OMG Data Distribution Service详解:从平台中心系统到实时QoS的革新

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本文档概述了对象管理组织(Object Management Group, OMG)的Data Distribution Service (DDS),这是一种专为实时、分布式系统设计的高性能、自适应的消息传递框架。DDS旨在解决传统平台中心化军事系统的局限性,这些系统过去常常是孤立的(stovepiped)、专有且易碎,不适应变化,开发和升级成本高昂,并且对任何小改动都极为敏感,可能导致系统崩溃。 在过去的研发实践中,平台为中心的国防系统通常注重确保端到端的质量-of-service (QoS),如低延迟、减少抖动和资源占用。然而,静态资源分配和优先级管理的局限性意味着缺乏灵活性,一旦资源不足,就可能对整个系统造成严重影响。例如,实时QoS要求包括最小化延迟、控制优先级反转,并预先设定资源使用策略,但这往往限制了系统的适应性和扩展能力。 DDS的设计理念是打破这种平台依赖的僵局,提供一种动态、灵活的消息传递架构,可以更好地应对快速变化的需求。它支持自适应的QoS策略,允许客户端和服务器协商服务质量,根据需要动态调整资源分配,从而提高了系统的鲁棒性和可靠性。这种服务能够在不同节点间高效地传输数据,满足实时应用对高吞吐量、低延迟和容错性的需求。 与CORBA(对象请求代理体系结构)等早期的分布式计算标准相比,DDS提供了更强大的实时性能和可扩展性,使得它成为现代嵌入式、物联网(IoT)和云计算环境中理想的解决方案。通过采用DDS,开发者能够构建更加弹性和可维护的系统,即便在面对不断变化的环境和需求时也能保持高效运作。 总结来说,OMG的Data Distribution Service是一种关键的IT技术,它革新了实时通信的方式,促进了平台无关、适应性强的系统设计,从而在军事、工业自动化、航空航天等多个领域得到了广泛应用。理解并掌握DDS对于提升现代IT系统的性能和灵活性至关重要。

Write a program to 1.Setup a simulating backing store in memory. Read the data from pdata.bin to this backing store. 2.Initialize a page table for process p, set the frame number to be -1 for each page, indicating that the page is not loaded into memory yet. 3.Read logical addresses one by one from la.txt. 4.For each logical address, a)if its page has been loaded into physical memory, simply find the frame number in the page table, then generate physical address, find and print out the physical address and data inside this address. b)if the page is used for the first time, i.e., in page table, its frame number is -1,then the page that contains this address should be loaded into a free frame in physical memory (RAM). Then update the page table by adding the frame number to the right index in the page table. Then repeat 4a). Assumption: 1.Assume the file la.txt includes the sequence of generated addresses from CPU. 2.Use a part of memory as backing store that store data for a process. 3.The backing store size is 128 bytes 4.The size of process p is 128 bytes. 5.The contents of p is included in a file pdata.bin which is a binary file. 6.Use a part of memory as RAM. The size of physical memory is 256 bytes, from 0 to 255. All the physical memory is available, allocating starting from beginning in sequence. That is, allocate frame 0 first, then frame 1, then frame 2…. 7.The size of a frame is 32 bytes, i.e., 5 bits for the offset in a frame, total number of frames is 8. At beginning, no page table is available for process p.

2023-05-24 上传

Standard SPI Mode Standard SPI mode is selected when the Mode option in the Vivado IDE is set to Standard. The relevant parameters in this mode are: • Mode • Enable STARTUPE2 Primitive • Transaction Width • No. of Slaves • Frequency Ratio Send Feedback AXI Quad SPI v3.2 7 PG153 April 4, 2018 www.xilinx.com Chapter 1: Overview • Enable FIFO The properties of the core in standard SPI mode, including or excluding a FIFO, are described as: • The choice of inclusion of FIFO is based on the Enable FIFO parameter. FIFO Depth parameter is linked to Enable FIFO parameter. FIFO Depth limits the transmit and receive FIFO depth to 16 or 256 when FIFO is enabled. When FIFO is not enabled, the value of FIFO depth parameter is considered to be 0. A FIFO depth of 256 should be used because this is the most suitable depth in relation to the flash memory page size. • The valid values for the FIFO Depth option in this mode are 16 or 256 when FIFO is enabled through Enable FIFO parameter. When Enable FIFO is 0 and no FIFO is included in the core. Data transmission occurs through the single transmit and receive register. When FIFO Depth is 16 or 256, the transmit or receive FIFO is included in the design with a depth of 16 or 256 elements. The width of the transmit and receive FIFO is configured with the Transaction Width option. The AXI Quad SPI core supports continuous transfer mode. When configured as master, the transfer continues until the data is available in the transmit register/FIFO. This capability is provided in both manual and automatic slave select modes. As an example, during the page read command, the command, address, and number of data beats in the DTR must be set equal to the same number of data bytes intended to be read by the SPI memory. When the core is configured as a slave, if the slave select line (SPISEL) goes High (inactive state) during the data element transfer, the current transfer is aborted. If the slave select line goes Low, the aborted data element is transmitted again. The slave mode of the core is allowed only in the standard SPI mode.

2023-07-22 上传