gate logic: two-level simplification

49
2-1 Introduction Gate Logic: Two-Level Simplification Design Example: Two Bit Comparator Block Diagram and Truth Table A 4-Variable K-map for each of the 3 output functions F 1 1 0 0 0 0 1 0 0 0 0 1 0 0 0 0 1 F 2 0 1 1 1 0 0 1 1 0 0 0 1 0 0 0 0 F 3 0 0 0 0 1 0 0 0 1 1 0 0 1 1 1 0 D 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 C 0 0 1 1 0 0 1 1 0 0 1 1 0 0 1 1 B 0 1 0 1 A 0 0 1 1 =, >, < F 1 A B = C D F 2 A B < C D F 3 A B > C D A B C D N 1 N 2

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Gate Logic: Two-Level Simplification. Design Example: Two Bit Comparator. Block Diagram and Truth Table A 4-Variable K-map for each of the 3 output functions. Gate Logic: Two-Level Simplification. Design Example: Two Bit Comparator. F1 = F2 = F3 =. Gate Logic:Two-Level Simplification. - PowerPoint PPT Presentation

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Page 1: Gate Logic: Two-Level Simplification

2-1

IntroductionGate Logic: Two-Level SimplificationDesign Example: Two Bit Comparator

Block Diagramand

Truth Table

A 4-Variable K-mapfor each of the 3output functions

F 1 1 0 0 0 0 1 0 0 0 0 1 0 0 0 0 1

F 2 0 1 1 1 0 0 1 1 0 0 0 1 0 0 0 0

F 3 0 0 0 0 1 0 0 0 1 1 0 0 1 1 1 0

D 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1

C 0 0 1 1 0 0 1 1 0 0 1 1 0 0 1 1

B 0 1 0 1

A 0 0 1 1

=, >, < F 1 A B = C D F 2 A B < C D F 3 A B > C D

A B

C D

N 1

N 2

Page 2: Gate Logic: Two-Level Simplification

2-2

IntroductionGate Logic: Two-Level SimplificationDesign Example: Two Bit Comparator

F1 =

F2 =

F3 =

AB 00 01 11 10

1 0 0 0

0 1 0 0

0 0 1 0

0 0 0 1

00

01

11

10 C

CD

A

D

B

K-map for F 1

AB 00 01 11 10

0 0 0 0

1 0 0 0

1 1 0 1

1 1 0 0

00

01

11

10 C

CD

A

D

B

K-map for F 2

AB 00 01 11 10

0 1 1 1

0 0 1 1

0 0 0 0

0 0 1 0

00

01

11

10 C

CD

A

D

B

K-map for F 3

Page 3: Gate Logic: Two-Level Simplification

2-3

IntroductionGate Logic:Two-Level SimplificationDesign Example: Two Bit Comparator

F1 = A' B' C' D' + A' B C' D + A B C D + A B' C D'

F2 = A' B' D + A' C + B' C D

F3 = B C' D' + A C' + A B D'

AB 00 01 11 10

1 0 0 0

0 1 0 0

0 0 1 0

0 0 0 1

00

01

11

10 C

CD

A

D

B

K-map for F 1

AB 00 01 11 10

0 0 0 0

1 0 0 0

1 1 0 1

1 1 0 0

00

01

11

10 C

CD

A

D

B

K-map for F 2

AB 00 01 11 10

0 1 1 1

0 0 1 1

0 0 0 0

0 0 1 0

00

01

11

10 C

CD

A

D

B

K-map for F 3

Page 4: Gate Logic: Two-Level Simplification

2-4

IntroductionGate Logic: Two-Level SimplificationDesign Example: Two Bit Adder

Block Diagramand

Truth Table

A 4-variable K-mapfor each of the 3output functions

+ N 3

X 0 0 0 0 0 0 0 1 0 0 1 1 0 1 1 1

Y 0 0 1 1 0 1 1 0 1 1 0 0 1 0 0 1

Z 0 1 0 1 1 0 1 0 0 1 0 1 1 0 1 0

D 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1

C 0 0 1 1 0 0 1 1 0 0 1 1 0 0 1 1

B 0 1 0 1

A 0 0 1 1

A B

C D

N 1

N 2

X Y Z

Page 5: Gate Logic: Two-Level Simplification

2-5

IntroductionGate Logic: Two-Level SimplificationDesign Example (Continued)

