What are the challenges in implementing high-speed serial interfaces on microcontrollers?

High-speed challenges: Signal integrity (impedance matching, termination, controlled impedance PCB traces), Clock recovery (PLLs for synchronization, jitter requirements), EMI compliance (spread spectrum clocking, proper shielding), Protocol complexity (USB 2.0/3.0, PCIe, SATA state machines), Error handling (CRC, retry mechanisms), Power management (link states, suspend/resume), and Compliance testing (eye diagrams, protocol analyzers). Implementation approaches: Dedicated PHY with controller integration, SerDes macros with protocol layer software, and hardware protocol engines. PCB design critical: differential pairs, via optimization, reference planes, and proper decoupling.