Parallel port

In computing, a parallel port is an interface from a computer system where data is transferred in or out in parallel, that is, on more than one wire. A parallel port carries one bit on each wire thus multiplying the transfer rate obtainable over a single cable (contrast serial port). There are also several extra wires on the port that are used for control and status signals to indicate when data is ready to be sent or received, initiate a reset, indicate an error condition (such as paper out), and so forth. On many modern (2005) computers, the parallel port is omitted for cost savings, and is considered to be a legacy port.

Uses

Parallel ports are most often used by microprocessors to communicate with peripherals. The most common kind of parallel port is a printer port, e.g. a Centronics port which transfers eight bits at a time. Disks are also connected via special parallel ports, e.g. SCSI, ATA.

Related Topics:
Microprocessor - Communicate - Peripheral - Centronics - SCSI - ATA

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Before USB connections became widespread on mass-market computers, many external devices, such as portable disk drives for Windows systems, used a rather awkward pass-through connector so the device could share a parallel port with a printer. This was done because mass-market Windows boxes of the era lacked any equivalent of the SCSI connections then common on some other platforms; the only convenient connection was usually the single printer port.

Related Topics:
USB - SCSI

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The parallel port of an IBM-PC compatible is the only standard computer port that brings standard computer logic voltages directly out to a set of pins. It is much beloved by experimenters and engineers who often use it for inexpensive computer controlled projects. Standard logic voltages are virtually harmless: five volts (roughly the same as two run-down flashlight batteries), and ground (zero volts).

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