Ethernet Interface - 8.11 English

CPRI LogiCORE IP Product Guide (PG056)

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8.11 English

The Ethernet interface is known as the Fast C&M Channel in the CPRI specification. When the CPRI link starts up, the master and slave negotiate a rate for the Ethernet channel, based on the highest common rate available to both ends of the link. The preferred rate for the CPRI core can be set by programming the Ethernet pointer through the management interface before link start-up. If the preferred rate is changed after the core is in operational mode, then negotiation restarts based on that new rate.

On transmit, the Ethernet interface buffers the incoming data before sending it across the CPRI link. Similarly on receive, the data from the CPRI link is buffered before being reassembled and output on the Ethernet interface. The buffers are capable of storing up to 4096 bytes each, providing support for maximum length Ethernet frames. In MII mode the frame buffers have a width of 4 bits. In GMII mode the frame buffers have a width of 8 bits.