Question

The 8051 Microcontroller family has circuitry to support no. of integrated serial ports.

• A. 32
• B. 2
• C. 1
• D. 4

Hint:

Even though it has only one serial port, it can operate in four different modes, including a shift register mode for I/O expansion and three UART modes for standard communication.

Answer 1

The Correct Option is C

1. The 8051 UART: The standard 8051 microcontroller family features exactly

one integrated full-duplex serial port. This port is a Universal Asynchronous Receiver-Transmitter (UART).

2. Hardware Implementation: The serial port utilizes two specific pins on the microcontroller:

• RXD (Pin 3.0): Used for receiving data.

• TXD (Pin 3.1): Used for transmitting data.
Because it is "Full-Duplex," it can send and receive data simultaneously. It uses the SBUF (Serial Buffer) register to hold the data being transmitted or received and the SCON (Serial Control) register to manage the communication modes and status flags.