ASPI8-4 DSP Design Methodology

ASPI8-4: DSP Design Methodologies, AAU 1/66

ASPI8-4

DSP Design Methodology


Practical issues• Webpage: http://www.cs.aau.dk/~moullec/aspi8-4/

• Literature: available on the webpage and in your mailbox (or ask Dorthe)

• YOUR feedback about the course is most welcome:• during the lecture• after the lecture ([email protected])


Outline of the course• MM1: Design meta modelsIntroduction/Y-chart model/Rugby meta model

• MM2: Computational modelsFSMD/SDFG/CDFG/HCDFG/ASM-charts

• MM3: Design DomainsFunction/Communication/Data/Timing


MM1:

Design meta models

• Introduction

• Y-chart model

• Rugby meta model

• Conclusion


Introduction: the need for design methodologies• Pervasive computing with an always-on Internet infrastructure.• Voice activated controls enabled by speech synthesis.• Wireless communications that keep us in touch no matter where or when we need it. • A consumer industry dominated by a plethora of entertainment devices.


Introduction: the need for design methodologies

“ Digital signal processing (DSP) has become the technology of focus with consensus expectations of exponential growth. Everybody knows that DSP is the technology driver for the semiconductor industry,” Will Strauss, analyst, Forward Concepts Co., Tempe, AZ.



But ???

NEW PLATFORMS (DSPs, FPGAs, SoC,…) NEW METHODOLOGIES

Source: Xilinx



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}}}for (y=0; y<n lCore2; y++) {for (x=0; x<(nc); x++) {pImage Erode[(y * nc) + x]=0;}}











































Standards


















































StandardsStandards?But ???

INCREASED COMPLEXITY (multiple standards, Quality of Service, …) NEW METHODOLOGIES


• “The way in which you find out information; a methodology describes how something will be (or was) done. The methodology includes the methods, procedures, and techniques used to collect and analyze information”


What is a methodology ?

• “A documented approach for performing activities in a coherent, consistent, accountable, and repeatable manner”

• “A collection of methods, procedures, and standards that defines an integrated synthesis of engineering approaches to the development of a product”

• A method is not a methodology, it’s part of a methodology.



Introduction: elements for a design methodology

• Domains: functional, structural, physical, …

• Abstraction levels: system, algorithmic, RTL, logic, circuit, …

• Activities: analysis, synthesis, refinement, optimization …


• Functional domain: emphasis is on behavior (functionality, I/O), no reference to the implementation of this behavior

• Structural domain: interconnected functional components, possibly hierarchical

• Physical domain: a.k.a geometric, physical placement in space and physical properties, no direct relation to functionality

Specification domains for digital systems


Abstraction levels for digital systems

• System level: subsystems (modules,…) interacting with each other(for example exchanging messages). Structural elements: processsors, communication channels, memories,…

• Algorithmic level: a.k.a behavioral level, algorithm(s) describing the functionality. Structural elements: controller, netlist,…

• Register Transfer Level: a.k.a RTL level, operations described as transfer of data between registers and functional units.Structural elements: registers, ALUs, multiplexers, controller,…


Abstraction levels for digital systems

• Logic level: operations described as Boolean equations. Structural elements: gates and interconnections.

• Circuit level: differential equations describing the relation between voltage, current, …Structural elements: transistors, resistors, capacitors


Meta models : Y-chart and Rugby

• Meta model: a model used to describe and analyze other models

• Higher level of abstraction


Y-chart

• The Y-chart is a representation proposed by Gajski and Khan to capture specifications domains, abstraction levels and their inter-relation.

• Specification domains are represented as three axes (hence the Y)In each domain the specification can be at different abstraction levels.

• The Y-chart tries to capture the relation between design activities (synthesis activities) such as synthesis, partitioning, …


Domains and Levels of Modeling

high level of abstraction

FunctionalStructural

Geometric “Y-chart” by Gajski & Kahn

low level of abstraction




Geometric

Algorithm(behavioral)

Register-TransferLanguage

Boolean Equation

Differential Equation

“Y-chart” by Gajski & Kahn




Geometric

Processor-MemorySwitch

Register-Transfer

Gate

Transistor

“Y-chart” by Gajski & Kahn




Geometric “Y-chart” by Gajski & Kahn

Polygons

Sticks

Standard Cells

Floor Plan


Inverted as compared to previous slides



Design activities


Rugby meta model

Axel Jantsch, Shashi Kumar*, Ahmed Hemani

Royal Institute of TechnologyDepartment of electronicsElectronic systems design laboratoryElectrum 229S – 164 40 Kista, Sweden

* School of Engineering, Jönköping University, Jönköping, Sweden


Rugby meta model

“A conceptual framework, in which designs, design processes and design tools can be studied.

