Ring Shifter With Externally Selectable Modulus
Original Publication Date: 1985-Mar-01
Included in the Prior Art Database: 2005-Feb-18
This article describes a macro-type circuit for a ring shifter with externally selectable modules, which can be used in numerous places of VLSI system designs. More particularly, a ring shifter is described which provides a selectable modulus (i.e., selectable boundary at which the ring looping will occur) and a variable number of shifts. The modulus, Nc, is assumed to be stored as a binary value in a register or on 4 to 5 address lines. These signals supply the inputs to the modulus control gates, as shown in Figs. 1A, 1B and 1C. Only the logic for bits 1,2 (Fig. 1a) and 5 (Fig. 1b) are shown for a shifter having a maximum data width of Nm=8 and a minimum of 4, with a modulus varying from 4 to 8. For any given modulus value Nc, the number of shifts is less than or equal to Nc - 1.