Variable fixed multipliers using memory blocks

• US 6,943,579 B1
• Filed: 09/22/2003
• Issued: 09/13/2005
• Est. Priority Date: 12/20/2002
• Status: Expired due to Fees

• Current Assignee: Altera Corporation (Intel Corporation)
• Original Assignee: Altera Corporation (Intel Corporation)
• Inventors: Esposito, Benjamin, Hazanchuk, Asher
• Primary Examiner(s): Tan, Vibol
• Application Number:
  US10/668,449
• Time in Patent Office: 722 Days
• Field of Search: 326 38- 41, 708/505, 708/670, 708625-627, 708/230, 708/232, 708/620
• US Class Current: 326/39
• CPC Class Codes: G06F 2207/4802 Special implementations
• CPC Class Codes: G06F 7/523 Multiplying only

Abstract

A programmable logic device includes at least one RAM block generating a first multi-bit calculation result which may, but does not necessarily, involve a multiplication of two operands. A shift operation is driven by a second multi-bit calculation result shifts the second multi-bit calculation result by at least one bit to generate a shifted second multi-bit calculation result. A multi-bit adder coupled to the at least one RAM block adds the shifted second multi-bit calculation result to the first multi-bit calculation result.

Claims

1. A programmable logic device comprising:

at least one RAM block generating at least a first multi-bit calculation result;

a shift operation driven by a second multi-bit calculation result and that shifts the second multi-bit calculation result by at least one bit to generate a shifted second multi-bit calculation result; and

a multi-bit adder coupled to the at least one RAM block and which adds the shifted second multi-bit calculation result to the first multi-bit calculation result.

2. The programmable logic device of claim 1 wherein the at least one RAM block is configured with at least one look up table (“

LUT”

) for generating at least the first multi-bit calculation result.

3. The programmable logic device of claim 2 wherein the at least one LUT includes a first LUT for generating the first multi-bit calculation result and a second LUT for generating the second multi-bit calculation result.

4. The programmable logic device of claim 3 wherein the at least one RAM block includes:

a first input address port for inputting at least a first multi-bit word and the first LUT is configured to generate the first multi-bit calculation result the first multi-bit calculation result representing a multiplication of the first multi-bit word with at least a first predetermined coefficient; and

a second input address port for inputting at least a second multi-bit word and the second LUT is configured to generate the second multi-bit calculation result, the second multi-bit calculation result representing a multiplication of the first multi-bit word with at least a second predetermined coefficient.

5. The programmable logic device of claim 4 wherein the second predetermined coefficient is equal to the first predetermined coefficient.

6. The programmable logic device of claim 5 wherein the first multi-bit word is input into the first input address port substantially simultaneously with the second multi-bit word being input into the second input address port.

7. The programmable logic device of claim 6 wherein the first multi-bit word is a first portion of a larger multi-bit word and the second multi-bit word is a second portion of the larger multi-bit word.

8. The programmable logic device of claim 7 wherein the at least one RAM block includes a first RAM block and a second RAM block, the first RAM block being configured with the first LUT and the second RAM block being configured with the second LUT.

9. The programmable logic device of claim 7 wherein the first LUT and the second LUT are both included in a single RAM block having the first input address port and the second input address port.

10. The programmable logic device of claim 6 wherein the number of bits the shift operator shifts the second multi-bit calculation result is equal to the number of bits in the first multi-bit word.

11. The programmable logic device of claim 2 wherein the at least one RAM block includes an address port for inputting at least a first multi-bit word and a second multi-bit word and the at least one LUT includes a single LUT configured to generate at least the first multi-bit calculation result and a preliminary second multi-bit calculation result.

12. The programmable logic device of claim 11 wherein the first multi-bit calculation result represents a multiplication of the first multi-bit word with a predetermined coefficient and the preliminary second multi-bit calculation result represents a multiplication of the second multi-bit word with the predetermined coefficient.

13. The programmable logic device of claim 12 wherein at least the preliminary second multi-bit calculation result is fed into the multi-bit adder to generate the second multi-bit calculation result.

14. The programmable logic device of claim 13 further including at least one shift register that shifts based on a clock cycle and which inputs the first multi-bit word into the address port on a first clock cycle and inputs the second multi-bit word into the address port on a second clock cycle.

15. The programmable logic device of claim 14 wherein the first multi-bit word is a first portion of a larger multi-bit word and the second multi-bit word is a second portion of the larger multi-bit word.

16. The programmable logic device of claim 15 wherein an output of the multi-bit adder drives the shift operator and the output of the shift operation is fed back into the multi-bit adder.

17. The programmable logic device of claim 16 wherein the first multi-bit calculation result represents a multiplication of the first multi-bit word with a predetermined coefficient.

18. The programmable logic device of claim 16 wherein the first multi-bit calculation result represents a multiplication of a first portion of the first multi-bit word with a first coefficient summed with a multiplication of a second portion of the first multi-bit word with a second coefficient.

