Physical Coding Sublayer (PCS)
The PCS is a foundational component of the Ethernet PHY. It bridges the higher-level MAC and the lower-level analog PMA. Its primary function is to transform digital binary data into structured, reliable transmission blocks for optical or copper media.
Key functions of the PCS include:
Block & Line Encoding: Translates standard binary data into specific code groups (e.g., 64B/66B, 256B/257B) to ensure DC balance and sufficient signal transitions for clock recovery.
Synchronization & Alignment: High-speed connections distribute data across multiple parallel lanes. The PCS inserts alignment markers and performs lane deskewing to properly reassemble the data stream at the receiving end.
Scrambling & Descrambling: Randomizes data sequences to prevent long strings of identical bits (0s or 1s), which helps minimize electromagnetic interference (EMI) and maintain stable signal transmission.
Error Detection: Validates code blocks to monitor link health and identify transmission faults (e.g., “Local Fault” or “Remote Fault” ordered sets).
Forward Error Correction (FEC): In multi-gigabit and beyond links, the PCS utilizes FEC to automatically detect and correct data corruption without needing to retransmit packets.
Clear Rx Counters
PCS Variant & FEC Mode
Tx Lane Mapping & Skew
Rx Lane Status (Lock, Skew, Pre-FEC BER)
Total Error Counters
Rx FEC Symbol Error Statistics & Distribution