Methods and apparatus are provided for performing circular buffer
addressing. Upper boundaries, lower boundaries, circular buffer lengths,
addresses, and offsets are set to allow circular buffer access
efficiency. An addition/subtraction unit is provided to simplify
implementation. Comparators are rearranged and in some instances replaced
with combined adder/comparator logic units. The additional logic units
and the rearrangement allow efficient implementation of circular buffer
addressing, particularly on programmable chips.