Performance Evaluation of a Novel Direct Table Lookup Method and Architecture with Application to 16-bit Integer Functions

We describe several integer function properties which in combination allow direct lookup tables to be reduced in size and structure to simpler lookup trees. Our principal result is a novel table lookup method based on a mapping of a lookup tree to a row-by-column ROM with pre and post processing logic substantially reducing the table size. Our lookup architecture allows common 16-bit integer functions such as multiplicative inverse, square, and the discrete log to be realized with table size of order 2-8 Kbytes, in comparison to the 128 Kbyte size of an arbitrary 16-bits-in 16-bits-out function table. The lookup methodology is illustrated with specific development of the 16-bit integer discrete-log function. Implementation for both unnormalized and normalized indices are synthesized into standard cell netlists and performance and area results are given that demonstrate their effectiveness.