Software handshaking is a mechanism used in data communication to manage and control data flow between two devices using specific data characters or sequences within the transmitted data itself, rather than using separate dedicated lines or signals as in hardware handshaking. One of the most common software handshaking methods is XON/XOFF.

Key Points about Software Handshaking:

XON/XOFF Handshaking:

  • XON (Transmission On): It is a control character used to signal the transmitting device to resume sending data.
  • XOFF (Transmission Off): It is a control character used to signal the transmitting device to stop sending data temporarily. When the receiving device’s buffer starts to fill up and it needs the transmitting device to pause, it sends the XOFF character. Once it’s ready to receive more data (after processing or clearing its buffer), it sends the XON character to resume transmission.

Embedded in Data Stream: Unlike hardware handshaking that uses separate physical lines, software handshaking embeds control signals within the data stream itself.

Applications: Software handshaking is commonly used in serial communication where dedicated control lines might not be available or practical.

Advantages:

  • Simplicity in Wiring: No need for extra wires or pins on connectors, making it suitable for devices with limited physical connection options.
  • Flexibility: Can be easily implemented in software without changes to hardware.

Limitations:

  • Potential for Data Confusion: Since control signals are embedded within the data stream, there’s a risk of confusion if the transmitted data contains the same sequences as the control characters.
  • Reduced Data Rate: The need to check for control characters within the data stream can introduce a slight overhead, potentially reducing the effective data transmission rate.
  • Latency: Software-based flow control might introduce additional latency due to processing time, especially on slower or heavily-loaded systems.

In summary, software handshaking is a method of flow control in communications that uses special control characters embedded within the data stream to manage the rate of data transmission between devices. It offers simplicity and flexibility but has some inherent challenges compared to hardware-based handshaking.