Importance

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Abstract

A circuit for data stream buffer management, lane alignment, and clock compensation of data transfers across a clock boundary using a single first in first out (FIFO) buffer in each serial channel is described. The RapidIO® data channel, for example, operates using a clock recovered from the data stream. The RapidIO® data stream has embedded special characters, where a select sequence of embedded characters is a clock compensation pattern. A look ahead circuit is used to detect the clock compensation pattern early and generate a clock compensation indicator signal. The FIFO writes data and the associated clock compensation indicator signal in a clock compensation indicator bit in synchronism with the recovered clock. A read circuit using a second clock of a different frequency than the first clock reads data and clock compensation bits from the FIFO and generates an almost empty signal when appropriate. A multiplexer is used at the FIFO output to pad data to the system interface. A clock compensation control circuit generates a selection signal based on an AND of the almost empty signal and the clock compensation indicator bit associated with a data element read out of the FIFO and using the selection signal to control the multiplexer selection signal.

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First Claim