Method for selectively inverting words to be written to a memory and device for implementing same

A method for selectively inverting a word to be written to a memory, the memory comprising memory cells, each memory cell allowing at least two values associated with at least one bit to be stored, the method for selectively inverting comprising at least the following steps:

• associating an inversion bit with a plurality k of data bits of a data word to be written to the memory, the inversion bit having a predefined value indicating a non-inversion state of the k data bits;
• computing, with an error-correcting code, on the basis of the k data bits and of the inversion bit, a number r of check bits, the r check bits comprising s even check bits and r-s uneven check bits, and being such that the k data bits, the inversion bit and the r even and uneven check bits together form a code word v1 of k+1+r bits to be stored in the memory;
• defining, if not predefined, among the memory cells intended to store the code word, a number y of cells that are said to be sensitive, the values of the bits stored in these cells being liable to correspond to vulnerable values;
• determining, among the bits of said code word v1 that are intended to be stored in said y sensitive cells:
• a number n1 of bits of interest having a vulnerable value and for which an operation of inverting said code word would lead to the obtainment of a non-vulnerable value;
• and/or
• a number n2 corresponding, in said code word and among the bits intended to be stored in said y sensitive cells, to the number of bits for which an operation of inverting the code word would lead to the obtainment of a vulnerable value;
• evaluating the numbers n1 and/or n2 with a view to deciding whether or not to invert the code word;
• and
• if it is decided to carry out the inverting operation, inverting, in the code word:
• the k data bits, the inversion bit and the r-s uneven check bits in order to obtain a new code word v2.