User guide

System Generator for DSP User Guide www.xilinx.com 25
UG640 (v 12.2) July 23, 2010
System-Level Modeling in System Generator
Simulink scope), but does not alter sample rates. The scope output below shows the
unaltered and sampled versions of the sine wave.
Multirate Models
System Generator supports multirate designs, i.e., designs having signals running at
several sample rates. System Generator automatically compiles multirate models into
hardware. This allows multirate designs to be implemented in a way that is both natural
and straightforward in Simulink.
Rate-Changing Blocks
System Generator includes blocks that change sample rates. The most basic rate changers
are the Up Sample and Down Sample blocks. As shown in the figure below, these blocks
explicitly change the rate of a signal by a fixed multiple that is specified in the block’s
dialog box.
Other blocks (e.g., the Parallel To Serial and Serial To Parallel converters) change rates
implicitly in a way determined by block parameterization.
Consider the simple multirate example below. This model has two sample periods, SP1
and SP2. The Gateway In dialog box defines the sample period SP1. The Down Sample
block causes a rate change in the model, creating a new rate SP2 which is half as fast as SP1.