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Logic Gates. Logic Gates. Digital Signals Logic Gates NOT (Inverter) Gate AND Gate OR Gate NAND Gate NOR Gate XOR Gate. Each column represents a small amount of time. Digital Signals. Digital signals 0 (false) or 1 (true) Digital signal 1 is represented by a small voltage. - PowerPoint PPT Presentation
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Logic Gates
Logic Gates
• Digital Signals • Logic Gates• NOT (Inverter) Gate• AND Gate• OR Gate• NAND Gate• NOR Gate• XOR Gate
Digital SignalsDigital signals 0 (false) or 1 (true)Digital signal 1 is represented by a small voltage.Digital signal 0 is represented by no voltage.
Digital Waveforms
Each column represents a small amount of time
1 (3V)
0 (0V)
1 0 0 1 0 1 1 0
Logic GatesAn electronic system that performsa logical operation on an input signal
Gates process digital inputs to produce digital outputs.
How do computer processors make decisions? How do they do math? Display images? Etc.?
LOGIC
10
NOT (Inverter) GateA logic gate that changes its input logic level to the opposite state
Symbol
01Truth Table: A table listing all possible inputs to a circuit and the corresponding outputs
Truth TableNOT Gate
Input (A) Output (Y)
A Y
0 1
1 0
Logic Word Problems• If I am hungry and it is 5:00 p.m., then I will eat
dinner. • If I pedal harder or go downhill, then my bike will
go faster.• If it is windy and cold, then I am not going to
walk home.• If my battery is dead or I forget headphones,
then I cannot listen to my music.
Each word problem uses the same logic as a common gate.
AND Gate
If I am hungry AND it is 5:00 p.m., then I will eat dinner.
A logic circuit whose:Inputs both = 1 then,Output = 1Symbol
0010
AND Gate
Truth TableAND Gate
Input (A) Input (B) Output (Y)
A
B
0 00
Y
0 011 00
1 11
OR Gate
If I pedal harder OR go downhill, then my bike will go faster.
A logic circuit when:Either Input = 1 then,Output = 1Symbol
0111
OR Gate
Truth TableOR Gate
Input (A) Input (B) Output (Y)
A
B
0 00
Y
0 111 10
1 11
NAND Gate
If it is windy AND cold, then I am NOT going to walk home.
A logic circuit whose:Inputs both = 1 then,Output = 0Symbol
1110
NAND Gate
Truth TableNAND Gate
Input (A) Input (B) Output (Y)
A
B
0 10
Y
0 111 10
1 01
NOR Gate
If my battery is dead OR I forget headphones, then I will NOT listen to my music.
A logic circuit when:Either Input = 1 then,Output = 0Symbol
1000
NOR Gate
Truth TableNOR Gate
Input (A) Input (B) Output (Y)
A
B
0 10
Y
0 011 00
1 01
XOR Gate
I only have enough money for one friend to go to dinner with me. If either one (but not both) want to go to dinner, we’ll go to dinner.
A logic circuit when:If A or B = 1, but not both,then Output = 0Symbol
Possible Inputs (conditions) OutputsFirst Friend wants to go to dinner (T or F)
Second friend wants to go to dinner (T or
F)We will go to dinner
(T or F)
F F F
F T T
T F T
T T F
XOR Gate
Truth TableXOR Gate
Input (A) Input (B) Output (Y)0 000 111 10
1 01
0011A
BY
Logic Gates
• Digital Signals • Logic Gates• NOT (Inverter) Gate• AND Gate• OR Gate• NAND Gate• NOR Gate• XOR Gate
Image Resources
Microsoft, Inc. (2008). Clip Art. Retrieved September 10, 2008, from http://office.microsoft.com/en-us/clipart/default.aspx
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