No abstract

Creating a new FPGA is a challenging undertaking because of the significant effort that must be spent on circuit design, layout and verification. It currently takes approximately 50 to 200 person years from architecture definition to tape-out for a new FPGA family. Such a lengthy development time is necessary because the process is primarily done manually. Simplifying and shortening the design process would be advantageous since it could reduce the time to market for new FPGAs while also enhancing architecture explorations. One way to accomplish this is through automation and, in this paper, we describe our efforts to automate the entire process by making use of a previously developed set of tools that assist in the creation of the repeatable FPGA tile [25]. Our aim is to demonstrate the feasibility of a CAD flow that uses an input FPGA architecture description to generate a layout that can be sent for fabrication. We prove the feasibility of this proposition by actually designing and fabricating a complete FPGA. Initial functional testing of the FPGA appears promising but is inconclusive at this time. Through this architecture to layout process, we investigate the issues that are faced in the architecture selection, circuit design, layout and verification of such an automatically produced FPGA. We found that there are significant savings in design time. As well, we demonstrate that we can produce a layout using automated tools that is only 36% larger than a commercial FPGA device layout. Given the significant time savings and the relatively minor area penalty, we feel that this work demonstrates that automated layout of FPGAs is practical and advantageous.

No abstract

One of the most difficult and time-consuming steps in the creation of an FPGA is its transistor-level design and physical layout. Modern commercial FPGAs typically consume anywhere from 50 to 200 man-years simply in the layout step. To date, automated tools have only been employed in small parts of the periphery and programming circuitry. The core tiles, which are repeated many times, are subject to painstaking manual design and layout. In this paper we present a new system (called GILES, for Good Instant Layout of Erasable Semiconductors) that automatically generates a transistor-level schematic from a high-level architectural specification of an FPGA. It also generates a cell-level netlist that is placed and routed automatically. The architectural specification is the one used as input to the VPR [3] architectural exploration tool. The output is the mask-level layout of a single tile that can be replicated to form an FPGA array. We describe a new placement tool that simultaneously places and compacts the layout to minimize white space and wiring demand, and a special-purpose router built for this task. GILES can place and route a tile consisting of four 4-input LUT logic cells and all of its programmable wires in a 0.18µm CMOS process using 8 layers of metal and 25983µm 2 of area. When we generate the layout of an architecture similar to the Xilinx Virtex-E FPGA (built in a 0.18µm process) GILES requires only 47% more area than the original. The layout area of an architecture similar to the Altera Apex 20K400E (also built in a 0.18µm process) constructed by GILES requires 97% more area than the original.

One of the most difficult and time-consuming steps in the creation of an FPGA is its transistor-level design and physical layout. Modern commercial FPGAs typically consume anywhere from 50 to 200 man-years simply in the layout step. To date, automated tools have only been employed in small parts of the periphery and programming circuitry. The core tiles, which are repeated many times, are subject to painstaking manual design and layout. In this paper we present a new system (called GILES, for Good Instant Layout of Erasable Semiconductors) that automatically generates a transistor-level schematic from a high-level architectural specification of an FPGA. It also generates a cell-level netlist that is placed and routed automatically. The architectural specification is the one used as input to the VPR [3] architectural exploration tool. The output is the mask-level layout of a single tile that can be replicated to form an FPGA array. We describe a new placement tool that simultaneously places and compacts the layout to minimize white space and wiring demand, and a specialpurpose router built for this task.GILES can place and route a tile consisting of four 4-input LUT logic cells and all of its programmable wires in a 0.18µm CMOS process using 8 layers of metal and 25983µm 2 of area. When we generate the layout of an architecture similar to the Xilinx Virtex-E FPGA (built in a 0.18µm process) GILES requires only 47% more area than the original. The layout area of an architecture similar to the Altera Apex 20K400E (also built in a 0.18µm process) constructed by GILES requires 97% more area than the original.