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1: Serial vs. Parallel

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    Series vs. Parallel

    There are two basic ways of setting up wired communication, in series or in parallel.  Series communication lines transmit data one bit at a time, while parallel lines can simultaneously transmit multiple bits of data. You can look at the voltage as being on (high) or off (low) and by creating a "start" and "end" bit you can create a data frame that represents information similar to how computers store data in memory chips.  Although parallel lines are faster than serial, they are more expensive and the close proximity of multiple lines to each other cause signal distortion because as the voltage rises and falls in one line it induces a magnetic field that induces a current in adjacent wires in the opposite direction (see Faraday's Law of Induction-Lenz's Law). Parallel lines are typically used where speed is important, like when the CPU is communicating with memory modules. Most wired IOT devices use series communication protocols as they are cheaper, and you can run them for greater distances without inducing signal lose.


    clipboard_ef11780ce95d18df2bfa26af75d8a02c5.pngFigure \(\PageIndex{1}\): In parallel communication data is transferred multiple bits at a time, while in serial they are transffered one bit at a time. (cc 4.0 Sparkfun)


    Serial vs. parallel communication
      Serial Parallel
    Speed Slower, one bit is transferred at each clock pulse faster, multiple bits (8,16,32..) are transferred at each clock pulse
    Distance Good for Long Distance Good for Short Distance, May Suffer Signal Degradation Over Long Distance 
    Interference Less Prone to Crosstalk Prone to Crosstalk, when the signals of different wires induce flow in adjacent wires
    Bandwidth Limited High Bandwidth Potential
    Cost Tends to be Cheaper Tends to be More Expensive
    Applications sensors, peripherals (mice, keyboards) Inside CPU and RAM
    Issues simpler circuits, speed

    Needs More Wire, Crosstalk, Complicated, Clock Skew (bits may not transfer simultaneously)



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