is a domestic pull up port with quasi bi directional port within.

Pins 18 and 19 (XTAL1 & XTAL2):

• These are employed for interfacing an outer crystal to give system clock.

Pin 20 (Vss)

• it symbolizes ground (0 V) association.

Pins- 21-28(Port 2): 

• as Input/output port,
• senior order address bus indicators are multiplexed with this quasi bi directional port.

Pin- 29 (PSEN): 

• Program Store Enable or PSEN is employed to interpret sign from outer program memory.

Pin-30 (EA):

• External Access or EA input is employed to permit or prohibit outer memory interfacing.
• If there is no outer memory need, this pin is dragged high by linking it to Vcc.

Pin-31 (ALE):

• It is brought into play to de-multiplex the address data indication of port 0 (for outer memory interfacing).

Pins 32-39 (Port 0)

• as Input/output port
• low order data & address bus signals are multiplexed with this port (to provide the use of outer memory interfacing).
• This pin is a bi directional Input/output port (the single one in microcontroller 8051) and outer pull up resistors are necessary to utilize this port as Input/output.

Pin-40 (Vcc)

• it is the chief power supply.
• By and large it is +5V DC.