MemoryIO, a sort of extended I/O in embedded systems, is presented in this paper. MemoryIO makes it powerful for embedded systems to achieve the high-performance interconnect. In view of the facts that the main memory system is absolutely necessary in any embedded system, and not all embedded systems integrate HyperTransport (HT), PCI Express or RapidIO interface, the MemoryIO based interconnect in embedded systems has more universalities compared with that based on HT, PCI Express or RapidIO. MemoryIO can not only thoroughly compensates for the lack of high performance data transfer channel, but also efficiently utilizes the memory bus bandwidth and the direct memory access (DMA) engine to reduce the latency for data transfer in embedded systems. This paper discusses some key technologies of MemoryIO, and presents its application in DCNet and the implementation of MemoryIO IP core. The MemoryIO technology can be used in various systems, but not limited to embedded systems.