Interleaved word and bit disturbs in ratchet writing

Ratchet writing is employed as a means of storing information in certain NDRO memories. This mode of writing permits multiple-word organization. However, when this is done the memory elements are subjected to a new kind of worst-case disturb pattern consisting of interleaved bit- and word-disturb pulses. The interleaved pattern is more destructive than either bit or word disturbs alone. A theory is developed which explains this effect as being due to a reduction in the threshold field of the magnetic material between the storage and interrogate holes caused by a pair of ratchet pulses. Expressions are found which predict the amount of walkdown of stored information due to an interleaved disturb program in terms of core geometry and material properties. It is found that a minimum walkdown of about 17 percent can be expected in all cases.