The IEEE 1284 parallel interface standard is the usual way for connecting a computer to a printer over a parallel (eight bits of data at once) physical and electrical interface. The physical connection is analogous to that of the older Centronics interface, which the standard continues to support. Unlike the Centronics interface which only allowed data flow in one direction, IEEE 1284 also has room for two-way streaming of data.
In early 1990s, IBM and others came together to deliberate on a standard which would give more speed and two way communication. So their efforts were rewarded by the IEEE 1284 committee coming into existence and this was sustained by the funding from Institute of Electrical and Electronics Engineers (IEEE). The IEEE 1284 standard was accepted to be made public in March, 1994 (Meyers & Acuña, 2003).
The IEEE 1284 standard details five types of operation. Each type it grants data to stream in either the forward direction (computer to peripheral), reverse direction (peripheral to computer) or bi-directional (one directional flow at a time).
1. Compatibility type
2. Nibble type. This type is best used in printers. This allows data to flow back to the computer.
3. Byte type. This uses software drivers to disable the drivers that control the data lines so that data can be sent from the printer to the computer. The data is transferred at the same speed like when the data is transferred from the computer to the printer.
4. ECP type. This is an advanced bi-directional type for use with printers and scanners. Data transfers happen in two to four megabytes in a second (Docter et al, 2006).
5. EPP type. It provides a high-performances parallel interface that can also be used with the standard interface.
The computer will have to decide what the capabilities of the attached peripheral are and which type to employ. The idea developed to determine these factors is referred to as negotiation. This is a sequence of events on the parallel port interface that decides which IEEE 1284 types the device can support.
