VHDL Critique

Abstract

wo VHSIC hardware description language (or VHDL) lT reviews were held in 1984: One (in March)-an open, 2-day public review in Plano, Texas-resulted in VHDL's first public release, the "VHDL Language Reference Manual, Version 5.0." 1 The other review (in August)-a smaller, 4-day meeting held in l Orono, Maine and attended by VHDL contractors plus representatives of government (DoD), academy, and industry-resulted in the publication of the "VHDL Language Reference Manual, Version 7.0. ,2The "VHDL Language Reference Manual, Version 7.2" 3 published in August, 1985, is the VHDL version this article critiques.l | I 1 l lInnovative features VHDL represents a significant advance in state-of-the-art hardware description languages (or HDLs), and can be considered the "FORTRAN of hardware description languages" 4 in the sense that it provides the first generaly accepted standard HDL. The FORTRAN analogy is appropriate when comparing our current understanding of hardware description language to our understanding of programming languages in the 1950s. Much remains to be learned, but VHDL has made contributions. This section wiDl discuss VHDL features many reviewers have found useful and innovative.Packages. VHDL, the first hardware description language to employ the package concept originating in Ada, provides a mechanism encapsulating definitions and utility functions. This feature suits hardware description particularly wel because it provides the means to gather technology dependencies into one central location. Figure 1 gives an example of how one might encapsulate technology dependencies into a VHDL package. 0740-7475/86/0400-0054$O1.00 © 1986 IEEE 54 IEEE DESIGN &TEST

The impact of hardware description languages on the education of hardware design

“…Initiated by the Department of Defense, this language has been accepted as the standard media for communication of hardware design data. VHDL supports the documentation, design, and simulation of digital systems from high level behavioral to gate level [8].…”