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AR# 33733

CIC Compiler v1.3 - Why does the CIC overflow continually after applying a rate change to a programmable rate CIC?


When the rate of my CIC Compiler v1.3 filter is changed, by writing a new value to the DATA port, the output becomes unstable and continually overflows creating a triangle wave on the output.

Why does this occur?


This is due to the architecture of a programmable rate CIC filter which causes the CIC to become unstable when rates are changed. If there is any non-zero data in the pipeline when the rate change occurs, the output overflows continually.

To work around this issue, apply a new rate to the CIC Compiler v1.3 by performing the following:

  1. Drive DIN to 0 and hold it at 0 for the time being.
  2. Apply a core reset.
  3. Apply the desired rate change with the WE and DATA ports.
  4. Resume operation at the new rate.

This ensures that the data pipeline is clear when the rate change occurs, thus avoiding triggering the unstable CIC response.

For a detailed list of LogiCORE Cascaded Integrator Comb Compiler (CIC Compiler) Release Notes and Known Issues, see (Xilinx Answer 29297).

Linked Answer Records

Master Answer Records

Answer Number Answer Title Version Found Version Resolved
29297 LogiCORE IP Cascaded Integrator Comb Compiler (CIC Compiler) - Release Notes and Known Issues N/A N/A
AR# 33733
Date Created 11/06/2009
Last Updated 12/15/2012
Status Active
Type General Article
  • Cascaded Integrator Comb (CIC) Compiler