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Encyclopedia > Parallel port
A DB-25 parallel printer port, as on IBM-PC style, and a few other types of computers.
A DB-25 parallel printer port, as on IBM-PC style, and a few other types of computers.
Micro ribbon 36 pin female, such as on printers and on some (particularly industrial and early- and pre-1980s personal) computers.
Micro ribbon 36 pin female, such as on printers and on some (particularly industrial and early- and pre-1980s personal) computers.

A parallel port is a type of interface found on computers (personal and otherwise) for connecting various peripherals. It is also known as a printer port or Centronics port . The IEEE 1284 standard defines the bi-directional version of the 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. ... Image File history File linksMetadata Download high resolution version (1787x1340, 503 KB) Summary Licensing File links The following pages on the English Wikipedia link to this file (pages on other projects are not listed): Parallel port Metadata This file contains additional information, probably added from the digital camera or scanner... Image File history File linksMetadata Download high resolution version (1787x1340, 503 KB) Summary Licensing File links The following pages on the English Wikipedia link to this file (pages on other projects are not listed): Parallel port Metadata This file contains additional information, probably added from the digital camera or scanner... DB-25 is a RS-232 D-shell connector, with a total of 25 pins across two rows. ... Image File history File links Size of this preview: 800 × 301 pixelsFull resolution‎ (1,024 × 385 pixels, file size: 54 KB, MIME type: image/jpeg) Description: Micro ribbon connector Centronics 36pin female, on a circuitboard Author, date of creation: selfmade by Shaddack, 17 October 2005 Source: self-made Copyright: Public... Image File history File links Size of this preview: 800 × 301 pixelsFull resolution‎ (1,024 × 385 pixels, file size: 54 KB, MIME type: image/jpeg) Description: Micro ribbon connector Centronics 36pin female, on a circuitboard Author, date of creation: selfmade by Shaddack, 17 October 2005 Source: self-made Copyright: Public... The tower of a personal computer. ... A personal computer (PC) is a computer whose price, size, and capabilities make it useful for individuals. ... For other uses, see Centronics (disambiguation). ... Categories: Stub | Computer buses | IEEE standards ...

Contents

Current popularity

For the most part, the USB interface has replaced the Centronics-style parallel port. Also, some printers use an ethernet connection instead. As a result, many personal computer manufacturers (beginning in the early 2000s) have begun omitting the parallel port to save cost. It is now considered to be a legacy port. For laptops, access to a parallel port is still commonly available via a docking station; and adapters are available for USB, etc. USB redirects here. ... Ethernet is a large, diverse family of frame-based computer networking technologies that operate at many speeds for local area networks (LANs). ... A legacy port is a port or connector on a PC that is considered fully or partially obsolete. ... Docking station. ...


Uses

  • Some printers
  • Zip drive
  • Some scanners
  • Some sound cards
  • Some Webcams
  • Some gamepads and joysticks
  • Peripheral devices such as EPROM programmers
  • SCSI devices via a Parallel to SCSI adapter
  • Experimental setups using the 12 TTL drivers.
  • External CD-Rom/RW drives

Iomega ZIP-100 Drive Logo An internal Zip drive. ... In computing, a scanner is a device that analyzes images, printed text, or handwriting, or an object (such as an ornament) and converts it to a digital image. ... A typical webcam A web camera (or webcam) is a real-time camera (usually, though not always, a video camera) whose images can be accessed using the World Wide Web, instant messaging, or a PC video calling application. ... This article does not cite any references or sources. ... For other uses, see Joystick (disambiguation). ... Scuzzy redirects here. ... A Motorola 68000-based computer with various TTL chips mounted on protoboards. ...

Implementation on IBMoid personal computers

Port addresses

Traditionally IBM PC systems have allocated their first three parallel ports according to the configuration in the table below.

PORT NAME Interrupt # Starting I/O Ending I/O
LPT1 IRQ 7 0x3bc 0x3bf
LPT2 IRQ 5 0x378 0x37f
LPT3 IRQ 5 0x278 0x27f

If there is an unused LPTx slot, the port addresses of the others are moved up. (For example, if a port at 0x3bc does not exist, the port at 0x378 will then become LPT1.) The IRQ lines, however, remain fixed (therefore, 0x378 at LPT1 would use IRQ 7). The port addresses assigned to each LPTx slot can be determined by reading the BIOS Data Area (BDA) at 0000:0408. In computing, an interrupt is an asynchronous signal from hardware or software indicating the need for attention. ... On a computer system, an I/O address is specific portion of address space in the CPU used to read/write to specific devices within the computer. ... On a computer system, an I/O address is specific portion of address space in the CPU used to read/write to specific devices within the computer. ... IRQ redirects here. ... IRQ redirects here. ... IRQ redirects here. ...


