Apparatus and method for product term allocation in programmable logic
AssigneeIntel Corporation
InventorRandy C. Steele
Life of this patent
Estimating the term…
Abstract
In a programmable logic device having a plurality of gates capable of being programmed according to a plurality of product terms representing logic functions, an apparatus for allocating the product terms to a plurality of outputs. A first set of product terms are steerable to one of at least two outputs. A second set of product terms is permanently assigned to a predetermined output. The second set is comprised of more product terms than the first set, wherein the average number of product terms per output is low, yet a user has the flexibility of implementing logic functions requiring a relatively large number of product terms.
Claims20
In a field programmable gate array chip having a plurality of gates capable of being programmed according to a plurality of product terms for performing a particular logic function, an input means for inputting a signal, a means for processing said signal according to said logic function, a plurality of output means for outputting said signal after said signal has been processed, an apparatus for allocating said plurality of product terms to said plurality of output means comprising:
- a means for selecting one of said plurality of output means;
- a means for steering at least one of said product terms to a selected output means;
- a means for assigning a number of said product terms to a particular predetermined output means, wherein a maximum number of product terms assignable to said particular predetermined output means is more than twice an average number of product terms available for one of said output means.
A programmable logic circuit comprising:
- a plurality of programmable AND gates for implementing a plurality of product terms representing logic functions of a digital circuit;
- a plurality of OR gates for implementing sum of products;
- a plurality of programmable macrocells for outputting said sum of products;
- a product term allocation means for directing a first set of product terms to one of at least two adjacent macrocells, wherein at least one of said plurality of macrocells has a second set of product terms permanently assigned to said macrocell, said number of product terms in said second set is greater than a number of product terms in said first set;
- and
- wherein said first set is comprised of at least two product terms and said second set is comprised of at least twelve product terms.
In a programmable logic device having a plurality of AND gates for implementing a plurality of product terms representing logic functions, a plurality of OR gates for implementing sums of products, a plurality of macrocells for outputting said sums of products, a method of allocating said product terms to said macrocells comprising the steps of:
- providing a first set of product terms permanently assigned to one of said macrocells;
- providing a second set of product terms which can be directed to one of at least two of said plurality of macrocells, wherein said second set is comprised of less product terms than said first set;
- selecting said one of at least two of said plurality of macrocells;
- directing said second set of product terms to said selected macrocells;
- implementing a multiplexer to control said selecting step;
- feeding back signals internal to said macrocells and signals on input/output pins to said AND gates;
- and implementing at least twelve product terms for said first set and at least two product terms for said second set.
A computer system having a programmable logic, comprising:
- a plurality of programmable AND gates for implementing a plurality of product terms representing a plurality of logic equations;
- a plurality of OR gates for implementing sums of products;
- a plurality of macrocells for outputting said sums of products;
- a product allocation means, wherein at least sixteen product terms are assigned to one of said macrocells and said programmable logic device is comprised of an average of six product terms per macrocell.
Dependencies are inferred from the claim text.