Noise-Tolerant Streaming Real-Time Data Acquisition Fabric for Pulsed Accelerators

Abstract

A noise-tolerant data communications fabric has been developed to meet the real-time data acquisition and control requirements of fast feedback loops, machine protection systems, pulse-to-pulse sequencing, and machine-experiment communications at next-generation pulsed accelerators such as the Next Linear Collider ("NLC"). The fabric is constructed from "platform" or "system-on-a-chip" field programmable gate arrays ("FPGAs") containing embedded processors, block memory, and multi-gigabit serial transceivers interconnected via an array of point-to-point fiber-optic physical links for standard networks such as gigabit Ethernet. The FPGA-based link hardware segments messages of varying priorities into a continuous sequence of fixed-length data cells, interrupting the cell stream of lower priority messages with those comprising higher priority traffic. A high level of noise-tolerance is provided by dedicating almost half the contents of each cell to Reed-Solomon forward error correcting code ("ECC") data. Further reliability is achieved by hardware implementation of algorithms for cell-by-cell receipt acknowledgment, receipt timeout and retransmission after a tunable round-trip propagation delay, and separate backpressure flow control for each priority.