VHDL Description Models VHDL VHDL can be looked at as a model of a - - PowerPoint PPT Presentation

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VHDL Description Models VHDL VHDL can be looked at as a model of a - - PowerPoint PPT Presentation

Aug 31, 2023 591 likes •765 views

VHDL Description Models VHDL VHDL can be looked at as a model of a digital system Powerful alternative to schematic based design A change (transition) on the input may lead to a new system state and consequently a change of the

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VHDL – Description Models

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VHDL

  • VHDL can be looked at as a model of a digital system

– Powerful alternative to schematic based design

  • A change (transition) on the input may lead to a new

system state and consequently a change of the output after a given time delay

  • Describes and simulates concurrent events

System/module IN OUT Representation of a digital system

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  • The entity describes the

interface to the outside world (connection pins of package)

  • The architecture describes the

functionality of the circuit inside the entity (package)

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Description models Structural Data-flow Behavioral

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Description models Structural Data-flow Behavioral

  • Interconnection of components (black boxes)
  • Concurrent execution of statements
  • Can be used to create hierarchy in the code
  • Keywords: component & port map
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Example of structural model

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Example of structural model

Can not directly connect together the input/output of a component to another component’s output/input! Must use an internal signal (such as int1 in this example), unless a connection to a port is made

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A component is an entity that is used in another entity

Component

entity declaration architecture declaration component component port port port

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Description models Structural Data-flow Behavioral

  • Non-procedural
  • Describes flow of data using concurrent statements

– Concurrent execution of statements – Statement ”activated” by change on input

  • No correspondence between the order of elements / statements

in the code

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Code structure

Concurrent statements area

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Description models Structural Data-flow Behavioral

  • Procedural
  • Describes circuit in terms of behaviour ( Algorithmic )
  • High abstraction level (no details of actual HW implementation)
  • Keywords: process
  • Execution of a process is equivalent to a single concurrent statement.

– All VHDL processes execute concurrently

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Code structure

Concurrent statements area process: a concurrent VHDL statemen

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Code structure

Concurrent statements area process: a concurrent VHDL statemen

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RTL – Register Transfer Level

Q clk D

comb. logic

Q clk D Design abstraction which models a synchronous digital circuit in terms of

  • the flow digital signals (data) between hardware registers,
  • And the logical operations performed on those signals

comb. logic comb. logic

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LUT DFF

Switch matrix

A B C D clk q y MUX Logic block Combinational logic Synchronous / Sequential logic

Programmable logic block

Boolean logic