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Transcript of Introduction to Digital Design. Text Book Digital Design by - John F. Wakerly - you will find some...
![Page 1: Introduction to Digital Design. Text Book Digital Design by - John F. Wakerly - you will find some solutions at this site. .](https://reader035.fdocuments.in/reader035/viewer/2022062300/56649e535503460f94b49e3a/html5/thumbnails/1.jpg)
Introduction to
Digital Design
![Page 2: Introduction to Digital Design. Text Book Digital Design by - John F. Wakerly - you will find some solutions at this site. .](https://reader035.fdocuments.in/reader035/viewer/2022062300/56649e535503460f94b49e3a/html5/thumbnails/2.jpg)
Text Book• Digital Design by - John F. Wakerly
• www.ddpp.com - you will find some solutions at this site.
• www.xilinx.com - Xlinix Web site
![Page 3: Introduction to Digital Design. Text Book Digital Design by - John F. Wakerly - you will find some solutions at this site. .](https://reader035.fdocuments.in/reader035/viewer/2022062300/56649e535503460f94b49e3a/html5/thumbnails/3.jpg)
Digital Design• Digital Design is also know as “Logical Design”.
• The purpose is to build Digital Systems.
![Page 4: Introduction to Digital Design. Text Book Digital Design by - John F. Wakerly - you will find some solutions at this site. .](https://reader035.fdocuments.in/reader035/viewer/2022062300/56649e535503460f94b49e3a/html5/thumbnails/4.jpg)
Analog versus Digital
• Analog systems process time-varying signals that can take on any value across a continuous range of voltages (in electrical/electronics systems).
• Digital systems process time-varying signals that can take on only one of two discrete values of voltages (in electrical/electronics systems).– Discrete values are called 1 and 0 (ON and OFF,
HIGH and LOW, TRUE and FALSE, etc.)
![Page 5: Introduction to Digital Design. Text Book Digital Design by - John F. Wakerly - you will find some solutions at this site. .](https://reader035.fdocuments.in/reader035/viewer/2022062300/56649e535503460f94b49e3a/html5/thumbnails/5.jpg)
Digital Revolution
• Digital systems started back in 1940s.
• Digital systems cover all areas of life:– still pictures– digital video– digital audio– telephone– traffic lights– Animation
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Benefits of Digital over Analog
• Reproducibility
• Not effected by noise means quality
• Ease of design
• Data protection
• Programmable
• Speed
• Economy
![Page 7: Introduction to Digital Design. Text Book Digital Design by - John F. Wakerly - you will find some solutions at this site. .](https://reader035.fdocuments.in/reader035/viewer/2022062300/56649e535503460f94b49e3a/html5/thumbnails/7.jpg)
Digital Devices
• Gates
• Flip-Flops
• PLDs
• FPGAs
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Gates
• The most basic digital devices are called gates.
• Gates got their name from their function of allowing or blocking (gating) the flow of digital information.
• A gate has one or more inputs and produces an output depending on the input(s).
• A gate is called a combinational circuit.
• Three most important gates are: AND, OR, NOT
![Page 9: Introduction to Digital Design. Text Book Digital Design by - John F. Wakerly - you will find some solutions at this site. .](https://reader035.fdocuments.in/reader035/viewer/2022062300/56649e535503460f94b49e3a/html5/thumbnails/9.jpg)
Digital Logic• Binary system -- 0 & 1, LOW & HIGH,
negated and asserted.
• Basic building blocks -- AND, OR, NOT
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AND, OR, NOT Gates
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Electronic Aspects of Digital Design
• How we represent digital information in electronic devices?
• By discrete voltages.
![Page 13: Introduction to Digital Design. Text Book Digital Design by - John F. Wakerly - you will find some solutions at this site. .](https://reader035.fdocuments.in/reader035/viewer/2022062300/56649e535503460f94b49e3a/html5/thumbnails/13.jpg)
What is the Basic Digital Element
in Electronics?
a Switch
![Page 14: Introduction to Digital Design. Text Book Digital Design by - John F. Wakerly - you will find some solutions at this site. .](https://reader035.fdocuments.in/reader035/viewer/2022062300/56649e535503460f94b49e3a/html5/thumbnails/14.jpg)
Using Switch to represent digital information
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Digital Abstraction
• It is difficult to make ideal switches means a switch is completely ON or completely OFF.
• So, we impose some rules that allow analog behavior to be ignored in most cases, so circuits can be modeled as if they really did process 0s and 1s, known as digital abstraction.
• Digital abstraction allows us to associate a noise margin with each logic values (0 and 1).
![Page 16: Introduction to Digital Design. Text Book Digital Design by - John F. Wakerly - you will find some solutions at this site. .](https://reader035.fdocuments.in/reader035/viewer/2022062300/56649e535503460f94b49e3a/html5/thumbnails/16.jpg)
Real Switches to represent digital information
5v 5v
1k
10k
5v 4.5v
Output Output
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Logic levels• Undefined region
is inherent– digital, not analog– amplification,
weak => strong• Switching threshold varies with voltage, temp, process,
phase of the moon– need “noise margin”
• The more you push the technology, the more “analog” it becomes.
