SRIO协议分析.docx

_Serial RapidIO协议分析1. 物理层特性1.1 Two transmitters(short run and long run) and a single receiver are specified for each of three baudrates, 1.25, 2.50, and 3.125 GBaud.1.2 The short run transmitter should be used mainly for chip-to-chip connections on either the same printed circuit board or across a single connector.1.3 The long run transmitter specifications use larger voltage swings that are capable of driving signals across backplanes. This allows a user to drive signals across two connectors and a backplane.1.4 The most common equalization techniques that can be used Pre-emphasis on the transmitter A passive high pass filter network placed at the receiver. This is often referred to as passive equalization. The use of active circuits in the receiver. This is often referred to as adaptive equalization.2. 信号定义2Signal pin descriptions for a RapidIO 1x/4x LP-Serial port. The interface is defined either as a single- or four-lane, full duplex, point-to-point interface using differential signaling. A single-lane implementation consists of 4 wires and a four-lane implementation consists of 16 wires.3. Electrical Specifications33.1 Short Run Transmitter Specifications2.5 GBaud、3.125 GBaud特性与1.25GBaud Short Run Transmitter AC Timing Specifications基本相同，区别在于：2.5 GBaud UI 400ps3.125 GBaud UI 320ps3.2 Long Run Transmitter Specifications2.5 GBaud、3.125 GBaud特性与1.25GBaud Long Run Transmitter AC Timing Specifications基本相同，区别在于：2.5 GBaud UI 400ps3.125 GBaud UI 320ps3.3 Receiver Specifications2.5 GBaud、3.125 GBaud特性与1.25GBaud Receiver Specifications基本相同，区别在于：2.5 GBaud UI 400ps3.125 GBaud UI 320ps4. 10G级互连技术比较协议类型软件实现TCP/IP 协议栈的以太网4x PCI Express4x SRIO备注软件开销高中低 SRIO 协议栈简单，一般都由硬件实现，软件开销很小硬件纠错重传不支持支持 支持 传输模式消息DMADMA，消息 拓扑结构任意 PCI树任意 SRIO支持直接点对点或通过交换器件实现的各种拓扑结构直接点对点对等互连支持 不支持支持 SRIO互连双方可对等的发起传输。传输距离长 中中SRIO针对嵌入式设备内部互连，传输距离一般小于1米数据包最大有效载荷长度1500字节4096字节 256字节嵌入式通信系统对实时性要求高，SRIO小包传输可减少传输时延打包效率 (以传输256字节数据为例)79% (TCP包)82%9296%打包效率是有效载荷长度与总包长的比率。SRIO支持多种高效包格式。5. 帧结构l ACKID：向Packet发送端响应Packet接收确认信息；l RSVD：保留域；l PRIO：Packet优先级；l TT：器件ID长度；l Ftype：Logi_Inf的格式类型；l Dest_Addr：目的器件ID号；l Src_Addr：源器件ID号；l Logi_Inf：逻辑层信息，包括数据长度、数据地址、邮箱号等；l Payload：数据净核；l CRC：采用多项式X16+X12+X5+1生成16bit CRC码；6. 协议结构RapidIO协议定义了3个层：逻辑层、传输层和物理层。12345677.1 逻辑层逻辑层定义了操作协议和相应的包格式。RapidIO支持的逻辑层业务主要是：直接IO/DMA （Direct IO/Direct Memory Access）和消息传递（Message Passing）。l 直接IO/DMA直接IO/DMA模式的前提是主设备知道被访问端的存储器映射。主设备可以直接读写从设备的存储器。直接IO/DMA在被访问端的功能往往完全由硬件实现，被访问的器件无任何软件负担。对上层应用来说，发起直接IO/DMA传输主要需提供以下参数：目地器件ID、数据长度、数据在目地器件存储器中的地址。直接IO/DMA模式又可进一步分为以下几种传输格式：NWRITE: 写操作，不要求接收端响应。 NWRITE_R: 带响应的NWRITE（NWRITE with Response），要求接收端响应。 SWRITE：流写（Stream Write），数据长度必须是8字节的整数倍，不要求接收端响应。 NREAD: 读操作。 l 消息传递消息传递（Message Passing）模式则类似于以太网的传输方式，它不要求主设备知道被访问设备的存储器状况。数据在被访问设备中的位置则由邮箱号（类似于以太网协议中的端口号）确定。从设备根据接收到的包的邮箱号把数据保存到对应的缓冲区，这一过程无法完全由硬件实现，而需要软件协助。对上层应用来说，发起消息传递主要需提供以下参数：目地器件ID、数据长度、邮箱号。7.2 传输层RapidIO是基于包交换的互连技术，传输层定义了包交换的路由和寻址机制。RapidIO网络主要由两种器件，终端器件（End Point）和交换器件（Switch）组成。终端器件是数据包的源或目的地，不同的终端器件以器件ID来区分。RapidIO支持8 bits 或 16 bits器件ID，因此一个RapidIO网络最多可容纳256或65536个终端器件。与以太网类似，RapidIO也支持广播或组播，每个终端器件除了独有的器件ID外，还可配置广播或组播ID。交换器件根据包的目地器件ID进行包的转发，交换器件本身没有器件ID。RapidIO的互连拓扑结构非常灵活，除了通过交换器件外，两个终端器件也可直接互连。7.3 物理层RapidIO 1.x 协议定义了1x/4x SRIO协议，具体参照1-3节。7. 错误检测和恢复机制SRIO协议采用错误检测和重发机制对发送数据进行保护和恢复，重传纠错的功能由物理层完成。协议规定，每个数据包的传输需得到接收端的确认，并在发送端为每个传输的数据包保留备份，直至收到一个数据包接收确认或发送端口确定该数据包遇到不可恢复的错误。协议可检测以下4种错误：l An idle sequence errorl A control symbol errorl A packet errorl A time-out waiting for an acknowledgment control symbol88.1 Idle sequence error空闲码由A、K、R字符组成，输入端检测到无效的字符或有效字符但不是A、K、R字符时，进入Error-stopped recovery process。8.2 Control symbol error协议可检测以下2种symbol error：l An uncorrupted control symbol that violates the link protocoll A corrupted control symbolLink protocol violations include the following: Unexpected packet-accepted, packet-retry, or packet-not-accepted control symbol Packet acknowledgment control symbol with an unexpected packet_ackID value Link time-out while waiting for an acknowledgment control symbolInput ports detect the following types of control symbol corruption. A control symbol containing invalid characters or valid but non-data characters A control symbol with an incorrect CRC value8.3 Packet ErrorsInput ports detect the following types of packet corruption Packet with an unexpected ackID value Packet with an incorrect CRC value Packet containing invalid characters or valid non-data characters Packet that overruns defined boundary such as the max payload.8.4 Time-out waiting等待确认信号的链接超时作为违反链接协议的情况处理，参照8.2节。8. 参考标准l RapidIOTM Interconnect Specification Part 6: 1x/4x LP-Serial Physical Layer Specification Rev. 1.3l 串行RapidIO: 高性能嵌入式互连技术(TI forum)l RapidIOTM Interconnect Specification Part 6: 1x/4x LP-Serial Physical Layer Specification Rev. 2.0 Welcome ToDownload !欢迎您的下载，资料仅供参考！精品资料