An experimental 64-bit decoded Josephson NDRO random access memory

The design and testing of an experimental fully decoded 64-bit Josephson NDRO (nondestructive readout) RAM chip are described. Tree decoders were used to access the memory cells. The basic memory cell was a ring cell containing a single write gate. The chips were built in a coarse 25 /spl mu/m technology since neither speed nor density were stressed in this study. An access time of 4 ns with full margins and of 2.3 ns with reduced margins were demonstrated. The corresponding full memory cycle times were 5 and 3.5 ns, respectively. Good agreement with computer simulations was obtained throughout.