On Magnetic Bubble Logic Circuits

This paper is concerned with the realization of logic functions by using two-input magnetic bubble logic elements. A magnetic bubble logic element is the multiple-output logic element whose number of ``1'' 's of the output is equal to that of corresponding input, and fanout of each output terminal of the element is restricted to one. In order to realize some functions, it is necessary to use the generators which correspond to constant-supplying elements. First, the number of generators which are necessary and sufficient to realize an arbitrary functions is obtained for a given set of elements. In particular, it is shown that an arbitrary function can be realized by using I B elements and at most two generators. Since the I B element is a universal element in the above sense and is considered to be rather easily realized by magnetic bubble interactions, the I B logic circuits are mainly discussed. The I B minimum circuit defined here is a circuit which consists of minimum number of generators and minimum number of I B elements. In the last half of this paper, it is shown that the minimum circuits of most functions have the characteristic circuit structure called ``1-4 form.''