The CN8478, CN8474A, CN8472A, and CN8471A are advanced Multichannel Synchronous Communication Controllers (MUSYCCs) that format and deformat up to 256 (CN8478), 128 (CN8474A), 64 (CN8472A), or 32 (CN8471A) HDLC channels in a single CMOS integrated circuit.

MUSYCC operates at Layer 2 of the Open Systems Interconnection (OSI) protocol reference model.

MUSYCC provides a comprehensive, high-density solution for processing HDLC channels for internetworking applications such as Frame Relay, ISDN D-channel signaling, X.25, Signaling System 7 (SS7), DXI, ISUP, and LAN/WAN data transport.

Under minimal host supervision, MUSYCC manages a linked list of channel data buffers in host memory by performing Direct Memory Access (DMA) of the HDLC channels.