Data processing device with a memory location in which data is stored according to a wom (write once memory) code

Abstract

A device contains a memory that stores a WOM codeword that encodes successive generations of data values. When the codeword must be updated to represent a new data value, the device determines which updates of the dataword can be realized by feasible single bit updates to the WOM (Write Once Memory) codeword. If no feasible single bit update is possible, feasible two-bit updates are considered. Under control of the new data values a connection circuit routes feasibility signals for various updates, that signal the single-bit feasibility of the updates. Routing brings together pairs of feasibility signals for updates that together produce a WOM codeword that encodes the new data value. A pair is selected in which both feasibility signals indicate feasibility and the codeword is updated according to the updates involved in the pair. Preferably, the routing is realized with a connection circuit that comprises a number of layers of subcircuits, each routing the feasibility signals dependent on a respective bit of the new dataword. Also preferably, the WOM code is designed so that each of a number of updates to the data word can be realized by setting singles ones of a plurality of bits.