To whom it may concern: I have been asked about the all-digital frequency-locked loop circuit on caravel (which I need to stop calling a PLL, because it's not). Yesterday I added ngspice-compatible netlists and testbenches to the ngspice/ directory on caravel for anyone who would like to take a look at how it operates, and also for one method of doing a full mixed-mode simulation in ngspice using the built-in xspice digital event simulator.