Browse Prior Art Database

# High Speed Digital Comparators

IP.com Disclosure Number: IPCOM000088495D
Original Publication Date: 1977-Jun-01
Included in the Prior Art Database: 2005-Mar-04
Document File: 3 page(s) / 35K

IBM

## Related People

Weinberger, AW: AUTHOR

## Abstract

The structure of comparisons may be simplified, by its use of equal to or greater or equal to or less instead of equal, to aid in generating greater than or less than functions, respectively, and by the use of (EGR*)ij or (EL*)ij, instead of Eij to generate GRij or Lij, respectively, where (EGR*)ij is Eij with GRij included as don't care conditions, while (EL*)ij is Eij with Lij included as don't care conditions. Furthermore, a variety of carry-look-ahead methods can be used to speed up and/or reduce hardware of the comparator.

This text was extracted from a PDF file.
At least one non-text object (such as an image or picture) has been suppressed.
This is the abbreviated version, containing approximately 77% of the total text.

Page 1 of 3

High Speed Digital Comparators

The structure of comparisons may be simplified, by its use of equal to or greater or equal to or less instead of equal, to aid in generating greater than or less than functions, respectively, and by the use of (EGR*)ij or (EL*)ij, instead of Eij to generate GRij or Lij, respectively, where (EGR*)ij is Eij with GRij included as don't care conditions, while (EL*)ij is Eij with Lij included as don't care conditions. Furthermore, a variety of carry-look-ahead methods can be used to speed up and/or reduce hardware of the comparator.

Let Ai, Bi be the two n-bit numbers to be compared, where i = 0, ..., n1, high-to-low order

E = the function A equal to B

L = the function A less than B

GR = the function A greater than B

U = the function A unequal to B

EGR = the function A equal to ir greater than B

EL = the function A equal to or less that B

The functions L (A less than B) can be expressed as a function of single- bit functions, as show in Equations (1).

(Image Omitted)

Similarly, the function GR (A greater than B) can be expressed as a function of single-bit functions, as shown in Eqs. (2).

(Image Omitted)

The complement functions are shown in Eqs (3) and (4).

(Image Omitted)

Eqs. (5) and (6) illustrate one level of intermediate functions.

(Image Omitted)

Efficient implementations of (EL*)ij and (EGR*)ij generally take form of Eqs. (7) and (8).

(Image Omitted)

The complement functions of Eqs. (5) and (6) are shown in eqs. (9) and
(10).

1

P...