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Bridging the Gaps : Electronic Interconnect Protocols
 

Bridging the Gaps : Electronic Interconnect Protocols

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    Bridging the Gaps : Electronic Interconnect Protocols Bridging the Gaps : Electronic Interconnect Protocols Presentation Transcript

    • Bridging the Gaps Electronic Interconnect Protocols Chintalagiri Shashank Department of Physics Indian Institute of Technology, Kanpur February 16, 2008 Vyakhya, Techkriti'08 chintal@iitk.ac.in
    • Introduction The technical world depends on various discrete elements, each having its own peculiarities. Each of these elements need to communicate with each other for many reasons, and the subsystems responsible for this communication have to efficiently allow the systems to talk to each other without compromising on the individuality of each of the elements. In the talk, I intend to introduce the basic elements of an arbitrary communication protocol, touching upon the fundamental tasks involved in getting an arbitrary packet of information from one system to another. I will be concentrating on communication between nearby systems in a small number, as opposed to ethernets and TCP/IP. February 16, 2008 Vyakhya, Techkriti'08 chintal@iitk.ac.in
    • Agenda  The need for communication.  Common communication protocols  Synchronizing communication - clocks and timing  Serial vs Parallel, why new protocols tend to be serial  Bringing order to the chaos - Bus Masters February 16, 2008 Vyakhya, Techkriti'08 chintal@iitk.ac.in
    • The Need for Communication  Any technical system involves multiple disparate systems. element 2  In the absence of inter-device communication, a human being element 1 would potentially require to interact with multiple systems. element 3  Some elements may not be amenable to easy Human User Interface without a major increase in price and complexity User February 16, 2008 Vyakhya, Techkriti'08 chintal@iitk.ac.in
    • Inter-device Communication  Making each of the individual elements talk to each other element 2 could reduce human interface requirements to a element 1 single element.  In many cases, inter-device element 3 communication could reduce the processing load on the user. Processing / User Interface element User February 16, 2008 Vyakhya, Techkriti'08 chintal@iitk.ac.in
    • Is this new?  Traditional instrumentation rarely possess inter-device communication capability.  Instrumentation available today have started to have multiple device interfaces.  Why is the trend going towards extensive inter-device communication? February 16, 2008 Vyakhya, Techkriti'08 chintal@iitk.ac.in
    • Why is this new?  Electronic datastreams are much faster than they were in the past.  Cheap and easily accesible high-performance computing helps ease the communication process and enhances the data processing capability within the system. February 16, 2008 Vyakhya, Techkriti'08 chintal@iitk.ac.in
    • Network Configurations Star Bus element element element element element element element element 1 element element element element  A real life network is usually a combination of the star and bus configurations February 16, 2008 Vyakhya, Techkriti'08 chintal@iitk.ac.in
    • Common Communication Protocols  USART / RS-232  Parallel Ports  Serial Peripheral Interface (SPI)  2-Wire Bus (I2C)  GPIB (IEEE 488.2)  Universal Serial Bus (USB) February 16, 2008 Vyakhya, Techkriti'08 chintal@iitk.ac.in
    • Requirements of Communication  Physical Layer  Electromagnetic Wave Guides  Standard Datastream Format  Synchronization  Bus Clocks  Timing  Checks and Balances  Negotiation for Communication Line Control February 16, 2008 Vyakhya, Techkriti'08 chintal@iitk.ac.in
    • Synchronizing Communication  Why synchronize?  Packets of data lose meaning if bits are displaced  Unsyncronized communication causes significant data loss, and makes for a very inefficient communication technique.  Clocks vs Timing  Clocks need an extra wire, increase the possibility of errors over physical distances.  Timing requires very precise electronics February 16, 2008 Vyakhya, Techkriti'08 chintal@iitk.ac.in
    • Checks and Balances  Physical Communication Lines cannot always be trusted :  Signal deterioration over the length of the waveguide  Momentary desynchronization of the datastream  Electromagnetic Interference from external EM sources  Hardware failures  Inappropriate datastreams from bad elements on the bus February 16, 2008 Vyakhya, Techkriti'08 chintal@iitk.ac.in
    • Checks and Balances  Data Verification Procedures  Parity checks  Data Recieved Acknowledgement  Hashes and Sums  Data Integrity Issues are more pronounced with  High Speed Data Transfer  Transmission over longer distances  Large number of communicating devices on the bus February 16, 2008 Vyakhya, Techkriti'08 chintal@iitk.ac.in
    • Serial vs Parallel  These two represent diametrically opposite paradigms in the way communication is done  Serial communication send bits one a time on a single wire.  Parallel communication sends all the bits in one shot.  Absolutely parallel communication is usually not practically feasible February 16, 2008 Vyakhya, Techkriti'08 chintal@iitk.ac.in
    • Serial vs Parallel  Newer generic communication protocols are predominantly serial in nature  Serial communication sends less information per clock  Serial communication can run at greater clocks beacuse each bit can be sent faster  Waiting for multiple lines to settle, especially at high speeds, is the key.  Serial communcation also has narrower cables. Smaller number of data lines makes for less EM Interference February 16, 2008 Vyakhya, Techkriti'08 chintal@iitk.ac.in
    • A Cacophony of Data element 1 element 2 element 3  If every device starts talking at the same time, noise ensues.  There needs to be a mechanism to maintain a semblance of order. February 16, 2008 Vyakhya, Techkriti'08 chintal@iitk.ac.in
    • Bus Masters element 1 element 2 element 3 Bus Master  A single device on the bus is given a special privilege – control of the communication lines.  The Bus Master decides who talks when, and in some cases also orders a particular device to listen.  The Bus Master is usually a computer or a microcontroller – an 'intelligent' device.  In general, the Bus Master generates the clock February 16, 2008 Vyakhya, Techkriti'08 chintal@iitk.ac.in
    • More (about) Bus Masters Inactive Bus Master element 2 element 3 Active Bus Master (Slave)  When you need more than one device to have control, your communication protocol becomes more complex.  Procedures for control negotiation between the Masters are built into some procedures.  These are called Multi-Master Busses. February 16, 2008 Vyakhya, Techkriti'08 chintal@iitk.ac.in
    • Questions February 16, 2008 Vyakhya, Techkriti'08 chintal@iitk.ac.in