Final answer:
The push/pull configuration allows a microcontroller to directly drive a high or low voltage on an output pin, while an open drain configuration relies on an external pull-up resistor to determine the high voltage and connects to ground for a low voltage.
Step-by-step explanation:
The difference between outputting a logic 1 on an output pin in a push/pull configuration versus a pin in an open drain configuration is essentially how the voltage is set on the output pin. In a push/pull configuration, the microcontroller directly drives the output pin. When the pin is set to logic 1, the transistor connecting to the positive voltage rail inside the microcontroller is closed, creating a direct connection from the power rail to the pin, resulting in a high voltage equivalent to logic 1. Conversely, a logic 0 is achieved by opening the transistor connected to the positive rail and closing the one connected to the ground, pulling the pin down to a low voltage. In an open drain configuration, the pin is connected to ground through a transistor, which is normally open for a logic 1, meaning no connection is made and the voltage on the pin is determined by an external pull-up resistor. For a logic 0, the transistor connects to ground, pulling the pin down to Low.