Multi-port static random-access memory (sram) with buffered read port and p and n pass gates to same write bit line

Abstract

A multi-port memory cell has a write-only cell and a buffered read port. The write-only cell has cross-coupled inverters and transmission gates to write bit lines. Each transmission gate has n-channel and p-channel transistors in parallel that both turn on during writing but remain off for reading. A node in the cross-coupled inverters is applied to a gate of a buffer transistor that has a channel in series with a channel of a read pass transistor to a read bit line. The buffered read port can be an inverter and a transmission gate, or can have p-channel and n-channel buffer and pass transistors in a four-transistor stack. The number of p-channel and n-channel transistors can be equal for use in a standard-cell or macro library layout, and the standard-cell logic power supply can be used for the memory cells even for ultra-low supply voltages.