This lesson explains how data is moved from one device to another. You will compare serial and parallel transmission, the three directions of flow (simplex, half-duplex and full-duplex), how data is broken into packets with a header, payload and trailer, and the features and benefits of the USB standard.
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Serial and parallel transmission
Serial transmission sends the bits of data one after another, one at a time, down a single wire or channel.
Parallel transmission sends several bits at the same time, side by side, down several wires at once (for example 8 bits along 8 wires).
Serial is more reliable over long distances and uses fewer wires, so it is cheaper and less prone to bits arriving out of step (skew).
Parallel can be faster over very short distances because several bits travel together, but skew and interference make it unsuitable over long distances.
Check you've got it
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1. Which statement correctly describes serial transmission?
2. A walkie-talkie lets two people talk, but only one can speak at any moment. Which mode of data flow does this describe?
3. In a data packet, which part contains the destination address and the packet number?
4. Which of these is a genuine benefit of the USB standard?