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Hardware trigger problem with NI PCIe 6535b

Hello everybody,


I have been confronting a problem with the PCIe 6535b DIO working in slave mode and want your help.


I notice that when the card works in slave mode (i.e., I use a function generator to trigger the card for digital output), the trigger signal from the function generator will be affected by the card.  Without connection to the line PFI4 (which I am supposed to use to trigger the card), the trigger signal from the oscilloscope is perfect. After I connect the cable to the function generator, the trigger signal is getting weird. The amplitude is a summation of the trigger signal itself and some signal from the card as shown in the attached pictures. What's worse, the trigger signal is getting very noisy which makes it impossible for me to use the same function generator to trigger other devices.


I checked that the card didn't send out signals through line PFI4 which made sense because it worked in slave mode. So what's the problem here? How can I remove the noise caused by the card?  


For your information, I use the NI SHC68-H1X38 cable to connect the card and my device. The connection should be fine.


Any suggestions will be welcome. Thank you in advance.




I use the NI SHC68-H1X38 cable to connect the card and my device.

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If you happen to know how to solve this problem, please let me know. Any suggestion will be appreciated.

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