0
\$\begingroup\$

Suppose a pin can be set to three modes, high (5V), low (0V), and high impedance (?V). What is the voltage associated with high impedance? I.e. if I stuck a probe on a pin set to high impedance, what voltage would I read?

Does high impedance mean no current? If so, does that mean voltage measured would be 0 because of V=IR? If so, how would you differentiate high impedance and logic level low?

\$\endgroup\$
0

1 Answer 1

3
\$\begingroup\$

If you set a microcontroller or FPGA IO pin to high impedance, the voltage there will be determined by whatever other components you hook that pin.

If you provide a pull-down resistor, the voltage will go low. If you provide a pull-up resistor, the voltage will go high. (It might also be possible to program the chip itself to provide a pull-up or pull-down resistor)

If you don't connect anything that can set the voltage, then it could even float randomly up and down, respond to capacitive coupling from nearby objects (like your body), etc.

\$\endgroup\$

Not the answer you're looking for? Browse other questions tagged or ask your own question.