Abstract In this paper a new conception of safety logic microcontroller (BML) is described, together with its physical hardware realization. The unit has various mechanisms which increase its safety and reliability, so that it can satisfy rigorous requirements of safety-critical systems. Thus, the BML unit uses some untypical and innovative technical solutions. The new approach to safety systems development allowed to propose a new conception. The paper describes also physical realization of small multiprocessor BML unit for management of decision-control systems adopted to critical usage.