In some embodiments, an electronic chip includes a doped semiconductor substrate of a first conductivity type, and wells of the second conductivity type on the side of the front face of the chip, in and on which wells circuit elements are formed. One or more slabs of a second conductivity type are buried under the wells and are separated from the wells. The electronic chip also includes, for each buried slab, a biasable section of the second conductivity type, which extends from the front face of the substrate to the buried slab. A first MOS transistor with a channel of the first conductivity type is disposed in the upper portion of each section, where the first transistor is an element of a flip-flop. A circuit is used for detecting a change in the logic level of one of the flip-flops.