X =

Z =

Y =

AB 00 01 11 10

0 0 0 0

0 0 1 0

0 1 1 1

0 0 1 1

00

01

11

10 C

CD

A

D

B

K-map for X

AB 00 01 11 10

0 0 1 1

0 1 0 1

1 0 1 0

1 1 0 0

00

01

11

10 C

CD

A

D

B

K-map for Y

AB 00 01 11 10

0 1 1 0

1 0 0 1

1 0 0 1

0 1 1 0

00

01

11

10 C

CD

A

D

B

K-map for Z

Page 6: Gate Logic: Two-Level Simplification

2-6

IntroductionGate Logic: Two-Level SimplificationDesign Example (Continued)

X = A C + B C D + A B D

Z = B D' + B' D = B xor D

Y = A' B' C + A B' C' + A' B C' D + A' B C D' + A B C' D' + A B C D

= B' (A xor C) + A' B (C xor D) + A B (C xnor D)

= B' (A xor C) + B (A xor B xor C)gate countreduced if

XOR available

1's on diagonal suggest XOR!Y K-Map not minimal as drawn

AB 00 01 11 10

0 0 0 0

0 0 1 0

0 1 1 1

0 0 1 1

00

01

11

10 C

CD

A

D

B

K-map for X

AB 00 01 11 10

0 0 1 1

0 1 0 1

1 0 1 0

1 1 0 0

00

01

11

10 C

CD

A

D

B

K-map for Y

AB 00 01 11 10

0 1 1 0

1 0 0 1

1 0 0 1

0 1 1 0

00

01

11

10 C

CD

A

D

B

K-map for Z

Page 7: Gate Logic: Two-Level Simplification

2-7

IntroductionGate Logic: Two-Level SimplificationDesign Example (Continued)

Two alternativeimplementations of Ywith and without XOR

Note: XOR typicallyrequires 4 NAND gates

to implement!

X XOR Y

X

Y

\ D \ A \ C

Y 1

A

C

D

\ B

B

Y 2

Page 8: Gate Logic: Two-Level Simplification

2-8

IntroductionGate Logic: Two-Level SimplificationDesign Example: BCD Increment By 1

W =

X =

Y =

Z =

AB 00 01 11 10

0 0 X 1

0 0 X 0

0 1 X X

0 0 X X

00

01

11

10 C

CD

A

D

B

AB 00 01 11 10

0 1 X 0

0 1 X 0

1 0 X X

0 1 X X

00

01

11

10 C

CD

A

D

B

AB 00 01 11 10

0 0 X 0

1 1 X 0

0 0 X X

1 1 X X

00

01

11

10 C

CD

A

D

B

AB 00 01 11 10

1 1 X 1

0 0 X 0

0 0 X X

1 1 X X

00

01

11

10 C

CD

A

D

B

Z Y

X W

Page 9: Gate Logic: Two-Level Simplification

2-9

IntroductionGate Logic: Two-Level Simplification

W = B C D + A D'

X = B C' + B D' + B' C D

Y = A' C' D + C D'

Z = D'

AB 00 01 11 10

0 0 X 1

0 0 X 0

0 1 X X

0 0 X X

00

01

11

10 C

CD

A

D

B

AB 00 01 11 10

0 1 X 0

0 1 X 0

1 0 X X

0 1 X X

00

01

11

10 C

CD

A

D

B

AB 00 01 11 10

0 0 X 0

1 1 X 0

0 0 X X

1 1 X X

00

01

11

10 C

CD

A

D

B

AB 00 01 11 10

1 1 X 1

0 0 X 0

0 0 X X

1 1 X X

00

01

11

10 C

CD

A

D

B

Z Y

X W

Page 10: Gate Logic: Two-Level Simplification

2-10

IntroductionGate Logic: Two Level SimplificationDefinition of Terms

implicant: single element of the ON-set or any group of elements that can be combined together in a K-map

prime implicant: implicant that cannot be combined with another implicant to eliminate a term

essential prime implicant: if an element of the ON-set is covered by a single prime implicant, it is an essential prime

