Miniaturization, integrated design and comprehensive information utilization are increasing in popularity in embedded system design. In this paper, we present UM-BUS, an online fault-tolerant bus suited for embedded systems. UM-BUS is a high-speed, dynamic reconfigurable serial bus with N (≤32) concurrent lanes of mutual redundant structure. It provides the capability of remote memory accessing with maximum communication distance of up to 40 meters. In the case of allowing performance reduction of 50%, any faults in N/2 lanes can be tolerated by reconfiguring the lanes online. Based on the topology of UM-BUS, we introduce a new type of plug and play architecture for embedded systems. It can break the traditional chassis bounds of embedded systems by distributing their in-chassis modules to remote locations. Through an experimental validation system, we demonstrate the feasibility of UM-BUS on real-world applications.