Such SIO communication can be asynchronous with start and stop bits, or synchronous with additional synchronization bits. Serial asynchronous transmission is more flexible than synchronous transmission, which makes better use of the available bandwidth.
For years, SIO technology was relatively slow. Only through the use of advanced semiconductor technologies, could data rates of several hundred megabits per second (Mbit/s) be achieved. Well-known interfaces with SIO technology are the USB interface, Firewire and IEEE 1394.