FPGA (Field-Programmable Gate Array)

FPGA (Field-Programmable Gate Array) is a PAL, GAL, CPLD and other programmable devices based on the further development of the product. It is as specific integrated circuit (ASIC) in the field of a semi-custom circuits occurs, which addresses the lack of custom circuits, and programmable devices to overcome the existing shortcomings of a limited number of gates.BackgroundCurrently the hardware description language (Verilog or VHDL) of the complete circuit design can be simplified throughSynthesis and layout of a single, quick to the FPGA on the test burn is the proven technology of modern IC design mainstream. These components can be used to edit to achieve some basic logic gates (eg AND, OR, XOR, NOT) or a combination of more complex functions such as decoders or mathematical equations. In most of the FPGA inside, where these components can be edited also includes components such as memory triggers (Flip-flop) or other more complete memory block.System designers can be edited through the connection of the internal FPGA logic blocks connected together, like a breadboard was placed on a chip. After a factory finished FPGA logic blocks and connections can be changed according to the designer, so the FPGA can complete the required logic function.Generally speaking, than the FPGA ASIC (application specific integrated chip) slower, can not complete a complex design, and consume more power. But they also have many advantages such as fast product, can be modified to correct errors in the program and cheaper cost. Manufacturers may also offer cheap but poor editing of FPGA. Because these chips are relatively poor ability to edit, so these design development is done on the FPGA in general, and then transferred to a design similar to the ASIC chip. Another method is to use CPLD (complex programmable logic device equipment).The relationship between CPLD and FPGABack in the mid-1980s, FPGA devices have been rooted in the PLD. CPLD and FPGA, including some relatively large number of programmable logic unit. CPLD logic gate densities in the thousands to tens of thousands of logic cells between the FPGA usually in tens of thousands to several million.The main difference between CPLD and FPGA is their system architecture. CPLD is a bit restrictive structure. This structure consists of one or more editable, and the results of a logical group of columns and some relatively small amount of lock registers. The result is the lack of editing flexibility, but there can be expected to delay the connection unit and logic unit high ratio of benefits. The FPGA is connected with many units, so although it can be more flexible editing, but the structure is more complex.CPLD and FPGA Another difference is that most of the FPGA with high-level built-in module (such as adders and multipliers) and the built-in memory. Therefore, the important difference is that a lot of new FPGA support full or partial re-configuration of the system. Allowing them to design with dynamic reconfiguration of system upgrades or changes. Some FPGA devices can re-edit part of the normal operation of the other parts continue.