Programmable Logic Implementation
Mark S. Nixon · 1995
Implementation of digital circuits historically concerned finding a selection of chips that had the right functionality and the right attributes. Design was then a process of intimate knowledge and use of data books (and suppliers!). Nowadays programmable systems dominate design, though, often for reasons of cost, standard devices are still used where appropriate, including in particular buffers and registers. Programmable implementations require a language to specify the operation of the programmable logic device (PLD). There are many, often specific to a particular manufacturer, their programming (or development ) system, or their device technology. The main programmable technologies are: memory — using (computer) memory chips to implement logic functions; programmable array logic — where fixed logic outputs are driven by programmable inputs; programmable logic arrays — where programmable inputs drive programmable outputs; gate arrays — which provide collections of uncommitted gates and the designer specifies how the gates are connected together; and application specific integrated circuits — where the designer uses gates with interconnection specific to a chosen application.