Field-Programmable Gate Arrays (FPGAs)
Field-programmable gate arrays are given this name because they are structured very much like a gate array ASIC. Like an ASIC, the FPGA consists of a regular array of logic, an architecture that lends itself to very complex designs.
29.1 FPGA Architectures
Each FPGA vendor has its own FPGA architecture, but in general terms they are all a variation of that shown in Figure 29.1. The architecture consists of configurable logic blocks, configurable I/O blocks, and programmable interconnect to route signals between the logic blocks and I/O blocks. Also, there is clock circuitry for driving the clock signals to each flip-flop in each logic block. Additional logic resources such as ALUs, memory, ...