Objective:

grow implicants into prime implicants

cover the ON-set with as few prime implicants as possible

essential primes participate in ALL possible covers

Page 11: Gate Logic: Two-Level Simplification

2-11

IntroductionGate Logic: Two Level Simplication

Examples to Illustrate Terms

6 Prime Implicants:

A' B' D, B C', A C, A' C' D, A B, B' C D

essential

Minimum cover = B C' + A C + A' B' D

5 Prime Implicants:

B D, A B C', A C D, A' B C, A' C' D

essential

Essential implicants form minimum cover

AB 00 01 11 10

0 1 1 0

1 1 1 0

1 0 1 1

0 0 1 1

00

01

11

10 C

CD

A

D

B

AB 00 01 11 10

0 0 1 0

1 1 1 0

0 1 1 1

0 1 0 0

00

01

11

10 C

CD

A

D

B

Page 12: Gate Logic: Two-Level Simplification

2-12

IntroductionGate Logic: Two Level SimplificationMore Examples

Prime Implicants:

B D, C D, A C, B' C

essential

Essential primes form the minimum cover

AB 00 01 11 10

0 0 0 0

0 1 1 0

1 1 1 1

1 0 1 1

00

01

11

10 C

CD

A

D

B

Page 13: Gate Logic: Two-Level Simplification

2-13

IntroductionGate Logic: Two-Level SimplificationAlgorithm: Minimum Sum of Products Expression from a K-Map

Step 1: Choose an element of ON-set not already covered by an implicant

Step 2: Find "maximal" groupings of 1's and X's adjacent to that element.Remember to consider top/bottom row, left/right column, andcorner adjacencies. This forms prime implicants (always a powerof 2 number of elements).

Repeat Steps 1 and 2 to find all prime implicants

Step 3: Revisit the 1's elements in the K-map. If covered by single primeimplicant, it is essential, and participates in final cover. The 1's itcovers do not need to be revisited

Step 4: If there remain 1's not covered by essential prime implicants, thenselect the smallest number of prime implicants that cover theremaining 1's

Page 14: Gate Logic: Two-Level Simplification

2-14

IntroductionGate Logic: Two Level SimplificationExample: F(A,B,C,D) = m(4,5,6,8,9,10,13) + d(0,7,15)

Initial K-map

AB 00 01 11 10

X 1 0 1

0 1 1 1

0 X X 0

0 1 0 1

00

01

11

10 C

CD

A

D

B

Page 15: Gate Logic: Two-Level Simplification

2-15

IntroductionGate Logic: Two Level SimplificationExample: F(A,B,C,D) = m(4,5,6,8,9,10,13) + d(0,7,15)

Initial K-map Primes aroundA' B C' D'

AB 00 01 11 10

X 1 0 1

0 1 1 1

0 X X 0

0 1 0 1

00

01

11

10 C

CD

A

D

B

AB 00 01 11 10

X 1 0 1

0 1 1 1

0 X X 0

0 1 0 1

00

01

11

10 C

CD

A

D

B

Page 16: Gate Logic: Two-Level Simplification

2-16

IntroductionGate Logic: Two Level SimplificationExample: F(A,B,C,D) = m(4,5,6,8,9,10,13) + d(0,7,15)

Initial K-map Primes aroundA' B C' D'

Primes aroundA B C' D

AB 00 01 11 10

X 1 0 1

0 1 1 1

0 X X 0

0 1 0 1

00

01

11

10 C

CD

A

D

B

AB 00 01 11 10

X 1 0 1

0 1 1 1

0 X X 0

0 1 0 1

00

01

11

10 C

CD

A

D

B

AB 00 01 11 10

X 1 0 1

0 1 1 1

0 X X 0

0 1 0 1

00

01

11

10 C

CD

A

D

B

Page 17: Gate Logic: Two-Level Simplification

2-17

IntroductionGate Logic: Two-Level SimplificationExample Continued

Primes aroundA B' C' D

AB 00 01 11 10

X 1 0 1

0 1 1 1

0 X X 0

0 1 0 1

00

01

11

10 C

CD

A

D

B

Page 18: Gate Logic: Two-Level Simplification

2-18

IntroductionGate Logic: Two-Level SimplificationExample Continued

Primes aroundA B' C' D'

