At system start up and reset, the hardware sets all digital I/O lines to high-impedance inputs by default.

The USB-6423 does not drive the signal high or low. Each line has a weak pull-down resistor connected to it.

NI-DAQmx supports programmable power-up states for digital I/O lines. Software can program any value at power up to the P0 line. You can set the digital I/O lines in the following ways:

  • A high-impedance input with a weak pull-down resistor (default)
  • An output driving a 0
  • An output driving a 1