Margaret,
Unfortunately, A single counter cannot be used for both pulse generation and frequency measurement at the same time. Most of our multifunction DAQ boards do, however, have 2 counters. This allows you to use 1 counter for pulse generation and another for frequency measurement. These two tasks can occur at the same time. It is also possible to do analog output and digital input at the same time, as well.
Hope this helps.
Ryan Verret
Product Marketing Engineer
Signal Generators
National Instruments