I have a PCI-6509 measuring 96 digital signals. The signals I'm reading are supplied by device that outputs HIGH by pulling to a 3.3V rail through a 10K and a LOW by a transistor pulling it to ground. The system is not reliably detecting the HIGH/LOW state. It measures most of the channels correctly most of the time but there are occasional glitches.
I still have some work to do in verifying the signal integrity of the test fixture (especially the grounding on the DUT PCBs) as the system was designed and wired by a Mechanical Engineer 
but I have also ordered a PCIe version of the 6509 card due to its programmable Pull-Up / Pull-Down option in case it is needed.
I'm working to modify the LabVIEW software to add the Pull-Down feature on the lines I'm reading but I cannot find any documentation on it. The feature is mentioned in the 6509 manual but it simply says: " Refer to the software documentation for information about how to program the pull setting using NI-DAQmx with LabVIEW ". What software documentation does that refer to?
Does anyone have any advice on reading 3.3V digital logic with the TTL-based 6509 cards and/or information on who to set the pull option?
Thanks & Regards,
NQ