Apparatus and method for implementing efficient arithmetic circuits in programmable logic devices

Abstract

Efficient implementation of arithmetic circuits in programmable logic devices by using Look-Up Tables (LUTs) to store pre-calculated values. A table look-up operation is performed in place of complex arithmetic operations. In this way, at the expense of a few LUTs, many logic elements can be saved. This approach is particularly applicable to circuits for calculating reciprocal values and circuits for performing normalized LMS algorithm.

1 .- 10 . (canceled)  
   
   
       11 . A circuit for performing normalized least-mean-squared calculations, comprising: 
 an input for receiving a μ-Law encoded data value; and    a look-up table coupled to the input, the look-up table having stored therein a plurality of pre-calculated intermediate data values, the pre-calculated intermediate data values being operands for normalized least-mean-squared calculations, wherein the look-up table is configured to provide a corresponding one of the re-calculated intermediate data values in response to the μ-Law encoded data value.    
   
   
       12 . The circuit of  claim 11 , wherein the plurality of pre-calculated intermediate data values comprise a plurality of pre-calculated μ-Law expansion values.  
   
   
       13 . The circuit of  claim 11 , wherein the look-up table stores a plurality of possible input values associated with the plurality of pre-calculated intermediate data values.  
   
   
       14 . The circuit of  claim 13 , wherein the look-up table uses the plurality of possible input values as indices.  
   
   
       15 . A circuit for performing normalized least-mean-squared calculations, comprising: 
 an input for receiving an A-Law encoded data value; and    a look-up table coupled to the input, the look-up table having stored therein a plurality of pre-calculated intermediate data values, the pre-calculated intermediate data values being operands of normalized least-mean-squared calculations, wherein the look-up table is configured to provide a corresponding one of the pre-calculated intermediate values in response to the A-Law encoded data value.    
   
   
       16 . The circuit of  claim 15 , wherein the plurality of pre-calculated intermediate data values comprise a plurality of pre-calculated A-Law expansion values.  
   
   
       17 . The circuit of  claim 15 , wherein the look-up table stores a plurality of possible input values associated with the plurality of pre-calculated intermediate data values.  
   
   
       18 . The circuit of  claim 17 , wherein the look-up table uses the plurality of possible input values as indices.  
   
   
       19 . A method of performing normalized least-mean-squared calculations, the method comprising: 
 receiving an input data, the input data comprising a μ-Law encoded data value; and    using the input data as an index to retrieve a pre-calculated intermediate data value from a look-up table, the look-up table having stored therein a plurality of pre-calculated intermediate values, wherein the pre-calculated intermediate data values comprise operands for normalized least-mean-squared calculations and correspond to a pre=determined range of μ-Law encoded data values.    
   
   
       20 . The method of  claim 19 , wherein the plurality of pre-calculated intermediate values comprise a plurality of pre-calculated i-Law expansion values.  
   
   
       21 . A method of performing normalized least-mean-squared calculations, the method comprising: 
 receiving a A-Law encoded data value; and    using the A-Law encoded data value as an index to retrieve a pre-calculated intermediate data value from a look-up table, the look-up table having stored therein a plurality of pre-calculated intermediate values, wherein the pre-calculated intermediate data values comprise operands for normalized least-mean-squared calculations and correspond to a pre-determined range of A-Law encoded data values.    
   
   
       22 . The method of  claim 21 , wherein the plurality of pre-calculated intermediate values comprise a plurality of pre-calculated A-Law expansion values.  
   
   
       23 .- 26 . (canceled)