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Chapter 7: 1000BASE-X with RocketIO Transceivers

Virtex-4 FX Devices

Figure 7-6illustrates sharing clock resources across multiple instantiations of the core when using MGTs. Note that the example design, when using the Virtex-4 family, can be generated to connect either a single instance of the core, or connect a pair of core instances to the transceiver pair present in an MGT tile. Figure 7-6shows two instantiations of the block level, where each block contains a pair of cores, subsequently illustrating clock sharing between four cores in total.

More cores can be added by continuing to instantiate extra block-level modules. Share clocks only between the MGTs in a single column. For each column, use a single brefclk_p and brefclk_n differential clock pair and connect this to a GT11CLK_MGT primitive. The clock output from this primitive should be shared across all used RocketIO tiles in the column. See the Virtex-4 RocketIO Multi-Gigabit Transceiver User Guide (UG076) for more information.

To provide the 125 MHz clock for all core instances, select a TXOUTCLK1 port from any MGT. This can be routed onto global clock routing using a BUFG as illustrated, and shared between all cores and MGTs in the column. Although not illustrated in Figure 7-6, dclk (the clock used for the calibration blocks and for the Dynamic Reconfiguration Port (DRP) of the MGTs) can also be shared.

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Ethernet 1000BASE-X PCS/PMA or SGMII v9.1

 

 

UG155 March 24, 2008

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Xilinx 1000BASE-X manual Virtex-4 FX Devices