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Transcript of ELEC 2200-002 Digital Logic Circuits Fall 2015 Switching Algebra (Chapter 2) Vishwani D. Agrawal...
ELEC 2200-002Digital Logic Circuits
Fall 2015Switching Algebra (Chapter 2)
Vishwani D. AgrawalJames J. Danaher Professor
Department of Electrical and Computer EngineeringAuburn University, Auburn, AL 36849http://www.eng.auburn.edu/~vagrawal
Fall 2015, Sep 30 . . .Fall 2015, Sep 30 . . . ELEC2200-002 Lecture 4ELEC2200-002 Lecture 4 11
Switching Algebra
A Boolean algebra, where Set K contains just two elements, {0, 1}, also
called {false, true}, or {off, on}, etc. Two operations are defined as, + ≡ OR, · ≡
AND.
Fall 2015, Sep 30 . . .Fall 2015, Sep 30 . . . ELEC2200-002 Lecture 4ELEC2200-002 Lecture 4 22
+ 0 1
0 0 1
1 1 1
· 0 1
0 0 0
1 0 1
Claude E. Shannon (1916-2001)Claude E. Shannon (1916-2001)
Fall 2015, Sep 30 . . .Fall 2015, Sep 30 . . . ELEC2200-002 Lecture 4ELEC2200-002 Lecture 4 33
http://www.kugelbahn.ch/sesam_e.htm
Shannon’s Legacy
A Symbolic Analysis of Relay and Switching Circuits, Master’s Thesis, MIT, 1940. Perhaps the most influential master’s thesis of the 20th century.
An Algebra for Theoretical Genetics, PhD Thesis, MIT, 1940.
Founded the field of Information Theory.
C. E. Shannon and W. Weaver, The Mathematical Theory of Communication, University of Illinois Press, 1949. A “must read.”
Fall 2015, Sep 30 . . .Fall 2015, Sep 30 . . . ELEC2200-002 Lecture 4ELEC2200-002 Lecture 4 44
Switching Devices
Electromechanical relays (1940s)
Vacuum tubes (1950s)
Bipolar transistors (1960 - 1980)
Field effect transistors (1980 - )
Integrated circuits (1970 - )
Nanotechnology devices (future)
Fall 2015, Sep 30 . . .Fall 2015, Sep 30 . . . ELEC2200-002 Lecture 4ELEC2200-002 Lecture 4 55
Example: Automobile Ignition
Engine turns on when
Ignition key is applied ANDCar is in parking gear OR
Brake pedal is on
ANDSeat belt is fastened OR
Car is in parking gear
Fall 2015, Sep 30 . . .Fall 2015, Sep 30 . . . ELEC2200-002 Lecture 4ELEC2200-002 Lecture 4 66
Switching logicSwitching logic
Fall 2015, Sep 30 . . .Fall 2015, Sep 30 . . . ELEC2200-002 Lecture 4ELEC2200-002 Lecture 4 77
Battery
Key
Parking gear
Brake pedal Parking gear
Seat belt
Motor
Define Boolean VariablesDefine Boolean Variables
Fall 2015, Sep 30 . . .Fall 2015, Sep 30 . . . ELEC2200-002 Lecture 4ELEC2200-002 Lecture 4 88
Battery
Key
Parking gear
Brake pedal Parking gear
Seat belt
Motor
K = {0, 1}
P = {0, 1}
B = {0,1} P = {0, 1}
S = {0, 1}
0 means switch “off” or “open”1 means switch “on” or “closed”
M = {0, 1}
Write Boolean FunctionWrite Boolean Function
Fall 2015, Sep 30 . . .Fall 2015, Sep 30 . . . ELEC2200-002 Lecture 4ELEC2200-002 Lecture 4 99
Battery
Key
Parking gear
Brake pedal Parking gear
Seat belt
Motor
K = {0, 1}
P = {0, 1}
B = {0,1} P = {0, 1}
S = {0, 1}
Ignition function:
M = K AND (P OR B) AND (S OR P) = K(P + B)(S + P)
M = {0, 1}
Simplify Boolean FunctionSimplify Boolean Function
Fall 2015, Sep 30 . . .Fall 2015, Sep 30 . . . ELEC2200-002 Lecture 4ELEC2200-002 Lecture 4 1010
M = K AND (P OR B) AND (S OR P)
= K(P + B)(S + P)
= K(P + B)(P + S) Commutativity
= K (P + B S) Distributivity
Construct an Optimum CircuitConstruct an Optimum Circuit
Fall 2015, Sep 30 . . .Fall 2015, Sep 30 . . . ELEC2200-002 Lecture 4ELEC2200-002 Lecture 4 1111
Battery
Key
Parking gear
Brake pedal Seat belt
Motor
K = {0, 1}
P = {0, 1}
B = {0,1} S = {0, 1}
M = K (P + B S)
M = {0,1}
This is a relay circuit.Earlier logic circuits, even computers,were built with relays.
