Implementation and analysis of ring oscillator circuits on xilinx FPGAs

This chapter gives an extensive description of ring oscillators (ROs) implemented on Xilinx FPGA technology, aiming at providing a basic primitive to define physically unclonable functions based on ROs and illustrating, through detailed analyses, frequency distributions. As for the implementation, we detail in the chapter any step required to implement a RO and measure its frequency. In particular, we illustrate how to accomplish such operation by means of Xilinx ChipScope. Furthermore, we show main design parameters, such as the number of stages, of the RO and how they impact on the frequency characterization. At the end, we provide other characterization by means of dynamic parameters variations, such as temperature and aging effects.