The PC’s parallel (LPT) port will be used to control our circuit. In addition to controlling the direction of rotation, we will use the port for a few other things:

Checking the limit switches.
Turning AC power to the monitor on or off.
Controlling the monitor’s degaussing circuit.

The LPT port pins we will use as outputs (controls) are:

Pin 2 - H-bridge low level control 1, rotate clockwise
Pin 3 - H-bridge low level control 2, rotate counter clockwise
Pin 5 - Monitor degauss
Pin 6 - Monitor On/Off
 

LPT pins used as inputs:

Pin 12 - limit switch 1, paired with output pin 2. Detects end of clockwise rotation.
Pin 13 - limit switch 2, paired with output pin 3. Detects end of counterclockwise rotation.

Pins 18-25 can be tied together and used as ground. (Or any one of these pins can be used as ground)

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