I2C Parallel printer port adaptor

The circuit in the diagram permits I2C software programs to communicate via the Centronics outputs of any IBM compatible PC in conjunction with a buffer IC Type 74LSO5. This IC has open collector outputs to facilitate the parallel switching of I2C applications on the bus. A slight drawback of the present circuit is that everything is done via software, but that is countered by the fact that everything is under full control. Note, however, that some programming languages, such as Visual BASIC. do not allow writing directly to I/O addresses. Most of the ‘older’ languages do.

The circuit shown is used by Philips in the demonstration packages for IC  application . Note that the +5 V supply line cannot be taken from the

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