Primes aroundA B' C' D

AB 00 01 11 10

X 1 0 1

0 1 1 1

0 X X 0

0 1 0 1

00

01

11

10 C

CD

A

D

B

AB 00 01 11 10

X 1 0 1

0 1 1 1

0 X X 0

0 1 0 1

00

01

11

10 C

CD

A

D

B

Page 19: Gate Logic: Two-Level Simplification

2-19

IntroductionGate Logic: Two-Level SimplificationExample Continued

Primes aroundA B' C' D'

Primes aroundA B' C' D

AB 00 01 11 10

X 1 0 1

0 1 1 1

0 X X 0

0 1 0 1

00

01

11

10 C

CD

A

D

B

AB 00 01 11 10

X 1 0 1

0 1 1 1

0 X X 0

0 1 0 1

00

01

11

10 C

CD

A

D

B

AB 00 01 11 10

X 1 0 1

0 1 1 1

0 X X 0

0 1 0 1

00

01

11

10 C

CD

A

D

B

Essential Primeswith Min Cover

Page 20: Gate Logic: Two-Level Simplification

2-20

IntroductionGate Logic: Two-Level Simplification

5-Variable K-maps

F(A,B,C,D,E) = m(2,5,7,8,10,13,15,17,19,21,23,24,29 31)

=

BC DE

BC DE

A =0

A =1

00 01 11 10 00

01

11

10

00 01 11 10 00

01

11

10

0 4 12 8

1 5 13 9

3 7 15 11

2 6 14 10

16 20 28 24

17 21 29 25

19 23 31 27

18 22 30 26

1

00

1

10

1

10 BC

DE 00 01 11

00

01

11

10

A=0

BC DE 00 01 11

01

11

10

A=1

1 1

1

1 1

1

1 1

1 1 1

Page 21: Gate Logic: Two-Level Simplification

2-21

IntroductionGate Logic: Two-Level Simplification

5-Variable K-maps

F(A,B,C,D,E) = m(2,5,7,8,10,13,15,17,19,21,23,24,29 31)

= C E + A B' E + B C' D' E' + A' C' D E'

BC BC DE

BC DE

A =0

A =1

00 01 11 10 00

01

11

10

00 01 11 10 00

01

11

10

0 4 12 8

1 5 13 9

3 7 15 11

2 6 14 10

16 20 28 24

17 21 29 25

19 23 31 27

18 22 30 26

BC DE 00 01 11 10

00

01

11

10

A=0

BC DE 00 01 11 10

00

01

11

10

A=1

1 1

1

1

1 1

1

1

1 1 1

1 1 1

Page 22: Gate Logic: Two-Level Simplification

2-22

IntroductionGate Logic: Two Level Simplification6- Variable K-Maps

F(A,B,C,D,E,F) =m(2,8,10,18,24,

26,34,37,42,45,50,53,58,61)

=

CD EF

CD EF

AB =00

AB =01

00 01 11 10 00

01

11

10

00 01 11 10 00

01

11

10

0 4 12 8

1 5 13 9

3 7 15 11

2 6 14 10

16 20 28 24

17 21 29 25

19 23 31 27

18 22 30 26

CD EF

AB =11

00 01 11 10 00

01

11

10

48 52 60 56

49 53 61 57

51 55 63 59

50 54 62 58

CD EF

AB =10

00 01 11 10 00

01

11

10

32 36 44 40

33 37 45 41

35 39 47 43

34 38 46 42

CD EF

CD EF

AB =00

AB =01

00 01 11 10 00

01

11

10

00 01 11 10 00

01

11

10

CD EF

AB =11

00 01 11 10 00

01

11

10

CD EF

AB =10

00 01 11 10 00

01

11

10

1

1 1

1

1 1

1 1

1 1

1 1

1 1

Page 23: Gate Logic: Two-Level Simplification

2-23

IntroductionGate Logic: Two Level Simplification6- Variable K-Maps

F(A,B,C,D,E,F) =m(2,8,10,18,24,

26,34,37,42,45,50,53,58,61)

