Introduction to VLSI
Design
VLSI (Very Large Scale Integration) design involves the creation
of complex integrated circuits that contain millions or billions of
transistors on a single chip. This field combines electrical
engineering, computer science, and materials science to develop
advanced electronic devices and systems.
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by devesh verma
System Design and Their Types
Digital Systems
Analog Systems
Mixed-Signal Systems
These systems use discrete
These systems work with
These systems combine both
digital signals, such as binary
continuous signals and are used
digital and analog components,
data, to process information.
for tasks like signal processing,
allowing for the processing and
Examples include
amplification, and control.
integration of both types of
microprocessors, digital
Examples include amplifiers,
signals. Examples include audio
controllers, and logic circuits.
filters, and sensors.
systems and image sensors.
Tools and Techniques of VLSI
1
Electronic Design Automation (EDA)
2
Software tools for designing, simulating, and
Hardware Description Languages
(HDLs)
Programming languages like Verilog and VHDL
verifying integrated circuits,
used to model and describe the behavior of
electronic systems.
3
Layout and Verification
4
Simulation and Testing
Tools for creating the physical layout of the chip
Techniques to validate the design, identify and fix
and ensuring its functionality and compliance with
errors, and ensure the chip meets performance
design rules.
requirements.
Software: Xilinx Vivado
Integrated Design Environment
Powerful Synthesis and Implementation
Vivado is a comprehensive design suite that supports
Vivado includes advanced algorithms for
the entire FPGA and SoC development lifecycle, from
synthesizing RTL designs into optimized gate-level
design to implementation and verification.
netlists and implementing them on the target FPGA
device.
Intuitive User Interface
Integrated with Verilog and VHDL
The Vivado GUI provides a user-friendly interface for
Vivado seamlessly integrates with both Verilog and
managing design files, running simulations, and
VHDL, allowing designers to choose the HDL best
analyzing results, making the design process more
suited for their project.
efficient.
HDL Coding Concept
1
Hardware Description
HDLs, such as Verilog and VHDL, allow designers to describe the
behavior and structure of electronic systems at different levels of
abstraction.
2
Simulation and Verification
HDLs enable the simulation and verification of designs, allowing
designers to identify and fix errors before implementation.
3
Synthesis and Implementation
HDL code can be automatically synthesized into gate-level netlists
and then implemented on the target FPGA or ASIC device.
Structure of Verilog Code
1
Modules
Verilog code is organized into modules, which serve as the
building blocks of the design and encapsulate the
functionality of the circuit.
2
Ports
Modules have input, output, and inout ports that define the
interface and communication with other modules or the
external environment.
3
Behavioral and Structural
Verilog supports both behavioral and structural descriptions,
allowing designers to describe the system at different levels
of abstraction.
Coding Style in Verilog with Examples
Dataflow And Behavioral Modelling
Gate Level Modelling
Behavioral modeling describes the functionality of a
Gate level modeling in digital design refers to describing
digital system using high-level constructs similar to
a digital circuit in terms of its fundamental logic gates
those in software programming languages. This style
and their interconnections. This approach is commonly
focuses on what the system does rather than how it is
used in hardware description languages (HDLs) like
implemented.​
Verilog and VHDL. Only few logic logic gates are
Example:​
allowed for gate level modeling in verilog also known as
primitives.​
module counter (​
Example :-
input wire clk,​
module simple_circuit (​
input wire reset,​
input wire A,​
output reg [3:0] count​
input wire B,​
input wire C,​
);​
always @(posedge clk or posedge reset) begin​
if (reset)​
output wire Y
wire AND_out;​
);​
Structural Coding and
Simulations
Structural Coding
Describe the design using interconnected modules and
components, focusing on the structural aspects of the circuit.
Simulation
Use test benches and simulation tools to verify the functionality and
behavior of the design before implementation.
Synthesis
Translate the Verilog code into a gate-level netlist that can be
mapped to the target FPGA or ASIC device.
Data Types and Verilog Simulations
Wire
Register
Used to represent interconnections between modules and
Used to represent storage elements, such as flip-flops
components.
and registers.
Integer
Real
Used for wider range of integer values beyond the
Used to represent floating-point values for analog or
standard 1-bit logic.
mixed-signal designs.
Conditional Assignments and Verilog
Constructs
if-else
Used for conditional branching based on Boolean
expressions.
case
Provides a more efficient way to handle multiple
conditions.
for, while, repeat
Allows the execution of a block of code multiple times.
assign
Facilitates continuous assignments and updating of
signal values.
blocking/non-blocking
Determine the order of execution and assignment of
values.
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