ASCEnD-FreePDK45: An open source standard cell library for asynchronous design

An analysis of the state of art in asynchronous circuits reveals a lack of resources to support their design. When asynchronous cell libraries appear in the literature, they often accompany a demand from specific circuit designs, and are not proposed as general purpose resources to support semi-custom design styles. Moreover, currently proposed asynchronous libraries employ commercial technologies that cannot be distributed as open access. This work proposes and describes ASCEnD-FreePDK45, an open source standard cell library to support the design of asynchronous circuits. This first release of the library contains 30 different cells and is based on the FreePDK45 design kit, a predictive 45nm technology. Currently, the ASCEnD-FreePDK45 library supports both NCL and SDDS-NCL asynchronous design templates and is fully compatible with the NanGate FreePDK45 open cell library. ASCEnD-FreePDK45 relies on the ASCEnD-A design flow for its construction, which provides tools for transistor sizing, layout generation and electrical characterization. This article illustrates the use of the library with a semi-custom implementation of a 32-bit KoggeStone adder with cells from both the ASCEnD-FreePDK45 and the NanGate FreePDK45 libraries.