= D' E F' + A D E' F+ A' C D' F'

CD EF

CD EF

AB =00

AB =01

00 01 11 10 00

01

11

10

00 01 11 10 00

01

11

10

0 4 12 8

1 5 13 9

3 7 15 11

2 6 14 10

16 20 28 24

17 21 29 25

19 23 31 27

18 22 30 26

CD EF

AB =11

00 01 11 10 00

01

11

10

48 52 60 56

49 53 61 57

51 55 63 59

50 54 62 58

CD EF

AB =10

00 01 11 10 00

01

11

10

32 36 44 40

33 37 45 41

35 39 47 43

34 38 46 42

CD EF

CD EF

AB =00

AB =01

00 01 11 10 00

01

11

10

00 01 11 10 00

01

11

10

CD EF

AB =11

00 01 11 10 00

01

11

10

CD EF

AB =10

00 01 11 10 00

01

11

10

1

1 1

1

1 1

1 1

1 1

1 1

1 1

Page 24: Gate Logic: Two-Level Simplification

2-24

IntroductionGate Logic: CAD Tools for SimplificationQuine-McCluskey Method

Tabular method to systematically find all prime implicants

Implication Table

Column I 0000 0100 1000 0101 0110 1001 1010 0111 1101

1111

F(A,B,C,D) = m(4,5,6,8,9,10,13) + d(0,7,15)

Step 1: Fill Column 1 with ON-set and DC-set minterm indices. Group by number of 1's.

Stage 1: Find all prime implicants

Page 25: Gate Logic: Two-Level Simplification

2-25

IntroductionGate Logic: CAD Tools for SimplificationQuine-McCluskey Method

Tabular method to systematically find all prime implicants

Implication Table

Column I Column II 0000 0-00 -000 0100 1000 010- 01-0 0101 100- 0110 10-0 1001 1010 01-1 -101 0111 011- 1101 1-01

1111 -111 11-1

F(A,B,C,D) = m(4,5,6,8,9,10,13) + d(0,7,15)

Step 1: Fill Column 1 with ON-set and DC-set minterm indices. Group by number of 1's.

Step 2: Apply Uniting Theorem. Compare elements of group w/ N 1's against those with N+1 1's. Differ by one bit implies adjacent. Eliminate variable and place in next column.

E.g., 0000 vs. 0100 yields 0-00 0000 vs. 1000 yields -000

When used in a combination, mark with a check. If cannot be combined, mark with a star. These are the prime implicants.

Repeat until no further combinations can be made.

Stage 1: Find all prime implicants

Page 26: Gate Logic: Two-Level Simplification

2-26

IntroductionGate Logic: CAD Tools for SimplificationQuine-McCluskey Method

Tabular method to systematically find all prime implicants

Implication Table

Column I Column II Column III 0000 0-00 * 01-- * -000 * 0100 -1-1 * 1000 010- 01-0 0101 100- * 0110 10-0 * 1001 1010 01-1 -101 0111 011- 1101 1-01 *

1111 -111 11-1

F(A,B,C,D) = m(4,5,6,8,9,10,13) + d(0,7,15)

Step 1: Fill Column 1 with ON-set and DC-set minterm indices. Group by number of 1's.

Step 2: Apply Uniting Theorem. Compare elements of group w/ N 1's against those with N+1 1's. Differ by one bit implies adjacent. Eliminate variable and place in next column.

E.g., 0000 vs. 0100 yields 0-00 0000 vs. 1000 yields -000

When used in a combination, mark with a check. If cannot be combined, mark with a star. These are the prime implicants.

Repeat until no further combinations can be made.

