PCI6534 Having problems with noise/ringing, tried diode method,need help.

[chinook1]

Tried Schottky-Diode method, didn't help(per page D-7 of user manual). Any other new methods out there that can help.

Bus speed at 1meghz.

[mlloyd]

I know what you mean about the bad ringing...

The 6534 is not a matched impedance system.  The output of the the board is about 20 ohms, and the cable is about 90 ohms.  Therefore, it's necessary to use an AC termination scheme.  Checkout the article "Terminating the Outputs of a NI-653X Device" by doing a search of Support or the KnowledgeBase -- it shows a suggested voltage divider for an AC termination scheme.

Best of luck -- if you're able to try this termination scheme, I would be interested to know how it works because unfortunately I was not able to make hardware changes to my system to try this out...  Our poor little 244 buffers just have to deal with a 9V input!!!

Regards,

Michelle 

[chinook1]

Michelle

We tried the diode scheme with no success, currently working on the buffer circuit. Did you put pull up resistors on the input and output of the 244 IC?

THANKS

Chinook1:

[mlloyd]

We did not put pullup or pulldown resisters in our circuit, which is why we were having so much problem with ringing.  The suggestion from the article is to put (a pullup resistor) and (a pulldown resistor in series with a capacitor).

Regards,

Michelle

[chinook1]

Was able eliminate most of the ring noise with two 180 ohm resistors and a 220pf cap to ground.

See attached bitmap.

[mlloyd]

Very cool -- thanks for sharing your information!  I will put it in my record of "how to communicate with the PCI-6534".

Regards,

Michelle