chapter 4 gates and circuits. integrated circuits aka chips what’s in this thing???? 4–2

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Chapter 4 Gates and Circuits

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Page 1: Chapter 4 Gates and Circuits. Integrated Circuits aka CHIPS What’s in this thing???? 4–2

Chapter 4

Gates and Circuits

Page 2: Chapter 4 Gates and Circuits. Integrated Circuits aka CHIPS What’s in this thing???? 4–2

Integrated Circuits aka CHIPS

• What’s in this thing????

4–2

Page 3: Chapter 4 Gates and Circuits. Integrated Circuits aka CHIPS What’s in this thing???? 4–2

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Chapter Goals

• How to make a gate from transistors

• How to make integrated circuits using gates

• The basic gates and their behavior

• How gates are combined into (useful) circuits

Page 4: Chapter 4 Gates and Circuits. Integrated Circuits aka CHIPS What’s in this thing???? 4–2

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Chapter Goals

• Describe gates and circuits using:– Boolean expressions– Truth Tables– Logic Diagrams

• Understand half adders, full adders, and binary addition circuits

Page 5: Chapter 4 Gates and Circuits. Integrated Circuits aka CHIPS What’s in this thing???? 4–2

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Computers and Electricity

• Transistor A device that can be used to make gates

• Gate A device that performs a basic operation on bit(s)

• Circuits Gates combined to perform more complicated tasks

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Computers and Electricity

• 3 ways to describe the same thing– Boolean expressions– logic diagrams– truth tables

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Computers and Electricity

• Boolean expressions A mathematical notation for expressing TRUE/FALSE logic

• Example: F = AB + C

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Computers and Electricity

• Logic diagram A graphical representation of a circuit

Each type of gate is represented by a specific graphical symbol

• Truth table A table showing all possible input value and the associated output values

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Gates

• Let’s examine the processing of the following six types of gates– NOT– AND– OR– XOR– NAND– NOR

Page 10: Chapter 4 Gates and Circuits. Integrated Circuits aka CHIPS What’s in this thing???? 4–2

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NOT Gate

• A NOT gate accepts one input value and produces one output value

• Aka “an inverter”

Figure 4.1 Various representations of a NOT gate

Page 11: Chapter 4 Gates and Circuits. Integrated Circuits aka CHIPS What’s in this thing???? 4–2

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AND Gate

• An AND gate accepts two input signals

• If the two input values for an AND gate are both 1, the output is 1; otherwise, the output is 0

Figure 4.2 Various representations of an AND gate

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OR Gate

• If the two input values are both 0, the output value is 0; otherwise, the output is 1

Figure 4.3 Various representations of a OR gate

Page 13: Chapter 4 Gates and Circuits. Integrated Circuits aka CHIPS What’s in this thing???? 4–2

NAND and NOR Gates

• The NAND and NOR gates are essentially the opposite of the AND and OR gates, respectively

Figure 4.5 Various representations of a NAND gate

Figure 4.6 Various representations of a NOR gate

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Page 14: Chapter 4 Gates and Circuits. Integrated Circuits aka CHIPS What’s in this thing???? 4–2

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Constructing Gates

• Transistor A device that acts as a switch, either open or closed (on or off)

– A transistor has no moving parts, yet acts like a switch

– It is made of a semiconductor material, which is neither a particularly good conductor of electricity, such as copper, nor a particularly good insulator, such as rubber

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Constructing Gates

• Transistor terminals– Source– Base– Emitter

• If the electrical signal is grounded, it is allowed to flow through an alternative route to the ground (literally) where it can do no harm

Figure 4.8 The connections of a transistor

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Constructing Gates

• It turns out that, because the way a transistor works, the easiest gates to create are the NOT, NAND, and NOR gates

Figure 4.9 Constructing gates using transistors

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Combinational Circuits

• Consider the following Boolean expression A(B + C)

Page 100

Page 101

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Adders

• At the digital logic level, addition is performed in binary

• Addition operations are carried out by special circuits called, appropriately, adders

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A Half Adder

• Recall that 1 PLUS 1 = 10 in base two

• In other words: 0 with a carry of 1

Inputs OutputsA B Carry Sum

0 0 0 0

0 1 0 1

1 0 0 1

1 1 1 0

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Half Adder Circuit

• Two Boolean expressions:

sum = A Bcarry = AB

Page 103

Page 21: Chapter 4 Gates and Circuits. Integrated Circuits aka CHIPS What’s in this thing???? 4–2

A Full Adder

• A circuit called a full adder takes the carry-in value into account

Inputs Outputs

A B Carry InCarry-

Out Sum0 0 0 0 00 0 1 0 10 1 0 0 10 1 1 1 01 0 0 0 11 0 1 1 01 1 0 1 01 1 1 1 1

Page 22: Chapter 4 Gates and Circuits. Integrated Circuits aka CHIPS What’s in this thing???? 4–2

Integrated Circuits

• We can combine 4 full adders to make a Four-bit Adder Circuit (about 60 transistors)

Page 23: Chapter 4 Gates and Circuits. Integrated Circuits aka CHIPS What’s in this thing???? 4–2

Integrated Circuits aka CHIPS

• What’s in this thing????Chip Fabrication Technology

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Integrated Circuits

• Integrated circuit (also called a chip) A piece of silicon on which many gates have been embedded

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“Silicon Valley”

• Sand is mostly Silicon Dioxide

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“Silicon Valley”

• Silicon Dioxide ingots and wafers

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Page 27: Chapter 4 Gates and Circuits. Integrated Circuits aka CHIPS What’s in this thing???? 4–2

“Silicon Valley”

• Photolithography “Printed” with lots of copies of some circuit

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Page 28: Chapter 4 Gates and Circuits. Integrated Circuits aka CHIPS What’s in this thing???? 4–2

Integrated Circuits aka CHIPS

• What’s in this thing????Computer Architecture: Combining Abstractions into larger Abstractions

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Transistors and Gates

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Integrated Circuits

An simple chip containing 4 independent NAND gates (about 8 transistors)

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Integrated Circuits

• A four-bit Full Adder Circuit

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Integrated Circuits

• An Arithmetic Logic Unit (ALU) has adders and other things in it

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Integrated Circuits

• A simple Central Processing Unit, or CPU has an ALU and other things

• Take Engineering 303 Digital Logic Design!!

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CPU Chips

• A recent CPU chip (Intel Nehelem) 731 Million transistors

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The Future of the IC

• Global Competition

• Further Integration (ARM)

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