Unit 9 multiplexers decoders and programmable logic devices
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Unit 9 Multiplexers, Decoders, and Programmable Logic Devices. Ku-Yaw Chang [email protected] Assistant Professor, Department of Computer Science and Information Engineering Da-Yeh University. Contents. 9.1 Introduction 9.2 Multiplexers 9.3 Three-State Buffers

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Unit 9 multiplexers decoders and programmable logic devices

Unit 9Multiplexers, Decoders, and Programmable Logic Devices

Ku-Yaw Chang

[email protected]

Assistant Professor, Department of Computer Science and Information Engineering

Da-Yeh University


Contents
Contents

9.1 Introduction

9.2 Multiplexers

9.3 Three-State Buffers

9.4 Decoders and Encoders

9.5 Read-Only Memories

9.6 Programmable Logic Devices

9.7 Complex Programmable Logic Devices

9.8 Field Programmable Gate Arrays

Fundamentals of Logic Design


Buffer
Buffer

  • A gate output

    • Be connected to a limited number of other device inputs without degrading the performance

  • A simple buffer

    • Increase the driving capability of a gate input

Fundamentals of Logic Design


Add buffer
Add Buffer

  • No bubble

    • F = C

Fundamentals of Logic Design


Three state buffers
Three-State Buffers

  • A logic gate will not operate correctly if the outputs of two or more gates or other logic devices are directly connected to each other.

    • In some cases, damage to the gates may result.

Fundamentals of Logic Design


Three state buffers1
Three-State Buffers

  • Also called tri-state buffers

  • B = 1

    • The output C equals A

  • B = 0

    • The output C acts like an open circuit

    • A Hi-Z (high-impedance)

Fundamentals of Logic Design


Four types
Four Types

  • The symbol Z represents the high-impedance state.

Fundamentals of Logic Design


Data selection
Data Selection

  • The outputs of two three-state buffers are tied together.

    • B = 0

      • D = A

    • B = 1

      • D = C

    • D = B’A + BC

  • Logically equivalent to using a 2-to-1 multiplexer

Fundamentals of Logic Design


Two three state buffers
Two Three-State Buffers

  • Connect two three-state buffer outputs together

Fundamentals of Logic Design


Four sources
Four Sources

Fundamentals of Logic Design


Bi directional input output pin
Bi-Directional Input/Output Pin

Fundamentals of Logic Design


Contents1
Contents

9.1 Introduction

9.2 Multiplexers

9.3 Three-State Buffers

9.4 Decoders and Encoders

9.5 Read-Only Memories

9.6 Programmable Logic Devices

9.7 Complex Programmable Logic Devices

9.8 Field Programmable Gate Arrays

Fundamentals of Logic Design


3 to 8 line decoder
3-to-8 Line Decoder

  • Exactly one of the output lines will be 1 for each combination of the values of the input variables.

Fundamentals of Logic Design


4 to 10 line decoder
4-to-10 Line Decoder

Fundamentals of Logic Design


4 to 10 line decoder1
4-to-10 Line Decoder

Fundamentals of Logic Design


Decoder
Decoder

  • In general, an n-to-2n line decoder generate all 2n minterms (or maxterms) of the n input variables.

  • The outputs are defined as follows:

    • yi=mi , i =0 to 2n-1 (noninverted outputs)

    • yi=mi’ = Mi , i=0 to 2n-1 (inverted outputs)

Fundamentals of Logic Design


Decoder1
Decoder

  • n-variable functions

    • be realized by ORing together selected minterm outputs from a decoder

    • outputs are inverted

      • Use NAND gates

Fundamentals of Logic Design


Realization of a multiple output circuit using a decoder
Realization of a Multiple-Output Circuit Using a Decoder

  • f1(a,b,c,d) = m1 + m2 + m4

    • f1 = (m1’m2’m4’)’

  • f2(a,b,c,d) = m4 + m7 + m9

    • f2 = (m4’m7’m9’)’

Fundamentals of Logic Design



Encoder
Encoder

  • Perform the inverse function of a decoder

Fundamentals of Logic Design


8 to 3 priority encoder
8-to-3 Priority Encoder

Fundamentals of Logic Design


Contents2
Contents

9.1 Introduction

9.2 Multiplexers

9.3 Three-State Buffers

9.4 Decoders and Encoders

9.5 Read-Only Memories

9.6 Programmable Logic Devices

9.7 Complex Programmable Logic Devices

9.8 Field Programmable Gate Arrays

Fundamentals of Logic Design


ROM

  • Read-Only Memories

    • An array of semiconductor devices that are interconnected to store an array of binary data

    • Can be read out whenever desired

    • Cannot be changed under normal operation conditions

Fundamentals of Logic Design


ROM

  • ABC = 010

    • F0F1F2F3 = 0111

  • Word

  • Address

Fundamentals of Logic Design


ROM

  • n input lines and m output lines

    • 2n words

    • Each word is m bits long

Fundamentals of Logic Design


ROM

  • A 2n * m ROM can realize m functions of n variables

  • Sizes for commercial available ROMs range

    • From 32 words * 4 bits

    • To 512K words * 8 bits or larger

Fundamentals of Logic Design


ROM

  • Consist of

    • A decoder

    • A memory array

Fundamentals of Logic Design


Internal structure
Internal Structure

Fundamentals of Logic Design


Internal structure1
Internal Structure

F0 = ∑m(0, 1, 4, 6)

= A’B’+AC’

F1 = ∑m(2, 3, 4, 6, 7)

= B+AC’

F2 = ∑m(0, 1, 2, 6)

= A’B’+BC’

F3 = ∑m(2, 3, 5, 6, 7)

= AC’+B

Fundamentals of Logic Design


Hexadecimal to ascii code converter
Hexadecimal to ASCIICode Converter

  • Multiple-output combinational circuits can easily be realized using ROMs.

Fundamentals of Logic Design


Hexadecimal to ascii code converter1
Hexadecimal to ASCIICode Converter

Fundamentals of Logic Design


Rom realization of code converter
ROM Realization of Code Converter

Fundamentals of Logic Design


Rom types
ROM Types

  • Mask-programmable ROMs

    • Require a special mask

    • Programmed during the manufacturing process

    • Economically feasible only if a large quantity

  • Programmable ROMs (PROMs)

    • Be written only once

      • PROM programmer or PROM burner

    • Be manufactured as blank memory

Fundamentals of Logic Design


Rom types1
ROM Types

  • Erasable Programmable ROMs (EPROMs)

    • Retain contents until being exposed to ultraviolet light

    • Reprogram the memory

  • Electrically Erasable Programmable ROMs (EEPROMs)

    • Be erased by exposing it to an electrical charge

    • Reprogram the memory

Fundamentals of Logic Design


Rom types2
ROM Types

  • Flash memory (Flash EEPROMs)

    • Be erased and reprogrammed in blocks instead of one byte at a time

Fundamentals of Logic Design


Flash memory
Flash Memory

  • Many modern PCs have their BIOS stored on a flash memory chip so that it can easily be updated if necessary.

    • Such a BIOS is sometimes called a flash BIOS.

Fundamentals of Logic Design


Flash memory1
Flash Memory

  • Compact Flash (CF) Card

    • Digital cameras, music players…

    • Type I CF cards: 3.3 mm thick

    • Type II CF cards: 5.5 mm thick

  • Secure Digital (SD) Card

  • MultiMedia Card (MMC)

Fundamentals of Logic Design


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