In asynchronous serial communication, what is the role of "Hardware Handshaking" (e.g., using RTS/CTS lines)?

Question

In asynchronous serial communication, what is the role of "Hardware Handshaking" (e.g., using RTS/CTS lines)?

1. A. To provide error detection using parity bits
2. B. To synchronize the internal clocks of both devices
3. C. To encrypt data before transmission
4. D. To prevent data loss by managing buffer overflow (Correct answer)

Correct Answer

Option D — To prevent data loss by managing buffer overflow

Detailed Solution & Explanation

The correct answer is To prevent data loss by managing flow control.

Key Points

• Hardware handshaking using the RTS (Request To Send) and CTS (Clear To Send) lines is a flow control mechanism.
• The receiver signals on these dedicated lines when it is ready to accept more data, so the sender pauses rather than overrunning a full buffer — which is how data loss is prevented.
• It performs no error detection, no clock synchronisation and no encryption, which rules out the other options.

Additional Information

• The alternative is software handshaking, which sends XON/XOFF control characters within the data stream instead of using separate wires — simpler wiring but unusable for binary data containing those byte values.
• In asynchronous transmission there is no shared clock; framing is provided by start and stop bits around each character, with an optional parity bit for basic error detection.
• RS-232 is the classic serial standard defining these control lines.
• Baud rate measures signalling events per second, which equals bits per second only when each symbol carries a single bit.