Spring 2007 W. Rhett Davis with minor editing by J. Dean Brock UNCA ECE 406-602Slide 1 ECE 406 – Design of Complex Digital Systems Lecture 1: Introduction

Spring 2007W. Rhett Davis with minor editing by J. Dean Brock UNCA ECE 406-602 Slide 1

ECE 406 – Design of Complex ECE 406 – Design of Complex Digital SystemsDigital Systems

Lecture 1: Lecture 1: IntroductionIntroduction

Spring 2007Spring 2007W. Rhett DavisW. Rhett Davis

NC State UniversityNC State Universitywith significant material from Paul Franzon, Bill Allen, & Xun with significant material from Paul Franzon, Bill Allen, & Xun

LiuLiu


Announcements

Projects are the labs» Jeremy Brown will be the TA

HW#1 Due in 12 Days


Today’s Lecture

Introduction

Brief Review of ECE 212

Syllabus


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.

REG

in1

in2

in3

in4

out

How would you build it?


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?


Comparison of Approaches

Cost» Manufacturing / Materials (Recurring)» Design (Non-Recurring)

Performance» Speed» Power


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

ModemsKodak DSC


Kodak DSC System Overview

source: http://www/ti.com Blue is on-chip, white is off-chip

built around a TMS320DSC25 chip from Texas Instruments


Hardware vs. Software

When to use a Hardware approach instead of a Software approach?

New Hardware is generally created whenever a micro-processor can’t be found that’s 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» You’ll design an LC-3 Microcontroller before it’s over


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.

REG

in1

in2

in3

in4

out

Block Diagram (Sketch)

D Q

D Q

D Q

D Q

in1

in2

in3

in4

out

sel[1:0]

clock

Schematic


Parts of a Schematic

D Q

D Q

D Q

D Q

in1

in2

in3

in4

out

sel[1:0]

clock

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


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.


What is a Digital System?Structure of digital systems: “system” vs. “module”

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

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

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


What is a Digital System?Single module system:

moduledata in

control

data out

control

System


What is a Digital System?Multiple module system:

module

data in

control

data out

control

System

module

module

data in

control


Inside the TMS320DSC25 chip

How do we go about designing this?Or how to computer engineers go about designing this?


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?


Step 2: Simulate the Behavior

Automatically generate a timing diagram / waveforms to verify the behavior

In[0]

In[1]

In[2]

In[3]

clock

Out[0]

Out[1]

Out[2]

Out[3]

Clock

In

Out

F 1 A 5

x F 2 A A


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 don’t need to specify each gate.

» But how do we get the final hardware?


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 tool’s

methodology

HDLs simplify Design Capture & Design Automation


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

Place&Route

Verify


IC Design Approaches

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

D-flip-flop NOR gate

Place and Route Tool


…IC Design Approaches

and Field Programmable Gate Arrays (FPGAs):

Xilinx FPGAarchitecuture 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


Summary

Explain the differences between the following terms:

» Schematic vs. Block Diagram

» Port vs. Net

» Symbol vs. Instance

» System vs. Module

» HDL vs. RTL

Documents

Spring 2007 W. Rhett Davis with minor editing by J. Dean Brock UNCA ECE 406-602Slide 1 ECE 406 – Design of Complex Digital Systems Lecture 1: Introduction