Hi Sergey,
This information is in the VISA programmers manual. It should have been installed by default in the NI-VISA directory located in your start menu. In case its not, here it is:
Description
The viBufRead() operation is similar to viRead() and does not perform any kind of data
formatting. It differs from viRead() in that the data is read from the formatted I/O read
buffer�the same buffer used by viScanf() and related operations�rather than directly
from the device. You can intermix this operation with viScanf(), but you should not mix it
with viRead().
VI_NULL is a special value for the retCount parameter. If you pass VI_NULL for retCount,
the number of bytes transferred is not returned. You may find this useful if you need to know
only whethe
r the operation succeeded or failed.
Best Regards,
Aaron K.
Application Engineer
National Instruments