Bit to Pin Mapping for the Standard Parallel Port (SPP):

Address MSB LSB
Bit: 7 6 5 4 3 2 1 0
Base Pin: 9 8 7 6 5 4 3 2
Base+1 Pin: ~11 10 12 13 15
Base+2 Pin: ~17 16 ~14 ~1

~ indicates a hardware inversion of the bit. The binary representation of decimal 149, with the MSB highlighted. ... The binary representation of decimal 149, with the lsb highlighted. ...


Program interface

In versions of Microsoft Windows that did not use the Windows NT kernel (as well as MS-DOS and some other operating systems), programs could access the parallel port with simple outportb() and inportb() subroutine commands. In operating systems such as Windows NT and Unix (NetBSD, FreeBSD, Solaris, 386BSD, etc), the microprocessor is operated in a different security ring, and accesses to the parallel port is inhibited, unless using the required driver. This improves security and arbitration of device contention. Microsoft Corporation, (NASDAQ: MSFT, HKSE: 4338) is a multinational computer technology corporation with global annual revenue of US$44. ... 1. ... Windows NT (New Technology) is a family of operating systems produced by Microsoft, the first version of which was released in July 1993. ... Microsofts disk operating system, MS-DOS, was Microsofts implementation of DOS, which was the first popular operating system for the IBM PC, and until recently, was widely used on the PC compatible platform. ... Windows NT (New Technology) is a family of operating systems produced by Microsoft, the first version of which was released in July 1993. ... Filiation of Unix and Unix-like systems Unix (officially trademarked as UNIX®, sometimes also written as or ® with small caps) is a computer operating system originally developed in 1969 by a group of AT&T employees at Bell Labs including Ken Thompson, Dennis Ritchie and Douglas McIlroy. ... NetBSD is a freely redistributable, open source version of the Unix-like BSD computer operating system. ... FreeBSD is a Unix-like free operating system descended from AT&T UNIX via the Berkeley Software Distribution (BSD) branch through the 386BSD and 4. ... Solaris is a computer operating system developed by Sun Microsystems. ... 386BSD, also known as JOLIX, is a free BSD operating system for the Intel 80386. ...


Pinouts

Pinouts for a DB25 connector are: Pinout is a term used in electronics to describe how an electrical connector is wired. ...

Pin No (DB25) Signal name Direction Register - bit Inverted
1 nStrobe Out Control-0 Yes
2 Data0 In/Out Data-0 No
3 Data1 In/Out Data-1 No
4 Data2 In/Out Data-2 No
5 Data3 In/Out Data-3 No
6 Data4 In/Out Data-4 No
7 Data5 In/Out Data-5 No
8 Data6 In/Out Data-6 No
9 Data7 In/Out Data-7 No
10 nAck In Status-6 No
11 Busy In Status-7 Yes
12 Paper-Out In Status-5 No
13 Select In Status-4 No
14 Linefeed Out Control-1 Yes
15 nError In Status-3 No
16 nInitialize Out Control-2 No
17 nSelect-Printer Out Control-3 Yes
18-25 Ground - - -

Monodirectional parallel ports

In early parallel ports the data lines were monodirectional (data out only) so it was not easily possible to feed data in to the computer. However, a workaround was possible by using 4 of the 5 status lines. A circuit could be constructed to split each 8-bit byte into two 4-bit nibbles which were fed in sequentially through the status lines. Each pair of nibbles was then re-combined into an 8-bit byte. For other uses, see Nibble (disambiguation). ...


See also

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. ... In telecommunication, parallel transmission is: The simultaneous transmission of the signal elements of a character or other data item. ...

References


  Results from FactBites:
 
Parallel port - Wikipedia, the free encyclopedia (616 words)
Over a parallel port, binary information is transferred in parallel: each bit in a particular value is sent simultaneously as an electrical pulse across a separate wire (see parallel communications), in contrast to a serial port, which requires each bit to be sent in series over a single wire.
Parallel ports are most often used by microprocessors to communicate with peripheral devices.
However, when people refer to a parallel port, they are usually referring to a printer port, either on a printer or a PC.
  More results at FactBites »

 
 

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