ABSTRACT
Traditional programmable logic devices (PLDs) and field programmable gate arrays (FPGAs) allow circuit designers to implement logic circuits with fewer chips relative to standard gate level designs based on primitive gates and flip-flops. As a result, layout and unit production costs are generally reduced. In this chapter, we use the term
programmable device
to refer to the class of moderately complex single-chip devices, in which the user in the field can program the function of the device. We include such devices as the programmable logic array (PLA), programmable array logic (PAL), programmable read-only memory (PROM), and the field programmable gate array (FPGA). Since most commercial vendors provide software design aids for mapping designs to their specific chips, initial design costs and time to market are low. Another important advantage of programmable device designs is
flexibility
. Design changes do not require physical changes to the printed circuit board as long as the revised functions still fit onto the same programmable chip. The low cost of design revisions makes programmable chips very
attractive for prototype design and low volume production. Designers often move up the design ladder once proven designs move into high volume production.
