CPRI Intel® FPGA IP User Guide

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ID 683595
Date 4/04/2022
Public

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3.20.2. CPRI Intel® FPGA IP Core Self-Synchronization Feature

Intel® provides a self-synchronization testing feature that supports an RE slave in a CPRI link external loopback configuration. This feature is intended to work correctly only for Layer 1 testing.

By default, only an REC master can function correctly in a CPRI link external loopback configuration. An RE slave in external loopback configuration cannot achieve frame synchronization, because the CPRI RX interface must lock on to the K28.5 character before the CPRI TX interface can begin sending K28.5 characters. Therefore, no K28.5 character is ever transmitted on the RE slave loopback CPRI link.

However, in an RE slave CPRI IP you can specify that the CPRI TX interface begin sending K28.5 characters before the CPRI Rx interface locks on to the K28.5 character from the CPRI link. This feature supports a CPRI RE slave in achieving frame synchronization without being connected to a CPRI master, and allows you to test your CPRI RE slave without the need for an additional CPRI IP.

To turn on this feature, connect your CPRI RE slave in a CPRI link external loopback configuration, and set the tx_enable_force field of the L1_CONFIG register to the value of 1.

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