41 lines
981 B
Markdown
41 lines
981 B
Markdown
# Clock Drift
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Recalibrate clocks when out of sync:
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- Async Transmission
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- Send a small amount of data, then 1, then 0, then some more data.
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- Manchester Encoding
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- Send each bit as 2 values
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- Original 10MBase-T uses this
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- HDB3 encoding
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- 3 logic levels to ensure no static sequences
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- Used for long distance cables
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- 4B5B encoding
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- Transmit 5 bits of signalling to represent 4 bits of data
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- 100MBase-T uses this.
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# Quantities in Digital Communication
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## Bit
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- Short for "binary digit". Byte = 8 bits
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## Data Rate
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- Bits per second
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## Baud Rate
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- Times per second the transmitted signal changes.
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### Examples
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- A modem used for dialup will encode at least six bits of data for each unit of signalling.
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- Ethernet uses between 1.2 and 2 units of signalling per bit of data.
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# Text Encoding Communication
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- The word "Up" -> ASCII is 85, 112
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- Binary stream -> 010101010110000
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This demonstrates the worst case scenario for 4B5B, and 4 zeros to demonstrate HDB3.
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