Implementing with Relays
An electromechanical relay contains:Electromagnet
Current source
A switch, spring-loaded, normally open or closed
Switch has two states, open (0) or closed (1).
The state of switch is controlled by “not applying” or “applying” current to electromagnet.
Fall 2015, Sep 30 . . .Fall 2015, Sep 30 . . . ELEC2200-002 Lecture 4ELEC2200-002 Lecture 4 1212
One Switch Controlling Other
Switches X and Y are normally open.
Y cannot close unless a current is applied to X.
Fall 2015, Sep 30 . . .Fall 2015, Sep 30 . . . ELEC2200-002 Lecture 4ELEC2200-002 Lecture 4 1313
XY
Y = X
Inverting Switch
Switch X is normally closed and Y is normally open.
Y cannot open unless a current is applied to X.
Fall 2015, Sep 30 . . .Fall 2015, Sep 30 . . . ELEC2200-002 Lecture 4ELEC2200-002 Lecture 4 1414
XY
Y = X
Boolean Operations
AND – Series connected relays.
OR – Parallel relays.
Fall 2015, Sep 30 . . .Fall 2015, Sep 30 . . . ELEC2200-002 Lecture 4ELEC2200-002 Lecture 4 1515
A BF
F = A B
BF
A
F = A + B
Complement (Inversion)
Fall 2015, Sep 30 . . .Fall 2015, Sep 30 . . . ELEC2200-002 Lecture 4ELEC2200-002 Lecture 4 1616
AF
F = A
B
F
A
F = A + B
= A · B
Relay ComputersRelay ComputersConrad Zuse (1910-1995)Conrad Zuse (1910-1995)
Fall 2015, Sep 30 . . .Fall 2015, Sep 30 . . . ELEC2200-002 Lecture 4ELEC2200-002 Lecture 4 1717
Z1 (1938)
Z3 (1941)
Electronic Switching DevicesElectronic Switching Devices
Fall 2015, Sep 30 . . .Fall 2015, Sep 30 . . . ELEC2200-002 Lecture 4ELEC2200-002 Lecture 4 1818
Electron TubeFleming, 1904
de Forest, 1906
Point Contact TransistorBardeen, Brattain, Shockley, 1948
Transistor, 1948 Transistor, 1948
Fall 2015, Sep 30 . . .Fall 2015, Sep 30 . . . ELEC2200-002 Lecture 4ELEC2200-002 Lecture 4 1919
The thinker, the tinkerer, the visionary and the transistorJohn Bardeen, Walter Brattain, William Shockley
Nobel Prize, 1956
Bell Laboratories, Murray Hill, New Jersey
Fall 2015, Sep 30 . . .Fall 2015, Sep 30 . . . ELEC2200-002 Lecture 4ELEC2200-002 Lecture 4 2020
Fall 2015, Sep 30 . . .Fall 2015, Sep 30 . . . ELEC2200-002 Lecture 4ELEC2200-002 Lecture 4 2121
Bipolar Junction Transistor (BJT)Bipolar Junction Transistor (BJT)
Fall 2015, Sep 30 . . .Fall 2015, Sep 30 . . . ELEC2200-002 Lecture 4ELEC2200-002 Lecture 42222
Field Effect Transistor (FET)Field Effect Transistor (FET)
Fall 2015, Sep 30 . . .Fall 2015, Sep 30 . . . ELEC2200-002 Lecture 4ELEC2200-002 Lecture 4 2323
a.k.a.metal oxidesemiconductor(MOS) FET.
