Aiken Pang - Beginning FPGA: Programming Metal

Aiken Pang and Peter Membrey 2017

Aiken Pang 1 and Peter Membrey 2

F ield- p rogrammable g ate a rrays (FPGA) are a special type of integrated circuits (ICs ) or chip that can be programmed in the field after manufacture and has three basic building blocks: logic gates, flip-flops + memories, and wires. In this chapter we will quickly review what FPGA is and some of the things it can do.

An IC has input and/or output pins (the gray color in Figure ). The black box is the brain of the IC and most ICs have white or gray markings on top of the black box. Most of the ICs mention their specific functions in their datasheet (e.g., is it an amplifier, a processor, a counter, an Ethernet MAC, or a combination of the lot). If you read the FPGA's datasheets and are looking for a specific function, you will probably get very frustrated. Thats because they dont mention the purpose or any of the FPGAs feature sets. All you will be able to find is how many logic gates, how much memory, and how to program the FPGA, but you wont find functions or features. You just cannot figure them out from the datasheet.

FPGAs allow designers to modify their designs very late in the design cycle even after the end product has been manufactured and deployed in the field. Sound familiar? It should sound a lot like Windows updates or Android/Apple phone software updates. That's one of the most powerful and compelling features of an FPGA but please dont treat FPGA design as a software programming exercise for a microcontroller or processor. An FPGA is not a processor with software. It is an amazing device that allows the average person to create his or her very own digital circuit. You are designing a hardware digital circuit when you are creating an FPGA design. You are going to use a hardware description language (which, incidentally, is used by Intel CPU chip designers too) to design your FPGA. This is a very important concept. We will provide more details when we are putting together some example designs in the later chapters. In the following sections well provide a little bit more detail about field-programmable, gates, and arrays and what they can do.