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THE WORLD OF VLSI & VHDL

Yesterday, Today & Tomorrow


The World of VLSI • History of the Integrated Circuit (IC) design • The IC Technologies


 History of the IC designIn 1947 Transistor was

invented & demonstrated @ Bell Labs  The first IC appeared in the market in 1961  ~14 years after the transistorFlip-flop:  2 transistors & resistorsCost  ~$100

• The Silicon Technology is Growing... • Now on the same amount of Silica  ~500 times  faster operations 10 million transistors,  1/2 mile of interconnectCost few cents!!!  The Technology changes compared to the IC Design cycle


Moore’s Law  In 1965, GardonMoore stated that the silicon

technology will double the number of transistors on a chip every 2 years!!!  And it is happening !!!!!!


The Search of products  “How to reduce the high designing cost for

future success of this technology ??? ”:  1968 Noyce  Reduce the cost of design process  Find product with large market-Regular structure,

Many applications 1968 :Noyce, Moore & Grove Forms Intel !!SemiconductorMemory Chip


Microprocessor Technology  Microprocessor = IC Tech +SoftwareProcessor

 Power+Memory capacity

Software market


Advantages of VLSI ?  Less AREA (compactness at system levels)  Less POWERConsumption

 Less TESTING(more complex testing)  Higher RELIABILITY

(due to improved on-chip interconnects)  Higher SPEED(due to reduced interconnect length)  Significant COST SAVINGS


The goal of the IC designer  Meet the market requirements  Satisfying customers need  Beating the competition

 Increasing performance or functionality of the product

Reducing cost compared to the available solutions  Achieved by:  Using next generation Silicon technologies  New design concepts & tools  High level of integration

 The Design is an optimization problem with

parameters as Technology, Time, Cost and Customer requirements


Design Approaches  Custom  full control of design

 best results, slowest design time.

 Semi-custom (std cell)  use Cell libraries from vendor  cad tools, faster design time

 EPLA/EPLD -FPGA  Electrically Programmable (in the Field)


ASIC(Application Specific Integrated Circuit)  Implements custom functions according to description  Not off-the-shelf

 Can be described in HDL (Verilog,VHDL)  in an abstract technology Independent fashion

 Verified using a simulator  Analogous to software debugger

 Constructed out of logical function cells  (AND,OR) and Re-Usable Macro

 Building blocks (ADDERs, REGISTERs)  Mapped or translated using Synthesis products

Implemented in

 Field Programmable, Standard Cell or Gate Array families

 For high volume production  Designers pay CAD vendors ~$50K -$500K for Design tools  Designer pay foundry( ~ $200K -.5M) and per part agreement


Field Programmable Gate Array  A chip that can be configured by a user to

implement different digital logic circuits  Invented in 1984

 FPGA building blocks:  Programmable logic blocks  Programmable interconnectField


To compress the digital world. To explore the hidden perfection and create

the brain of a machine.

*The above two are considered as a very difficult tasks in the field of electronics engineering, where in fact it’s a very simple technology.


 VHDL is for coding models of a digital system.  Reasons for modeling: ◦ Requirements specification ◦ Documentation ◦ Testing using simulation ◦ Formal verification ◦ Synthesis  Goal: ◦ Most ‘reliable’ design process, with minimum cost and time ◦ Avoid design errors!


 VHDL is a programming language that allows one

to model and develop complex digital systems in a dynamic environment.  Object Oriented methodology for you C people

can be observed -- modules can be used and reused.  Allows you to designate in/out ports (bits) and

specify behavior or response of the system.


 C is procedural language whereas VHDL is semi

concurrent & semi sequential language.  C is

Case Sensitive whereas VHDL is case insensitive.

 There

are some similarities, as with any programming language, but syntax and logic are quite different.


• Interfaces (PORTS) • Behavior • Structure

• Test Benches • Simulation • Synthesis


Dataflow Behavioral Structural Kind of BORING sounding huh??

Well, it gets more exciting with the details !! :)


Uses statements that defines the actual flow of data..... such as, x <= y

-- this is NOT less than equal to -- told you its not C

this assigns the Boolean signal x to the value of Boolean signal y... i.e. x = y this will occur whenever y changes....


Entity declarationâ&#x20AC;Ś (Describes the input/output ports of a module) entity name

port names

entity reg4 is port ( d0, d1, d2, d3, en, clk : in bit; q0, q1, q2, q3 : out bit ); end entity reg4;

reserved words

port type

port mode (direction)

punctuation


 Architecture body  Describes an implementation of an entity  May be several per entity

 Behavioral architecture  Describes the algorithm performed by the module  Contains Process statements, each containing  Sequential statements, including Signal assignment statements and Wait statements


ď&#x192;&#x2DC; Omit entity at end of entity declaration. ď&#x192;&#x2DC; Omit architecture at end of architecture body. ď&#x192;&#x2DC; Omit is in process statement header.

entity reg4 is port ( d0, d1, d2 : in bit d3, en, clk : in bit; q0, q1, q2, q3 : out bit ); end reg4;

architecture behav of reg4 is begin process (d0, ... ) ... begin ... end process ; end behav;


 Structural architecture  implements the module as a composition of

subsystems  contains ○ signal declarations, for internal interconnections  the entity ports are also treated as signals

○ component instances  instances of previously declared entity/architecture pairs

○ port maps in component instances  connect signals to component ports


 An architecture can contain both behavioral

and structural parts  Process statements and component instances ○ Collectively called concurrent statements

 Processes can read and assign to signals

 Example: register-transfer-level (RTL) model  Data path described structurally

 Control section described behaviorally


multiplier

multiplicand

shift_reg

control_ section

shift_ adder

reg

product


 Testing a design by simulation  Use a test bench model  A model that uses your model  Apply test sequences to your inputs  Monitors values on output signals

 Either using simulator.  Or with a process that verifies correct operation  Or logic analyzer.


 Discrete event simulation  Time advances in discrete steps.  When signal values change—events occur.

 A processes is sensitive to events on input

signals  Specified in wait statements.  Resumes and schedules new values on output

signals. ○ Schedules transactions. ○ Event on a signal if value changes.


Initial Design Entry

Logic Optimization Technology Mapping Placement Routing

Programming Unit

VHDL, Schematic, State Diagram Optimize Boolean Expression into a standard form -To optimize area or speed Minimized Blocks -To minimize area Where the logic block is placed ? -With optimum routing wire Connection between cells -To minimize area.

Used to configure the final circuit


 Implement the VHDL portion of coding for synthesis.  Identify the differences between behavioral and

structural coding styles.  Distinguish coding for synthesis versus coding for

simulation.  Use scalar and composite data types to represent information.  Use concurrent and sequential control structure to regulate information flow.  Implement common VHDL constructs (Finite State Machines [FSMs], RAM/ROM data structures).


• • • • • •

Executable specification. Functionality separated from implementation. Simulate early and fast (Manage complexity) Explore design alternatives. Get feedback (Produce better designs) Automatic synthesis and test generation (ATPG for ASICs) • Increase productivity (Shorten time-to-market) • Technology and tool independence. • Portable design data (Protect investment)


 Digital Signal Processing.  IC Testing & Analysis.  FPGA Design Verification.  FPGA Development.  Hardware Design.  IC designing.  ASIC Development.


• THANK YOU E-Mail Gaurav_rai@live.com


Summer Training-VHDL