Does USB-6501 support tristate?

[Rando]

hi,

I am using LabVIEW 8.0 with USB-6501. The driver version is NI-DAQmx 8.0.I will like to know if USB-6501 supports tristate. I tried to use an example program which sets the digital output to tristate but after checking the line, it is still not in tristate. I checked this by measuring the voltage which is still about 5V. The example program I used is attached as a screen capture

[Travis G.]

Hello Rando,

The USB-6501 does support tristate mode, and the example program you are using shows the correct method for setting a line to tristate.  When you set a line to tristate, it is not being driven high or low, but instead to a high-impedance floating state.  When the output is floating, it is putting no load on the circuit, and it is impossible to determine what the state of the line will be when measured.  It can be driven low or high depending on the device used to measure the state of the line.  What tristate is useful for is if you have two sources driving the same signal, but only want one to drive it at a time.  

Hopefully this helps!

Travis G.
Applications Engineering