ECE 406

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ECE 406 Design of Complex Digital
SystemsLecture 1 Introduction
Spring 2007 W. Rhett Davis NC State
University with significant material from Paul
Franzon, Bill Allen, Xun Liu
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Announcements

• Projects are the labs
• Jeremy Brown will be the TA
• HW1 Due in 12 Days

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Todays Lecture

• Introduction
• Brief Review of ECE 212
• Syllabus

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ECE 406 A course in building stuff

• Specification Build a piece of hardware to read
  in 4 bits and allow the user to select one bit
  for output.

How would you build it?
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Approaches

• ECE 206/306 Approach (Software)
• Microcontroller memory on an evaluation board,
  assembly language or C code to implement behavior
• ECE 212 Approach (Hardware)
• Discrete logic chips (flip-flops, AND OR gates,
  multiplexers), breadboard, wires
• Which approach is better?

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Comparison of Approaches

• Cost
• Manufacturing / Materials (Recurring)
• Design (Non-Recurring)
• Performance
• Speed
• Power

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What are you likely to design?

• Digital Still Camera (DSC)
• CD Player
• Satellite TV/Radio Receiver
• Digital Cable Set-Top Box
• Cellular Telephone
• Wireless LAN Cards
• HDTV Receivers
• Cable Modems / DSL Modems

Kodak DSC
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Kodak DSC System Overview
built around a TMS320DSC25 chip from Texas
Instruments
source http//www/ti.com
Blue is on-chip, white is off-chip
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Hardware vs. Software

• When to use a Hardware approach instead of a
  Software approach?
• New Hardware is generally created whenever a
  micro-processor cant be found thats fast enough
  for a given application
• Higher resolution camera
• Higher quality video
• Faster data-rate modem
• 70 of embedded applications run within 250 Mhz
• ECE 406 is a HARDWARE DESIGN CLASS
• Youll design an LC-3 Microcontroller before its
  over

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Review of ECE 212

• Specification Design a piece of hardware to
  read in 4 bits and allow the user to select one
  bit for output.

Block Diagram (Sketch)
Schematic
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Parts of a Schematic

• Ports / Terminals
• interface to outside world
• how many?
• Nets
• internal connections
• how many?
• Symbols
• simple (or abstract) representation of hardware
• how many?
• Instances
• An occurrence of a symbol
• how many

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What is a Digital System?
It is a organized collection of digital elements
which is designed to perform specified operations
on a set of digital inputs and to generate a set
of digital responses.
A digital system can be as simple as a block of
combinational logic or as complex as a
microprocessor.
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What is a Digital System?
Structure of digital systems system vs.
module

• A digital system can be created as a monolithic
  structure.

• Complex systems often need to be partitioned
  into some
• number of subsystems -- modules

• For small systems which can be conveniently
  designed
• monolithically the terms system and module
  may be
• used interchangeably.

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What is a Digital System?
Single module system
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What is a Digital System?
Multiple module system
System
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Inside the TMS320DSC25 chip
How do we go about designing this? Or how to
computer engineers go about designing this?
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Step 1 Describe the Hardware

• One approach Simply describe the whole system
  as a set of schematics.
• Then send your description off to a semiconductor
  company to fabricate for you.
• What problems arise with this approach?
• Drawing schematics takes too much time
• How do you know for certain that it will work?

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Step 2 Simulate the Behavior

• Automatically generate a timing diagram /
  waveforms to verify the behavior

In0
Out0
Out1
In1
In2
Out2
In3
Out3
clock
Clock In Out
F 1 A 5
F
2
A
A
x
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Role of Hardware Description Languages

• Modern digital chip and system design centers on
  the use of Hardware Description Languages (HDL)
  to capture the design at the Register Transfer
  Level (RTL)
• RTL specifies all registers (flip-flops) and the
  combinational logic between the flip-flops
• Capturing the design in RTL is much faster than
  drawing a schematic, because you dont need to
  specify each gate.
• But how do we get the final hardware?

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Step 3 Synthesize the Hardware

• Modern design depends heavily on the use of
  Computer-Aided Design tools
• To synthesize the RTL design into a schematic
• To turn the schematic into a chip layout, FPGA
  mapping or board layout
• To verify the original design, and verify that
  the more detailed designs are consistent with the
  original design
• Good designers depend critically on their ability
  to operate effectively with the CAD tools
• Just knowing how to design logic is not enough
• Unfortunately, you must learn a lot of tools and
  learn how to deal with their complexity and bugs
• Its important to form a good understanding of the
  tools methodology

HDLs simplify Design Capture Design Automation
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Synthesis-based chip design

• The chip is designed using synthesis tools
• Used when time-to-market is the most important
  issue
• Basic Steps
• Write HDL
• Simulate
• Snythesize
• PlaceRoute
• Verify

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IC Design Approaches

• HDL and synthesis based design is used in both
  Application Specific Integrated Circuits (ASICs)

NOR gate
D-flip-flop
Place and Route Tool
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IC Design Approaches

• and Field Programmable Gate Arrays (FPGAs)

Xilinx FPGA architecuture
Configurable Logic Block (CLB)

• cost and time-to-market pressures are forcing
  implementation of embedded applications to move
  from ASICs to FPGAs Tanurhan, Computer, Nov
  2006

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Summary

• Explain the differences between the following
  terms
• Schematic vs. Block Diagram
• Port vs. Net
• Symbol vs. Instance
• System vs. Module
• HDL vs. RTL