An electronic device as described herein implements a scheme to secure a data mapping function from scan access. The protection scheme can be used as a security measure for proprietary lookup tables, secret constants, digitally implemented algorithms, and the like. The electronic device employs a reconfigurable data mapping arrangement that can be reconfigured for a normal operating mode and a scan testing mode. While in the normal operating mode, a normal data mapping arrangement generates valid output data in accordance with the data mapping function. While in the scanning mode, however, a scanning data mapping arrangement generates invalid but testable output data in accordance with a data masking function that conceals, hides, masks, or obfuscates the data mapping function. Using the data masking function in this manner protects the data mapping function against reverse engineering attacks that attempt to derive the data mapping function from scan testing results.