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A serial port is a serial communication interface through which information transfers in or out sequentially one bit at a time. [1] This is in contrast to a parallel port , which communicates multiple bits simultaneously in parallel .
Parallel versus serial communication In data transmission , parallel communication is a method of conveying multiple binary digits ( bits ) simultaneously using multiple conductors. This contrasts with serial communication , which conveys only a single bit at a time; this distinction is one way of characterizing a communications link .
For example, on the original IBM PC, a male D-sub was an RS-232-C DTE port (with a non-standard current loop interface on reserved pins), but the female D-sub connector on the same PC model was used for the parallel "Centronics" printer port. Some personal computers put non-standard voltages or signals on some pins of their serial ports.
Serial communication is used for all long-haul communication and most computer networks, where the cost of cable and difficulty of synchronization make parallel communication impractical. Serial computer buses have become more common even at shorter distances, as improved signal integrity and transmission speeds in newer serial technologies ...
The name refers to the way the data is sent; parallel ports send multiple bits of data at once (parallel communication), as opposed to serial communication, in which bits are sent one at a time. To do this, parallel ports require multiple data lines in their cables and port connectors and tend to be larger than contemporary serial ports , which ...
Parallel ports send multiple bits at the same time over several sets of wires. Serial ports send and receive one bit at a time via a single wire pair (Ground and +/-). After ports are connected, they typically require handshaking, where transfer type, transfer rate, and other necessary information is shared before data is sent.
Each device internally uses a shift register for serial communication, which together forms an inter-chip circular buffer. Sub devices should use tri-state outputs so their MISO signal becomes high impedance (electrically disconnected) when the device is not selected. Subs without tri-state outputs cannot share a MISO line with other subs ...
In general, parallel interfaces are quoted in B/s and serial in bit/s. The more commonly used is shown below in bold type. On devices like modems , bytes may be more than 8 bits long because they may be individually padded out with additional start and stop bits; the figures below will reflect this.