User guide

110 www.xilinx.com System Generator for DSP User Guide
UG640 (v 12.2) July 23, 2010
Chapter 1: Hardware Design Using System Generator
A demo included in the System Generator demos library also shows an efficient way to
implement a MAC-based interpolation filter. To see the demo, type the following in the
MATLAB command window:
>> demo blockset xilinx
then select FIR filtering: Polyphase 1:8 filter using SRL16Es from the list of demo designs.
Design Overview
This design uses the random number source block from the DSP Blockset library to drive
two different implementations of a FIR filter:
• The first filter is the one that could be implemented in a Xilinx device. It is a fixed-
point FIR filter implemented with a dual-port Block memory and a single multiply-
accumulator.
• The second filter is what is referred to as reference filter. It is a double-precision,
direct-form II transpose filter.
The frequency response of each filter is then plotted in a transfer function scope.
Open and Generate the Coefficients for this FIR Filter
1. From the MATLAB console window, cd into the directory
<ISE_Design_Suite_tree>/sysgen/sysgen/examples/mac_fir.
2. Open the design model by typing mac_df2t from your MATLAB command window.
For the purpose of this tutorial, the variables coef, coef_width, coef_binpt,
data_width, data_binpt and Fs are not defined. You will first use these variables as
mask parameters to the MAC Based FIR block and then design and assign the filter