1.6 PLAs

PLAs are Programmable Logic Arrays. These devices contain both programmable AND and OR terms, which allow any AND term to feed any OR term. As a result, PLAs have greater flexibility than PALs with regard to logic functionality. They typically have feedback from the OR array back into the AND array, which may be used to implement asynchronous state machines. Most state machines, however, are implemented as synchronous machines. With this in mind, manufacturers created a type of PLA called a Sequencer, which has registered feedback from the output of the OR array into the AND array.