Lattice Semiconductor Corporation

Chong M Lee

Om P Agrawal

Larry R Metzger

Claudia A Stanley

Xiaojie (Warren) He

Kerry A Ilgenstein

Robert M Balzli, Jr

A method of assigning logic functions to macrocells assures that a maximum number of macrocells are assigned two or more logic functions. A first logic function is assigned to a macrocell without restriction. Rules are then applied to the macrocell to determine whether a second logic function may be assigned to the macrocell, and, if so, whether any restrictions exist on what the second logic function may be.

Method of assigning logic functions to macrocells in a programmable logic device

An improved, high density CPLD includes a plurality of macrocell sections. Each macrocell section can receive a relatively large number of independent input terms and can generate as a base cluster, at least as many as 5 different product term signals (PT's) therefrom. Part or all of the macrocell's local 5 PT's may be used for generating a local sum-of-products (SoP) signal in a local, first-level ORring operation. Additionally SoP's generated in neighboring macrocell sections may be selectively and incrementally cascaded (cross-laced) for supplemental summing into the local SoP signal. SoP signals of neighboring sections may be further selected in a sums sharing array for second level summing. The combination of the first-level cascading (cross-lacing) and second-level sums sharing provides a wide range of programmably selectable granulations including that of having relatively fast generation of a sum of just a few PT's (e.g., &lE;5 PT's) to having slower generation of sums of a much larger number of PT's (e.g., &lE;160 PT's).

Enhanced macrocell module having expandable product term sharing capability for use in high density CPLD architectures

An improved CPLD includes a plurality of macrocell modules (MM's) where each MM can receive a relatively large number of independent inputs (at least 80) and can generate at least 5 different product term signals (PT's) therefrom. All 5 PT's may be used for generating a local sum-of-products (SoP). Any of the 5 PT's may be stolen (steered-away) to instead provide a local control for its macrocell module. Each module includes a local SoS-producing gate that can produce a sums-of-sums signal (SoS) that represents a Boolean sum of one or more of the local SoP signal, of SoP signals of neighboring macrocell modules, and of SoS signals of neighboring macrocell modules. Simple allocation and super-allocation may be used to produce sums-of-sums signals of relatively large, one-pass function depth, such as 160PT's in one pass.

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Chong M Lee