Programmable logic device with redundant circuitry

Abstract

A programmable logic device is provided that allows a redundant row of programmable logic to be shifted into place to repair the device when a defect is detected in a row of programmable logic on the device. The redundant row is shifted into place by routing programming data into the normal logic and the redundant logic while bypassing the row of logic containing the defect. Switching circuitry may be used to direct programming data into the serial inputs of various data registers that are then used to load the programming data into the device. The patterns of programmable connections that are made between programmable logic regions on the device and vertical and horizontal conductors also allow redundant logic to be shifted into place. Some connections between the logic and the horizontal and vertical conductors may be identical within a column to facilitate shifting. Other connections may only partially overlap between respective rows. The partially overlapping pattern allows the connections to be less regular, which increases flexibility when routing signals on the device.