  We introduce a new, reduced nonlinear oscillator model governing the
spontaneous creation of sharp pulses in a damped, driven, cubic nonlinear
Schroedinger equation. The reduced model embodies the fundamental connection
between mode synchronization and spatiotemporal pulse formation. We identify
attracting solutions corresponding to stable cavity solitons and Turing
patterns. Viewed in the optical context, our results explain the recently
reported $\pi$ and $\pi/2$ steps in the phase spectrum of microresonator-based
optical frequency combs.
