Programmable inverter circuit used in a programmable logic cell

Abstract

A programmable logic cell has four cell input nodes and a plurality of combinational logic circuits. Four inverter circuits are provided for programmably inverting respective input logic signals, each inverter circuit having an inverter input node connected to a respective cell input node for accepting its respective input logic signal therefrom. Each inverter is programmable into a first state wherein a logic signal representing the complement of the input logic signal is provided to the inverter output node, and a second state wherein a logic signal representing the non-complement of the input logic signal is provided to the inverter output node. The inverter circuits buffer their input logic signals in both their first and second states. A first logic gate of the plurality of combinational logic circuits has first and second inputs each connected to a respective output node of one of two of the four inverter circuits, and a second logic gate has first and second inputs each connected to a respective output node of one of the other two of the four inverter circuits. The inverter circuits may be implemented as XNOR gates.