A data processing method for safe Instrumentation and Control Systems (I&C Systems) based on data processing in safety I&C Systems consisting of self-diagnosable modules of the platform with the unified architecture, to use specifically developed computing facilities implemented in FPGA, to design and configure the modules with the unified architecture of the unified units, to use units operation in different clock domains and diversity technologies, to design and configure the computing facilities, to provide mutual diagnostics and self-diagnostics for hardware, computing facilities, interfaces and data transfer at both modular and system levels implemented by hardware design tools and module platform logic, to use different software for application diverse logic design, to provide I&C System functional safety, to simplify design of modules and I&C Systems, to provide unified process and diagnostics and self-diagnostics coverage, to simplify user operation, to simplify I&C System maintenance and support.