Lab 3 page 1

ENT-DIGI-210Lab 3 Notes

©Paul GodinUpdated September 2007

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Digital Logic Chips

Basic Chip Configuration

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Basic Digital Chips

◊ Digital logic devices are usually in a familiar chip format, although sometimes can be found in a different package style.

◊ The chips are often identified with a manufacturer logo, a part number or model number, and additional information about the manufacturing or other details.

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Basic Digital Chips

◊ A standard series for basic logic devices start with numbers 74, 4, or 14.◊ Examples

◊ 7404: inverter chips◊ 7408: 2-input AND◊ 7432: 2-input OR◊ 4081B: 2-input AND

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Basic Digital Chips

◊ The naming structure (nomenclature) of the devices differs between manufacturers but most follow a common practice for naming their devices (this is called a defacto standard).

◊ Manufacturers publish nomenclature information on their web sites.

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Chip information

Information on this IC:

Second Line= Device Description

DM 74 = Device Family08 = Device TypeN = Packaging (moulded DIP)

First Line = Manufacture Information

M = Wafer made in USAP = Assembled in Malaysia9 = last number of year03 = month of manufacture0V = Die Run Code

National Semiconductor (http://www.advanced-tech.com/ic_logos/ic_logos.htm)

Other information available from http://www.national.com/quality/marking_conventions.html

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Chips

◊ Basic logic chips often come in 14-pin DIP packages, but package sizes and styles vary. (DIP = Dual In-line Package)

◊ Pin 1 is typically indicated with a dot, half-circle, cut corner, sloped edge or other indicator. It’s important to check the specification sheet.

◊ Numbers are read counter-clockwise from pin 1 (viewing the top of the chip)

Pin 1 Pin 7

Pin 14 Pin 8

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Chips – Specification Sheet

Diagram from http://www.ti.com

Voltage

Ground

The voltage and ground pins must be connected for the device to function. Check the specification sheet for the Vcc and GND pins.

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Logic Diagram Labels

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Labelling a Diagram

Step 1: Design the circuitStep 2: Add component labels

Changing the component labels in EWB:•Right-click on the component•Select “Component Properties”•Choose:

• “Display” to remove extra labels

• “Label” to add a label• “Value” to change the label

on a switch

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Labelling a Diagram (continued)

Step 3: Look up the IC specification and its layout. •The IC for the AND gate is a 74LS08•Match the logic diagram to the package.

Diagrams from http://www.ti.com

Logic Diagram Package Diagram

1

2

3

4

AND gate #1 •Inputs are pins 1 and 2•Output is pin 3.•Vcc is pin 14•GND is pin 7

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Labelling a Diagram (continued)

Step 4: Add Pin Numbers to the diagram

Adding labels in EWB:Select menu “M”, then “A”

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Chip label U1:1 where:• U1 is the chip• :1 is the number of the

gate within the chip

Labelling a Diagram (continued)

Step 5: Add chip labels and Vcc/GND pins

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Example of a Properly Labelled diagram

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Wiring the chipVcc

Vcc

IN

IN

OUT

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Steering or Control Gates

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Introduction

◊ An application for a logic circuit is to control one digital signal with another digital signal.

◊ The AND and the OR gates can function as signal Control, or Steering Gates.

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Control Gates Worksheet (AND, OR)

Control Signal Y Status

0 0

0 1

1 0

1 1

Control Signal Z Z’ Status

0 0

0 1

1 0

1 1

Control

Signal

Y

Z

Z’

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Proper Wiring

“My circuit doesn’t work and I can’t find the error.” “Can you help me? Please?”

Lab 3 page 20Features of a properly-wired circuit

RED reserved for Vcc connections

BLACK reserved for GND Connection

Wires routed around the IC

Wires the proper length

Wires routed along horizontal

and vertical plane

Little or no exposed

conductor

IC is fully visible and accessible

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Can you find the errors in this circuit?

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Exposed conductors

Short Circuit

Bent Contact

Wires routed over component

Wrong color (shouldn’t be black or red)

Wire too long

Wrong color (should be black)Wires not on

vertical or horizontal plane

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Wire Tips

◊ Use properly-adjusted wire strippers only (not cutters or teeth). Stripping must not affect the conductor in any way (scrapes, cuts or nicks).

◊ The strip length should the height of the breadboard minus approximately 2 mm. ◊ If wires are too short, there may be poor electrical contact.◊ If the wires are too long there is risk of a short circuit.

END