User`s guide

3 Basic Procedures
3-34
The Duration value specifies the number of contiguous points of data to be
collected in each buffer of data. We recommend that you enter a
Duration
value equal to the total number of sample points that you need to collect
rather than relying on a series of buffers to be continuous.
If you enter a value less than the total number of sample points, you will lose
sample points during the time needed to transfer values from the data buffer
to the MATLAB workspace. The Real-Time Windows Target ensures that
points are continuous only within one buffer. Between buffers, because of
transfer time, some samples will be omitted.
We also recommend setting the time axis for Simulink Scope blocks equal to
the sample interval (in seconds) times the number of points in each data
buffer. This setting will display one buffer of data across the entire Simulink
Scope plot.
The
Signal & Triggering dialog box will look similar to the figure below.