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Computer Busses by William Buchanan

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17

Enhanced Parallel Port

17.1 Introduction

The Centronics parallel port only allows data to be sent from the host to a peripheral. To overcome this the IEEE published the 1284 standard, entitled ‘Standard Signaling Method for a Bidirectional Parallel Peripheral Interface for Personal Computers’. It allows for bidirectional communication and high communication speeds, while being backwardly compatible with existing parallel ports.

The IEEE-1284 standard defines the following modes:

 Compatibility mode (forward direction only) – This mode defines the transfer of data between the PC and the printer (Centronics mode, as covered in the previous chapter).

 Nibble mode (reverse direction) – This mode defines how four bits are transferred, at a time, using ...

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