Serial communications system with optional data path and control plane features

Integrated circuits compliant with a serial communications protocol with optional features are provided. The optional features include control plane features such as flow control, retry-on-error, clock tolerance compensation, and idle codes and include data path features such as streaming and packetized data modes, configurable data ports and user-defined data channel multiplexing. An integrated circuit compliant with the protocol can transmit streaming data with or without clock tolerance compensation codes. A priority data port can be used to implement retry-on-error functions while user-defined data channels carry user data. The data ports can be individually configured to perform different levels of cyclic redundancy checking. Logic design tools are used to create compliant circuits and systems.