Re-evaluates the combinational logic for the given timestep - used if a combinational input has changed

Run an existing fast simulation up to the given number of steps. This function will mutate the write-once data arrays of simulation data and only simulate the new steps needed, so it may return immediately doing no work. If the simulation data arrays are not large enough they are extended up to a limit. After that, they act as a circular buffer. TimeOut if not None is the cutoff time after which the simulation terminates execution unfinished. Use fs.ClockTick to determine whether simulation has completed. returns speed, in clock cycles per ms, or None if complete