A PROGRAMMABLE LOGIC DEVICE WITH MACROCELL CONTROLLED BY A PLA

摘要

A programmable logic device (PLD) includes a macrocell which controls the output path of the logic signals output by one or more logic arrays implementing user logic functions. Complex control terms are implemented and provided to the macrocell by a programmable logic array (PLA), which includes at least one (and typically a plurality) of Sum terms (OR gates) electrically programmably coupled to a plurality of Product terms (AND gates) receiving input logic signals. In a favorable embodiment, the PLD includes a plurality of macrocells coupled via a communication channel to the PLA which generates the control terms. The PLA has the advantage of improving density and flexibility, so that complex control terms may be implemented without the need to implement multiple paths through the user logic arrays, thereby avoiding decreases in speed and poaching of capacity from the user logic arrays.