Black Box Explains...IEEE 1284.
Introduced in 1994, the IEEE 1284 standard addresses data-transfer speeds and distance for parallel interfaces. Standard parallel interfaces support speeds of up to 150 kbps at distances of up to 6 feet (1.8 m); IEEE 1284 parallel interfaces can send your data over 100 times faster at up to five times the distance!
Although the Centronics® interface enabled only unidirectional computer-to-peripheral data flow, the IEEE 1284 interface enables bidirectional flow so peripherals can send data to the computer.
The IEEE 1284 standard covers five separate parallel modes, from the original Centronics (with which it’s compatible) to the high-performance Enhanced Parallel Port (EPP) mode. The computer negotiates with the attached device to determine which mode to use.