CIC Compiler

CIC filters (also known as Hogenauer filters) are computationally efficient for extracting baseband signals from narrow-band sources using decimation and for constructing narrow-band signals from processed baseband signals using interpolation.

Therefore, CIC allows for an economical and multiplier-free hardware implementation of a filter, and is widely used in sample rate conversion designs such as digital downconverters (DDC) and digital upconverters (DUC). See Figures 1 and 2.

The Altera® CIC MegaCore® function provides an easy-to-use MegaWizard® interface for parameterization and hardware generation of a fully parameterizable CIC function, which allows you to set the following parameters:

* Selectable decimation or interpolation filter types
* Configurable number of stages (1 to 12)
* Interpolation and decimation rate change factors (1 to 32,000)
* Two differential delay options (1 or 2)
* Configurable input data width (1 to 32 bits)
* Configurable output data width (1 to full resolution data width)
* Selectable output rounding modes (truncation, convergent rounding, rounding up, or saturation)
* Single clock domain
* Up to 1,024 channels


The CIC function supports the following additional features:

* Intellectual property (IP) functionalsimulation models for use in Altera supported VHDL and Verilog HDL simulators
* Support for OpenCore Plus evaluation
* DSP Builder ready
* Hogenauer pruning support
* Data ports compatible with the Avalon® streaming interface


Figure 1. Three-Stage Decimating CIC Filter Used in DDC



Figure 2. Three-Stage Interpolating Filter Used in DUC