Hardwired Networks on Chip in FPGAs to Unify Functional and Con?guration Interconnects

We propose that networks on chip (NOC) are hardwired in Field-Programmable Gate Arrays (FPGA). Although some area of the FPGA then has a fixed function, this loss of flexibility is outweighed by the following benefits. First, implementation cost is much reduced. Second, a hardwired NOC solves physical problems such as timing closure and high cost of global wiring. Third, dynamic partial reconfiguration can be better exploited. Compared to current soft or firm interconnects, a hardwired NOC poses fewer restrictions on the (re)placement of IP blocks in the FPGA. Finally, we also propose that the hardwired NOC is used for both the functional interconnect between the IP blocks and the configuration interconnect that transports the bitstreams. We give a detailed overview of our NOC architecture, and its configuration and programming. The proposed scheme enhances the on-line generation of bitstreams and the on-line verification of loaded bitstreams to detect tampering with the device. In our experiment, a hardwired NOC has acceptable (≤ 10%) overhead for IP sizes with approximately 1400 lookup tables (LUT), enabling a fine-grained combined functional and configuration interconnect. A hardwired NOC offers significantly better functional performance than a soft NOC. Moreover, the configuration and programming of the hard NoC is much faster than when using a soft NOC.