IEEE Transactions on Very Large Scale Integration (VLSI) Systems vol:15 issue:8 pages:881-894
The need for efficient interconnect architectures beyond the conventional time-division multiplexing (TDM) protocol-based interconnects has been brought on by the continued increase of required communication bandwidth and concurrency of small-scale digital systems. To improve the overall system performance without increasing communication resources and complexity, this paper presents a cost-effective interconnect architecture, communication protocol, and signaling technology that exploits parallelism in board-level communication, resulting in shorter latency and higher concurrency on a shared bus or link: the proposed source synchronous CDMA interconnect (SSCDMA-I) enables dual concurrent transactions on a single wire line as well as flexible input/output (I/O) reconfiguration. The SSCDMA-I utilizes 2-bit orthogonal CDMA coding and a variation of source synchronous clocking for multilevel superposition; a single 3-level SSCDMA-I line operates as if it consists of dual virtual time-multiplexed interconnects, which exploits communication parallelism with a reduced number of pins, wires, and complexity. The unique multiple access capability of the SSCDMA-I improves real-time communication between multiple semiconductor intellectual property (IP) blocks on a shared link or bus by reducing the bus contention interference from simultaneous traffic requests and by taking advantage of shorter request latency. The prototype transceiver chip is implemented in 0.18-mu m CMOS and the 10-cm test PC board system achieves an aggregate data rate of 2.5 Gb/s/pin between four off-chip (2Tx-to-2Rx) I/Os.