Designers of space-based application must be concerned with the effect of single-event upsets (SEUs) on FPGA configuration memory. Changes to configuration memory can cause changes in the functionality and performance of the device. This application note describes the use of configuration scrubbing and readback in Virtex™-4 FPGAs for the purpose of detecting and correcting single-event upsets to the configuration memory array induced by cosmic rays. It is essential for the reader to have a basic understanding of the Virtex-4 SelectMap interface as well as configuration and readback operations. An in-depth review of UG070, Virtex-4 User Guide, is strongly encouraged.