Stage 1: Find all prime implicants

Page 27: Gate Logic: Two-Level Simplification

2-27

IntroductionGate Logic: CAD Tools for SimplificationQuine-McCluskey Method Continued

Prime Implicants:

0-00 = A' C' D'

100- = A B' C'

1-01 = A C' D

-1-1 = B D

-000 = B' C' D'

10-0 = A B' D'

01-- = A' B

AB

CD 00 01 11 10

00

01

11

10

D

B

C

A

X 1 0 1

0 1 1 1

0 X X 0

0 1 0 1

Page 28: Gate Logic: Two-Level Simplification

2-28

IntroductionGate Logic: CAD Tools for SimplificationQuine-McCluskey Method Continued

Prime Implicants:

0-00 = A' C' D'

100- = A B' C'

1-01 = A C' D

-1-1 = B D

-000 = B' C' D'

10-0 = A B' D'

01-- = A' B

Stage 2: find smallest set of prime implicants that cover the ON-set

recall that essential prime implicants must be in all covers

another tabular method : the prime implicant chart

AB

CD 00 01 11 10

00

01

11

10

D

B

C

A

X 1 0 1

0 1 1 1

0 X X 0

0 1 0 1

Page 29: Gate Logic: Two-Level Simplification

2-29

IntroductionGate Logic: CAD Tools for Simplification

rows = prime implicantscolumns = ON-set elementsplace an "X" if ON-set element is covered by the prime implicant

Prime Implicant Chart

Page 30: Gate Logic: Two-Level Simplification

2-30

IntroductionGate Logic: CAD Tools for Simplification

rows = prime implicantscolumns = ON-set elementsplace an "X" if ON-set element is covered by the prime implicant

Prime Implicant Chart

If column has a single X, than theimplicant associated with the rowis essential. It must appear inminimum cover

Page 31: Gate Logic: Two-Level Simplification

2-31

IntroductionGate Logic: CAD Tools for SimplificationPrime Implicant Chart (Continued)

Eliminate all columns covered byessential primes

Page 32: Gate Logic: Two-Level Simplification

2-32

IntroductionGate Logic: CAD Tools for SimplificationPrime Implicant Chart (Continued)

Eliminate all columns covered byessential primes

Find minimum set of rows thatcover the remaining columns

F= A B' D' + A C' D + A' BF= A B' D' + A C' D + A' B

Page 33: Gate Logic: Two-Level Simplification

2-33

IntroductionGate Logic: CAD Tools for SimplificationESPRESSO Method

Problem with Quine-McCluskey: the number of prime implicants grows rapidly with the number of inputs

upper bound: 3 /n, where n is the number of inputsn

finding a minimum cover is NP-complete, i.e., a computational expensive process not likely to yield to any efficient algorithm

Espresso: trades solution speed for minimality of answer

don't generate all prime implicants (Quine-McCluskey Stage 1)

judiciously select a subset of primes that still covers the ON-set

operates in a fashion not unlike a human finding primes in a K-map

Page 34: Gate Logic: Two-Level Simplification

2-34

IntroductionGate Logic: CAD Tools for SimplificationEspresso Method: Overview

1. Expands implicants to their maximum sizeImplicants covered by an expanded implicant are removed from further considerationQuality of result depends on order of implicant expansionHeuristic methods used to determine orderStep is called EXPAND

Irredundant cover (i.e., no proper subset is also a cover) is extracted from the expanded primesJust like the Quine-McCluskey Prime Implicant ChartStep is called IRREDUNDANT COVER

Solution usually pretty good, but sometimes can be improvedMight exist another cover with fewer terms or fewer literalsShrink prime implicants to smallest size that still covers ON-setStep is called REDUCE

Repeat sequence REDUCE/EXPAND/IRREDUNDANT COVER to find alternative prime implicantsKeep doing this as long as new covers improve on last solution

A number of optimizations are tried, e.g., identify and remove essential primes early in the process

2.

3.

4.

5.

