To put it simply, Serial communication refers to the process of sending data one bit at a time, sequentially. This is performed over either a "communication channel" or a "computer bus". The contrast to serial communication is "Parallel Communication" in which serveral bits are sent as a whole over a link with multiple parallel channels.
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## Why do we use serial over parallel communications?
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**Data Transmission**
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Think of each type of system as a road, in a parallel cable (8 bit, 16 bit, 32 bit, 64 bit, 124 bit) you have 1 lane per bit, when all of those lanes hit the junction (reciever), they have to all stop and stabalize before they are able to move on, so you end up with congestion. On a serial system, there is only 1 or sometimes (in a full duplex serial connection) 2 lanes. The data is never held up like traffic at a junction as only 1 bit of data can be in any lane at any one time.
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**Simplification**
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Serial connections also require fewer wires, 3 or 5 Wires (Half Duplex | Full Duplex) whereas parallel connections require 1 wire per bit, so an 8 bit parallel line requires 9 wires.
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**Crosstalk**
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Parallel connections are naturally a lot more prone to crosstalk. Signals traveling on wire one can interfere with signals on another nearby wire, leading to data errors.
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**Distance**
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Serial connections are better suited for long-distance transmissions due to it's almost perfect data accuracy at high speeds.
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### Benefits to parallel over serial communication
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The key benefit of parallel communication is speed, as a generic rule, more wires = more speed. In the correct applications with quite a lot of engineering to iron out bit-level timing issues, the data transfer potential of parallel communications can far exceed that of serial communications.
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## Most common Serial Protocols
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The most common Serial Protocols are listed below: