8051 Microcontroller Ports details

8051 microcontrollers have 4 I/O ports each of 8-bit, which can be configured as input or output. Hence, total 32 input/output pins allow the microcontroller to be connected with the peripheral devices. Pin configuration, i.e. the pin can be configured as 1 for input and 0 for output as per the logic state. Input/Output (I/O) pin − All the circuits within the microcontroller must be connected to one of its pins except P0 port because it does not have pull-up resistors built-in. Input pin − Logic 1 is applied to a bit of the P register. The output FE transistor is turned off and the other pin remains connected to the power supply voltage over a pull-up resistor of high resistance. Port 0 − The P0 (zero) port is characterized by two functions − When the external memory is used then the lower address byte (addresses A0A7) is applied on it, else all bits of this port are configured as input/output. When P0 port is configured as an output then other ports consisting of pins with built-in pull-up resistor connected by its end to 5V power supply, the pins of this port have this resistor left out. Thank You for Watching