Methods for implementing arithmetic functions with user-defined input and output formats
First Claim
1. Circuitry configured to implement a function, comprising:
- a generic approximation circuit that generates output values for the function;
memory for storing a table of pre-computed output values for the function, wherein the function comprises a fixed-point arithmetic function having an input range, and wherein the pre-computed output values in the table correspond to input values within the input range for which the generic approximation circuit is incapable of generating sufficiently accurate output values; and
a multiplexing circuit that receives the output values from the generic approximation circuit, that receives the pre-computed output values in the table, and that is configured to route output values from a selected one of the generic approximation circuit and the table to a multiplexer output.
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Abstract
Methods for implementing fixed-point functions with user-defined input/output ranges and formats on a programmable integrated circuit are provided. A particular function may include one or more input intrusion intervals where generic fixed-point approximation methods are not sufficiently precise. Output values for these intrusion intervals may be pre-computed during function generation time using a mathematical library running on a computer-aided design tool and stored in a lookup table. During normal operation of the integrated circuit, a multiplexing network may be used to select among values generated by generic approximation methods and values obtained from one or more lookup tables depending on the current input to the function.
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Citations
19 Claims
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1. Circuitry configured to implement a function, comprising:
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a generic approximation circuit that generates output values for the function; memory for storing a table of pre-computed output values for the function, wherein the function comprises a fixed-point arithmetic function having an input range, and wherein the pre-computed output values in the table correspond to input values within the input range for which the generic approximation circuit is incapable of generating sufficiently accurate output values; and a multiplexing circuit that receives the output values from the generic approximation circuit, that receives the pre-computed output values in the table, and that is configured to route output values from a selected one of the generic approximation circuit and the table to a multiplexer output. - View Dependent Claims (2, 3, 4, 5, 6, 7)
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8. A method for operating computing circuitry to implement a function, the method comprising:
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using a generic approximation circuit to generate output values for the function; using memory to store a table of pre-computed output values for the function; with a multiplexing circuit, receiving the output values from the generic approximation circuit and the pre-computed output values in the table and providing output values selected from one of the generic approximation circuit and the table; and with an address encoder, receiving an input to the function and outputting a control signal to the multiplexing circuit. - View Dependent Claims (9, 10, 11, 12, 13)
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14. A method for using design tools running on computing equipment to implement a function on an integrated circuit, the method comprising:
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with the design tools running on the computing equipment, receiving an input range for the function; with the design tools running on the computing equipment, identifying a generic approximation method that is used to generate output values for the function in a portion of the input range; and with the design tools running on the computing equipment, determining whether the input range includes an intrusion interval for which the generic approximation method exhibits insufficient accuracy. - View Dependent Claims (15, 16, 17, 18, 19)
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Specification