Read only storage using a four state cell.

摘要

A bipolar ROM (read only memory) or ROS (read only storage) system in which the array devices (20) embody four different, two-terminal, device forms: low barrier Schottky diodes; standard or high barrier, Schottky diodes; junction diodes; and no diodes; thereby to make possible four levels of storage for each cell. This effectively doubles the information content for an array (10) with little increase in the array size.