EPP/ECP (Enhanced Parallel Port/Enhanced Capability Port)

EPP/ECP (Enhanced Parallel Port/Enhanced Capability Port) is a standard signaling method for bi-directional parallel communication between a computer and peripheral devices that offers the potential for much higher rates of data transfer than the original parallel signaling methods. EPP is for non-printer peripherals. ECP is for printers and scanners. EPP/ECP are part of IEEE Standard 1284, which also specifies support for current signaling methods (including Centronics, the de facto standard for printer communication) so that both old and new peripherals can be accommodated.

The new standard specifies five modes of data transfer. Three of them support the older mono-directional modes (a forward direction method from PC to Centronics printer and two reverse direction methods from peripheral to the PC). The fourth and fifth modes, EPP and ECP, are bi-directional signaling methods, meaning that they are designed for back-and-forth communication. Partly because these are being implemented in hardware, EPP and ECP will provide much faster data transfer. The first three methods offer an effective data transfer rate of 50 to 100 kilobytes per second. EPP and ECP offer the possibility of rates "in excess of 1 megabyte per second," according to Warp Nine, a chip manufacturer.

In order to get the maximum advantage of EPP/ECP, both operating system (or an I/O port controller, or both) and peripheral device must support the standard. Initially, you may get the best effect from EPP and a Zip drive. Even printers that support ECP are limited by the mechanical aspects of printing. Nevertheless, even users of the compatibility modes of Standard 1284 are also expected to see some benefit in data transfer to and from peripherals.

Windows operating systems have built-in support for IEEE 1284 in their parallel plug and play feature. Windows also supports ECP in forward direction, assuming you have a printer and a parallel port with ECP. It is likely that other vendors will provide ECP or EPP software for other operating systems.

EPP/ECP is described fully in IEEE Std. 1284-1994 Standard Signaling Method for a Bi-Directional Parallel Peripheral Interface for Personal Computers.