BTEC HNC - Combinational and Sequential Logic - Design and Build Circuits Using Combinational Logic

7/23/2019 BTEC HNC - Combinational and Sequential Logic - Design and Build Circuits Using Combinational Logic

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Design & Build Circuits Using

Combinational LogicCombinational & Sequential Logic

By Brendan Burr


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Brendan Burr BTEC Higher National Certificate in ElectronicsDesign & Build Circuits Using Combinational Logic

Table of Contents

TABLE OF CONTENTS ........................................................... 2

TASK 1 ................................................................................ 4

1.1 Identify a suitable device part no. for each of thefollowing types of functions by searching the Internet usingGoogle:- .............................................................................. 4

1.2 Provide data sheets (limited to a maximum of 4 pages) ofthe information as indicated for the following digital devices:-.......................................................................................... 4

Octal Transceiver ................................................................ 4

General description, logic diagram/symbol, function table,and electrical characteristics. .............................................. 4

Solution:- .........................................................................................4

3 to 8 Line Decoder ............................................................. 4

General description, logic symbol, pin descriptions, logicdiagram, and function/truth table. ....................................... 4

Solution:- .........................................................................................4

16 Line to 1 Line Multiplexer ................................................ 4

General description, logic symbol, pin descriptions, logicdiagram, and function/truth table. ...................................... 4

Solution:- .........................................................................................4

Programmable Logic Array or Programmable Memory ........... 4

General description, logic diagram, pin configurations,functional/truth table, block diagrams. ................................. 4

Solution:- .........................................................................................4

TASK 2 ................................................................................ 5

Choose one of the devices in Task 1 above and compare thecharacteristics of the same device manufactured in thefollowing technology:- ......................................................... 5

a) TTL ................................................................................. 5

b) CMOS ............................................................................. 5

3.5 Function Table ............................................................. 13

3.6 Write a full test schedule and the results expected. ....... 14

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EVALUATION ..................................................................... 15

CONCLUSION ..................................................................... 15

Books ............................................................................... 16

Catalogues ........................................................................ 16

Websites ........................................................................... 16

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Task 1

1.1 Identify a suitable device part no. for each of the following types offunctions by searching the Internet using Google:-

1.2 Provide data sheets (limited to a maximum of 4 pages) of the informationas indicated for the following digital devices:-

Octal Transceiver

General description, logic diagram/symbol, function table, and electricalcharacteristics.

Solution:-

74F245 Data Sheet Attached.

3 to 8 Line Decoder

General description, logic symbol, pin descriptions, logic diagram, andfunction/truth table.

Solution:-

74VHCT238A Data Sheet Attached.

16 Line to 1 Line Multiplexer

General description, logic symbol, pin descriptions, logic diagram, andfunction/truth table.

Solution:-

MM74C150 and MM82C19 Data Sheet Attached

Programmable Logic Array or Programmable Memory

General description, logic diagram, pin configurations, functional/truth table,block diagrams.

Solution:-

NMC9307 Data Sheet Attached.

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Task 2

Choose one of the devices in Task 1 above and compare the characteristicsof the same device manufactured in the following technology:-

a) TTL

b) CMOS

TTL stands for Transistor-Transistor Logic, it is called this because it is madeup of Bipolar Junction Transistors and Resistors, and the logic gating functionand the amplifying function are performed by transistors. It was invented in1961 and was largely beneficial to the developing IC Market, the last widelyavailable family is called the 74AS/ALS Advanced Schottky, which wasintroduced in 1985

CMOS stands for Complementary Metal-Oxide-Semiconductor, it usescomplementary symmetrical pairs of p-type and n-type MOSFET transistorsfor its logic functions. It was developed in the 1980s and was a firmcompetitor against the TTL technology.There are various differences between CMOS and TTL, which I will talk aboutin further detail after explaining a bit of back ground information on the twotechnologies.The two technologies have different benefits to each, as shown below.

TTL:

TTL Chips are less susceptible to static against CMOS chips which are easily

damaged by it.TTL is more powerful and durable that CMOS.CMOS:

CMOS Chips have a higher range of immunity against noise.They are smaller so take up less space than TTL.CMOS has a good packaging density.This chip can power a larger number of inputs and consume less power.They can run on a range of supply voltages, compared to TTL which require a5V supply.This technology uses less power so is more suitable for battery applications,however it cannot run as fast as TTL.

Having discussed this it is clear to see the benefits of using CMOS over TTLfor some applications, however if it is likely that the circuit will be in contactwith static energy then to prevent susceptibility it would be beneficial to useTTL.The 74VHCT238A 3 to 8 line decoder is a CMOS Technology, but has a TTLThreshold on its inputs. This allows the beneficial characteristics of bothtechnologies to be used in the chip. This type of dual technology usage isbeing more greatly used to utilise these good characteristics and eliminate thebad characteristics such as excessive power consumption.

The chip is also equipped with protections circuits at all of its inputs andoutputs to protect against static discharge, giving them 2KV electrostaticdischarge immunity and transient excess voltage.

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Task 3

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3.5 Function Table

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3.6 Write a full test schedule and the results expected.

The circuit has been designed to generate an arrangement of logic states toproduce a number generated on a 7 Segment Display. It works on theprinciple that an operator will press the push to make latching switches toforce the logic state to go low, or remain high at the various inputs on the74LS147D Chip. The outputs of this chip are then inverted, by using a74LS04D Chip, and become the inputs to the 74LS47D. The outputs of thischip are then fed into the 7 Segment Display and will light up a, b, c, d, e, f org LEDs located in the display.

To begin the testing the Integrated Chips need to be supplied with theappropriate voltage of 5 Volts. The 7 Segment Display also needs to besupplied with 5 Volts. The 9 push to make switches need to be connected to

0 volts to provide the 74LS147D Inputs the opportunity to receive a Logic LowState.

