Lattice Semiconductor Corporation
Flexible ripple mode device implementation for programmable logic devices

Abstract:

Various techniques are provided to efficiently implement user designs in programmable logic devices (PLDs). In one example, a programmable logic device (PLD) includes a plurality of programmable logic blocks (PLBs) and a plurality of logic cells within at least one of the PLBs, where each logic cell includes a four input lookup table (4-LUT) configured to provide a 4-LUT output signal to associated carry logic. Each logic cell is configurable according to at least two selectable operational modes including a logic function output mode and a ripple arithmetic output mode, and at least three of the 4-LUT inputs are interchangeable when a selected operational mode comprises the ripple arithmetic output mode.