Nuclear power plants have already adopted PROFIBUS and HART fieldbus intelligent instruments. However, most fieldbus devices are developed using dedicated protocol chips and embedded modules, which may have undetected security vulnerabilities. Hackers can exploit these vulnerabilities to infiltrate the instrumentation and control system of nuclear power plants, potentially leading to safety accidents. To address this issue, this paper conducts a technical study on implementing the PROFIBUS and HART protocol stacks based on microprocessor chips, FPGA chips, and self - developed code. PROFIBUS master station and HART master station devices are developed. These devices meet the requirements of autonomy at the physical layer and data link layer. After verification, they satisfy the technical requirements of the nuclear power instrumentation and control system based on fieldbus.