PCI-6120 External Scan clock and Trigger

[CLema]

I am trying to do external triggered and scan clock sampling using a PCI-6120.  After the external trigger 20 seperate external scan clock pulse bursts of 500 Khz that last 4.096 ms each are sent.  So 2048 samples of data are collected with each pulse burst until a total of 40960 samples have been collected on each channel (hence using all 4 channels 4*40960 = 163840 samples).

I have tried this at 125 Khz and at 250 Khz and it works fine.  However at 500 Khz the data is all over the place.  I am not sure but sometimes it seems as if the buffer is not being cleared ( weather i set the buffer to 163840 scans 600000 scans or 2048 scans).

I am not using Labview so i assume the onboard memory is not used.

Any ideas what might be causing this behaviour at 500 Khz would be greatly appreciated

Thanks

Charlie  

[Raajit_Lall]

Hello Charlie,

When you say that your data is all over the place, could you please elaborate on that a little bit more. Also, what is the function you are using to set the buffer size and what is the programming environment that you are using?

Regards,