A Radiation-Tolerant, Multigigabit Serial Link Based on FPGAs

Multigigabit serial links implemented by means of static random access memory (SRAM)-based field-programmable gate arrays (FPGAs) are extensively used in trigger and data acquisition systems of high-energy physics experiments. Their usage is mostly in areas without radiation, due to the sensitivity of FPGA configuration memory to single-event upsets. In order to use these links in radiation environments, some mitigation techniques can be used. In this article, we present a bidirectional link running at 6.25 Gbps implemented in Xilinx Kintex-7 FPGAs. Transferred data are protected against radiation effects by means of a Reed-Solomon (RS) code and symbol interleaving. Logic features triple modular redundancy in critical blocks. The design includes a custom scrubber based on majority voting of configuration frames. Our custom protocol can vary the protection level of the RS code to cope with different rates of radiation-induced transmission errors, trading off the available bandwidth for reliability. We present the test results carried out using fault injection and a 62-MeV proton beam at the Istituto Nazionale di Fisica Nucleare (INFN) Laboratori Nazionali del Sud (Catania, Italy). We show the performance of the link in terms of mean time between failures and mean time between losses of lock.