IEEE 1284

IEEE 1284
Name	IEEE 1284
Caption	Parallel port connector and cable
Introduced	1994
Designer	IEEE
Type	Computer peripheral interface
Connector	DB-25, Centronics 36
Maxdata	2 MB/s (ECP/EPP modes)

IEEE 1284 IEEE 1284 is a standard defining a bi-directional parallel peripheral interface for personal computers and printers. It specifies electrical characteristics, connector pinouts, cable assemblies, and multiple signaling modes to support devices such as printers, scanners, and external storage across platforms including desktop and workstation systems. The standard formalizes interoperability among manufacturers, linking corporate adopters, standards bodies, and computing hardware ecosystems.

Overview

IEEE 1284 defines a parallel communication interface enabling peripheral devices to exchange data with host systems. The specification addresses physical connectors like DB-25, parallel printer interfaces used by companies such as Hewlett-Packard, Epson, and Canon, and cabling conventions adopted by firms including Centronics', IBM, and Compaq. It codifies electrical rules that relate to implementations found in products from Intel, Microsoft, and Sun Microsystems, and was ratified within the broader standards environment involving organizations such as Institute of Electrical and Electronics Engineers, International Organization for Standardization, and International Electrotechnical Commission.

History and Development

Development of the standard traces to parallel communication practices originating with the Centronics parallel port adopted by companies like Xerox and Tandy, and later integrated into systems from Apple Computer and Atari. Work on formalizing bi-directional operation involved contributors from Hewlett-Packard, Xerox PARC, and academic labs at institutions such as Massachusetts Institute of Technology and Stanford University. The standardization process included review by members of IEEE Standards Association, influenced by industry consortia and initiatives linked to product lines from Compaq, Dell, and Gateway 2000, with revisions coinciding with shifts toward interfaces like USB and IEEE 1394 championed by Apple Inc. and Sony.

Technical Specifications

IEEE 1284 specifies voltage levels, timing parameters, handshake control lines, and maximum cable lengths. Electrical characteristics reference driver and receiver requirements comparable to signaling rules used by RS-232 implementations developed by Bell Labs and chipset behaviors associated with Intel Corporation microcontrollers. Timing constraints and throughput expectations parallel design considerations in interfaces such as USB 1.1 and data-transfer concepts discussed in contexts like Advanced Technology Attachment and Small Computer System Interface device interactions from firms like Seagate and Western Digital.

Connector and Cable Types

The standard details connector families including the 25-pin parallel D-sub (DB-25) and 36-pin Centronics 36 types used by manufacturers such as HP, Epson, and Brother Industries. Cable specifications address impedance, shielding, and pin wiring used in assemblies supplied by vendors including Belkin, Molex, and 3M. Variants and adaptors created for systems from IBM PC/AT compatibles and Apple Macintosh models are documented alongside conversions used in legacy equipment retained by institutions like National Institutes of Health labs and university computer centers.

Modes of Operation and Signaling

IEEE 1284 defines several modes: Compatibility (Standard Parallel Port), Nibble Mode, Byte Mode, Enhanced Parallel Port (EPP), and Extended Capabilities Port (ECP). EPP and ECP modes offer higher throughput and DMA-assisted transfers used in devices deployed by Canon, Lexmark, and Xerox. Mode negotiation and handshaking mirror control-line interactions analogous to signaling in V.24 interfaces and influenced driver stacks developed for operating systems such as Microsoft Windows, Linux, and FreeBSD supported by communities including Debian and Red Hat.

Implementations and Use Cases

Implementations span printers from Hewlett-Packard, scanners from Kodak, external ZIP drives sold by Iomega, and legacy parallel-port network adapters used in small offices and embedded systems by Siemens and Texas Instruments. Software drivers integrating IEEE 1284 support were distributed by Microsoft Corporation for Windows 95/Windows 98 and by open-source projects maintained by contributors at GNU Project and The NetBSD Foundation. The interface saw use in industrial control equipment supplied by firms such as Rockwell Automation and Schneider Electric as well as educational computing deployments at institutions like University of California, Berkeley.

Compatibility and Legacy Issues

Compatibility challenges arose with the transition to serial and high-speed interfaces like USB 2.0 and PCI Express promoted by the USB Implementers Forum and PCI-SIG, leading to adapter products from companies including Trendnet and StarTech.com. Legacy systems relying on IEEE 1284 faced driver support issues on modern platforms such as Windows 10 and macOS maintained by Apple Inc., prompting virtualization and emulation strategies used by researchers at Carnegie Mellon University and MIT Lincoln Laboratory. Preservation efforts for historical computing environments involve museums like the Computer History Museum and archives at Smithsonian Institution.

Category:Computer buses