How is data detected in a UART?

In a Universal Asynchronous Receiver-Transmitter (UART), data is detected using a clock signal. The UART is a popular communication interface that allows serial communication between devices. It is commonly used to connect microcontrollers, computers, and other electronic devices.

Understanding the UART

The UART operates in asynchronous mode, which means that the data is not synchronized with a clock signal. Instead, it uses start and stop bits to frame each data packet. This allows for variable-length data packets and provides flexibility in data transmission.

Data Detection in UART

When data is transmitted over a UART interface, it is sent one bit at a time. The receiver needs to detect the start and stop bits to properly frame the data. The clock signal is used to precisely time the detection of these bits.

Explanation of the Correct Answer (Option C)

The correct answer, option 'C' (clock), is the mechanism used to detect data in a UART. Here's how it works:

1. Clock Generation: The UART receiver generates a clock signal based on the baud rate (data rate) of the transmission. The baud rate specifies the number of bits transmitted per second.

2. Start Bit Detection: When a UART transmission begins, the sender sends a start bit, which is always a logic low (0). The receiver continuously monitors the incoming data line for any changes.

3. Clock Synchronization: The receiver waits for the start bit to begin clock synchronization. It aligns its clock signal with the incoming data stream.

4. Bit Sampling: Once the clock is synchronized, the receiver samples the incoming data line at specific intervals defined by the clock signal. This allows it to detect the value of each bit.

5. Data Reception: After the start bit, the remaining data bits are transmitted one by one. The receiver samples each bit and stores them in a buffer.

6. Stop Bit Detection: After receiving the data bits, the sender sends one or more stop bits to indicate the end of the transmission. The stop bits are always logic high (1). The receiver uses the clock signal to detect the stop bits.

7. Data Framing: The receiver uses the start and stop bits to frame the data packet. It removes the start and stop bits from the received data and passes the actual data to the higher-level processing logic.

Conclusion

In summary, the clock signal is used to detect data in a UART. It enables the receiver to synchronize with the incoming data stream, sample each bit accurately, and properly frame the data packet. Understanding this process is essential for correctly receiving data over a UART interface.