IEEE 1284

What is IEEE 1284?

An Institute of Electrical and Electronics Engineers (IEEE) standard for high-speed bidirectional parallel communication. IEEE 1284 defines the high-speed printer interface called the Enhanced Parallel Port (EPP), which is compatible with the Centronics port used for connecting parallel port printers to computers.

IEEE 1284 enables bidirectional communication between computers and attached printers. It also enables computers to spool jobs to printers at more than 10 times the speed of a traditional parallel port interface.

How IEEE 1284 Works

To make bidirectional printing work using IEEE 1284, you need the following:

• A print device that supports bidirectional printing.
• A printer driver that supports bidirectional printing.
• A correctly configured parallel port on the connected computer (print server). For example, if the parallel port is configured as AT-compatible, change it to PS/2 mode.
• An IEEE 1284–compliant cable.

For example, Microsoft Windows 98 can detect plug and play print devices by communicating with them. The bidirectional communication allows the print device to return information to the computer that queried it for hardware information. This information can include IEEE 1284 device ID values, printer memory, installed fonts, and other information that the printer driver on the server can use to install and configure the printer. Bidirectional communication also allows the print device to send status messages (such as an “out of paper” message) to the server.

IEEE 1284 specifies two electrical interfaces:

• Level I interface, which functions at a lower speed and provides only reverse-mode capabilities
• Level II interface, which functions at a higher speed and provides bidirectional communication

The connectors for the IEEE 1284 interface also come in several types:

• Type A connectors, which are standard 25-pin DB25 connectors
• Type B connectors, which are 36-pin centerline Champ connectors with bale locks to hold the cable in place for physical security
• Type C connectors, which are 36-pin centerline miniconnectors with clips for physical security