a configurable device uses a plurality of parallel units which are made up of cells for storing individual bits of information . these cells are identified by address signals and selected to be interrogated . the selected cells are interrogated to determine information stored therein and a signal is produced which corresponds to that information . if a nonfunctional cell is detected within a parallel unit , that parallel unit may be decoupled from the interrogator . the remainder of the parallel units are shifted to different interrogators thereby effectively eliminating use of the decoupled parallel unit which contains the nonfunctional cell .