Characterizing a portable subset of behavioral VHDL-93

Goossens defined a structural operational semantics for a subset of VHDL87 and proved that the parallelism present in VHDL is benign. We extend this work to include VHDL-93 features such as shared variables and postponed processes that change the underlying semantic model. In the presence of shared variables, nondeterministic execution of VHDL-93 processes destroys the unique meaning property. We identify and characterize a class of portable VHDL-93 descriptions for which unique meaning property can be salvaged. Our specification can serve as a correctness criteria for a VHDL-93 simulator. Keywords VHDL, formal specification, simulation, shared variables 1 INTRODUCTION VHDL has been designed to facilitate specification, documentation, communication and formal manipulation of hardware designs at various levels of abstraction (Bhaskar 1994). The semantics of VHDL-93 are given in English prose in (IEEE 1993). The goal of developing formal semantics is to provide a complete and unambigu..