A read only 70-NS waffle iron memory

The implementation of a new high-speed read only memory with waffle iron structure, allowing ease of information change and high bit density, is described. Information is stored on a copper plate where an anisotropic Permalloy film (10 000 Å) has been electrodeposited and etched according to the data pattern. This plate is positioned into contact with a polished ferrite slab insuring flux closure paths. The storage cell utilizes the coupling between orthogonal word and sense lines obtainable through the magnetic film overlay to represent a one. At zero locations the coupling is cancelled when etching away the magnetic film from the copper plate. A 512-word by 32-bit memory makes use of eight waffles. The worst case access time including one level of decoding is measured to be 40 ns; the corresponding cycle time is 70 ns.