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Introduction

The Parallel Port is the most commonly used port for interfacing home made projects. This port will allow the input of up to 9 bits or the output of 12 bits at any one given time, thus requiring minimal external circuitry to implement many simpler tasks. The port is composed of 4 control lines, 5 status lines and 8 data lines. It's found commonly on the back of your PC as a D-Type 25 Pin female connector. There may also be a D-Type 25 pin male connector. This will be a serial RS-232 port and thus, is a totally incompatible port. Newer Parallel Port’s are standardized under the IEEE 1284 standard first released in 1994.
This standard defines 5 modes of operation which are as follows,
1. Compatibility Mode.
2. Nibble Mode. (Protocol not Described in this Document)
3. Byte Mode. (Protocol not Described in this Document)

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for more details, please visit
http://beyondlogicspp/parallel.pdf

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4. EPP Mode (Enhanced Parallel Port).
5. ECP Mode (Extended Capabilities Port).
The aim was to design new drivers and devices which were compatible with each other and Interfacing the Standard Parallel Port