Page 35: Gate Logic: Two-Level Simplification

2-35

IntroductionGate Logic: CAD Tools for SimplificationEspresso Inputs and Outputs

.i 4

.o 1

.ilb a b c d

.ob f

.p 100100 10101 10110 11000 11001 11010 11101 10000 -0111 -1111 -.e

-- # inputs-- # outputs-- input names-- output name-- number of product terms-- A'BC'D'-- A'BC'D-- A'BCD'-- AB'C'D'-- AB'C'D-- AB'CD'-- ABC'D-- A'B'C'D' don't care-- A'BCD don't care-- ABCD don't care-- end of list

F(A,B,C,D) = m(4,5,6,8,9,10,13) + d(0,7,15)

Espresso Input Espresso Output

.i 4

.o 1

.ilb a b c d

.ob f

.p 31-01 110-0 101-- 1.e

F= A C' D + A B' D' + A' B

Page 36: Gate Logic: Two-Level Simplification

2-36

IntroductionGate Logic: CAD Tools for Simplification

Espresso: Why Iterate on Reduce, Irredundant Cover, Expand?

Initial Set of Primes found bySteps1 and 2 of the Espresso

Method

4 primes, irredundant cover,but not a minimal cover!

Result of REDUCE:Shrink primes while still

covering the ON-set

Choice of order in which to perform shrink is important

AB

CD 00 01 11 10

00

01

11

10

D

B

C

A

1 1 0 0

1 1 1 1

0 0 1 1

1 1 1 1

AB

CD 00 01 11 10

00

01

11

10

D

B

C

A

1 1 0 0

1 1 1 1

0 0 1 1

1 1 1 1

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IntroductionGate Logic: CAD Tools for SimplificationEspresso Iteration (Continued)

Second EXPAND generates adifferent set of prime implicants

IRREDUNDANT COVER found byfinal step of espresso

Only three prime implicants!

AB

CD 00 01 11 10

00

01

11

10

D

B

C

A

1 1 0 0

1 1 1 1

0 0 1 1

1 1 1 1

AB

CD 00 01 11 10

00

01

11

10

D

B

C

A

1 1 0 0

1 1 1 1

0 0 1 1

1 1 1 1

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IntroductionPractical Matters

Technology Metrics

Metric Bipolar MOS

Gate Delay Low Medium

Integration Low High

Power High Low

Noise Good Good

Cost Low Medium

Fan-out Fair Good

Drive Good Low

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IntroductionPractical Matters

TTL Packaged Logic

Small and Medium Scale Integration dual in-line package (DIP)

Subfamilies of TTL Components have been designed so that they can be interconnected without too much concern about proper electrical operation

74XX 74HXX : high speed 74LXX : low power 74SXX : Schottsky TTL, faster than 74HXX and same power as 74LXX 74LSXX : low power Schottsky TTL AS TTL : 2 times faster than S TTL ALS TTL : less power than LS TTL with higher speed

Speed-Power Product compare the efficiency of logic families multiply the delay through a gate by the power it consumes smaller number - reduced delay and reduced power

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IntroductionPractical Matters

Schematic Documentation Standards

Standard Schematic Symbols

Names

Polarization and Bubbles

Crossovers and Connections

Hierarchical Documentation and Cross-References

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IntroductionPractical Matters

Standard SSI gate symbols

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IntroductionPractical Matters

• MSI component schematic

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IntroductionPractical Matters

• Use of a detail letter

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IntroductionPractical Matters

• Example of polarity inversion

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IntroductionPractical Matters

• Incorrect bubble matching

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IntroductionPractical Matters

• Correct bubble matching

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IntroductionPractical Matters

• A case where polarity and bubbles don’t match

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IntroductionPractical Matters

• Wiring connection(top) and crossover(bottom)

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IntroductionChapter Summary

Primitive logic building blocksINVERTER, AND, OR, NAND, NOR, XOR, XNOR

Canonical FormsSum of Products, Products of Sums

Incompletely specified functions/don't cares

Logic Minimization

Goal: two-level logic realizations with fewest gates and fewest number of gate inputs

Obtained via Laws and Theorems of Boolean Algebra

or Boolean Cubes and the Uniting Theorem

or K-map Methods up to 6 variables

or Quine-McCluskey Algorithm

or Espresso CAD Tool