(metaloxide)
Integrated Circuit (1958)Integrated Circuit (1958)
Fall 2015, Sep 30 . . .Fall 2015, Sep 30 . . . ELEC2200-002 Lecture 4ELEC2200-002 Lecture 4 2424
Jack Kilby (1923-2005), Nobel Prize, 2000
MOSFET (Metal Oxide Semiconductor MOSFET (Metal Oxide Semiconductor Field Effect Transistor)Field Effect Transistor)
Fall 2015, Sep 30 . . .Fall 2015, Sep 30 . . . ELEC2200-002 Lecture 4ELEC2200-002 Lecture 4 2525
Gate
Drain
Source
Gate
Drain
Source
NMOSFET PMOSFET
Shortor
Open
Shortor
Open
VGS VGS
VGS = 0, openVGS = high, short
VGS = 0, shortVGS = high, open
Reference:R. C. Jaeger and T. N. Blalock, Microelectronic Circuit Design, Third Edition, McGraw Hill.
NMOSFET NOT Gate (Early Design)NMOSFET NOT Gate (Early Design)
Fall 2015, Sep 30 . . .Fall 2015, Sep 30 . . . ELEC2200-002 Lecture 4ELEC2200-002 Lecture 4 2626
Ground = 0 volt
Power supplyVDD volts
w.r.t. ground
AA
Problem: When A = 1,current leakage causespower dissipation.
Solution: ComplementaryMOS design proposed by
F. M. Wanlass and C.-T. Sah, “Nanowatt Logic Using Field-Effect Metal-Oxide Semiconductor Triodes,” International Solid State Circuits Conference Digest of Technical Papers, Feb 20, 1963, pp. 32-33.
A: Boolean variable
A = VDD volts; 1, true, onA = 0 volt; 0, false, off
CMOS CircuitCMOS Circuit
Fall 2015, Sep 30 . . .Fall 2015, Sep 30 . . . ELEC2200-002 Lecture 4ELEC2200-002 Lecture 4 2727
Wanlass, F. M. "Low Stand-By Power Complementary Field Effect Circuitry.“U. S. Patent 3,356,858 (Filed June 18, 1963. Issued December 5, 1967).
CMOS NOT Gate (Modern Design)CMOS NOT Gate (Modern Design)
Fall 2015, Sep 30 . . .Fall 2015, Sep 30 . . . ELEC2200-002 Lecture 4ELEC2200-002 Lecture 4 2828
VDD = 1 volt; voltage depends on technology.
Ground
A A
A = VDD = 1 volt is state “1”A = GND = 0 volt is state “0”
Power supply
GND
Truth Table
A A
0 1
1 0
A A
ElectricalCircuit
Symbol
Boolean Function
CMOS Logic Gate: NANDCMOS Logic Gate: NAND
Fall 2015, Sep 30 . . .Fall 2015, Sep 30 . . . ELEC2200-002 Lecture 4ELEC2200-002 Lecture 4 2929
VDD
A F
GND
Truth Table
A B F
0 0 1
0 1 1
1 0 1
1 1 0
A
B
B
F
ElectricalCircuit
Boolean FunctionSymbol
CMOS Logic Gate: NORCMOS Logic Gate: NOR
Fall 2015, Sep 30 . . .Fall 2015, Sep 30 . . . ELEC2200-002 Lecture 4ELEC2200-002 Lecture 4 3030
VDD
A
F
GND
Truth Table
A B F
0 0 1
0 1 0
1 0 0
1 1 0
A
B
B
F
ElectricalCircuit
Boolean Function
Symbol
CMOS Logic Gate: ANDCMOS Logic Gate: AND
Fall 2015, Sep 30 . . .Fall 2015, Sep 30 . . . ELEC2200-002 Lecture 4ELEC2200-002 Lecture 4 3131
Truth Table
A B F
0 0 0
0 1 0
1 0 0
1 1 1
A
BF
Boolean Function
Symbol
A
BFF ≡
CMOS Logic Gate: ORCMOS Logic Gate: OR
Fall 2015, Sep 30 . . .Fall 2015, Sep 30 . . . ELEC2200-002 Lecture 4ELEC2200-002 Lecture 4 3232
Truth Table
A B F
0 0 0
0 1 1
1 0 1
1 1 1
F
Boolean Function
Symbol
FF≡
A
B
A
B
CMOS Gates
Logic functionNumber of transistors
1 or 2 inputs N inputs
NOT 2 -
AND 6 2N + 2
OR 6 2N + 2
NAND 4 2N
NOR 4 2N
Fall 2015, Sep 30 . . .Fall 2015, Sep 30 . . . ELEC2200-002 Lecture 4ELEC2200-002 Lecture 4 3333
Optimized Ignition LogicOptimized Ignition Logic
Fall 2015, Sep 30 . . .Fall 2015, Sep 30 . . . ELEC2200-002 Lecture 4ELEC2200-002 Lecture 4 3434
M = K (P + B S) = KP + KBS
K
P
KP
SB
KBS
M
3 gates, 20 transistors. Can we reduce transistors?
