PPT: A Simple ALU (Binary Logic) | GATE Notes & Videos for Electrical Engineering - Electrical Engineering (EE) PDF Download

 Page 1


1
A Simple ALU
Binary Logic
Page 2


1
A Simple ALU
Binary Logic
2
Outline
l Binary Logic
l Representation of Logic Gates
l Constructing a 1-bit adder
l Constructing an n-bit adder
Page 3


1
A Simple ALU
Binary Logic
2
Outline
l Binary Logic
l Representation of Logic Gates
l Constructing a 1-bit adder
l Constructing an n-bit adder
3
Binary Logic
l A computer works using digital electronics.
l There are only High and Low voltages
l All computer logic is based on the
manipulation of these
l Abstractly,
» High is interpreted as 1 (true)
» Low is interpreted as 0 (false)
Page 4


1
A Simple ALU
Binary Logic
2
Outline
l Binary Logic
l Representation of Logic Gates
l Constructing a 1-bit adder
l Constructing an n-bit adder
3
Binary Logic
l A computer works using digital electronics.
l There are only High and Low voltages
l All computer logic is based on the
manipulation of these
l Abstractly,
» High is interpreted as 1 (true)
» Low is interpreted as 0 (false)
4
Logic Circuit
l A logic circuit takes in a number of input
lines (A, B, C, ...)
» and has a number of output lines (X,Y,Z,...)
A
B
C
X
Y
Z
Page 5


1
A Simple ALU
Binary Logic
2
Outline
l Binary Logic
l Representation of Logic Gates
l Constructing a 1-bit adder
l Constructing an n-bit adder
3
Binary Logic
l A computer works using digital electronics.
l There are only High and Low voltages
l All computer logic is based on the
manipulation of these
l Abstractly,
» High is interpreted as 1 (true)
» Low is interpreted as 0 (false)
4
Logic Circuit
l A logic circuit takes in a number of input
lines (A, B, C, ...)
» and has a number of output lines (X,Y,Z,...)
A
B
C
X
Y
Z
5
Logic Basics
l Every expression evaluates to 1  or 0
l NOT
» ~A (“A bar”)
– is the complement of A,   i.e. 1-A
l OR
» A + B
– is 1 if and only if at least one of A or B is 1, else 0
l AND
» A.B
– is 1 if and only if both A and B are 1, else 0