Multi-core processors point out the mainstream direction of processor development, but there are many challenges in hard real-time assurance. By analyzing the real-time requirements and the current application of multi-core processors, we propose an asymmetric multiprocessing program based on general-purpose processors. In this study, we focus on the overall software design, the management of shared resources, and the designs of image loading and starting of slave processors and inter-core communication in the asymmetric multiprocessing mode. The low-voltage protection device for measuring and control is developed by ourprogram, and its on-site operation shows that the program meets the real-time performance requirements of secondary power equipment.