For the CERN LHC Run 3, the ALICE experiment completely redesigned the Inner Tracking System (ITS), which now consists of seven cylindrical layers instrumented with 24 120 Monolithic Active Pixel Sensors, covering an area of 10m$^2$ . The ITS is controlled and read out by 192 custom Readout Units, which employ commercial SRAM-based FPGAs and will operate in a radiation field, requiring specific FPGA design to ensure system reliability. This contribution focuses on the techniques developed for designing radiation tolerant finite state machines, discussing the theoretical background, the actual implementation, and their validation with fault injections and proton irradiation tests.