Investigate conditions for {\it non-ambiguous behavior} of a timed Petri net which also contains immediate transitions. Non-ambiguity here means that the net behavior is uniquely determined by some given set of {\it control parameters}. For this, we study the {\it limit policy} in which immediate transitions are treated as (``limits'' of) timed transitions whose durations tend uniformly to $0$, yielding a unique semantics; we give conditions under which this limit semantics exists.