Hardware interview practice
Explain SerDes Encoding and Transition Density
A serial receiver recovers sampling phase from data transitions. A legacy link uses 8b/10b encoding before serialization. Which statement correctly describes the link and encoding purpose?
Choose one
Answer choices
- A. 8b/10b compresses ten payload bits into eight line bits, increasing payload bandwidth by 25% with no redundancy.
- B. The PCS maps each 8-bit symbol to 10 line bits before serialization; the code provides bounded disparity and transition density for AC coupling/CDR, with 80% raw coding efficiency before other protocol overhead.
- C. The serializer itself guarantees frequent transitions for any payload, so encoding cannot affect clock recovery or DC balance.
- D. 8b/10b eliminates the need for a receiver clock-data-recovery loop because every line bit arrives with a separate clock wire.