Further OptimizationFurther Optimization
Fall 2015, Sep 30 . . .Fall 2015, Sep 30 . . . ELEC2200-002 Lecture 4ELEC2200-002 Lecture 4 3535
M = K (P + B S) = KP + KBS (Distr. law)
= KP + KBS (Theorem 3, involution)
= KP · KBS (De Morgan’s theorem)
K
P
KP
SB
KBS
M
3 gates, 14 transistors.
NAND gates4+6 transistors
Fall 2015, Sep 30 . . .Fall 2015, Sep 30 . . . ELEC2200-002 Lecture 4ELEC2200-002 Lecture 4 3636
Fall 2015, Sep 30 . . .Fall 2015, Sep 30 . . . ELEC2200-002 Lecture 4ELEC2200-002 Lecture 4 3737
Fall 2015, Sep 30 . . .Fall 2015, Sep 30 . . . ELEC2200-002 Lecture 4ELEC2200-002 Lecture 4 3838
BinaryArithmetic
Switching
Theory
Semiconductor
Technology
Digital SystemsDigital Systems
Fall 2015, Sep 30 . . .Fall 2015, Sep 30 . . . ELEC2200-002 Lecture 4ELEC2200-002 Lecture 4 3939
Boolean
Algebra
DIGITALCIRCUITS
Digital Logic Design
Representation of switching function:Truth table
Canonical forms
Karnaugh map
Logic minimization: Minimize number of literals.
Technology mapping: Implement logic function using predesigned gates or building blocks from a technology library.
Fall 2015, Sep 30 . . .Fall 2015, Sep 30 . . . ELEC2200-002 Lecture 4ELEC2200-002 Lecture 4 4040
Truth TableTruth table is an exhaustive description of a switching function. Contains 2n input combinations for n variables.
Example: f(A,B,C) = A B +A,B,C) = A B +A C + AA C + ACC
Fall 2015, Sep 30 . . .Fall 2015, Sep 30 . . . ELEC2200-002 Lecture 4ELEC2200-002 Lecture 4 4141
n Input variables, n = 3 Output
A B C f(A,B,C)
0 0 0 0
0 0 1 1
0 1 0 0
0 1 1 1
1 0 0 1
1 0 1 0
1 1 0 1
1 1 1 1
2n = 8 rows
How Many Switching Functions?Output column of truth table has length 2n for n input variables.
It can be arranged in ways for n variables.
Example: n = 1, single variable.
Fall 2015, Sep 30 . . .Fall 2015, Sep 30 . . . ELEC2200-002 Lecture 4ELEC2200-002 Lecture 4 4242
n22
Input Output functions
A F1(A) F2(A) F3(A) F4(A)
0 0 0 1 1
1 0 1 0 1
DefinitionsBoolean variable: A variable denoted by a symbol; can assume a value 0 or 1.
Literal: Symbol for a variable or its complement.
Product or product term: A set of literals, ANDed together. Example, a bc.
Cube: Same as a product term.
Sum: A set of literals, Ored together. Example, a + b +c.
Fall 2015, Sep 30 . . .Fall 2015, Sep 30 . . . ELEC2200-002 Lecture 4ELEC2200-002 Lecture 4 4343
More DefinitionsSOP (sum of products): A Boolean function expressed as a sum of products.
Example: f(A,B,C) = A B +A,B,C) = A B +A C + AA C + ACC
POS (product of sums): A Boolean function expressed as a product of sums.
