Data Communication

Overview
Data Communication will be no match for you if you pay attention to the DataComm Oracle. If you become overwhelmed just keep things simple and always remember, most devices are merely clusters of smaller devices.

Buses: Connections Within a Device

 * Bus
 * Subsystem that transfers data between computer componnets inside a computer or between computers. Buses.png
 * Types of Buses
 * Parallel Buses: carry data words in parallel on multiple wires.IEEE 1284 "printer port, SCSI, PCI
 * Serial Buses: carry data in bit-serial form.
 * USB (Universal Serial Bus), FireWire, Ethernet, T1, Serial AT
 * Wikipedia Bus Link

Peripherals: Connected Devices

 * Three Main Connection Methods
 * Interrupt: a device like a mouse of a keyboard, which will be sending very little data.
 * Bulk: a device like a printer, which receives data in one big packet. A block of data is sent and then verified to make sure it is correct.
 * Isochronous: a streaming device (such as speakers), data streams between the device and the host in real-time, and there is no error correction.

Closer Look at Serial Buses: USB & Firewire

 * How USB Works
 * Divides available bandwidth into frames.
 * Controlled by host
 * 1500 bytes per frame
 * Data is sent as packets
 * Inside a USB cable
 * Two wires for power (red) and ground (brown), and a twisted pair of wires (yellow and blue) to carry data.


 * USB bit rates
 * USB 1.0 - 1.4 Mbit/sec
 * USB 1.1 - 12 Mbit/sec
 * USB 2.0 - 480 Mbit/sec
 * USB 3.0 - 5 Gbit/sec
 * USB 3.0
 * Released November 17, 2008
 * AKA SuperSpeed USB
 * Uses parallel optical cable
 * Backward compatible with 1.0 and 2.0
 * Commercially available in 2010
 * Firewire
 * IEEE 1394 High Speed Serial Bus
 * Firewire 400 is the older protocol
 * There is also 800, S1600 and S3200
 * 400- 3200 Mbits/sec
 * USB vs. Firewire Comparison Chart

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 * USB vs. Firewire Video Demonstration

Other Buses

 * HDMI: High Definition Multimedia Interface
 * Replaces coaxial (analog) and DVI (digital).
 * Contains 6 connector pins - 3 audio and 3 video.
 * Wikipedia HDMI Link
 * VGA: Video Graphics Array
 * Lowest common denominator for graphics on computers.


 * SATA: Serial Advanced technology Attachment SATA.png
 * 7 connectors - 3 ground, 4 data lines
 * More efficient space use

Data Communication Equipment (DCE)

 * Codecs
 * Terminal Adapters (TAs)
 * Interface adapter for connection one or more non-ISDN devices to an ISDN network.
 * Channel Service Units (CSUs) and Data Sevice Unites (DSUs)
 * Interface the user environment and digital local loop.
 * Modems
 * Needed to interface with the analog local loops standardized at ITU, v series
 * Include compression and error correction.
 * How Stuff Works Explanation on Modems
 * Data Modulation
 * Amplitude Shift Keying (ASK)
 * Frequency Modulation Keying (FSK)
 * Phase Modulation Keying (PSK)
 * Modem Speeds
 * 300 bps - 1960s through 1983
 * 1200 bps - gained popularity in 1984 and 1985
 * 9600 bps - first appeared in late 1990
 * 56 Kbps - became the standard in 1998
 * ADSL max of up to 8 Mbps - gained popularity in 1999
 * Modern Modems
 * Increase bit rate within standard bandwidth of telephone line
 * Use multiple signal levels
 * Vary both amplitude and phase - known as quadrature amplitude modulation (QAM)

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