Slow GPCTR_Read_Buffer transfer

[Walter Tansini]

I'm using a PXI-6602 counter card to do a buffered counter measurement on 4 counters (together with an AI). When executing my application I've fount that each read from the buffered counters takes over 0,1 seconds on interrups, and much longer with DMA transfers. Is this normal behaviour? How can I speed things up?

I've attached a MS-VISIO drawing on how my system works.

[Walter Tansini]

And as often happens, as soon as one posts the question, the answer arizes.
The buffer read mark was set to ND_WRITE_MARK, which is - according to the manual - the latest date. I seems that it's the position where the next data is written. giving an offset of -1 solved the problem.