1. EET 450 - Advanced Digital Chapter 21 Serial Ports

2. Serial Communications Contrasting with parallel communications - the individual bits are transmitted one at a time. Uses time division multiplexing versus space division multiplexing

3. Modern Serial Options classic - RS 232 ACCESS.bus IrDA optical Universal Serial bus P1394

4. Transfer rate/characteristics RS232 - standard for years max rate 115,200 bps uses twisted pair 1 device per port ACCESS.bus - inexpensive option max rate 100 Kbps 4-wire shielded cable 125 devices per port

5. IrDA - optical serial version 4 Mbps no cable 126 devices USB - high speed serial 12 Mbps Special 4-wire cable 127 devices

6. IEEE 1394 - firewire 100 Mbps Special 6-wire cable 16 devices per port

7. Basic Serial Communications Clocking 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 data

8. Serial Communications Frames bits are collected into frames of data frame is delineated with stop/start bits Within the frame is data and error correction information.

9. Serial Communications Each 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 example AddressDescriptionDataError Chk

10. Packets Packets 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 throughput

11. RS-232C The traditional COM port Port speeds are restricted by internal clock of PC 150:300:600:1200:2400:4800:9600 19200:38400:57600:115200 physical connection Standard connectors  DB25  DB9

12. RS-232C Signals include Transmit Data  from the Data Terminal Equipment Receive Data  to the DTE (from DCE) Data Terminal Ready  From DTE to DCE - ready to receive

13. RS-232C Data Set Ready  DSR - to DTE from DCE - ready Request to send  RTS - opposite of DSR Clear to send CTS to DTE opposite of DTR

14. RS-232C Carrier Detect For modem signaling - the modem carrier signal is detected Ring Indicator Again for modems - indicates a ring signal on incoming line

15. Flow Control Two methods of controlling the sending/receiving of data on a serial connection. Hardware - uses signal wires from physical layer above Software - uses control signals - either XON/XOFF or ETX/ACK

16. Cables designed to run on unshielded twisted pair (UTP) Shielded cable can extend effective range Wiring depends on flow control Software - 3 wires needed (XMIT/RCV/Ground) Hardware - all wires as above Connectors - DB25 or DB9 (m/f)

17. Cables Crossover 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.

18. Chips UART - Universal Asynchronous Receive r/Transmitter 8250 16450 16550

19. Access.bus Allows 125 devices to a single port Simple - Slow Software flow control Three layers Physical Base Application

20. IrDA Infrared Developers Association Laptop standard Adaptec Airport Data Rates 9600 bps - 4 Mbps

21. Universal Serial Bus USB - now the standard on most systems 12Mbps capable (1.5Mbps in a lower speed) Connects up to 127 devices Hub/function architecture Cable special 4 wire cable Vcc, Ground, +/- data

22. IEEE-1394 Used 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)

23. IEEE-1394 100Mbps - with upgrades to 200Mbps and 400Mbps expected Can (is) used to connect everything to a computer system - monitor, printer, hard disk drives, CDRoms, etc.