A phase assignment method for virtual-wire-based hardware emulation

In a hardware emulator consisting of multiple field-programmable gate arrays (FPGAs), the utilization of the FPGA logic resource is usually very low due to the limitation on the number of I/O pins. Virtual wire technology not only increases the inter-FPGA communication capability, but it also increases the logic resource utilization by means of time division multiplexing (TDM). TDM allows one physical wire to be shared by multiple logical wires. For TDM to be effective, each transportation of an inter-FPGA signal must be carefully assigned to a slot of the time division. In this note, we show that the phase assignment problem is exactly same as the resource-constrained operation scheduling problem. We adopt the static-list scheduling heuristic for the task, and present some experimental results on a set of benchmark circuits from the MCNC. The experiments show that the proposed method can increase the number of effective I/O pins as many as ten times.