I've designed Vernier Delay Line TDC, So Start and Stop signals are there, rather than pulse Input. I'm using vpwl to generate Start and Stop signals. I'm using Fixed Start Signal and varying Stop signal that's how I'm observing Thermometer Codes.
Could you please elaborate how to measure the Single Shot Precision...?
In this case you would measure by cross() the start and stop,
difference being the single shot time. Use realistic threshold
for the (digital) signals. This will be your X axis (in Cadence
you change the chart X-axis properties from time, to the
Calculator expression for delta-time.