Sunday, October 3, 2010


VLSI And Embedded System Contrasted

Embedded System

  • In Embedded System we embedd a software in electronic circuit intended to run a particular application and hence the name.

  • The instructions are executed one by one and hence slow.

  • There is a wastage of components since we don't use all the resources of a microcontroller to perform a particular task which will add to increase in silicon area, cost and energy consumption.
VLSI Design

  • A digital circuit is integrating into an IC.

  • Works as a digital circuit; follows concurrency, delay...

  • Since it is an ASIC(Application Specific Integrated Circuit) there is no wastage of resources and hence small foot print, low cost(on mass production), low power consumption

Using Modelsim
Make one library (FILE -> NEW ->LIBRARY)
Make new project(File -> new -> project)
                NOTE : make the default library the library you made
Make new Source file for vhdl (same way)
                NOTE : Must give the extension as vhd or vhdl. Then only it ll be considered as vhdl file.

Introduction to program : Unlike Sequential language (Software executes instruction by instruction); HDL ll execute as circuit behaves (Cuncurrently and considers delay in circuit)

Two sections
   1. Entity          :- The pinouts of the IC are declared here
   2. Architecture :- The internal connections of IC. Architecture can be in 3 three different ways
                             i. DATAFLOW      : Draw the circuit first and then describe how data is flowing through the circuit in text form .
                            ii. STRUCTURAL   : Makes the blocks which performs the basic functions and we can reuse as many times according to the requirements.
                           iii. BEHAVIOURAL : Say wat output u need wen this i/p cums

Now see a sample program.

entity andgate is
                     a,b : in bit;
                     c :out bit
 end entity;

architecture df of and gate is
        c<=a and b;
Now save it and see colours of the text.
Now compile it
See the name of the entity under ur library(Find the library by clicking view and then library)
now rt click the entity name and simulate it.
View the objects(click view and then objects)
Now give the i/p  values by forcing
Now run for some time say 100ns

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