The model has similar objectives as the well known Y chart but its scope is extended to handle designs and design processes required for complex systems requiringconcurrent processes and mixed HW/SW implementation.

The Rugby model has four domains, namely, Computation, Communication, Data and Time. “

Axel Jantsch, Shashi Kumar, Ahmed Hemani


Rugby meta model

“The behavioral domain of the Y chart is replaced with more restricted computation domain.

The structural and physical domain of the Y chart are merged into a more generic domain called Communication.

The new domains Data and Time have become necessary to model data abstractions used at various levels of design, and to explicitly model timing constraints at various levels in the design process, respectively”.



Rugby meta model

“The Rugby model is able to represent mixed HW/SW designs and design processes for HW/SW codesign at various levels of abstraction.

It not only can represent state-of-the-art of current electronic systems and electronic system design automation, but it also points to gaps in the availability of tools and methodologies for designing complex system”.



Rugby meta model

Domain, Hierarchy, and Abstraction: “Abstraction and hierarchy are two different means to handle complexity.

Hierarchy partitions a system into smaller parts; abstraction replaces one model with another model which contains significantly less detail and information. Both reduce the amount of information and details that must be considered for a particular purpose.

A third way to tackle complexity is the analytical slicing of models into domains. Unlike hierarchy and abstraction it does not lead to physically separate models or parts of a model, but it is an analytical means to study different aspects of a model separately”.



Rugby meta model

Hierarchy: “A hierarchy is a, possibly recursive, partitioning of a design model such, that the details of each part is hidden into a lower hierarchical level.

Hierarchy defines the amount of information presented and visible at a particular hierarchical level of a model.

At all hierarchy levels the same modelling concepts are used. The motivation for hierarchy is to hide information when it is not needed and to display details when they are useful”.



Rugby meta model

Abstraction: “An abstraction level defines the modelling concepts and their semantics for representing a system.The type of information available at different levels is different. A higher level ignores some irrelevant information at a lower level and encodes it using different concepts.

Abstraction defines the type of information present in a model. Unlike hierarchy, abstraction is not concerned with the amount of information visible, but with the semantic principles of a model. In general, the movement from high to low abstraction levels includes a decision making process”.



Rugby meta model

Domain: “A domain is an aspect of a model which can logically be analysed independently from otheraspects.A domain focuses on one design aspect. Real models always contain several aspects or domainsbut different models may emphasize one domain more than another. Models, which focus on one particulardomain use modelling notations and constructs to model the design aspect of concern explicitly.Other design aspects may be implicitly part of the models. Whereas hierarchy and abstraction simpli-fies the design, domain partitioning helps the developers of tools and methodologies to cope with thecomplexity. The domains considered in this article are computation, communication, data, and time.”



Rugby meta model

“While hierarchical partitioning is mostly a manual endeavour, the definition of abstraction levels and transformations between them, is behind most of the advances in design automation. While hierarchy is a general and important concept, it is not explicit in the Rugby model. We assume, hierarchy is possible at all abstraction levels in any domain.

The Rugby model is based on these definitions and identifies four domains, computation, communication, time and data, and several abstraction levels for each domain.

Hierarchy is not further discussed but we assume, that a model at any abstraction level can have an arbitrary number of hierarchy levels.”



“The model derives its name from the similarity of its visual representation (see figure 4) to the shape of a Rugby, with the domain lines forming the seams.”


































Rugby summary

• Separates the modeling issues computation, communication, time and data;

• Defines abstraction levels in these four domains independently;

• Allows to organize the design phases with respect to the abstraction levels;


ConclusionsWhat have we seen in the lecture ?

• motivation for DSP design methodologies• some elements for DSP design methodologies

Domains, abstraction level and design activities• the Y-chart model• the rugby meta-model• illustration of the rugby meta-model

• Meta-models can be used to define the domains of design• they can be used to analyze and describe other methods (SPU, OO…)• they make the design domains explicit• they can be used to map a particular design method• they can be used to find room for improvement in existing methods


Conclusions

Exercices:

1) define the new terms encountered in the articles:

• A Model of Design Representation and Synthesis• The Rugby Meta-Model

2) For those who know the SPU method, try to put in line with the rugby model

Documents

ASPI8-4 DSP Design Methodology