6585 LVDS Adapter - frequency acquisition

[CyGa]

Hi !

Currently using a 6585 LVDS adapater with my 7962R FlexRIO card, I'm facing some problems acquiring data @ the speed of 125MHz.

I'm using the 'Basic Connector' CLIP, so I'm getting U16 data from my read nodes on the FPGA. I read in the specification that the maximum data rate is 200MBit/s (SDR mode).

Does that mean I can get the state of all lines of a conntor (so a U16 data) at the maximum speed of 200MHz ? Or does this mean that the maximum frequency I can read my connector state is '200M/16' Hz ?

Also, I'm trying to generate data on the other connector... But looking at it on my oscilloscope doesn't show signals varaiting @ '125M/10' Hz... (cf . FPGA_Gen_12-5MHz.png).

Any idea ?

thanks

[Joe_S]

Hello zyl17,

If you're using the Basic Connector CLIP, then the I/O node that you are accessing should be reading data from all 16 channels on the connecter. Thus, each channel's data is then stored as one bit in the resulting U16. Therefore, we can say that all of our channels are receiving the same clock signal and operating at the same rate, up to a maximum of 200 MHz.

The generation should work the same way. But I'm curious, though, about your description of your readings from your oscilloscope. You say that it "doesn't show signals varaiting @ '125M/10' Hz". What does your oscilloscope show?

There should be some acquisition and generation example projects that could serve as a good starting point to demonstrate the expected behavior of the inputs and outputs. Hope that helps!

Regards,

Joe S.

[CyGa]

Hi Joe,

Sorry for the delay.

I made some more tests : if I try to generate data @ speed greater than 5 MHz the signal is 'curved'... Just like is there was a capacitor on the line.

My oscilloscope doesn't allow me to save traces so I can't post them here. Anyway my experiment is far to be 'stat of the art'. I didn't use the LVDS probes, but a BNC Cable that I cut to get the signal and it's 'reference' on the mass shield of the cable...

I made this experiment to validate acquisition code on my 7962R + 6585 system... but I do not need it anymore... So it's not a probelm for me anymore.