Electronic digital logic circuitry – Multifunctional or programmable – Array
Patent
1998-06-09
2000-03-07
Santamauro, Jon
Electronic digital logic circuitry
Multifunctional or programmable
Array
326 41, H03K 19177
Patent
active
060345462
ABSTRACT:
A macrocell for a programmable logic device includes a carry generator for generating a carry input to the macrocell, the carry generator having an inverting input and at least one non-inverting input. A carry decoupler controls the carry generator and allows any macrocell to be decoupled from a next adjacent macrocell. An XOR gate having a first input is coupled to the output of the carry generator and a second input thereof is connected to a logic input to the macrocell. A register is coupled to the output of the XOR gate. A macrocell output selector includes a first input coupled to an output of the register and a second input coupled to the output of the XOR gate. A method for implementing a carry chain for macrocells within a product term based programmable logic device according to the present invention includes the steps of logically ANDing a carry input with a user-configurable input to produce an intermediate result; selecting one of two carry input product terms from a product term array based upon the intermediate result, the selected carry product term being a carry input to a current macrocell; propagating the carry input of the current macrocell to a next macrocell; and repeating the ANDing, selecting and propagating steps until a last macrocell of the chain is reached.
REFERENCES:
patent: 5220214 (1993-06-01), Pedersen
patent: 5245226 (1993-09-01), Hodd, Jr. et al.
patent: 5359242 (1994-10-01), Veenstra
patent: 5481206 (1996-01-01), New et al.
Jones Christopher W.
Marshall Jeffery Mark
Cypress Semicondutor Corp.
Le Don Phu
Santamauro Jon
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