Is the delay only when you start? If so, this is expected you may experience an initial delay as the board is configured. If you need immediate response then you may want to try performing a triggered output.
If not, are seeing a delay from the time you change the buffer data to the time the data is physically being output on the pins? There will be a delay as it will take time for the card to output the buffer, but time for the card to output a half buffer will vary with buffer size and update rate. How are you measuring your delay? And what point is your time delay measured from? If you can be a little more specific with the questions it will be easier help you find solutions.
Kevin R
