IEEE 1284
An IEEE standard for an enhanced parallel interface (parallel port) for personal computers, superseding the Centronics interface. Introduced in 1994, IEEE 1284 can send addresses, allowing individual components in a multifunction device (printer, scanner, fax, etc.) to be addressed independently. Unlike the Centronics interface, the specifications of the cable are defined in IEEE 1284, providing a cable length up to 32 feet. A legacy interface today, IEEE 1284 has been superseded by USB and network connections. See Centronics interface and USB.
Five Modes of Operation
IEEE 1284 defines five modes, and the driver determines which to use based on the connected device. Compatibility mode enables data transfer with the earlier Centronics interface at 150 KB/sec.
Enhanced Capabilities Port (ECP) mode and Enhanced Parallel Port (EPP) mode provide bidirectional speeds up to 1.5 MB/sec. ECP was proposed by HP and Microsoft for printers, and EPP was proposed by Intel, Xircom and Zenith Data Systems for other peripherals.
Byte and Nibble modes provide an 8-bit and 4-bit channel respectively from the peripheral to the host. They are used to enhance the bidirectional capability of the Centronics standard.
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| IEEE 1284 Printer Cable |
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| Using the same connectors as the Centronics interface, but with a higher quality cable, IEEE 1284 cables can be up to 32 feet long. The PC contains a 25-pin, female DB-25 socket, while the printer has a 36-pin, female Centronics socket. |