Asynchronous Communication

What Does Asynchronous Communication Mean?

Asynchronous communication is a transmission technique commonly used by personal computers (PCs) to connect to modems, printers, fax machines, modems, etc. With asynchronous communication, a series of bytes or ASCII characters can be sent via a single wire.


The data is transmitted as a series of bits. A shift register found either in the hardware or in the software can be used to serialize every data byte into a series of bits. These bits are then delivered via the wire with the help of a bus driver and an input/output (I/O) port to establish a connection with the cable.

Techopedia Explains Asynchronous Communication

The asynchronous communication method is generally employed to illustrate communications wherein data could be sent intermittently instead of sending it in a steady stream. Asynchronous communication is supported by nearly all types of computers. The most important benefit of asynchronous communication is that the receiver clock and the transmitter are independent and not synchronized.

Asynchronous communications include the following:

  • Communications between the devices inside a computer, for example, between the central processing unit (CPU) and the disk drives.
  • Communications between the computer and external devices, for example, between the computer and a printer, between the computer and a modem, and so on.

Asynchronous communications require that the receiver have the ability to differentiate between noise (random signals) and valid data. In communications triggered by computers, this is typically achieved by using special bits at the start and end of every message.

Characteristics of asynchronous communication:

  • Uses a simple interface
  • Used to connect printers, modems, terminals, home connections to the Web
  • No clock sent
  • Demands start and stop bits that offer byte timing and elevates overhead
  • Parity generally utilized to verify accurate reception

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Margaret Rouse
Technology Expert

Margaret is an award-winning technical writer and teacher known for her ability to explain complex technical subjects to a non-technical business audience. Over the past twenty years, her IT definitions have been published by Que in an encyclopedia of technology terms and cited in articles by the New York Times, Time Magazine, USA Today, ZDNet, PC Magazine, and Discovery Magazine. She joined Techopedia in 2011. Margaret's idea of a fun day is helping IT and business professionals learn to speak each other’s highly specialized languages.