Modulo address generation method and apparatus

Abstract

A two-stage, pipelined modulo address generator (MAG) ( ′) for generating from a current pointer into a circular buffer of size L, a next pointer into the buffer, is comprised of a pointer generation stage ( ′) and a modulo correction and pointer selection stage ( ′), each adapted to operate in a selected one of two modes. In the first operating mode: the pointer generation stage ( ′) generates a sequential pointer which is a selected offset from the current pointer; and the modulo correction and pointer selection stage ( ′) generates, modulo L, a modulo corrected sequential pointer, and provides as the next pointer the sequential pointer, if it is in the buffer, and the modulo corrected sequential pointer, otherwise. In the second operating mode: the pointer generation stage ( ′) generates a lookahead pointer which is twice the selected offset from the current pointer; and the modulo correction and pointer selection stage ( ′) generates, modulo L, a modulo corrected lookahead pointer and, modulo 2L, a double-modulo corrected lookahead pointer, and provides as the next pointer the lookahead pointer, if it is in the buffer, the modulo corrected lookahead pointer, if the lookahead pointer is not in the buffer but the modulo corrected lookahead is in the buffer, and the double-modulo corrected lookahead pointer, otherwise.