Francis,
You can determine the base address for a National Instruments board by calling the NI-DAQ function Get_DAQ_Device_Info (see NI-DAQ Help for deatils.)
If you are looking for a Register Map of this board, there is not one available, thus you will need to use NI-DAQ Functions to use the 6602.
You can see examples of how to do this by installing NI-DAQ support for C/C++ when you install NI-DAQ. The examples for the 6602 will be in your NI-DAQ\Examples\VisualC\ctr folder. You can also find more examples at zone.ni.com -> Resourse Library search for NI-TIO.
Nick Wilson
National Instruments
www.ni.com/ask