Parallel port

The parallel interface called a digital input or output of a computer or a peripheral device. In data transmission over a plurality of bits, a parallel interface are transmitted in parallel, as opposed to the serial interface, in which the bits are successively transmitted.

In terms of peripherals is nowadays usually meant by " parallel port " a port IEEE 1284, which, after its use as a printer port or printer port (English line printing terminal, short- LPT ) is called; usually still the port number was the appended, so for example, LPT1 or LPT2. The LPT port has 25 pins. Before formulating the IEEE 1284 only one-way communication with devices possible (Centronics interface), which limited the application to printer or special software drivers for individual applications was such as required scanner. The achievable data rate is at least the EPP mode at 2 MB / s per direction, in use.

With the development and wide availability of equipment for the USB from around 2002, and FireWire parallel interfaces are practically only used for older peripherals or from older computers and thus. Than outdated interface, English legacy port, out.

Control blocks for parallel ports

The link between the connectable peripherals and the microprocessor or microcontroller used in the device is for this purpose specially optimized block that mostly as a PIO (English: parallel input / output) or PPI (English: programmable peripheral interface ) is called. Among his most important tasks is only to control the data transfer and cache the data also often adjusting the signal level. Building blocks for parallel ports are to be found in many forms and variations. Depending on the manufacturer, the wiring diagram of the blocks was such that it is particularly easy to a specific processor family, usually the manufacturer, for example Zilog ( Z80 -PIO for the Z80 CPU) or Intel ( 8255 for the 8080 / 8086 family) could connect.

Standards on board level

Bus standards:

  • VMEbus for industrial computer on 68xxx - based Motorola and Philips
  • NuBus bus system from Apple, NeXT and TI
  • ATA bus in PC bus 80xxx base (predecessor from the PCI bus )
  • ISA bus (XT or AT bus)
  • PCI and AGP bus
  • Europe Card Bus and DENYS systems

Communication of the order 0.1-20 m

  • ATA / ATAPI hard disk and CD / DVD drives
  • SCSI for hard drives, scanners, CD / DVD drives
  • IEC -625 bus, HP- IB or IEEE -488 for measuring devices, plotters, printers
  • IEEE 1284, EPP, ECP Centronics printer interface
Motherboard Gameport Centronics#The interface IEEE 1394 Flow control (data) Intel 8255 Intel 8080 Accelerated Graphics Port
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