Sign in Subscribe

RTS (ready to send)

Last updated on 


In the context of communication protocols, RTS stands for "Ready To Send." It is a control signal used in certain communication systems to coordinate the transmission of data between two devices, typically in a serial communication setup.

RTS is part of the hardware flow control mechanism, which allows devices to regulate the flow of data between them to prevent data loss or buffer overflow. It is often used in situations where the transmitting device has a limited buffer capacity and needs to ensure that the receiving device is ready to receive data before sending it.

Here's how the RTS mechanism works:

  1. RTS Signal: In a typical setup, both the transmitting device (sender) and the receiving device (receiver) have RTS lines, which are control signals. The RTS line is usually controlled by the sender and indicates whether it is ready to send data.
  2. RTS Assertion: When the sender has data to transmit and its buffer is ready to accept more data, it asserts the RTS line, setting it to a logical high state. This action indicates that the sender is ready to send data.
  3. RTS Handshaking: Upon receiving the RTS signal, the receiving device acknowledges the readiness to receive data. This acknowledgment is usually done through another control signal called CTS (Clear To Send). The CTS line is controlled by the receiver.
  4. CTS Signal: When the receiving device is ready to receive data, it asserts the CTS line, indicating that it is clear to receive data.
  5. Data Transmission: With RTS asserted and CTS received, the sender can start transmitting data to the receiver. The data transmission can continue until the sender completes sending its data or until it decides to pause the transmission.
  6. RTS Deassertion: Once the sender finishes transmitting data or decides to pause the transmission, it deasserts the RTS line, indicating that it is no longer ready to send data.
  7. CTS Deassertion: Upon detecting the deassertion of RTS, the receiver can deassert the CTS line, indicating that it is no longer ready to receive data.

By using RTS and CTS signals, the sender and receiver can coordinate the data transfer process, ensuring that data is transmitted only when the receiver is ready to receive it. This flow control mechanism helps avoid data loss, buffer overflow, and data transmission errors in situations where the transmission rate of the sender is faster than the reception rate of the receiver.

It's important to note that the RTS/CTS mechanism is just one of several flow control methods employed in communication systems. Other methods include software-based flow control, such as XON/XOFF, which rely on specific control characters sent within the data stream to pause or resume transmission. The choice of flow control mechanism depends on the specific communication protocol and the devices involved.