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US 2008/0270441 A1Published application
Sparse-coded look-up table
AssigneeWolfson Microelectronics plc
InventorDavid Richard Eke
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AssigneeWolfson Microelectronics plc
InventorDavid Richard Eke
Estimating the term…
A look-up table (LUT) is arranged as a plurality of rows each indexed by an index value and storing at least a coefficient for each index value for use in processing digital data. The LUT contains repeated sections in which m coefficients stored for successive index values form a cycle. The number m is not an integer power of 2. For example the LUT may be used when converting a digital count to a gain in dB, in which case m may be 6 or 12, the coefficients representing dB or fractional-dB steps in gain. The LUT contains n additional blank rows inserted after every repeated section of m rows storing the cycle of m coefficients, n being 1 or more and (m+n) being an integer power of two (such as 8 or 16). By feeding an initial index value through encoding logic which takes account of the additional rows, it can be ensured that these are never indexed. Thus, a sparse-coded LUT is provided. Although each repeated section is increased in size, the actual size of the LUT in terms of circuit area or programming logic is reduced because the repeating length is now a power of two.
A logic system comprising:
A LUT arranged as a plurality of rows each indexed by an index value and storing at least a coefficient associated with each index value, the coefficients stored for successive index values forming a series which repeats after a non-binary-length number m of coefficients, such that the same series of coefficients is repeated a plurality of times within the LUT,
A method of converting first digital data to second digital data using a LUT by applying an index to a LUT having, for each possible index value, a row containing a corresponding coefficient, the coefficients repeating in a cycle after a series of said rows of a number which is not an integer power of two, and applying the corresponding coefficient to the first digital data to obtain the second digital data, the method comprising a step of providing, in the LUT, one or more blank rows in association with each series of rows containing said cycle of coefficients, the number of blank rows when added to the series of rows forming an integer power of two.
Dependencies are inferred from the claim text.