Hardware ConsiderationsTopicsSample real-time systemsXINU and RouterProtocol Layering and function of a router (From Cornell Univ.)Protocol layering & RouterProtocol layering and RouterProtocol layering and routerSlide 9Protocol layering & routerSlide 11Slide 12Wireless LAN configuration: From ColourisWRT54GL: Wireless router from LinksysHardware BasicsStandard InterfacesMIL-STD-1533BSCSI (“Scuzzy”)IEEE 1394 FirewireMemory TechnologiesMemory organization and mapInput/outputDirect memory access (DMA)Memory mapped IOInterruptsEnhancing PerformanceTransducersSummary01/14/19 1Hardware ConsiderationsChapter 201/14/19 2TopicsLast lecture leftoversWhat is XINU? What is Embedded XINU? What is a Linksys router? What is an openWRT? What can we do with all these?Installment 1Hardware consideration – Chapter 201/14/19 3Sample real-time systemsLets discuss the sample systems listed in the text books.We will also go over the exercises at the end of chapter 1.01/14/19 4XINU and RouterXinu is a small, elegant system that follows a hierarchical structure. http://en.wikipedia.org/wiki/XinuRouter: lets look at relationship between network protocol layering and a router.Wireless router: Access points, wireless communication WRT54GL: Wireless broadband routerLinkEmbedded XinuIts goal is to port the XINU Operating System to the MIPS platform by specifically targeting LinkSys WRT54GL routers. http://xinu.mscs.mu.edu/OpenWRTOpenWRT is essentially a Linux distribution for embedded systems, specifically routers. http://xinu.mscs.mu.edu/OpenWRT01/14/19 5Protocol Layering and function of a router (From Cornell Univ.)BrowserprocessHTTPTCPLink1IPLink1IPLink2Web serverprocessHTTPTCPLink1IPPhysical Link 1 Physical Link 2Router01/14/19 6HTTPProtocol layering & RouterBrowserprocessTCPLink1IPLink1IPLink2Web serverprocessHTTPTCPLink1IPPhysical Link 1 Physical Link 2RouterHBrowser wants to request a page. Calls HTTP with the web address (URL).HTTP’s job is to convey the URL to the web server.HTTP learns the IP address of the web server, adds its header, and calls TCP.01/14/19 7HTTPProtocol layering and RouterBrowserprocessTCPLink1IPLink1IPLink2Web serverprocessHTTPTCPLink1IPPhysical Link 1 Physical Link 2HTCP’s job is to work with server to make sure bytes arrive reliably and in order.TCP adds its header and calls IP.(Before that, TCP establishes a connection with its peer.)TRouter01/14/19 8HTTPProtocol layering and routerBrowserprocessTCPLink1IPLink1IPLink2Web serverprocessHTTPTCPLink1IPPhysical Link 1 Physical Link 2HIP’s job is to get the packet routed to the peer through zero or more routers.IP determines the next hop from the destination IP address.IP adds its header and calls the link layer (i.e. Ethernet) with the next hop address.TRouterI01/14/19 9HTTPProtocol layering and routerBrowserprocessTCPLink1IPLink1IPLink2Web serverprocessHTTPTCPLink1IPPhysical Link 1 Physical Link 2HThe link’s job is to get the packet to the next physical box (here a router).It adds its header and sends the resulting packet over the “wire”.TRouterI L101/14/19 10HTTPProtocol layering & routerBrowserprocessTCPLink1IPLink1IPLink2Web serverprocessHTTPTCPLink1IPPhysical Link 1 Physical Link 2HThe router’s link layer receives the packet, strips the link header, and hands the result to the IP forwarding process.TRouterI01/14/19 11HTTPProtocol layering & routerBrowserprocessTCPLink1IPLink1IPLink2Web serverprocessHTTPTCPLink1IPPhysical Link 1 Physical Link 2HThe router’s IP forwarding process looks at the destination IP address, determines what the next hop is, and hands the packet to the appropriate link layer with the appropriate next hop link address.TRouterI01/14/19 12HTTPProtocol layering and routerBrowserprocessTCPLink1IPLink1IPLink2Web serverprocessHTTPTCPLink1IPPhysical Link 1 Physical Link 2HThe packet goes over the link to the web server, after which each layer processes and strips its corresponding header.TRouterI L2H T IH TH01/14/19 13Wireless LAN configuration: From ColourisLANServerWirelessLANLaptopsBase station/access pointPalmtopradio obstructionA B CDE01/14/19 14WRT54GL: Wireless router from LinksysFirmware running the operationsNeed to communicate with the firmwareUpdate the firmwareLoad OpenWRT/XINU or other home brewed code into the routerNeed basic access through a serial port to the firmwareNeed console access to the firmwareThat is the purpose of the hardware update you will be doing.01/14/19 15Hardware BasicsVon Neumann ArchitectureHardware interfacingLatching: recording the appearance of a signal for later processingEdge vs. level triggeringTristate logic: high, low, tristatedWait stateSystem interfaces and buses: address, data, control (2.2.5) Universal asynchronous synchronous relay terminal (UART) is typically used for parallel to serial transferSee Fig. 2.301/14/19 16Standard InterfacesMIL-STD-1553BSmall Computer system interface (SCSI)IEEE 1394 firewire01/14/19 17MIL-STD-1533BWidely used in military and commercial avionicsSpecifies hardware configuration and transmission and receipt protocols1533-bus protocol is a master-slave protocol: one module on the bus acts as a master and others as slaves and respond to master’s commands.Coupling of the devices is such that one device failure does not affect the others.Master puts out device number followed by the packets to that device.Also standard provides specification for handling of failure of the master.See 2.3 and 2.401/14/19 18SCSI (“Scuzzy”)Parallel interface to many devicesSCSI 1, 2, 3, narrow, wide, fast , ultra, ultra-2, ultra-160 SCSI supports daisy chained devicesSCSI supports Fiber Channel and Firewire besides familiar ribbon cableDaisy chained devices can communicate independentlyDevice 0 is the boot device and other devices get non-0 id.Examples: interfaces to hard drive, CDROMs, scanners and other peripherals01/14/19 19IEEE 1394 FirewireStandard specifies very fast external bus that supports data transfer rates of up to 400 megabits per sec. (1394a) and 800 Mbps in 1394b.Apple developed the technologyCan connect up to 63 devicesMultiple speeds on single bus, thus avoiding daisy chaining and peer-peerHot pluggable: devices can be added and removed when the bus is activeTwo types of transfer: asynchronous and isochronousIsochronous:
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