ram showing an example of an arrangement in which a plurality of memory cells is disposed, FIG. 15A is a timing chart showing a write/read operation in the memory cell, FIG. 15B is a timing chart showing a comparing operation in the memory cell, FIG. 16 is a block diagram showing an example of the structure of a CAM array including the memory cell illustrated in FIG. 1, FIG. 17 is a block diagram