Example:f(A,B,C) = (A +B +C) (A + B +C) ( A +B + C)
Fall 2015, Sep 30 . . .Fall 2015, Sep 30 . . . ELEC2200-002 Lecture 4ELEC2200-002 Lecture 4 4444
MintermA product term in which each variable is present either in true or in complement form.
For n variables, there are 2n unique minterms.
Fall 2015, Sep 30 . . .Fall 2015, Sep 30 . . . ELEC2200-002 Lecture 4ELEC2200-002 Lecture 4 4545
Minterm Product
m0 A BCm1 A B Cm2 A BCm3 A B Cm4 A BCm5 A B Cm6 A B Cm7 A B C
Minterms are Canonical FunctionsMinterms are Canonical Functions
Fall 2015, Sep 30 . . .Fall 2015, Sep 30 . . . ELEC2200-002 Lecture 4ELEC2200-002 Lecture 4 4646
000 001 010 011 100 101 110 111
Input
Val
ue
of
min
term
1
0
m0 m1 m2 m3 m4 m5 m6 m7
Canonical SOP Forma.k.a. Disjunctive Normal Form (DNF)
A Boolean function expressed as a sum of minterms.
Example: f(A,B,C) = A B +A,B,C) = A B +A C + AA C + ACC
= = AABC +BC +ABC + AABC + ABBC + ABC + ABC + ABCC + ABC
= m= m11+m+m33+m+m44+m+m66+m+m77 = = m(1, 3, 4, 6, 7) m(1, 3, 4, 6, 7)
Fall 2015, Sep 30 . . .Fall 2015, Sep 30 . . . ELEC2200-002 Lecture 4ELEC2200-002 Lecture 4 4747
Row No. A B C f(A,B,C)
0 0 0 0 0
1 0 0 1 1
2 0 1 0 0
3 0 1 1 1
4 1 0 0 1
5 1 0 1 0
6 1 1 0 1
7 1 1 1 1Tru
th ta
ble
with
ro
w n
um
bers
MaxtermA summation term in which each variable is present either in true or in complement form.
For n variables, there are 2n unique maxterms.
Fall 2015, Sep 30 . . .Fall 2015, Sep 30 . . . ELEC2200-002 Lecture 4ELEC2200-002 Lecture 4 4848
Maxterm Sum
M0 A + B + CM1 A + B +CM2 A +B + CM3 A +B +CM4 A + B + C M5 A + B +C M6 A +B + C M7 A + B + C
Canonical POS Forma.k.a. Conjunctive Normal Form (CNF)
A Boolean function expressed as a product of maxterms.
Example: f(A,B,C) = A B +A,B,C) = A B +A C + AA C + ACC
= (A + B + C)(A += (A + B + C)(A +B + C)(B + C)(A + B +A + B +C)C)
= M= M00 M M22 M M55 = = M(0, 2, 5) M(0, 2, 5)
Fall 2015, Sep 30 . . .Fall 2015, Sep 30 . . . ELEC2200-002 Lecture 4ELEC2200-002 Lecture 4 4949
Row No. A B C f(A,B,C)
0 0 0 0 0
1 0 0 1 1
2 0 1 0 0
3 0 1 1 1
4 1 0 0 1
5 1 0 1 0
6 1 1 0 1
7 1 1 1 1Tru
th ta
ble
with
ro
w n
um
bers
Canonical Forms are UniqueA canonical form completely defines a Boolean function. That is, for every input the canonical form specifies the value of the function.
To determine canonical form:Construct truth table and sum minterms corresponding to 1 outputs, or multiply maxterms corresponding to 0 outputs.
Alternatively, use Shannon’s expansion theorem (see Section 2.2.3, page 101).
Two Boolean functions are identical if and only if their canonical forms are identical.
Fall 2015, Sep 30 . . .Fall 2015, Sep 30 . . . ELEC2200-002 Lecture 4ELEC2200-002 Lecture 4 5050
Why Generate Canonical Form?
Example: Are the following Boolean Functions Identical?
Generate canonical forms, e.g., minterms, and compare.
