Part 2 answers: Where does a message start and end?
Once a receiver can sample bits, it still has to find structure in them: where a word starts, where a packet ends, which symbols are control and which are data. Encoding also has to keep enough transitions for clock recovery and keep the line balanced.
This part covers line codes, framing methods, packet anatomy, bit stuffing, block codes and their overhead, scrambling, lock, ordered sets, and flits.
Name five ways a receiver finds packet boundaries.
Compute the overhead of 8b/10b, 64b/66b and 128b/130b.
Explain how a receiver gains and loses block lock.
Answer each in your head before opening it. If two or more feel shaky, revisit Part 1: Timing and Clocking first.
Clock-to-output, flight time, skew and setup must all fit in one clock period. Flight time grows with distance, so the period has to grow too.
Each frame starts with a start bit that resynchronises the receiver, which then samples mid-bit using its own clock. The frame is short enough that a small rate mismatch does not accumulate past half a bit.
The small frequency difference (ppm offset) between the transmitter's and receiver's clocks, by inserting or deleting filler symbols.
# | Lesson | Level | Status |
|---|---|---|---|
2.1 | F · Foundation | Ready | |
2.2 | F · Foundation | Ready | |
2.3 | F · Foundation | Ready | |
2.4 | W · Working | Ready | |
2.5 | W · Working | Ready | |
2.6 | W · Working | Ready | |
2.7 | W · Working | Ready | |
2.8 | S · Senior | Ready | |
2.9 | S · Senior | Ready | |
2.10 | S · Senior | Ready | |
— | all levels | Ready | |
— | all levels | Ready |
Every lesson in this part is ready. Work through them in order: each one sets up the problem the next one solves.
This course teaches why protocols are designed the way they are. These lessons show how to build or sign off the same ideas, so this part links to them instead of repeating them.