For a history of the Centronics interface, refer to the Centronics page. Centronics logo 23 June 1986 Centronics logo 1971 Centronics Data Computer Corporation was a pioneering American manufacturer of computer printers, now remembered only for the parallel interface that bears their name. ...

An IEEE 1284 compliant printer cable, with both DB-25 and 36 pin Centronics connectors.

IEEE 1284 is a standard that defines bi-directional parallel communications between computers and other devices. In the 1970s, Centronics developed the now familiar printer parallel interface that soon became a de facto standard. The standard became non-standard as enhanced versions of the interface were developed, such as the HP Bitronics implementation released in 1992. In 1991 the Network Printing Alliance was formed to develop a new standard. In March of 1994, the IEEE 1284 specification was released. An IEEE 1284-compliant printer cable. ... An IEEE 1284-compliant printer cable. ... A male DE-9 connector. ... Micro ribbon 36 pin female panel mount connector with bail locks The micro ribbon connector is a common type of electrical connector used particularly in various computer, telecommunication and other applications. ... In computing, a parallel port is an interface from a computer system where data are transferred in or out in parallel, that is, on more than one wire. ... The 1970s decade refers to the years from 1970 to 1979, inclusive. ... Centronics logo 23 June 1986 Centronics logo 1971 Centronics Data Computer Corporation was a pioneering American manufacturer of computer printers, now remembered only for the parallel interface that bears their name. ... To meet Wikipedias quality standards, this article or section may require cleanup. ... This article needs to be cleaned up to conform to a higher standard of quality. ... De facto is a Latin expression that means in fact or in practice. It is commonly used as opposed to de jure (meaning by law) when referring to matters of law or governance or technique (such as standards), that are found in the common experience as created or developed without... ... 1991 (MCMXCI) was a common year starting on Tuesday of the Gregorian calendar. ... The Printer Working Group charter is to develop standards that make printers, operating systems and aplications work better. ...

The IEEE 1284 standard allows for faster throughput and bidirectional data flow with a theoretical maximum throughput of 4 megabits per second, with actual around 2 depending on hardware. In the printer venue, this allows for faster printing and back channel status and management. Since the new standard allowed the peripheral to send large amounts of data back to the host, devices that had previously used SCSI interfaces could be produced at a much lower cost. This included scanners, tape drives, hard disks, computer networks connected directly via parallel interface, network adapters and other devices. No longer was the consumer required to purchase an expensive SCSI card- they could simply use their built in parallel interface. These low cost devices provided a platform to leapfrog the faster USB interface into its present popularity, displacing the parallel devices. However, the parallel interface remains highly popular in the printer industry with displacement by USB only in consumer models. SCSI stands for Small Computer System Interface, and is a standard interface and command set for transferring data between devices on both internal and external computer buses. ... CanoScan9950F Desktop scanner, with the lid raised. ... DDS tape drive. ... Typical hard drives of the mid-1990s. ... Note: USB may also mean upper sideband in radio. ...

Specifications

IEEE 1284 can operate in five modes:

• Compatibility Mode, also known as Centronics, standard or SPP, is a uni-directional implementation with only a few differences from the original Centronics design.
• Nibble Mode is a uni-directional interface that allows the device to transmit data four bits at a time using status lines for data. This is the Bi-tronics mode introduced by HP and is generally used for enhanced printer status.
• Byte Mode allows the device to transmit eight bits at a time using data lines.
• Enhanced Parallel Port (EPP) is a half-duplex bi-directional interface designed to allow non-printer devices to transmit large amounts of data to the host.
• Extended Capability Port (ECP) is a half-duplex bi-directional interface designed that allows RLE compression.

A IEEE compliant cable must meet several standards of wiring and quality. Three types of connectors are defined: A nibble (or less commonly, nybble) is the computing term for the aggregation of four bits, or half an octet (an octet being an 8-bit byte). ... ... Run-length encoding (RLE) is a very simple form of data compression in which runs of data (that is, sequences in which the same data value occurs in many consecutive data elements) are stored as a single data value and count, rather than as the original run. ...

• DB-25 (type A) for the host connection.
• Centronics (type B) 36 pin for the printer or device connection.
• Mini-Centronics (type C, MDR36) 36 pin, a smaller alternative for the device connection that has not proven popular.

IEEE 1284-I device uses IEEE 1284-A and IEEE 1284-B connectors, while IEEE 1284-II device uses IEEE 1284-C connectors. A male DE-9 connector. ... Micro ribbon 36 pin female panel mount connector with bail locks The micro ribbon connector is a common type of electrical connector used particularly in various computer, telecommunication and other applications. ...

1. ↑ IEEE-1284 Specification itself does not specify minimum guaranteed length for level 2 device, only amount of current, voltage, and pull-up resistant for the lines. In early PC interface, control signals is limited to sinking only 7 mA at 0.8 V, which practically limits cable length to 2 metres.
2. ↑ Specification itself only claims transfer rate depends on the speed of the host computer, the driver implementation, and the peripheral being used. However, output pulse is specified to 2 MHz, signals take 5 nanosecond to rise or fall. Listed speeds are confirmed maximum (without compression), calculated based on minimum time needed to completely transfer 1 byte of data and to perform any handshake necessary to start transferring the next byte of data. Ideal line condition is assumed. Timing excludes handshakes for negotiating a transfer mode or busy signal.

In IEEE 1284 Daisy Chain Specification, up to 8 devices can be connected to a single parallel port.

For detailed specifications, including pin-outs, refer to the links below.

IEEE 1284 standards

• IEEE 1284-1994: Standard Signaling Method for a Bi-directional Parallel Peripheral Interface for Personal Computers
• IEEE 1284.1-1997: Transport Independent Printer/System Interface- a protocol for returning printer configuration and status
• IEEE 1284.2: Standard for Test, Measurement and Conformance to IEEE 1284 (not approved)
• IEEE 1284.3-2000: Interface and Protocol Extensions to IEEE 1284-Compliant Peripherals and Host Adapters- a protocol to allow sharing of the parallel port by multiple peripherals (daisy chaining)
• IEEE 1284.4-2000: Data Delivery and Logical Channels for IEEE 1284 Interfaces- allows a device to carry on multiple, concurrent exchanges of data

See also

• Parallel Port
• FireWire
• S-ATA

In computing, a parallel port is an interface from a computer system where data are transferred in or out in parallel, that is, on more than one wire. ... The FireWire color logo FireWire (also known as i. ... A SATA power connector. ...

External links

• Warp Nine Engineering's introduction to the IEEE 1284-1994 standard
• Howstuffworks- How Parallel Ports Work
• IEEE 1284 - Updating the PC Parallel Port
• IEEE 1284 summary
• Draft IEEE 1284 specification