Most of FPGAs have Configurable Logic Blocks (CLBs) to implement combinational and sequential circuits and block RAMs to implement Random Access Memories (RAMs) and Read Only Memories (ROMs). Circuit design that minimizes the number of clock cycles is easy if we use asynchronous read operations. However, most of FPGAs support synchronous read operations, but do not support asynchronous read operations. The main contribution of this paper is to provide one of the potent approaches to resolve this problem. We assume that a circuit using asynchronous ROMs designed by a non-expert or quickly designed by an expert is given. Our goal is to convert this circuit with asynchronous ROMs into an equivalent circuit with synchronous ones. The resulting circuit with synchronous ROMs can be embedded into FPGAs. We also discuss several techniques to decrease the latency and increase the clock frequency of the resulting circuits.

Efforts have been devoted to maximizing memory array densities. However, as the devices are scaled down in dimension and getting closer to each other, electrical interference phenomena among devices become more prominent. Various features of 3-D memory devices are proposed for the enhancement of memory array density. In this study, we mention 3-D NAND flash memory device having pillar structure as the representative, and investigate the paired cell interference (PCI) which inevitably occurs in the read operation for 3-D memory devices in this feature. Furthermore, criteria for setting up the read operation bias schemes are also examined in existence with PCI.