Ordered binary decision diagrams are an important
data structure for the representation of Boolean functions.
Typically, the underlying variable ordering is used as
an optimization parameter.
When finite state machines are represented by OBDDs
the state encoding can be used as an additional
optimization parameter.
In this paper, we analyze the influence of the state encoding on the
OBDD-representations of counter-type
finite state machines.
In particular, we prove lower bounds, derive
exact sizes for important
encodings and construct a worst-case encoding which leads to
exponential-size OBDDs.