The Connection-Then-Credit Flow Control Protocol for Networks-On-Chips: Implementation Trade-offs

Abstract

The Connection-Then-Credit (CTC) end-to-end flow control protocol is an extension to the normal Credit-Based (CB) flow control. CTC was introduced to address the message dependent deadlock problem in best-effort Networks-On-Chips (NoC) while offering an area-efficient network interface with respect to the normal CB end-to-end flow control protocol, which needs a lot of buffering resources. Nevertheless, only simulation results of the CTC versus CB were presented. In this paper, we introduce an implementation of both protocols; their RTL design is presented and synthesized in TSMC 40nm CMOS technology. Post-synthesis implementation results are analyzed and compared. The CTC and CB interfaces performance were evaluated and compared using standard traffic patterns and the theoretical equations of the protocols are validated through the implementation of a complete NoC, including network interfaces, routers, and mesochronous links in mesh topology.