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Structured Logic Design With VHDL

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Introduction

• VHDL - VHSIC Hardware Description Language
• VHSIC - Very High Speed Integrated Circuit
• Development of a hardware description language model as a step in digital design at a high level of abstraction
• Development of VHDL began in 1983,sponsored by Department of defense, further developed by the IEEE and released as IEEE Standard 1076 in 1987
• Today it is De facto industry standard for hardware description languages

Structured Design Concepts The abstraction hierarchy

• The abstraction hierarchy employed by digital designers is a set of interrelated system representation
• Can be expressed in two domains: structural domain, behavioral domain
• Structural domain – component model is described in terms of an interconnection of more primitive components
• Behavioral domain input/output response – component model is described by defining its
• VHDL is used for behavioral description

Structured Design Concepts

The abstraction hierarchy

• Six abstraction hierarchy levels of detail commonly used in design: silicon, circuit, gate, register, chip and system

Structured Design Concepts

Types of behavioral descriptions

• Two types of behavioral description – algorithmic and data flow
• Algorithmic – a procedure or program defining the I/O response with no implies of any particular physical implementation
• Data flow – a behavioral description in witch the data dependencies is the description match those in a real implementation (^) Docsity.com8/

Structured Design Concepts

Design process

• Design – a series of transformations from one representation of a system to another until a representation exists that can be fabricated
• The design cycle consists of a series of transformations - synthesis steps :

(1) Transformation from English to an

Structured Design Concepts

Design process

Structured Design Concepts

Structural design decomposition

• The structural form of the design hierarchy implies a design decomposition process
• Two types of design: full tree design and partial tree design

Structured Design Concepts

The digital design space

• Major criteria can be considered to be dimensions in Digital Design Space ,with different tracks for various designs
• Example - circuits A and B implement the same logic function,

Design tools

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Design tools

CAD tool taxonomy

Design tools

CAD tool taxonomy

• Editors – textual (circuit level – SPICE gate, register,chip – VHDL) or graphic (used at all levels)
• Simulators – stochastic (system level,determines for example the percentage of time that a particular unit is busy) or deterministic (all levels above the silicon level)
• Checkers and Analyzers – employed at all Docsity.com18/

Design tools

Schematic editors

(2) A system of graphic windows which can be used to create

an interconnect of graphic tokens

(3) Commands for creating wire lists

Design tools

Simulators

• Major tools used in the development of digital systems
• Programs which models the response of a system to input stimuli
• Modeling approach – system is modeled in interconnected net of digital elements, mapping the function of a digital logic element onto one or more processes Docsity.com^2172