In asynchronous serial communication, start and stop bits are primarily used…

Concept

Asynchronous serial communication does not transmit a separate clock with each character, so the receiver must recover timing from the data frame itself.

A start transition aligns the receiver's sampling clock with the incoming character, while the stop interval marks the return to the idle state and separates successive characters.

Application

For this item, the start and stop bits provide the timing reference and frame boundaries that let the receiver sample the data bits at the intended instants.

Cross-check and contrast

• Error detection is performed by redundancy checks such as parity, checksums, or cyclic redundancy checks.

• Error correction requires an error-correcting code or a retransmission mechanism.

• Communication speed is governed mainly by the configured baud or symbol rate; start and stop bits add framing overhead but are not a speed-control setting.

A UART receiver detects the start edge, samples the following data bits at the configured baud timing, and then expects the stop state before it begins looking for the next start edge.

Result

Therefore, the required purpose is synchronization.