When pressing push to make switch 1, the 7 segment display shoulddisplay the number 1, illuminating LEDs b and c.

When pressing push to make switch 2, the 7 segment display shoulddisplay the number 2, illuminating LEDs a, b, d, e and g.

When pressing push to make switch 3, the 7 segment display shoulddisplay the number 3, illuminating LEDs a, b, c, d and g.

When pressing push to make switch 4, the 7 segment display shoulddisplay the number 4, illuminating LEDs b, c, f and g.

When pressing push to make switch 5, the 7 segment display shoulddisplay the number 5, illuminating LEDs a, c, d, f and g.

When pressing push to make switch 6, the 7 segment display shoulddisplay the number 6, illuminating LEDs c, d, e, f and g.

When pressing push to make switch 7, the 7 segment display shoulddisplay the number 7, illuminating LEDs a, b, and c.

When pressing push to make switch 8, the 7 segment display shoulddisplay the number 8, illuminating LEDs a, b, c, d, e, f and g.

When pressing push to make switch 9, the 7 segment display shoulddisplay the number 9, illuminating LEDs a, b, c, f and g.

When none of the push to make switches are being pressed, the 7segment display should display the number 0, illuminating LEDs a, b,c, d, e, f and g.

If two push to make switches are pressed at the same time, then thehigher valued number will be displayed. For example if 5 and 9 push tomake switches are pressed then the 7 segment display will show thenumber 9.

This is the expected set of results and on pages 9-13 are the graphical resultswhich clearly identify that the above expectant results are correct.

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Evaluation

During this assignment I found that there is a large amount of information on

Datasheets. The first task was to search for datasheets on the internet, Imanaged to easily find the first three (Octal Transceiver, 3 to 8 Line Decoder,and the 16 Line to 1 Line Multiplexer) however had difficulty finding all of therequirements for the Programmable Logic Array or the ProgrammableMemory. I settled for an Erasable Programmable Memory IC, havingconfirmed with Alan Dyson that it had enough of the required information.The second task I found slightly more difficult as I was unable to find a chipwhich was entirely CMOS or TTL, they were all dual technology types. Toovercome this problem I decided to talk about the two technologies and thenrelate them to one of my chips, explaining that the usage of both technologiesin the chip was because there a large benefits of both.

Task three was interesting, we began work on this in the second week of theyear and went through the design and board layout of the circuit on Multisimand Ultiboard. I hadnt used Ultiboard before this task so it was a good lessonin using the package. After a few routing problems with the software, Imanaged to completely finish the board, which can be seen in a screen shoton page 6.Writing the test schedule and expected results was also good, as it meant thatI had to understand what was happening with the circuit, rather than justconnecting some IC together.

Conclusion

I am pleased to have completed this assignment. It was challenging in placeswhich tested my ability of researching and collaborating the data as well asmaking use of it.I have learnt a bit more on the technologies behind integrated chips and thebenefits from combining these technologies to get the best from them.I also understand the production of truth/function tables as this allows you tosee what should be expected and where the high and low points are.

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Bibliography

Through guidance from my lecturer, the following text books, catalogues andwebsites I was able to complete this assignment:

Books

Higher Engineering Mathematics (John Bird)ISBN: 0-7506-8152-7

Catalogues

N/A

Websites

http://en.wikipedia.org/wiki/Transistor%E2%80%93transistor_logichttp://en.wikipedia.org/wiki/Cmoshttp://www.helpwithpcs.com/jargon/ttl.htmhttp://www.datasheetcatalog.com/datasheets_pdf/7/4/F/2/74F245.shtmlhttp://www.alldatasheet.com/datasheet-pdf/pdf/21872/STMICROELECTRONICS/74VHCT238A.htmlhttp://www.datasheetcatalog.com/datasheets_pdf/M/M/7/4/MM74C150.shtmlhttp://www.alldatasheet.com/datasheet-pdf/pdf/89720/NSC/NMC9307.html

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http://en.wikipedia.org/wiki/Transistor%E2%80%93transistor_logichttp://en.wikipedia.org/wiki/Cmoshttp://www.helpwithpcs.com/jargon/ttl.htmhttp://www.datasheetcatalog.com/datasheets_pdf/7/4/F/2/74F245.shtmlhttp://www.alldatasheet.com/datasheet-pdf/pdf/21872/STMICROELECTRONICS/74VHCT238A.htmlhttp://www.alldatasheet.com/datasheet-pdf/pdf/21872/STMICROELECTRONICS/74VHCT238A.htmlhttp://www.datasheetcatalog.com/datasheets_pdf/M/M/7/4/MM74C150.shtmlhttp://www.alldatasheet.com/datasheet-pdf/pdf/89720/NSC/NMC9307.htmlhttp://en.wikipedia.org/wiki/Transistor%E2%80%93transistor_logichttp://en.wikipedia.org/wiki/Cmoshttp://www.helpwithpcs.com/jargon/ttl.htmhttp://www.datasheetcatalog.com/datasheets_pdf/7/4/F/2/74F245.shtmlhttp://www.alldatasheet.com/datasheet-pdf/pdf/21872/STMICROELECTRONICS/74VHCT238A.htmlhttp://www.alldatasheet.com/datasheet-pdf/pdf/21872/STMICROELECTRONICS/74VHCT238A.htmlhttp://www.datasheetcatalog.com/datasheets_pdf/M/M/7/4/MM74C150.shtmlhttp://www.alldatasheet.com/datasheet-pdf/pdf/89720/NSC/NMC9307.html

BTEC HNC - Combinational and Sequential Logic - Design and Build Circuits Using Combinational Logic

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