Floyd, Digital Fundamentals, 10
th
ed
EET
1131 Unit 3
Basic Logic Gates
Read
Kleitz
, Chapter 3.
Homework
#3 and Lab #3 due next
week.
Quiz next week.
© 2009 Pearson Education, Upper Saddle River, NJ 07458. All Rights Reserved
Floyd, Digital Fundamentals, 10
th
ed
The inverter performs the Boolean
NOT
operation. When the
input is
LOW (0),
the output is
HIGH (1);
when the input is
HIGH, the output is LOW.
The Inverter
A
X
Input
A
X
Output
0 1
1 0
The
NOT
operation (complement) is shown with an overbar.
Thus, the Boolean expression for an inverter is
X
=
A
.
© 2009 Pearson Education, Upper Saddle River, NJ 07458. All Rights Reserved
Floyd, Digital Fundamentals, 10
th
ed
The Inverter
Example waveforms:
A
X
A
X
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Floyd, Digital Fundamentals, 10
th
ed
The
AND gate
produces a HIGH output when all inputs are
HIGH; otherwise, the output is LOW. For a 2

input gate,
the truth table is
The AND Gate
The
AND
operation is usually shown with a dot between the
variables but it may be implied (no dot). Thus, the AND
operation is written as
X
=
A
.
B
or
X = AB.
Inputs
A B
X
Output
0 0
0 1
1 0
1 1
0
0
0
1
A
B
X
&
A
B
X
© 2009 Pearson Education, Upper Saddle River, NJ 07458. All Rights Reserved
Floyd, Digital Fundamentals, 10
th
ed
Example waveforms:
A
X
The AND Gate
A
B
X
B
&
A
B
X
© 2009 Pearson Education, Upper Saddle River, NJ 07458. All Rights Reserved
Floyd, Digital Fundamentals, 10
th
ed
The AND Gate
A Multisim circuit is shown. XWG1 is a word generator set in
the count down mode. XLA1 is a logic analyzer with the
output of the AND gate connected to first (upper) line of the
analyzer. What signal do you expect to on this line?
The output (line 1) will be
HIGH only when all of the
inputs are HIGH.
© 2009 Pearson Education, Upper Saddle River, NJ 07458. All Rights Reserved
Floyd, Digital Fundamentals, 10
th
ed
The
OR gate
produces a HIGH output if any input is HIGH;
if all inputs are LOW, the output is LOW. For a 2

input gate,
the truth table is
The OR Gate
The
OR
operation is shown with a plus sign (+) between the
variables. Thus, the OR operation is written as
X
=
A
+
B.
Inputs
A B
X
Output
0 0
0 1
1 0
1 1
0
1
1
1
A
B
X
A
B
X
≥
1
© 2009 Pearson Education, Upper Saddle River, NJ 07458. All Rights Reserved
Floyd, Digital Fundamentals, 10
th
ed
Example waveforms:
A
X
The OR Gate
B
A
B
X
A
B
X
≥
1
© 2009 Pearson Education, Upper Saddle River, NJ 07458. All Rights Reserved
Floyd, Digital Fundamentals, 10
th
ed
The OR Gate
A Multisim circuit is shown. XWG1 is a word generator set
to count down. XLA1 is a logic analyzer with the output
The output (line 1) will be
HIGH if any input is HIGH;
otherwise it will be LOW.
connected to first (top) line of the analyzer. The three 2

input OR gates act
as a single 4

input gate. What signal do you expect on the output line?
© 2009 Pearson Education, Upper Saddle River, NJ 07458. All Rights Reserved
Floyd, Digital Fundamentals, 10
th
ed
The
NAND gate
produces a LOW output when all inputs
are HIGH; otherwise, the output is HIGH. For a 2

input
gate, the truth table is
The NAND Gate
Inputs
A B
X
Output
0 0
0 1
1 0
1 1
1
1
1
0
A
B
X
A
B
X
&
The
NAND
operation is shown with a dot between the
variables and an overbar covering them. Thus, the NAND
operation is written as
X
=
A
.
B
(Alternatively,
X = AB.)
© 2009 Pearson Education, Upper Saddle River, NJ 07458. All Rights Reserved
Floyd, Digital Fundamentals, 10
th
ed
Example waveforms:
A
X
The NAND gate is particularly useful because it is a
“universal” gate
–
all other basic gates can be constructed
from NAND gates.
The NAND Gate
B
A
B
X
A
B
X
&
© 2009 Pearson Education, Upper Saddle River, NJ 07458. All Rights Reserved
Floyd, Digital Fundamentals, 10
th
ed
The NAND Gate
A Multisim circuit is shown. XWG1 is a word generator set in
the count up mode. A four

channel oscilloscope monitors the
inputs and output. What output signal do you expect to see?
The output (channel D) will be
LOW only when all of the
inputs are HIGH.
Inputs
© 2009 Pearson Education, Upper Saddle River, NJ 07458. All Rights Reserved
Floyd, Digital Fundamentals, 10
th
ed
The
NOR gate
produces a LOW output if any input is
HIGH; if all inputs are LOW, the output is HIGH. For a
2

