Hardware handshaking is a mechanism used in data communication to manage and control data flow between two devices using dedicated hardware lines or signals. It helps in preventing data loss by ensuring that the transmitting device doesn’t send data faster than the receiving device can accept and process it.

Key Points about Hardware Handshaking:

Physical Lines: Hardware handshaking uses actual physical lines (wires or pins) for control signals, separate from the data lines.

RTS/CTS Handshaking:

  • RTS (Request to Send): Used by the transmitting device to signal that it is ready to send data.
  • CTS (Clear to Send): Used by the receiving device to grant permission to the transmitting device to send data. When the transmitter wants to send data, it asserts (sets active) the RTS signal. If the receiver is ready to accept the data, it asserts the CTS signal, indicating to the transmitter that it can start sending the data. If the receiver is not ready, it will de-assert the CTS signal, prompting the transmitter to pause data transmission.

DTR/DSR Handshaking:

  • DTR (Data Terminal Ready): Used by a device to indicate that it is ready to establish a communication link.
  • DSR (Data Set Ready): Used by the receiving device to acknowledge that it is ready to communicate.

Applications: Hardware handshaking is commonly used in serial communication, such as in RS-232 communication.

Advantages:

  • Immediate Response: Because it uses dedicated lines, hardware handshaking can provide almost instantaneous flow control feedback.
  • Reliability: Physical signals tend to be more reliable than software signals in certain applications, as they are less prone to software-induced delays or malfunctions.

Limitations:

  • Additional Wires: Requires extra wires or pins on connectors, which may not be feasible for devices with space constraints or for devices that prioritize simplicity.
  • Cost: Adding extra wires can increase the cost of cables and connectors.

In summary, hardware handshaking is a physical mechanism used to control data flow in communications, ensuring efficient and lossless data transfer by coordinating the readiness of transmitting and receiving devices.