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In a programmable logic device having a specialized functional block incorporating multipliers and adders, multiplication operations that do not fit neatly into the available multipliers are performed partially in the multipliers of the specialized functional block and partially in multipliers confi

In a programmable logic device having a specialized functional block incorporating multipliers and adders, multiplication operations that do not fit neatly into the available multipliers are performed partially in the multipliers of the specialized functional block and partially in multipliers configured in programmable logic of the programmable logic device. Unused resources of the specialized functional block, including adders, may be used to add together the partial products produced inside and outside the specialized functional block. Some adders configured in programmable logic of the programmable logic device also may be used for that purpose.

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What is claimed is: 1. A specialized functional block for use in a programmable logic device, said specialized functional block comprising: a plurality of block inputs; a plurality of dedicated multiplier circuits having multiplier inputs connected to said block inputs, and having multiplier output

What is claimed is: 1. A specialized functional block for use in a programmable logic device, said specialized functional block comprising: a plurality of block inputs; a plurality of dedicated multiplier circuits having multiplier inputs connected to said block inputs, and having multiplier outputs; a plurality of first-level dedicated adder circuits having first-level adder inputs and first-level adder outputs; and programmable connections between said multiplier outputs and said first-level adder inputs whereby said specialized functional block is configurable to add together in said first-level adders products output by said dedicated multiplier circuits; wherein: said programmable connections include respective programmable bit-shifting circuitry associated with each respective one of said dedicated multiplier circuits, for programmably shifting, to more significant bits, bits of said product output by said respective one of said dedicated multiplier circuits, said respective programmable bit shifting circuitry comprising bit diversion circuitry for diverting bits of lesser significance, in a respective product output by said respective one of said dedicated multiplier circuits, from said first-level adder inputs. 2. The specialized functional block of claim 1 further comprising: a second-level dedicated adder circuit for adding together sums output by said first-level dedicated adder circuits, said second-level dedicated adder circuit having second-level adder inputs programmably connected to said block inputs; whereby: data on said block inputs is added to a sum output by one of said first-level dedicated adder circuits. 3. A programmable logic device comprising the specialized functional block of claim 1. 4. A digital processing system comprising: processing circuitry; a memory coupled to said processing circuitry; and a programmable logic device as defined in claim 3 coupled to the processing circuitry and the memory. 5. A printed circuit board on which is mounted a programmable logic device as defined in claim 3. 6. The printed circuit board defined in claim 5 further comprising: memory circuitry mounted on the printed circuit board and coupled to the programmable logic device. 7. The printed circuit board defined in claim 6 further comprising: processing circuitry mounted on the printed circuit board and coupled to the memory circuitry. 8. An integrated circuit device comprising the specialized functional block of claim 1. 9. A digital processing system comprising: processing circuitry; a memory coupled to said processing circuitry; and an integrated circuit device as defined in claim 8 coupled to the processing circuitry and the memory. 10. A printed circuit board on which is mounted an integrated circuit device as defined in claim 8. 11. The printed circuit board defined in claim 10 further comprising: memory circuitry mounted on the printed circuit board and coupled to the integrated circuit device. 12. The printed circuit board defined in claim 11 further comprising: processing circuitry mounted on the printed circuit board and coupled to the memory circuitry. 13. A specialized functional block for use in a programmable logic device, said specialized functional block comprising: a plurality of block inputs; a plurality of dedicated multiplier circuits having multiplier inputs connected to said block inputs, and having multiplier outputs; a plurality of first-level dedicated adder circuits having first-level adder inputs and first-level adder outputs; first programmable connections between said multiplier outputs and said first-level adder inputs whereby said specialized functional block is configurable to add together in said first-level adders products output by said dedicated multiplier circuits; respective bit diversion circuitry associated with each respective one of said dedicated multiplier circuits, for diverting bits of lesser significance, in a respective product output by said respective one of said dedicated multiplier circuits, from said first-level adder inputs; a second-level dedicated adder circuit, having second-level adder inputs, for adding together sums output by said first-level dedicated adder circuits; and second programmable connections between said block inputs and said second-level adder inputs for adding data on said block inputs to a sum output by one of said first-level dedicated adder circuits. 14. A programmable logic device comprising the specialized functional block of claim 13. 15. A digital processing system comprising: processing circuitry; a memory coupled to said processing circuitry; and a programmable logic device as defined in claim 14 coupled to the processing circuitry and the memory. 16. A printed circuit board on which is mounted a programmable logic device as defined in claim 14. 17. The printed circuit board defined in claim 16 further comprising: memory circuitry mounted on the printed circuit board and coupled to the programmable logic device. 18. The printed circuit board defined in claim 17 further comprising: processing circuitry mounted on the printed circuit board and coupled to the memory circuitry. 19. An integrated circuit device comprising the specialized functional block of claim 13. 20. A digital processing system comprising: processing circuitry; a memory coupled to said processing circuitry; and an integrated circuit device as defined in claim 19 coupled to the processing circuitry and the memory. 21. A printed circuit board on which is mounted an integrated circuit device as defined in claim 19. 22. The printed circuit board defined in claim 21 further comprising: memory circuitry mounted on the printed circuit board and coupled to the integrated circuit device. 23. The printed circuit board defined in claim 22 further comprising: processing circuitry mounted on the printed circuit board and coupled to the memory circuitry. 24. A specialized functional block for use in a programmable logic device, said specialized functional block comprising: a plurality of block inputs; a plurality of dedicated multiplier circuits having multiplier inputs connected to said block inputs, and having multiplier outputs; a plurality of dedicated adder circuits having adder inputs and adder outputs; first programmable connections between said multiplier outputs and said adder inputs whereby said specialized functional block is configurable to add together in said adders products output by said dedicated multiplier circuits, said first programmable connections including respective bit diversion circuitry associated with each respective one of said dedicated multiplier circuits, for diverting bits of lesser significance, in a respective product output by said respective one of said dedicated multiplier circuits, from said adder inputs; and second programmable connections between said block inputs and said adder inputs for adding data on said block inputs to a product output by one of said dedicated multiplier circuits. 25. A programmable logic device comprising the specialized functional block of claim 24. 26. A digital processing system comprising: processing circuitry; a memory coupled to said processing circuitry; and a programmable logic device as defined in claim 25 coupled to the processing circuitry and the memory. 27. A printed circuit board on which is mounted a programmable logic device as defined in claim 25. 28. The printed circuit board defined in claim 27 further comprising: memory circuitry mounted on the printed circuit board and coupled to the programmable logic device. 29. The printed circuit board defined in claim 28 further comprising: processing circuitry mounted on the printed circuit board and coupled to the memory circuitry. 30. An integrated circuit device comprising the specialized functional block of claim 24. 31. A digital processing system comprising: processing circuitry; a memory coupled to said processing circuitry; and an integrated circuit device as defined in claim 30 coupled to the processing circuitry and the memory. 32. A printed circuit board on which is mounted an integrated circuit device as defined in claim 30. 33. The printed circuit board defined in claim 32 further comprising: memory circuitry mounted on the printed circuit board and coupled to the integrated circuit device. 34. The printed circuit board defined in claim 33 further comprising: processing circuitry mounted on the printed circuit board and coupled to the memory circuitry.