Optimizing construction of scheduled data flow graph for on-line testability

The objective of this work is to develop a new methodology for behavioural synthesis using a flow of synthesis, better suited to the scheduling of independent calculations and non-concurrent online testing. The traditional behavioural synthesis process can be defined as the compilation of an algorithmic specification into an architecture composed of a data path and a controller. This stream of synthesis generally involves scheduling, resource allocation, generation of the data path and controller synthesis. Experiments showed that optimization started at the high level synthesis improves the performance of the result, yet the current tools do not offer synthesis optimizations that from the RTL level. This justifies the development of an optimization methodology which takes effect from the behavioural specification and accompanying the synthesis process in its various stages. In this paper we propose the use of algebraic properties (commutativity, associativity and distributivity) to transform readable mathematical formulas of algorithmic specifications into mathematical formulas evaluated efficiently. This will effectively reduce the execution time of scheduling calculations and increase the possibilities of testability

Behavioral synthesis from VHDL using structured modeling

This dissertation describes work in behavioral synthesis involving the development of a VHDL Synthesis System VSS which accepts a VHDL behavioral input specification and performs technology independent synthesis to generate a circuit netlist of generic components. The VHDL language is used for input and output descriptions. An intermediate representation which incorporates signal typing and component attributes simplifies compilation and facilitates design optimization.A Structured Modeling methodology has been developed to suggest standard VHDL modeling practices for synthesis. Structured modeling provides recommendations for the use of available VHDL description styles so that optimal designs will be synthesized.A design composed of generic components is synthesized from the input description through a process of Graph Compilation, Graph Criticism, and Design Compilation. Experiments were performed to demonstrate the effects of different modeling styles on the quality of the design produced by VSS. Several alternative VHDL models were examined for each benchmark, illustrating the improvements in design quality achieved when Structured Modeling guidelines were followed

Measurements, Models, Systems and Design

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High level optimizations in compiling process descriptions to asynchronous circuits

technical reportAsynchronous/'Self-Timed designs are beginning to attract attention as promising means of dealing with the complexity of modern VLSI technology. In this paper, we present our views on why asynchronous systems matter. We then present details of our high level synthesis tool SHILPA that can automatically synthesize asynchronous circuits from descriptions in our concurrent programming language, hopCP. We outline some of the high level communication abstractions available in hopCP. We illustrate how these abstractions are realized in the asynchronous circuits generated by SHILPA. We then present a series of examples that present many of the high level optimization strategies used by SHILPA. Some of these optimizations aim to speed up the generated circuits by avoiding un-necessary waiting. Others synthesize components that are much easier to realize in a variety of technologies. We also discuss some of the tradeoffs possible between optimizations and timing constraints

A bibliography on formal methods for system specification, design and validation

Literature on the specification, design, verification, testing, and evaluation of avionics systems was surveyed, providing 655 citations. Journal papers, conference papers, and technical reports are included. Manual and computer-based methods were employed. Keywords used in the online search are listed

From process-oriented functional specifications to efficient asynchronous circuits

technical reportA methodology for high-level synthesis and performance optimization of asynchronous circuits is described. A specification language called hopCP which is based on a simple extension to classical flow graphs is introduced. The extension involves the addition of expression actions to a flow graph, to model computational aspects of hardware behavior in a purely functional framework. Control and Communication aspects are modeled explicitly just as in Hoare's CSP. A systematic methodology to synthesize asynchronous circuits from hopCP based on the notion of a self-timed block is presented. The compilation methodology based on self-timed blocks coupled with the functional flavor of hop CP gives us the ability to exploit several optimizations like quick return, intra-loop pipelining and speculative evaluation of conditional expressions. The specification language hopCP, the synthesis procedure and the optimizations are illustrated in design of an asynchronous iterative multiplier

Introduction to Logic Circuits & Logic Design with VHDL

The overall goal of this book is to fill a void that has appeared in the instruction of digital circuits over the past decade due to the rapid abstraction of system design. Up until the mid-1980s, digital circuits were designed using classical techniques. Classical techniques relied heavily on manual design practices for the synthesis, minimization, and interfacing of digital systems. Corresponding to this design style, academic textbooks were developed that taught classical digital design techniques. Around 1990, large-scale digital systems began being designed using hardware description languages (HDL) and automated synthesis tools. Broad-scale adoption of this modern design approach spread through the industry during this decade. Around 2000, hardware description languages and the modern digital design approach began to be taught in universities, mainly at the senior and graduate level. There were a variety of reasons that the modern digital design approach did not penetrate the lower levels of academia during this time. First, the design and simulation tools were difficult to use and overwhelmed freshman and sophomore students. Second, the ability to implement the designs in a laboratory setting was infeasible. The modern design tools at the time were targeted at custom integrated circuits, which are cost- and time-prohibitive to implement in a university setting. Between 2000 and 2005, rapid advances in programmable logic and design tools allowed the modern digital design approach to be implemented in a university setting, even in lower-level courses. This allowed students to learn the modern design approach based on HDLs and prototype their designs in real hardware, mainly field programmable gate arrays (FPGAs). This spurred an abundance of textbooks to be authored teaching hardware description languages and higher levels of design abstraction. This trend has continued until today. While abstraction is a critical tool for engineering design, the rapid movement toward teaching only the modern digital design techniques has left a void for freshman- and sophomore-level courses in digital circuitry. Legacy textbooks that teach the classical design approach are outdated and do not contain sufficient coverage of HDLs to prepare the students for follow-on classes. Newer textbooks that teach the modern digital design approach move immediately into high-level behavioral modeling with minimal or no coverage of the underlying hardware used to implement the systems. As a result, students are not being provided the resources to understand the fundamental hardware theory that lies beneath the modern abstraction such as interfacing, gate-level implementation, and technology optimization. Students moving too rapidly into high levels of abstraction have little understanding of what is going on when they click the “compile and synthesize” button of their design tool. This leads to graduates who can model a breadth of different systems in an HDL but have no depth into how the system is implemented in hardware. This becomes problematic when an issue arises in a real design and there is no foundational knowledge for the students to fall back on in order to debug the problem

hopCP: A concurrent hardware description language

Journal ArticlehopCP is a language for the specification, simulation, and synthesis of hardware systems. hopCP captures the behavior of a hardware system by specifying the causal relationships between actions that the system can perform. No specific timing discipline is implied by a hopCP specification. Hence, hopCP specifications can be implemented as synchronous, asynchronous, or mixed synchronous and asynchronous circuits. Salient features of hopCP include nonatomic actions, synchronous and asynchronous styles of value communication, broadcast channels, a purely functional sublanguage to express the computational aspects of hardware behavior, and an efficient tool (called parComp) to infer the composite behavior of a collection of hopCP modules. Operational Semantics of hopCP in terms of labeled transition systems is presented. A few examples are described to illustrate the expressive power of hopCP. A summary of the implementation is also presented