I have read this question and the answers that follow on the electrical stack exchange but I still face a difficulty in understanding the practical difference between high-Z state and 0 state. It is commonly used in hardware description languages. I know that the high-Z state is when the connection is removed. But I want to understand the physical difference.
My question is best understood with the help of this thought experiment:
Consider only the output terminal of a tri-state buffer is visible and available to me, and a demon (like the one in Maxwell's thought experiment) is applying 0 or 1 to the 2 inputs of the tri-state buffer. I have to detect when the terminal is tri-stated. I have only an LED and a NOT gate with me and both are of the same logic family as the tri-state buffer. I can ground my circuit.
First, I connect the LED to the output terminal of the buffer. I know that the LED will remain off when the output of the buffer is 0 and when the output of the buffer is tri-stated.
So instead, I'll place a NOT gate between the output of the tri-state buffer and the LED. So will the LED will be off only when a logic 1 is on the output of the tri-state buffer?
If so, is it possible to identify whether a terminal is tri-stated or 0 without measuring the resistance of the terminal?
When you stop pushing the button, the MCU input is disconnected from 4V supply, but since there is nothing to discharge that 4V from the parasitic capacitance, it will stay at 4V forever, and will never read as logic 0, no matter how long you wait.
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