Digital Electronics: Principles, Devices and Applications

614 Digital Electronics+V CC(a)+V DD(b)Figure 15.5(a) Basic bipolar memory cell and (b) a basic MOS memory cell.to as two-dimensional memories, and those with two decoders are referred to as three-dimensionalmemories.Figures 15.8(a) and (b) show the timing diagrams during ‘read’ and ‘write’ operations respectively.The diagrams are self-explanatory. Read and write cycle time intervals of a few nanoseconds to a fewtens of nanoseconds are common in the case of asynchronous SRAMs.