Systems and method for transferring data asynchronously between clock domains

Abstract

An asynchronous FIFO buffer communicates data between an input clock domain and a relatively slow output clock domain. The input clock frequency is not an even multiple of the output clock frequency, so the data transfer is asynchronous. The FIFO buffer includes a collection of input registers, a shift register, and some clock-comparison and write logic that controls the flow of data into, out of, and between these registers. The input data is loaded into the input registers in synchronization with the input clock. The clock-comparison and write logic compares the input and output clock signals and moves the data from the input registers to the shift register at an address value that may vary based on the result of the comparison of the input and output clock signals, skipping write cycles as necessary to avoid shifting data into the shift register faster than the data is shifted out.