Introduction to 1.1553B bus
MIL-STD-1553B bus is a standard bus for the U.S. Air Force electronic subsystem networking. It is a centralized serial bus. The bus composition includes a bus. The controller is responsible for bus scheduling and management. It is the initiator and organizer of bus communication; several (up to 31) remote terminals. In addition, there may be a device called a bus monitor to monitor the operation of the bus. This bus adopts command response mode to realize system communication, and adopts redundant channels and odd check and corresponding error handling to improve the reliability of system communication. 1553B is a standard for bus interface rules and signal characteristics. It has strict regulations on the electrical signal characteristics generated by hardware components at the physical layer, and the method of error detection and the format of command response at the data link layer and network layer. Strictly defined. Due to the extremely high reliability of the 1553B bus, it is widely used in electronic networking systems in aviation, aerospace, military and other fields.
1553B bus adopts asynchronous data transmission mode, code rate is 1Mbps (there is now a board that supports 4Mbps), that is, 106 bits per second, data coding adopts Manchester II code, differential transmission, generally shielded Twisted pair is used as the transmission medium.
2. Hardware topology structure
Figure 2.1 1553B topology structure
The topology structure of a typical 1553B bus hardware system is shown in Figure 2.1 1553B topology structure, the bus itself It is a two-redundant structure, including bus A and bus B, which are mutually redundant backups. All bus devices (also known as bus interface unit BusInterface Unit BIU) BC, RT, BM share the bus in parallel Main line part. The main line and the sub-line are connected by the bus controller BC (BUS CONTROLER) bus monitor BM (BUS MONITOR) remote terminal RT0 (REMOTE TERMINAL) remote terminal RT1 remote terminal RT30……. There can only be one bus controller BC and no more than 31 remote terminal RT on the bus (some documents also call it remote terminal or remote unit). The bus monitor is optional and is used to monitor bus communication and generally does not participate. communication.
3. Controller function introduction
3.1 Bus Controller (BC)
The bus controller is responsible for bus scheduling and management, and is the initiator of bus communication And organizer. Since the 1553B bus adopts centralized bus management, in the entire communication process, only the bus controller actively participates in the bus communication, all data transmission must be initiated by the bus controller, and the remote terminal can only passively receive or send data. Therefore, any communication process must be participated by the bus controller. The remote terminal can only passively receive or send data related to itself. For the remote terminal, the data that has nothing to do with itself is transparent (invisible). The bus controller actively organizes various remote terminals to participate in communication according to the preset communication protocol to complete data transmission. A reasonable communication protocol can enable the remote terminal to actively send a data transmission request to the bus controller, and the bus controller sends it according to the remote terminal. According to the data transmission request, organize the corresponding remote terminal to receive or send data. Generally speaking, the bus controller is a part of all the functions of a certain onboard equipment. The formulation of the communication protocol, the design of software and hardware must be considered in a unified manner, and various messages of the bus must be arranged from the height of the system.
3.2 Remote Terminal (RT)
Remote terminal can only passively receive or send data related to itself. For remote terminal, data that has nothing to do with itself is transparent ( invisible). The remote terminal receives and sends data according to the preset communication protocol. Because the remote terminal can only passively participate in the bus communication, the design of the software and the working mode of the bus controller are closely related, so there must be sufficient safety considerations in the design of the software. Like the bus controller, the remote terminal is generally part of the full functions of a certain spaceborne device. The remote terminal itself is just a communication bridge, and communication software is often used for data collection and distribution.
3.3 Bus Monitor (MT)
All communication processes on the bus are visible to the bus monitor, so the bus monitor can fully or selectively monitor the bus During the communication process, analyze and judge the communication status, and give the operating status and health status of the bus controller and each remote terminal participating in the bus communication. The bus monitor is not necessary as a spaceborne device. It is often used as a backup of the bus controller to monitor the health of the bus controller and replace it under necessary conditions.
4. Reference materials
“MIL-STD-1553B Protocol Detailed Explanation”