Hello Mark,
You should be able to use the DIG_BLOCK_CHECK to stop input at a half buffer value. DIG_BLOCK_IN tells the program the number of items to be transferred and DIG_BLOCK_CHECK returns the number of remaining samples still to be transferred. You should be able to stop the input by monitoring the remaining output.
As I look at that particular example, I think one easy way to stop at 9.5 buffers would be to change the loop condition.
You must have tried using either an older version of NI-DAQmx or something like that, because the PCI-6533 is supported in NI-DAQmx in version 7.4 and above (the current version of NI-DAQmx is version 8.1). You might give a later version of NI-DAQmx a try and be amazed by how easy it is to use
Regards,
Micaela N
National Instruments