The board code of the PCI-6503 is 256 (see documentation for
Init_DA_Brds). The NI 6519 is not supported under traditional DAQ. Thus
the board code is not relevant as Init_DA_Brds doesn't work for this
board. You can use NI-DAQmx attributes to read the board type as a
string (see also
this knowledge base article).
I hope that helps,
Jochen Klier
National Instruments Germany