input gate, the truth table is
The NOR Gate
Inputs
A B
X
Output
0 0
0 1
1 0
1 1
1
0
0
0
A
B
X
A
B
X
≥
1
The
NOR
operation is shown with a plus sign (+) between
the variables and an overbar covering them. Thus, the NOR
operation is written as
X
=
A
+
B.
© 2009 Pearson Education, Upper Saddle River, NJ 07458. All Rights Reserved
Floyd, Digital Fundamentals, 10
th
ed
Example waveforms:
A
X
The NOR operation will produce a LOW if any input is HIGH.
The NOR Gate
B
A
B
X
A
B
X
≥
1
Floyd, Digital Fundamentals, 10
th
ed
Enable/Disable Using AND Gate
14
Floyd, Digital Fundamentals, 10
th
ed
Enable/Disable Using OR Gate
15
© 2009 Pearson Education, Upper Saddle River, NJ 07458. All Rights Reserved
Floyd, Digital Fundamentals, 10
th
ed
Integrated Circuits
Plastic
case
Pins
Chip
Cutaway view of DIP (
D
ual

I
n

line
P
ackage)
chip:
The TTL series, available as DIPs are popular
for laboratory experiments with logic.
© 2009 Pearson Education, Upper Saddle River, NJ 07458. All Rights Reserved
Floyd, Digital Fundamentals, 10
th
ed
Integrated Circuits
DIP chips and surface mount chips
Pin 1
Dual in

line package Small outline IC (SOIC)
© 2009 Pearson Education, Upper Saddle River, NJ 07458. All Rights Reserved
Floyd, Digital Fundamentals, 10
th
ed
Integrated Circuits
Chip Densities:
•
Small scale integration (SSI): <=10 gates per chip.
•
Medium

scale integration (MSI): 10 to 100 gates per
chip.
•
Large

scale integration (LSI): 100 to 10,000 gates per
chip.
•
Very large

scale integration (VLSI): 10,000 to 100,000
gates per chip.
© 2009 Pearson Education, Upper Saddle River, NJ 07458. All Rights Reserved
Floyd, Digital Fundamentals, 10
th
ed
Programmable Logic
Programmable logic devices (PLDs) are an alternative to
fixed function devices. The logic can be programmed for a
specific purpose. In general, they cost less and use less
board space than fixed function devices.
© 2009 Pearson Education, Upper Saddle River, NJ 07458. All Rights Reserved
Floyd, Digital Fundamentals, 10
th
ed
Some common gate configurations are shown.
Fixed Function Logic
14
1
8
7
9
6
10
5
11
4
12
3
13
2
V
CC
GND
'
00
14
1
8
7
9
6
10
5
11
4
12
3
13
2
V
CC
GND
'
04
14
1
8
7
9
6
10
5
11
4
12
3
13
2
V
CC
GND
'
08
14
1
8
7
9
6
10
5
11
4
12
3
13
2
V
CC
GND
'
02
14
1
8
7
9
6
10
5
11
4
12
3
13
2
V
CC
GND
'
10
14
1
8
7
9
6
10
5
11
4
12
3
13
2
V
CC
GND
'1
1
14
1
8
7
9
6
10
5
11
4
12
3
13
2
V
CC
GND
'20
14
1
8
7
9
6
10
5
11
4
12
3
13
2
V
CC
GND
'21
14
1
8
7
9
6
10
5
11
4
12
3
13
2
V
CC
GND
'27
14
1
8
7
9
6
10
5
11
4
12
3
13
2
V
CC
GND
'32
14
1
8
7
9
6
10
5
11
4
12
3
13
2
V
CC
GND
'86
14
1
8
7
9
6
10
5
11
4
12
3
13
2
V
CC
GND
'30
Floyd, Digital Fundamentals, 10
th
ed
Website for Datasheets
Many websites have datasheets for
logic chips.
The best site is Texas Instruments:
www.ti.com
Type the chip number
(such as 7404)
i
n the Search box.
For some chips, the original part number is
obsolete and no longer available. In such
cases, inserting
LS
often works. Example:
74LS10.
© 2009 Pearson Education, Upper Saddle River, NJ 07458. All Rights Reserved
Floyd, Digital Fundamentals, 10
th
ed
•
Troubleshooting
means finding and fixing faults in a circuit
or system that’s not working correctly.
•
Your first
step in troubleshooting a digital circuit on the
breadboard
should always be to
verify that the voltage at
each chip’s power and ground pins are actually +5 V and 0V.
•
After that, use your knowledge of truth tables to find the
gates that are not producing the correct outputs.
Troubleshooting
•
Multisim
lets you insert the following kinds of faults into
digital components:
•
An open pin
•
Two pins shorted together
•
A pin shorted to
V
CC
(constant HIGH)
•
A pin shorted to ground (constant LOW)
•
Your book has
Multisim
troubleshooting problems that
I’ll assign on some
homeworks
. You can download the
files for these from the book’s
website
.
•
To troubleshoot them, attach switches to input pins
and probes to output pins.
Multisim
Troubleshooting
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