19. The programmable logic device of claim 18 wherein the input to the address port of the at least one RAM block includes a multi-bit bus driven by two smaller busses, each of the smaller busses including at least one shift register.

20. The programmable logic device of claim 1 wherein the shift operation and multi-bit adder are programmed programmable logic circuitry.

21. A programmable logic device comprising:

at least one RAM block configured with at least one LUT for generating at least a first multi-bit multiplication result;

a shift operation driven by a second multi-bit multiplication result and that shifts the second multi-bit multiplication result by at least one bit to generate a shifted second multi-bit multiplication result; and

an adder having a first input and a second input wherein the first input is driven by the first multi-bit multiplication result and the second input is driven by the shifted second multi-bit multiplication result, the adder adding the first multi-bit multiplication result to the second shifted multi-bit multiplication result.

22. The programmable logic device of claim 21 wherein the at least one RAM block includes at least a first LUT and a second LUT, the first LUT for generating the first multi-bit multiplication result and the second LUT for generating the second multi-bit multiplication result.

23. The programmable logic device of claim 22 wherein the at least on RAM block includes a first RAM block coupled to the adder and a second RAM block coupled to the shift operation.

24. The programmable logic device of claim 21 wherein an output of the adder drives the shift operation and the output of the shift operation is fed back into the multi-bit adder.

25. A method of carrying out a multi-bit calculation including:

inputting at least a first multi-bit word into at least one RAM block configured with at least one LUT;

generating at least a first multi-bit calculation result from the at least one LUT in the at least one RAM block;

generating at least a second multi-bit calculation result;

shifting the at least second multi-bit calculation result by at least one bit to generate a shifted second multi-bit calculation result; and

adding the shifted second multi-bit calculation result to the first multi-bit calculation result.

26. The method of claim 25 further including:

inputting a second multi-bit word into the at least one RAM block;

wherein configuring at least one LUT includes configuring a first LUT and a second LUT in the at least one RAM block;

generating at least a first multi-bit calculation result includes generating the first multi-bit calculation result from the first LUT; and

generating at least a second multi-bit calculation result includes generating the second multi-bit calculation result from the second LUT.

27. The method of claim 26 wherein:

generating at least a first multi-bit calculation result includes generating the first multi-bit calculation result representing a multiplication of the first multi-bit word with at least a first predetermined coefficient; and

generating at least a second multi-bit calculation result includes generating the second multi-bit calculation result representing a multiplication of the second multi-bit word with at least a second predetermined coefficient.

28. The method of claim 27 wherein the second predetermined coefficient is equal to the first predetermined coefficient.

29. The method of claim 28 wherein:

inputting the first multi-bit word into the at least one RAM block includes inputting the first multi-bit word into a first input address port in the at least one RAM block substantially simultaneously with inputting the second multi-bit word into a second input address port in the at least one RAM block.

30. The method of claim 29 wherein the first multi-bit word is a first portion of a larger multi-bit word and the second multi-bit word is a second portion of the larger multi-bit word.

31. The method of claim 30 wherein:

the at least one RAM block includes a first RAM block and a second RAM block; and

configuring at least one LUT includes configuring the first LUT in the first RAM block and configuring the second LUT is the second RAM block.

32. The method of claim 30 wherein configuring at least one LUT includes configuring the first LUT and the second LUT in a single RAM block having the first input address port and the second input address port.

33. The method of claim 25 further including inputting a second multi-bit word into the at least one RAM block and wherein:

configuring at least one LUT includes configuring a first LUT in the at least one RAM block to generate at least the first multi-bit calculation result from the first multi-bit word and a preliminary second multi-bit calculation result from the second multi-bit word; and

generating at least a second multi-bit calculation result includes generating the second multi-bit calculation result from an adder which adds shifted second multi-bit calculation result to the first multi-bit calculation result.

34. The method of claim 33 wherein:

generating the first multi-bit calculation result includes generating a result that represents multiplying the first multi-bit word with a predetermined coefficient; and

generating the preliminary second multi-bit calculation result includes generating a result that represents multiplying the second multi-bit word with the predetermined coefficient.

35. The method of claim 34 further including:

shifting the first multi-bit word into an address port in the at least one RAM block on a first clock cycle; and

shifting the second multi-bit word into the address port in the at least one RAM block on a second clock cycle.

36. The method of claim 35 wherein the first multi-bit word is a first portion of a larger multi-bit word and the second multi-bit word is a second portion of the larger multi-bit word.

37. The method of claim 33 wherein:

generating the first multi-bit calculation result includes generating a result that represents a multiplication of a first portion of the first multi-bit word with a first coefficient summed with a multiplication of a second portion of the first multi-bit word with a second coefficient.

38. The method of claim 37 including driving the address port of the at least one RAM block with a bus that is driven by two smaller busses, each of the smaller busses including at least one shift register.

39. The method of claim 25 wherein the multi-bit calculation is carried out in a programmable logic device.