• Logic voltage levels decreasing with new processors.– 5 -> 3.3 -> 2.5 -> 1.8 V
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MOS Transistors
NMOS
PMOS
Voltage-controlled resistance
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CMOS Inverter
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Switch model
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Alternate transistor symbols
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CMOS Gate Characteristics • No DC current flow into MOS gate terminal
– However gate has capacitance ==> current required for switching (CV2f power)• No current in output structure,
except during switching– Both transistors partially on– Power consumption related
to frequency– Slow input-signal rise times
==> more power• Symmetric output structure
==> equally strong drive in LOW and HIGH states
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Flip-flops
• A device that stores either a 0 or 1.
• Stored value can be changed only at certain times determined by a clock input.
• New value depend on the current state and it’s control inputs
• A digital circuit that contains filp-flops is called a sequential circuit
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Flip-flops
S-R latch symbols D flip-flop
J-K flip-flops
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Integrated Circuits
• A collection of one or more gates fabricated on a single silicon chip is called an integrated circuit (IC).
• ICs were classified by size:– SSI - small scale integration - 1~20 gates– MSI - medium scale integration - 20~200 gates– LSI - large scale integration - 200~200,000 gates– VLSI - very large scale integration - over 1M
transistors
• Pentium-III - 40 million transistors
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DIP Packages
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Gates in ICs
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Programmable Logic Devices
• PLDs allow the function to be programmed into them after they are manufactured.
• Complex PLDs (CPLD) are a collection of PLDs on the same chip.
• Another programmable logic chip is FPGA - field-programmable gate arrays.
![Page 29: Introduction to Digital Design. Text Book Digital Design by - John F. Wakerly - you will find some solutions at this site. .](https://reader035.fdocuments.in/reader035/viewer/2022062300/56649e535503460f94b49e3a/html5/thumbnails/29.jpg)
CPLDs and FPGAs
FPGACPLD
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Application Specific Ics (ASICs)
• Chips designed for a particular application are called semicustom ICs or application-specific ICs (ASICs).
• ASICs generally reduce the total component and manufacturing cost of a product by reducing chip count, physical size, and power consumption, and they often provide higher performance.
• But costly if not produced in bulk.
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Printed-Circuit Boards
• An IC is normally mounted on a printed-circuit board (PCB) that connects it to other ICs in a system.
• Individual wire connection or traces can be as narrow as 4 mils with 4 mils spacing (one-thousandth of an inch)
• Now a days, most of the components use surface mount technology.
• They are normally layered.
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Software Aspects of Digital Design• Today software tools are an essential part of digital
design.• Software tools improve productivity, correctness and
quality of designs• Software tools are:
– Schematic entry– HDL (Hardware Description Language) Editors – Simulators - to verify the behaviour of the design– Synthesis tools - circuit design– Timing analyzers and verifiers
![Page 33: Introduction to Digital Design. Text Book Digital Design by - John F. Wakerly - you will find some solutions at this site. .](https://reader035.fdocuments.in/reader035/viewer/2022062300/56649e535503460f94b49e3a/html5/thumbnails/33.jpg)
Digital Design Levels
• the lowest level of design is device physics and IC manufacturing processes.
• design at the transistor level
• level of functional building blocks
• level of logic design using HDLs
• computer design and overall system design.
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Different Design Levels
Consider a simple design example:
Build a multiplexer with two data inputs A and B, a control input S, and an output Z.
Switch model for the example multiplexer
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Designing at the transistor level
• Transistor-levelcircuit diagrams
• Gate symbols (for simple elements)
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• Logic designusing Truth tables
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• Logic designusing boolean algebra
Equations: Z = S A+ S B
• Logic diagrams
![Page 38: Introduction to Digital Design. Text Book Digital Design by - John F. Wakerly - you will find some solutions at this site. .](https://reader035.fdocuments.in/reader035/viewer/2022062300/56649e535503460f94b49e3a/html5/thumbnails/38.jpg)
• Prepackaged building blocks, e.g. multiplexer
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• Various hardware description languages– ABEL
– VHDL
• We’ll start with gates and work our way up
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• Name of the program module
• the type of PLD
• pin numbers
• ABEL statement to achieve the multiplexer
• Standard library
• and a set of definitions
• Inputs and outputs
• functions behaviour
![Page 41: Introduction to Digital Design. Text Book Digital Design by - John F. Wakerly - you will find some solutions at this site. .](https://reader035.fdocuments.in/reader035/viewer/2022062300/56649e535503460f94b49e3a/html5/thumbnails/41.jpg)
Structural VHDL program for the multiplexer
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Summery
• Design to minimize cost.
• Rule of thumb is to minimize the number of ICs.
• Though PLDs costs more but uses less PCB area.
• Unless mass production avoid ASIC design.
• Design to solve real life problems.