๐ก Transmission โ Extras
๐งฉ Framing
๐ Definition: Adding extra bits or patterns to a data packet so the receiver knows:
- ๐ Where the data starts
- ๐ Where it ends
- ๐ Sometimes extra info like packet length or error checks
๐ก Example (asynchronous): A UART byte might be framed like this:
โฑ Start bit | ๐ฆ Data bits | โ
Parity bit (optional) | ๐ Stop bit(s)This ensures the receiver can lock onto each byte without a shared clock
๐ Framing overhead: These extra bits do not carry payload data, so they reduce overall efficiency.
๐ Multi-drop
๐ Definition: A communication bus where multiple devices share the same physical set of wires, and any device can communicate (one at a time).
๐ Examples:
๐ง IยฒC: Many sensors and controllers share the same clock and data lines
๐ญ RS-485: Multiple industrial controllers on one twisted-pair cable
๐ Key point: Only one device โdrivesโ the bus at a time, others remain idle.
๐ช Called multi-drop because the cable is like a long backbone with โdropsโ to multiple devices.
โฐ Phase-Locked Loop (PLL)
๐ Definition: An electronic circuit that locks the phase and frequency of a local oscillator to a reference signal.
๐ก In data transmission:
๐ Adjusts the receiverโs internal clock to align with the senderโs bit timing
๐งญ Compensates for clock drift and jitter to keep sampling accurate
๐ฃ Analogy: Like running next to someone and adjusting your stride to match their footsteps โ you stay in sync without a fixed schedule.