The VITAL specification addresses the issues of interoperability,
backannotation and high performance simulation for sign-off quality ASIC
libraries in VHDL. VITAL provides modeling guidelines and a set of
pre-defined packages (containing pre-defined routines for modeling
functionality and timing) to facilitate the acceleration of designs
which use cells from a VITAL library. The VITAL Level-I guidelines
constrain the modeling capabilities provided by VHDL in order to
facilitate higher performance (Figure I). Accumulating "gains"
Constrained "flexibility" Higher performance & Increased capacity
Benefits Flexibility FujI VHDL 1076 Figure 1: VHDL and VITAL Even within
the Level-I guidelines, there are several ways in which a model can be
written. In this chapter, we highlight the various modeling trade-offs
and provide guidelines which can be used for developing efficient
models. We will also discuss the techniques that can be used by tool
developers to accelerate the simulation of VIT AL- based designs. 2.2.
OVERVIEW OF A VITAL LEVEL-l ARCIDTECTURE The VITAL specification is
versatile enough to support several modeling styles e.g., distributed
delay style, pin-to-pin delay style etc. In general, a VITAL Level-I
model can have the structure illustrated in Figure 2.