Programmable logic device macrocell with improved capability
AssigneeAltera Corporation
InventorsBruce B. Pedersen, John C. Costello
Life of this patent
Estimating the term…
Abstract
A macrocell for a programmable logic device includes circuitry for allowing a neighboring macrocell to borrow various numbers of the product terms of the macrocell. The macrocell can continue to make full use of its product terms that are not thus borrowed. This includes logically combining and registering the unborrowed product terms. The macrocell may include circuitry for feeding back to the AND array of the programmable logic device a combinatorial or registered signal of the macrocell, and also outputting such a combinatorial or registered signal from the macrocell. When a combinatorial signal is fed back, the register of the macrocell can be used for another signal of the macrocell.
Claims23
Macrocell circuitry for a programmable logic device comprising:
- a plurality of product term circuits, each of which produces a respective product term signal;
- product term utilization circuitry for using product term signals to produce a macrocell output signal;
- and
- programmable switching circuitry for allowing a plurality of different non-zero numbers of said product term signals to be used as product term signals by product term utilization circuitry of another macrocell on said programmable logic device, and for allowing product terms that are not thus used by said another macrocell to be used as product term signals by said product term utilization circuitry which produces said macrocell output signal.
Programmable logic device circuitry including a plurality macrocells, each of said macrocells comprising:
- a plurality of product term circuits, each of which produces a respective product term signal;
- first combinatorial circuitry for logically combining a first subplurality of said product term signals to produce a first combinatorial signal;
- second combinatorial circuitry for logically combining a second subplurality of said product term signals to produce a second combinatorial signal;
- third combinatorial circuitry for logically combining said first and second combinatorial signals and an allocate out signal from another of said macrocells;
- signal utilization circuitry for using an applied signal to produce an output signal of said macrocell;
- and
- switching circuitry which is programmable to select one of said first, second, and third combinatorial signals as an allocate out signal of said macrocell and to select one of said first, second, and third combinatorial signals as the signal applied to said signal utilization circuitry.
Macrocell circuitry for a programmable logic device comprising:
- a programmable array having a plurality of inputs and a plurality of outputs, each of said outputs being a programmable logical function of selected ones of said inputs;
- combinatorial circuitry for logically combining said outputs to produce a combinatorial signal;
- register circuitry for receiving and registering a signal dependent on at least one of said outputs and for producing a registered signal which is indicative of the signal received and registered by said register circuitry;
- a first programmable logic connector for applying to an input of said programmable array a feedback signal indicative of either said combinatorial signal or said registered signal;
- a second programmable logic connector for outputting from said macrocell circuitry an output signal indicative of either said signal dependent on at least one of said outputs or said registered signal;
- and
- programmable switching circuitry for selecting as said signal dependent on at least one of said outputs either a signal indicative of said combinatorial signal or a signal indicative of one of said outputs of said programmable array prior to combination with other outputs of said programmable array, said first programmable logic connector being connected so that it can select said combinatorial signal even if said programmable switching circuitry is not selecting a signal indicative of said combinatorial signal.
Dependencies are inferred from the claim text.