Store-and-forward CDC packet transmission in digital systems

Abstract

Data transmission across clock domains is a major point of interest by ASIC designers as a limited bandwidth can be responsible for a processing power bottleneck that affects the entire system. Clock domain crossing is inherently expensive in terms of area and latency as it requires overcoming issues related to the physical nature of integrated circuit latches, in particular metastability. These issues are dangerous as they do not manifest in RTL simulation. Due to this, designers often opt for generic data synchronisation solutions that are not fully suited to the nature of the data being transferred. This dissertation presents a clock domain crossing mechanism that allows two clock domains to share a common memory to transfer packet-based data. The mechanism consists in a memory controller that coordinates commands from a push (write) domain and a pop (read) domain. The main objective of the memory controller project consists in the implementation of efficient synchronisation methods in order to eliminate the need for separate synchronisation and storage memories. In essence, the controller is an extension of an asynchronous FIFO controller with added functionality, supporting multiple virtual FIFOs and variable length data packets.