NONVOLATILE SEMICONDUCTOR STORAGE DEVICE, SIGNAL PROCESSING SYSTEM, CONTROL METHOD FOR SIGNAL PROCESSING SYSTEM, AND REWRITE METHOD FOR NONVOLATILE SEMICONDUCTOR STORAGE DEVICE

摘要

A nonvolatile semiconductor storage device is provided with a memory cell array (102) which is provided with a data storage region (104) and a rewrite information storage region (106), and a rewrite information holding circuit (128) which stores data read from the rewrite information storage region (106). A reference level switching circuit (120) selects, according to the output of the rewrite information holding circuit (128), a read reference level from among a plurality of read reference levels generated by a reference level generation circuit (118). A read circuit (116) reads memory cell data in the data storage region (104) on the basis of the selected read reference level and outputs the memory cell data. Consequently, the deterioration of data holding characteristics due to rewriting is suppressed, and a desired operation is implemented without being influenced by power shutdown and resupply, thereby achieving a reduced circuit size and a high-speed read operation.