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The Extended Capabilities Port (ECP) is a parallel port for personal computers (PCs) that supports bi-directional communication between a computer and a peripheral device such as a printer. Parallel ports can usually be classified into four different types: standard parallel port (SPP), parallel port (PS/2), enhanced parallel port (EPP) and extended parallel port (ECP).
Techopedia Explains Extended Capabilities Port
Parallel ports were originally designed for communication between a computer and a printer. The first parallel port was the SPP or normal port, introduced in 1981. It allowed data to flow in one direction only and is the slowest of all types of parallel ports. The PS/2 port came into existence in 1987;this bi-directional port was capable of reading data from the peripheral device to the host. In 1994, the EPP was developed; this much faster bi-directional parallel port transmits large amounts of data while switching channel direction.The EPP is supported by an 8-bit bidirectional communication at Industry Standard Architecture (ISA) bus speeds.
The bi-directional ECP was launched in 1994 by Hewlett Packard and Microsoft. The ECP features provide an even faster data transfer than EPP. Unlike EPP, it has direct memory access (DMA) that allows certain types of data to bypass a microprocessor, a data hardware compression and a first-in/first-out (FIFO) buffer. FIFO organizes data in relation to priority and time.
With the increased diversity of parallel port hardware, standardizations were developed to avoid issues with incompatibility. The Standard Signaling Method for a Bi-directional Parallel Peripheral Interface for Personal Computers (IEEE 1284) standard was implemented to support bi-directional data flow. The IEEE 1284 specifies five modes of operation: compatibility mode, nibble mode, byte mode, ECP mode and EPP mode. Each mode supports data transfer in the backward direction, forward direction or bi-directional. To make sure that data integrity is upheld, the IEEE 1284 sets standard for the interface, cable and connector.
