Description

Solution

This article describes the restrictions on the TXOUTCLK and RXOUTCLK ports of the transceiver. To cope with these restrictions, the MMCM transmitter input now comes from the reference clock, IBUFDS_GTE2. And, the transceiver TXOUTCLK port is disabled. The receiver side clocking remains unchanged. You must also set the TXOUTCLKSEL input to the GTXE2_CHANNEL instance to "000".

1. Change the input to the k7_bufg_gen BUFG component in the <component_name>/example_design/gtx_and_clocks/gt_and_clocks.vhd file: k7_bufg_gen : BUFG port map (I => refclk, O => txoutclk_bufg);
2. Route the BUFG output to the refclk input of the tx_clk_gen instance.
3. Leave the GT0_TXOUTCLK_OUT port of the GTWIZARD instance open:
   GT0_TXOUTCLK_OUT => open,

Figure 1 shows the revised clocking scheme.

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For the LogiCORE CPRI Release Notes and Known Issues, see (Xilinx Answer 36969).

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