Programmable logic cell

摘要

A programmable logic cell (70) has four logic gates, two of which are configurable. The two configurable logic gates (88a,b) are positioned near the logic cell inputs. Each configurable logic gate (88a,b) has two inputs, each input being connected to one of the four logic cell inputs. The remaining two logic gates (90a,b) receive the outputs (100a,b) of the configurable logic gates (88a,b). Four independent logic cell input nodes (84a-d) are provided, each having associated therewith a programmable input multiplexer (78a-d). Each input multiplexer (78a-d) can have inputs connected to at least two types of interconnect conductors (L1-L4,72a,74a). The cell (70) also has two output paths, each having associated therewith an independently-controlled output multiplexer (98a,b). The output (116a,b) of each output multiplexer (98a,b) is connected to an input (104a,b) of the other output multiplexer (98a,b). Additional features include a multiplexer (96) having inputs (o,p) connected to two cell input nodes (84b,c), a select input (M) connected to a third logic cell input node (84a), and an output connected to a cell output node (116a); a system low-skew data (e.g., clock) input clock available to at least one of the input multiplexers (78a-d); a flip-flop (92) connected within the logic cell (70); and internal cell feedback (112). The preferred method of programming utilizes user-programmed SRAM memory cells (M1-M28; Fig.10). <IMAGE>