Design And Implementation Of UM-BUS Transport Layer

As technology advances and application requirements, aerospace and other applications require embedded systems with higher reliability, security and supportability. The bus as an important part of the system, have a major impact on its reliability, size and weight. In order to meet the high raliabibity, high secutity requirements for embedded systems in aerospace applications, UM-Bus was designed and implemented. It has the following features:It provides serial, high-speed, half-duplex, bi-directional data links which connect together enabled equipments directly. The physical layer of UM-BUS uses multipoint low voltage differential signaling (MLVDS)so that nodes can be connected directly, the maximum number of the nodes can reach to30. It has2to32communication channels where data can transmission concurrently, all lanes must fail before the system fails and the maximum communication rate is6.4Gbps. The UM-BUS can reconfigure the communication lanes automatically when fault is detected, in that way the reliability of the system and real-time capability can be significantly improved.The automatic reconfiguration of the Data packets based on the number of the health physical lanes is the key to the implementation of dynamic reconfiguration for UM-BUS.It can redistribute the whole data packets into small groups evenly, which can be retransmitted through the health lanes. The Transport layer of UM-Bus is responsible for the automatic reconfiguration of the Data packets, which is the main content of this paper and it’s researched by following three aspects:First, according to characteristics of the Physical layer, the MAC layer and the Transaction Layer, define the requirement and function of the Transport layer:it is mainly responsible for the data transmissiong of the Physical layer and the Transaction Layer.It distribute the Data packets to healthy lanes of the Physical layer when sending packets and organize the Bytes obtained from the Physical layer to send to the Transaction Layer when receiving packets.Second, according to the UM-BUS data packet formats and funtions, desingned and implemented a data buffer with four-body FIFO structure for UM-BUS, which not only simplify the transmission model, but also designed to deal with the data transferring problem between the Transaction Layer and Transport layer which are processing in asynchronous clock.Third, this paper designed the data transmission and management system model, uses a4*32matrix switch array to control data access and sending process, so that the Data packets will be transmitted through the health lanes and the link fault can be tolerant. This paper designed and implemented the UM-BUS transport layer, bulided a test system according to the characterists of UM-BUS Transport layer.This system can simulate a variety of combinations of lane faults. The data packets can be transmitted in health lanes evenly and efficiently by the transport layer in fault condition, and the communication process can be resumed...