Fall 2015, Sep 30 . . .Fall 2015, Sep 30 . . . ELEC2200-002 Lecture 4ELEC2200-002 Lecture 4 5151
D BD C B AF3
D C BD B AD C AF2
D C AD B AD B
AF1
Algebraic Procedure
Expand each term to contain all variables
RememberPostulate 6: Complement
Postulate 2: Identity elements
a + 0 = a, 0 is identity element for +
a · 1 = a, 1 is identity element for dot (·)
Fall 2015, Sep 30 . . .Fall 2015, Sep 30 . . . ELEC2200-002 Lecture 4ELEC2200-002 Lecture 4 5252
0aa
1aa
Fall 2015, Sep 30 . . .Fall 2015, Sep 30 . . . ELEC2200-002 Lecture 4ELEC2200-002 Lecture 4 5353
identical. are functions three ,Hence
)15 ,13 ,11 ,7 ,5(m3F
)15 ,13 ,11 ,7 ,5(mF2
Similarly,
)15 ,13 ,11 ,7 ,5(m
mmmmm
CDBAABCDDCABABCDDCBABCD
)BB(ACD)CC(ABD)CC(BD
ACDABDBD
11131557
A
A
A F1
Karnaugh Map
1952: Edward M. Veitch invented a graphical procedure for digital circuit optimization.
1953: Maurice Karnaugh perfected the map procedure:
“The Map Method for Synthesis of Combinational Logic Circuits,” Trans. AIEE, pt I, 72(9):593-599, November 1953.
Fall 2015, Sep 30 . . .Fall 2015, Sep 30 . . . ELEC2200-002 Lecture 4ELEC2200-002 Lecture 4 5454
Karnaugh Map: 2 Variables, A, BKarnaugh Map: 2 Variables, A, B
Fall 2015, Sep 30 . . .Fall 2015, Sep 30 . . . ELEC2200-002 Lecture 4ELEC2200-002 Lecture 4 5555
A = 0 A = 1
B = 0
B = 1
m0
m1
m2
m3
m3 = AB = 11(numerical interpretation)
00
01
10
11
UnitHammingdistancebetweenadjacent cells
Each cell isa minterm
Representing a FunctionRepresenting a Function
Fall 2015, Sep 30 . . .Fall 2015, Sep 30 . . . ELEC2200-002 Lecture 4ELEC2200-002 Lecture 4 5656
A = 0 A = 1
B = 0
B = 1
m0
m1
m2
m3
0
1
2
3
Place 1 in cellscorresponding tominterms in canonical form.For example, see F = A B + ABrepresented on the left.
1
1
Truth Table
A B F
0 0 0
0 1 0
1 0 1
1 1 1
Grouping Adjacent MintermsGrouping Adjacent Minterms
Fall 2015, Sep 30 . . .Fall 2015, Sep 30 . . . ELEC2200-002 Lecture 4ELEC2200-002 Lecture 4 5757
A = 0 A = 1
B = 0
B = 1
m0
m1
m2
m3
0
1
2
3
Adjacent cells differ inone variable, which iseliminated.
For example, F = A B + AB = A(B +B) = A1
1
Product term A
Karnaugh Map MinimizationCanonical SOP form represented on map
Example: F = AB + A B +A B
Find minimal cover (fewest groups of largest sizes),
F = A + B
Fall 2015, Sep 30 . . .Fall 2015, Sep 30 . . . ELEC2200-002 Lecture 4ELEC2200-002 Lecture 4 5858
A = 0 A = 1
B = 0
B = 1
m0
m1
m2
m3
1
11
product A
product B
A
B
F
Karnaugh Map: 3 Variables, A, B, CKarnaugh Map: 3 Variables, A, B, C
Fall 2015, Sep 30 . . .Fall 2015, Sep 30 . . . ELEC2200-002 Lecture 4ELEC2200-002 Lecture 4 5959
0 2 6 4
1 3 7 5
A
B
C
000
001
010
011
110
111
100
101
Check unit Hamming distance between adjacent cells.
Synthesizing a Digital FunctionStart with specification.
Create a truth table from specification.
Minimize (SOP with fewest literals):Either write canonical SOP
Reduce using postulates and theorems
Or find largest cubes from Karnaugh map
Minimized SOP gives a two-level AND-OR circuit.
NAND or NOR circuit for CMOS technology can be found using de Morgan’s theorem.
