Transcript Document

Lab 04 :Serial Data Control Systems :
Slide 2
NOR Gate:
Slide 3
NAND Gate:
Slide 4
XOR and XNOR Gate:
Slide 5
NOR / NAND Alternate Symbols:
Slide 6
Rule for using alternate symbols:
Slide 7
Serial Data Basics:
Slide 8
AND Gating Serial Data:
Lab 04 : NOR Gate
The NOR gate is equivalent to an OR gate with a NOT gate connected to its output.
NOR comes from the words Not OR. Continue to see the standard symbol for NOR.
NOR Symbol
Truth Table: The table shows that the NOR gate responds with a low at the output if
the signal applied to the input A or B is high.
System animation: In order to see how it works, the gate has been connected to 2 switches
and LED. Continue to see the system in action…
5v
NOR
Logic 0
1
5v
Input A
Output X
Input B
5v
Logic 1
0
A
B
X
0
0
1
0
1
0
1
0
0
1
1
0
Logic 0
1
Boolean Equation: here is the equation for the NOR gate.
Slide #2
X AB
Lab 04 : NAND Gate
The NAND gate is equivalent to an AND gate with a NOT gate connected to its
output. NAND comes from the words Not AND. Continue to see the standard symbol
for NAND.
NAND Symbol
Truth Table: The table shows that the NAND gate responds with a low at the output
if the signal applied to the input A and B is high.
System animation: In order to see how it works, the gate has been connected to 2 switches
and LED. Continue to see the system in action…
5v
NAND
Logic 0
1
5v
Input A
Output X
Logic 1
0
Input B
5v
A
B
X
0
0
1
0
1
1
1
0
1
1
1
0
Logic 0
1
Boolean Equation: here is the equation for the NAND gate.
Slide #3
X  AB
Lab 04 : XOR Gate
The XOR gate is an exclusive OR gate. It will output a logic 1 if there is an exclusive
logic 1 at input A or B. Exclusive means: Only one input can be high at one time.
Truth Table: The table shows that the XOR gate responds with a high at the output
if the signal applied to the input A or B is high (but not both high).
XOR
Input A
Output X
Input B
A
B
X
0
0
0
0
1
1
1
0
1
1
1
0
XOR Boolean Equation:
X  AB
The XNOR gate is an exclusive OR gate with an NOT gate at the output. It will output
a logic 0 if there is an exclusive logic 1 at input A or B.
XNOR
Input A
Input B
Slide #4
Output X
A
B
X
0
0
1
0
1
0
1
0
0
1
1
1
XOR Boolean Equation:
X  AB
Lab 04 : NOR and NAND Gate Alternate Symbols:
The NAND and NOR logic gate symbols you have studied are called the
“standard” symbols. Each gate also has an “alternate” symbol.
NOT
The “standard” logic symbols
for the NAND and NOR gates
indicates a gates response to
“logic 1” at the input.
NOR
A B
X
A B
X
0
0
1
0
0
1
0
1
0
0
1
1
1
0
0
1
0
1
1
1
0
1
1
0
NAND
Alternate NOR GATE: The bubbles at the input
of the NOR gate implies that a “logic 0” at input A
and a “logic 0” at input B are required to produce
a “logic 1” at output X (NO bubble at output).
Alternate NAND GATE: The bubbles at the input of the NAND gate implies
0 =to1produce a
that a “logic 0” at input A or a “logic 0” at input B 0
areAND
required
0 OR 0 = 1
“logic 1” at output X (NO bubble at output).
Slide #5
Alternate NOR
Alternate NAND
Lab 04 :Rule for Using the Alternate symbols :
The basic logic gates AND, OR, and NOT have standard logic symbols and alternate
logic symbols. A general rule for using alternate symbols exists. The rule is a guide and
not a strict rule. Some designers do not use the rule but many do.
=
=
Standard
Alternate
The rule is simple : Active high device connects to active high symbol : Active low device connects to the active
low symbol.
Example: Connect an LED to an AND gate:
There are two types of LED connections.
5V
A logic 1 lights the LED
1
Active High
LED
A logic 0 lights the LED
0
Active Low
LED
Active high device connects to active high symbol (standard).
Active low device connects to the active low symbol (alternate).
Slide #6
Lab 04 : Gating digital signals: Basic Theory
Digital systems communicate to each other using a Serial Data stream. You
will learn what Serial Data is and how logic gates can be used to control the
flow of this digital information.
Serial Data is a pulse waveform
The pulse waveform represents a series of 1’s and 0’s.
A Logic Gate and a Control Switch can be used to build a control system. This system can alter
the transfer of Serial Data from input B to output Y.
A
The
position
of 1’s
theand
Control
Switch
0) and
type of Logic Gate (AND, OR, NOR …) create
The
series of
0’s can
sent to(1a or
device
likethe
a printer.
different
control
control
schemes
generate
The printer
canschemes.
group theHowever
bits intoall
a code.
The
code could
be responses from a group of 4:
used to print out a character on a piece of paper.
5v
5v
Control Switch
A
Logic
Gate
B
1
Slide #7
0
0
1
1
1
0
1
0
Y
1
0
2- The
3- The
4inverse
Serial
of Data
the Serial
is blocked.
Data
1- The
Serial
Data
is
transferred.
is transferred. Y = B
Output Y= Logic 1
0.
Y=B
Lab 04 : AND Gating digital signals
The “And Gate” will be used to control the flow of Serial Data. Waveforms
will be drawn to determine the output response (Y).
5v
Control Switch
The position of the Control Switch is
represented by waveform A. When A=0
the switch is in the lower position. When
A=1 the switch is in the upper position.
Proceed to view the animation.
To draw the output response (Y) it is
helpful to draw vertical lines at each
transition of waveform A and B.
The vertical lines create horizontal
sections. These sections will be used
to determine the output response.
Continue
Start
The
Nownext
at
that
the
section
tothe
the
usewaveform
first
this
B=0
B=1
section
technique
andis A=1.
A=0.
drawn
B=1
toFor
and
A=0.
an
complete
weAND
can
Forproceed
gate
an
theAND
drawing
the to
response
gate
a more
ofthe
output
is
response
general
Y=0.
Y=1.
isdiscussion
Draw
waveform
Y=0.
Y Draw
forY.
that
about
Y for
section.
the
that
control
section.
system.
5v
A
B
B
1
0
0
1
1
1
0
0
1
A
Y
The AND gate blocks the Serial Data and Y=0 when the Control Switch is 0.
The AND gate passes the Serial Data and Y=B when the Control Switch is 1.
Slide #8
Y
AND
Gate
1
0