The Design of an SRAM - BasedField - Programmable Gate Array , Part I

| Field-Programmable Gate Arrays (FPGAs) are now widely used for the implementation of digital systems and many commercial architectures are available. Although the literature and data books contain detailed descriptions of these architectures, there is very little information on how the high-level architecture was chosen and no information on the circuit-level or physical design of the devices. This paper, Part I, describes the high-level architectural design of an SRAM-programmable FPGA. Part II will address the circuit design issues through to the physical layout. The logic block and routing architecture of the FPGA was determined through experimentation with benchmark circuits and custom-built CAD tools. The resulting logic block is an asymmetric tree of four-input lookup tables that are hard-wired together and a segmented routing architecture with a carefully chosen segment length distribution.