Fall 2015, Sep 30 . . .Fall 2015, Sep 30 . . . ELEC2200-002 Lecture 4ELEC2200-002 Lecture 4 6060
Example: Multiplexer
Inputs: A, B, C
Output: F
Function:F = A, when C = 1
F = B, when C = 0
Fall 2015, Sep 30 . . .Fall 2015, Sep 30 . . . ELEC2200-002 Lecture 4ELEC2200-002 Lecture 4 6161
3-Input Function: Multiplexer
Truth Table
row A B C F
0 0 0 0 0
1 0 0 1 0
2 0 1 0 1
3 0 1 1 0
4 1 0 0 0
5 1 0 1 1
6 1 1 0 1
7 1 1 1 1
Fall 2015, Sep 30 . . .Fall 2015, Sep 30 . . . ELEC2200-002 Lecture 4ELEC2200-002 Lecture 4 6262
0 2 6 4
1 3 7 5
A
B
C
1
1
1
1
F = A C + BC
A C
BC
A
C
B
F
Technology Optimization
Fall 2015, Sep 30 . . .Fall 2015, Sep 30 . . . ELEC2200-002 Lecture 4ELEC2200-002 Lecture 4 6363
F = A C + BCA
C
B
F
A
C
B
F
2 + 6 + 6 + 6 = 20 transistors
Optimized Multiplexer
Fall 2015, Sep 30 . . .Fall 2015, Sep 30 . . . ELEC2200-002 Lecture 4ELEC2200-002 Lecture 4 6464
A
C
B
F
X
Y
theorem sMorgan' de from
YXYXF
A
C
B
F
X
Y2 + 4 + 4 + 4 = 14 transistors
Karnaugh Map: 4 Variables, A, B, C, DKarnaugh Map: 4 Variables, A, B, C, D
0 4 12 8
1 5 13 9
3 7 15 11
2 6 14 10
Fall 2015, Sep 30 . . .Fall 2015, Sep 30 . . . ELEC2200-002 Lecture 4ELEC2200-002 Lecture 4 6565
Check unit Hamming distance between adjacent cells.
A
B
D
C
Adjacency of Edge CellsAdjacency of Edge Cells
Fall 2015, Sep 30 . . .Fall 2015, Sep 30 . . . ELEC2200-002 Lecture 4ELEC2200-002 Lecture 4 6666
0
1
3
2
8
9
11
10
0 4 12 810 14 6 2
Reexamine Three Functions from Slide 48
Example: Are the following Boolean Functions Identical?
This time generate Karnaugh maps, and compare.
Fall 2015, Sep 30 . . .Fall 2015, Sep 30 . . . ELEC2200-002 Lecture 4ELEC2200-002 Lecture 4 6767
D BD C B AF3
D C BD B AD C AF2
D C AD B AD B
AF1
Karnaugh Map of F1Karnaugh Map of F1
0 4 12 8
1 5 13 9
3 7 15 11
2 6 14 10
Fall 2015, Sep 30 . . .Fall 2015, Sep 30 . . . ELEC2200-002 Lecture 4ELEC2200-002 Lecture 4 6868
.
A
B
D
C
D C AD B AD B AF1
F1 = Σm(5, 7, 11, 13, 15)
1 1
1 1 1
Karnaugh Map of F2Karnaugh Map of F2
0 4 12 8
1 5 13 9
3 7 15 11
2 6 14 10
Fall 2015, Sep 30 . . .Fall 2015, Sep 30 . . . ELEC2200-002 Lecture 4ELEC2200-002 Lecture 4 6969
.
A
B
D
C
D C BD B AD C AF2
F2 = Σm(5, 7, 11, 13, 15) ⇒ F1 and F2 cover same area on map.
1 1
1 1 1
Karnaugh Map of F3Karnaugh Map of F3
0 4 12 8
1 5 13 9
3 7 15 11
2 6 14 10
Fall 2015, Sep 30 . . .Fall 2015, Sep 30 . . . ELEC2200-002 Lecture 4ELEC2200-002 Lecture 4 7070
.
A
B
D
C
D BD C B AF3
F3 = Σm(5, 7, 11, 13, 15) ⇒ F1, F2 and F3 cover exactly thesame area on map, hence, they are identical.
