EET 450 - Advanced DigitalSerial CommunicationsModern SerialTransfer rate/characteristicsPowerPoint PresentationSlide 6Basic Serial CommunicationsSlide 8Slide 9PacketsRS-232CSlide 12Slide 13Slide 14Flow ControlCablesSlide 17ChipsAccess.busIrDAUniversal Serial BusIEEE-1394Slide 23EET 450 - Advanced DigitalChapter 21 Serial PortsSerial CommunicationsContrasting with parallel communications - the individual bits are transmitted one at a time.Uses time division multiplexing versus space division multiplexingModern SerialOptions classic - RS 232ACCESS.busIrDA optical Universal Serial busP1394Transfer rate/characteristicsRS232 - standard for yearsmax rate 115,200 bpsuses twisted pair1 device per portACCESS.bus - inexpensive optionmax rate 100 Kbps4-wire shielded cable125 devices per portIrDA - optical serial version4 Mbpsno cable126 devicesUSB - high speed serial12 MbpsSpecial 4-wire cable127 devicesIEEE 1394 - firewire100 MbpsSpecial 6-wire cable16 devices per portBasic Serial CommunicationsClockingSynchronous communicationsbits are synchronized to a separate clock signalAsynchronous Bits are time from the start of a period - no universal clockIsosynchronous communicationstime critical dataSerial CommunicationsFramesbits are collected into frames of dataframe is delineated with stop/start bitsWithin the frame is data and error correction information.Serial CommunicationsEach byte of data is encapsulated in a frame.Provides timing & error checking Packets - blocks of bytes can be compiled into a packet of data. For exampleAddress Description Data Error ChkPacketsPackets range in size from a few bytes to a few kbytes. (256-2048 per text)May include routing information, commands, and error checking (CRC) This is overhead that decreases overall throughputRS-232CThe traditional COM portPort speeds are restricted by internal clock of PC 150:300:600:1200:2400:4800:960019200:38400:57600:115200physical connectionStandard connectorsDB25DB9RS-232CSignals includeTransmit Datafrom the Data Terminal EquipmentReceive Datato the DTE (from DCE)Data Terminal ReadyFrom DTE to DCE - ready to receiveRS-232CData Set ReadyDSR - to DTE from DCE - readyRequest to sendRTS - opposite of DSRClear to sendCTS to DTE opposite of DTRRS-232CCarrier DetectFor modem signaling - the modem carrier signal is detectedRing IndicatorAgain for modems - indicates a ring signal on incoming lineFlow Control Two methods of controlling the sending/receiving of data on a serial connection.Hardware - uses signal wires from physical layer aboveSoftware -uses control signals - either XON/XOFF or ETX/ACKCablesdesigned to run on unshielded twisted pair (UTP)Shielded cable can extend effective rangeWiring depends on flow controlSoftware - 3 wires needed (XMIT/RCV/Ground)Hardware - all wires as aboveConnectors - DB25 or DB9 (m/f)CablesCrossover cable uses available signals to lie to the ports - allows for software control only.Null Modem is the common name, though this is more properly a test plug.ChipsUART - Universal Asynchronous Receive r/Transmitter82501645016550Access.busAllows 125 devices to a single portSimple - SlowSoftware flow controlThree layersPhysicalBase ApplicationIrDAInfrared Developers AssociationLaptop standardAdaptec AirportData Rates9600 bps - 4 MbpsUniversal Serial BusUSB - now the standard on most systems12Mbps capable (1.5Mbps in a lower speed)Connects up to 127 devices Hub/function architectureCablespecial 4 wire cable Vcc, Ground, +/- dataIEEE-1394Used by AppleCorp as Firewire(note - although many in the industry have attributed the development of IEEE-1394 to Apple Corporation, this is not entirely true.)Wiring - 6 wire copper connection (expect to become glass)IEEE-1394100Mbps - with upgrades to 200Mbps and 400Mbps expectedCan (is) used to connect everything to a computer system - monitor, printer, hard disk drives, CDRoms,