A hierarchical memory structure having memory cells, and sense amplifiers and decoders coupled with the memory cells to form first tier memory module, and subsequent tiers being formed by having (n-1)-tier memory modules, which are coupled with (n)-tier sense amplifiers and (n)-tier decoders. Also provided are a single-ended sense amplifier having sample-and-hold reference, and a charge-share limited-swing-driver sense amplifier; an asynchronously-resettable decoder; a wordline decoder having row redundancy; a redundancy device having redundant memory cells operated by a redundancy controller; a diffusion replica delay circuit; a high-precision delay measurement circuit; and a data transfer bus circuit imposing a limited voltage swing on a data bus. Methods are provided for a write-after-read operation without an interposed precharge cycle, and write-after-write operation with an interposed precharge cycle are provided, either operation being completed in less than one memory access cycle.