1 1
1 1 1
Ignition FunctionMinterm K P B S M
0 0 0 0 0 0
1 0 0 0 1 0
2 0 0 1 0 0
3 0 0 1 1 0
4 0 1 0 0 0
5 0 1 0 1 0
6 0 1 1 0 0
7 0 1 1 1 0
8 1 0 0 0 0
9 1 0 0 1 0
10 1 0 1 0 0
11 1 0 1 1 1
12 1 1 0 0 1
13 1 1 0 1 1
14 1 1 1 0 1
15 1 1 1 1 1Fall 2015, Sep 30 . . .Fall 2015, Sep 30 . . . ELEC2200-002 Lecture 4ELEC2200-002 Lecture 4 7171
M = K AND (P OR B) AND (S OR P)
= K(P + B)(S + P)
Karnaugh Map: M(K, P, B, S)Karnaugh Map: M(K, P, B, S)
0 4 12 8
1 5 13 9
3 7 15 11
2 6 14 10
Fall 2015, Sep 30 . . .Fall 2015, Sep 30 . . . ELEC2200-002 Lecture 4ELEC2200-002 Lecture 4 7272
.
K
P
S
B
1
1
1 1
1
Karnaugh Map: Minimum CoverKarnaugh Map: Minimum Cover
0 4 12 8
1 5 13 9
3 7 15 11
2 6 14 10
Fall 2015, Sep 30 . . .Fall 2015, Sep 30 . . . ELEC2200-002 Lecture 4ELEC2200-002 Lecture 4 7373
.
K
P
S
B
1
1
1 1
1
KP
KBS
Minimized FunctionMinimized Function
Fall 2015, Sep 30 . . .Fall 2015, Sep 30 . . . ELEC2200-002 Lecture 4ELEC2200-002 Lecture 4 7474
M = KP + KBS
KP
BS
M
Using Inverting GatesUsing Inverting GatesBecause They Need Fewer TransistorsBecause They Need Fewer Transistors
Fall 2015, Sep 30 . . .Fall 2015, Sep 30 . . . ELEC2200-002 Lecture 4ELEC2200-002 Lecture 4 7575
M = KP + KBS
= KP · KBS Using de Morgan’s Theorem
KP
BS
M
Karnaugh Map on the WebKarnaugh Map on the Web
Fall 2015, Sep 30 . . .Fall 2015, Sep 30 . . . ELEC2200-002 Lecture 4ELEC2200-002 Lecture 4 7676
http://www.ee.calpoly.edu/media/uploads/resources/KarnaughExplorer_1.html
Minterm Clusters, Cubes or ProductsMinterm Clusters, Cubes or Products
0
14 12 8
1 5
113
19
3 7 15
111
1
2 6 14
110
1
Fall 2015, Sep 30 . . .Fall 2015, Sep 30 . . . ELEC2200-002 Lecture 4ELEC2200-002 Lecture 4 7777
Larger clusters are products with fewer variables.
A
B
D
C
DCBA
DCB
AC
ABD
ProductProduct
Fall 2015, Sep 30 . . .Fall 2015, Sep 30 . . . ELEC2200-002 Lecture 4ELEC2200-002 Lecture 4 7878
More variables in a product mean more transistors (hardware).
ABCD
DCBADCBAP 1
P1A
B
C
D
GROUND
VDD = 1 volt
PM
OS
tra
nsi
sto
rs
NMOS transistors
Signals are voltagesw.r.t. GROUNDA = 0 or 1 voltB = 0 or 1 voltC = 0 or 1 voltD = 0 or 1 volt
P1 =0 or 1 volt
ProductProduct
Fall 2015, Sep 30 . . .Fall 2015, Sep 30 . . . ELEC2200-002 Lecture 4ELEC2200-002 Lecture 4 7979
Fewer variables in a product mean fewer transistors (hardware).
A
C
ACACP 2
P2
A
C
GROUND
VDD = 1 volt
Signals are voltagesw.r.t. GROUNDA = 0 or 1 voltB = 0 or 1 voltC = 0 or 1 voltD = 0 or 1 volt P1 =
0 or 1 volt
ObservationsA larger minterm cluster is a product with fewer variables; requires fewer transistors.
Each gate input needs two transistors.
Smaller number of clusters is more efficient: Fewer gates to generate products.
Fewer inputs for the OR gate to produce the function.
Direct minterm implementation is most inefficient.
Fall 2015, Sep 30 . . .Fall 2015, Sep 30 . . . ELEC2200-002 Lecture 4ELEC2200-002 Lecture 4 8080