USB-6509 loopback test

[Mohkh]

I'm performing a loopback test for USB-6509

I will connect each port to another port (port 0 channel 0 to port 1 channel 0 .. and so on) 

I will write using port 0 and then read using port 1, then I will write using port 1 and I will read using port 0

my question is:

do i need to connect a pull-down resistor between each two channels ?

[santo_13 · Accepted solution]

No, you don't need to connect an external pulldown. There are inbuilt pull-up/down resistors on each channel configured by a single switch on the instrument,

It has to be either pulled up to 5V or down to GND and cannot be disconnected.

As for your loopback testing, no external components are required, just loop back port-port and implement the testing, but just make sure that at no point in time both the ports are DOs or you might damage the front-end electronics.

For more details, please refer the user guide -https://www.ni.com/pdf/manuals/372136a.pdf