ENT-DIGI-210
Lab 3 Notes
©Paul Godin
Lab 3 page
Updated September 2007
1
Digital Logic Chips
Basic Chip Configuration
Lab 3 page 2
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.
Lab 3 page 3
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
Lab 3 page 4
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.
Lab 3 page 5
Chip information
Information on this IC:
National Semiconductor
(http://www.advanced-tech.com/ic_logos/ic_logos.htm)
First Line = Manufacture Information
Second Line= Device Description
M = Wafer made in USA
P = Assembled in Malaysia
9 = last number of year
03 = month of manufacture
0V = Die Run Code
DM 74 = Device Family
08 = Device Type
N = Packaging (moulded DIP)
Other information available from http://www.national.com/quality/marking_conventions.html
Lab 3 page 6
Chips
◊
Basic logic chips often come in 14pin 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.
◊
Pin 14
Pin 8
Pin 1
Pin 7
Numbers are read counterclockwise from pin 1 (viewing the
top of the chip)
Lab 3 page 7
Chips – Specification Sheet
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.
Diagram from http://www.ti.com
Lab 3 page 8
Logic Diagram Labels
Lab 3 page 9
Labelling a Diagram
Step 1: Design the circuit
Step 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
Lab 3 page 10
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.
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
Diagrams from http://www.ti.com
Lab 3 page 11
Labelling a Diagram
(continued)
Step 4: Add Pin Numbers
to the diagram
Adding labels in EWB:
Select menu “M”, then “A”
Lab 3 page 12
Labelling a Diagram
(continued)
Step 5: Add chip labels
and Vcc/GND pins
Chip label U1:1 where:
• U1 is the chip
• :1 is the number of the
gate within the chip
Lab 3 page 13
Example of a Properly Labelled diagram
Lab 3 page 14
Wiring the chip
Vcc
IN
IN
OUT
Vcc
Lab 3 page 15
Steering or Control Gates
Lab 3 page 16
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.
Lab 3 page 17
Control Gates Worksheet (AND, OR)
Control
Y
Z
Z’
Signal
Control
Signal
0
0
0
0
1
0
1
1
0
1
0
1
1
1
1
Control
Signal
0
Y
Status
Z
Z’
Status
Lab 3 page 18
Proper Wiring
“My circuit doesn’t work and I can’t find the error.”
“Can you help me? Please?”
Lab 3 page 19
RED reserved for
Vcc connections
Wires routed
along horizontal
and vertical
plane
Wires routed
around the IC
IC is fully
visible and
accessible
Wires the
proper length
Little or no
exposed
conductor
BLACK reserved for
GND Connection
Features of a properly-wired circuit
Lab 3 page 20
Can you find the
errors in this circuit?
Lab 3 page 21
Short
Circuit
Exposed
conductors
Wires routed over
component
Bent
Contact
Wrong color (shouldn’t
be black or red)
Wire too long
Wires not on
vertical or
horizontal plane
Wrong color
(should be black)
Lab 3 page 22
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
Lab 3 page 23