Extended capabilities port

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Extended Capabilities Port ( ECP ) is a mode of the parallel interface of a computer. ECP was developed by Hewlett-Packard and Microsoft to improve communication with printers and scanners . ECP is a further development of SPP and EPP and, like these, is connected via a Centronics interface in accordance with IEEE 1284 .

The decisive advantage of ECP is that the data is sent in compressed form. The maximum compression rate of the run length coding is 64: 1, typically 4: 1 on average. It is efficiently implemented in the hardware's interface modules and is particularly effective when raw image data are transmitted.

In addition, a 16 kB FIFO buffer is used, which has the following advantages:

  • The effective bandwidth of the transmission is increased because several data words can be received and temporarily stored.
  • Loss of data is prevented if the CPU is busy and cannot read out data immediately.
  • Fewer interrupts relieve the CPU .