digital electronics revision

Digital Electronics Revision

Richard Harris

Semester 2 - 2006 Digital Electronics Slide 2

Objectives

• To identify the key points from the lecture material presented in the first section of this paper.

• What is in the examination and what is not…..


Presentation Outline

• Identifying the key points• Summary on a lecture by lecture basis• Supplementary material


Remember this!

• The Objectives slides in each lecture are:– intended as a guide to the things that you should be able to do

as a result of • participating in the lecture and • reading the suggested reference material

– (Remember that merely sitting in a lecture doesn’t produce learning, its an active process!)

• For each of the tutorial sheets there is also a summary of the important points from each of the lectures.

• Use these two things to guide you in your studies.• Use the tutors from the labs to help clarify points –

that’s what they are paid to do!


Lecture 01

• Topics– Characteristics of analogue and digital signals– Digital circuit states: on / off, high / low, open / closed– Representation of information: numbers, Gray code, ASCII– Digital circuits: AND, OR, NOT, NAND, NOR gates– Truth tables

• Key Points– Understand the important differences between analogue and digital signals.– Know how to represent more than two levels using digital signals.– Be aware of different codes for representing numbers and letters: natural

binary, signed binary, twos complement, offset binary, Gray codes, ASCII characters.

– Know how to convert between binary and base 10.– Recognise the logic symbols for AND, OR, NOT, NAND and NOR gates.– Be able to draw up a truth table to represent relationship between inputs and

outputs of a logic circuit.


Lecture 02

• Topics– Diode Transistor Logic– TTL– Schottky TTL– CMOS– Tristate logic outputs– Definitions:

• Noise margin, • fanout

Timing: rise and fall times, • propagation delay

Power dissipation– Power supply decoupling


Lecture 02 (Contd)

• Key Points– Know how diodes can be used to form logic gates (Diode

logic).– Understand the need for introducing transistors in the output

(DTL and TTL).– Understand why Schottky transistors improve the speed of

gates.– Be familiar with the operating principles of CMOS logic gates.– Know the definitions of noise margin, fanout, propagation

delay, rise and fall time.


Lecture 03

• Topics– Theorems: AND, OR, NOT, commutation, absorption, association,

distribution, DeMorgan's theorems– Completeness of NAND or NOR implementations– Reducing a circuit to symbolic form

• Key Points– Know the theorems of Boolean algebra– Be able to use these to check if two digital circuits are equivalent.– Know how to represent a logic function completely using either

NAND or NOR gates.– Be able to analyse a circuit to give a symbolic representation.– Understand how to interpret the symbolic representation of a logic

function.


Lecture 04

• Topics– Representing a circuit from its truth table– Minterm and maxterm circuit representations– Circuit simplification– Addition / subtraction circuits– Multiplexer / demultiplexer circuits

• Key Points– Understand what is mean by the minterm (sum of product)

and maxterm (product of sum) representations of a logic circuit.

– Know how to design a digital circuit from the truth table of itsfunction.

– Be familiar with adder and multiplexer circuits.


Lecture 05

• Topics– Circuit minimisation– Simplifications of 2, 3, and 4 variables– Handling more than 4 variables– Handling don't cares

• Key Points– Be able translate the information represented on a truth table

into a Karnaugh map and vice versa.– Know how to use a Karnaugh map to simplify expressions

containing 2, 3 and 4 variables.– Understand how to use a Karnaugh map to simplify

expressions containing 5 and 6 variables.– Be able to simplify expressions with don't care states.


Lecture 06

• Topics– Race conditions– Sequential circuits– Hazards– Sequential circuits and internal states– Latches (NAND and NOR)– Flipflops (JK and D)– Removing hazards with synchronous circuits

• Key Points– Realise the limitations of Boolean algebra and Karnaugh maps.– Understand what is meant by the terms "hazard" and "race", and their causes

in logic circuits.– Know the differences between combinatorial circuits and sequential circuits.– Be able to draw truth tables for sequential circuits.– Be familiar with D latches, RS latches, Toggle flip-flops, and JK flip-flops.– Know how to use latches to create synchronous circuits.


Lecture 07

• Topics– Shift registers and applications:

serial / parallel conversion; pseudo random binary sequences; delays;multipliers; memory register; counting

– Counter circuits: synchronous / asynchronous; up / down; presettable

• Key Points– Know how to construct shift registers and counters out of flip-flops.– Be familiar with some of the applications of shift registers.– Know the differences between a ripple counter, a ring counter, and a

synchronous counter.– Be able to construct a synchronous counter for any modulus.


Lecture 08

• Topics– State transition diagrams– Automatic controllers– Designing synchronous sequential circuits from state

transition diagrams• Key Points

– Know what a state transition diagram is.– Be able to analyse a sequential logic circuit, and draw the

corresponding state transition diagram.– Be able to design synchronous finite state machines for

simple problems.


Lecture 09

• Topics– One-hot state machines– Multiplexer based state machines– Asynchronous sequential circuits

• Key Points– Understand what is meant by a one-hot state machine.– Be able to design synchronous one-hot state machines for

simple problems.– Know how to implement a state machine using multiplexers.– Understand the differences between synchronous and

asynchronous state machine design.


Lecture 10

• Topics– Programmable logic arrays– PLA, PAL, and ROM formats– Programming languages for logic - CUPL

• Key Points– Understand what is meant by programmable logic– Be familiar with the differences between the 3 main programmable

architectures: PLA, PAL, and PROM– Know how to use a PLA to implement an arbitrary logic function– Know how to use a PLA to implement a synchronous finite state

machine– Be familiar with the basics of CUPL – a simple hardware language

used to program PLAs.


Lecture 11

• Topics– Memory as a bank of registers– Memory types: static / dynamic, volatile / nonvolatile– RAM, ROM, PROM, EPROM, EEPROM– Flash memory– Use of memory as a combinatorial circuit implementation

• Key Points– Know how to select one register or memory location from among all that are

connected.– Appreciate how tristate logic can simplify the design of memory circuits.– Be able to describe what is meant by the following terms as they apply to

memory circuits:address bus static dynamicrefresh volatile random access read only

– Understand how memory can be used to implement a combinatorial logic block.


Lecture 12

• Topics– Signal propagation along a wire– Transmission line effects: characteristic impedance, reflection,

matching– Need for repeaters: attenuation, dispersion– Signal pickup in cables

• Key Points– Understand the limitations caused by propagation delay along a

length of wire.– Know the basic characteristics of transmission lines.– Appreciate the need for impedance matching when sending signals

over any distance.– Be aware of the causes of cross-talk and signal pickup in lines or

cables.


Mid-semester test

• 50 minutes – BE ON TIME!• Closed book examination conditions. (No notes, books

etc) Standard calculator might be useful.• Will consist of short answers and requirements for

simple and brief explanations.• Marks are an indication of how much time you should

spend on answering the question. Spend 5 times longer answering a question worth 5 marks compared with a question worth only one mark!


Last Year!


Last Year (Continued)


This year ☺?


Examinations - Final

• Examination is in two parts• Each part has 4 questions• You will be required to answer a total of 5 questions• You must answer a minimum of two questions from

each part.• The fifth question can come from any part.


Conclusions

• Good luck with all your examinations!• See you next time.

digital electronics revision

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