Title page for ETD etd-06102009-063425
|Type of Document
||Mahadevan, Gayatri P.
||Automatic back annotation of timing into VHDL behavioral models
||Master of Science
|Armstrong, James R.
|Cyre, Walling R.
|Gray, Festus Gail
|Date of Defense
This thesis presents a design system that significantly speeds up development of VHDL
behavioral models with back annotated timing. The behavioral model is developed using
the CAD tool called Modeler's Assistant by inputting the model in the form of a Process
Model Graph. Then using the built-in primitive process library and user responses the
Modeler's Assitant generates a complete VHDL source description of the model. The
models developed can be classified into four classes. The first class of circuits are
combinational fanout free circuits in which the fanout of each process in the Process
Model Graph is one. Combinational circuits in which outputs of the processes are fed in as
input to more than one process are classified as Class 2 circuits. Sequential register
circuits are classified as class 3 circuits. Class 4 circuits are highly sequential circuits which
have either feedback loops or irregular register or flip-flop structures. The principle for
back annotating the generic delay values is discussed for the first three classes of circuits.
The back annotation tool Backann2 uses the VHDL description from the Modelers
Assistant, the CLSI -VTIP CAD tool and the Synopsys Design Compiler to calculate the
timing delays and to back annotate the delays into the behavioral model. The CLSI -VTIP
tool is used to extract the details from the VHDL model and store it in the form of data
structures. These details are used for computing the paths traversed by the signals
associated with the generics. The behavioral model is synthesized into a gate level design
and the end to end delays in the model are obtained using Synopsys Design Compiler.
With the end to end delays and the different paths traversed by the signals an algorithm to
find realistic and accurate delays has been found. Thus a system is available to designers
which builds behavioral models with accurate timing information.
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