Importance

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Abstract

A programmable integrated circuit includes configurable logic blocks (CLB's), configurable input/output blocks (IOB's) and a configurable interconnect network for providing program-defined routing of signals between the CLB's and IOB's. Each CLB includes a lookup table having inputs and outputs, a first multiplexer means for applying a selected subset of CLB input signals to the lookup table inputs, and a second multiplexer means for routing lookup table output signals to selectable destinations. The first multiplexer means can programmably route input signals to the lookup table inputs from a variety of sources including first through fourth direct-connect receiving terminals distributed symmetrically about the CLB, first through fourth longline receiving terminals distributed symmetrically about the CLB, first through fourth general-interconnect receiving terminals distributed symmetrically about the CLB, and first through fourth feedback means distributed symmetrically within the CLB. The second multiplexer means can programmably route output signals from the lookup table to first through fourth output macrocells distributed symmetrically about the CLB. The first through fourth output macrocells can respectively couple the routed signals to first through fourth direct-connect outputting terminals distributed symmetrically about the CLB, first through fourth tristate outputting terminals distributed symmetrically about the CLB, and the first through fourth feedback means.

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