Area Reduction of Filter Subsystem
To reduce the number of multipliers in the HDL implementation of a multifilter design, use the SharingFactor HDL Coder™ optimization.
The model includes a sinusoidal signal source feeding a filter subsystem targeted for HDL code generation.
The subsystem contains a Discrete FIR Filter block and a Biquad Filter block. This design demonstrates how the optimization tools share resources between multiple filter blocks.
The Discrete FIR Filter block has 43 symmetric coefficients. The Biquad Filter block has 6 coefficients, two of which are unity. With no optimizations enabled, the generated HDL code takes advantage of symmetry and unity coefficients. The nonoptimized HDL implementation of the subsystem uses 27 multipliers.
To enable streaming optimization for the Multi-Filter Subsystem, right-click the subsystem and select HDL Code > HDL Block Properties.
Set the SharingFactor to 27 to reduce the design to a single multiplier. The optimization tools attempt to share multipliers with matching data types. To reduce to a single multiplier, you must set the internal data types of the filter blocks to match each other.
To observe the effect of the optimization, under Configuration Parameters > HDL Code Generation, select Generate resource utilization report and Generate optimization report. Then, to generate HDL code, right-click the Multi-Filter Subsystem and select HDL Code > Generate HDL for Subsystem.
With the SharingFactor applied, the subsystem upsamples the rate by 27 to share a single multiplier for all the coefficients.
In the Code Generation Report window, click High-level Resource Report. The generated HDL code now uses one multiplier.