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Xilinx UG194 Virtex-5 FPGA Embedded Tri-Mode Ethernet MAC ...

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Chapter 6: Physical Interface<br />

“GMII Clock Management for <strong>Tri</strong>-Speed Operation Using Clock Enables”<br />

An alternative advanced clocking scheme for tri-speed operation, which saves on<br />

global clock resources.<br />

The advanced clocking schemes, Byte PHY and Clock Enables, both provide the same<br />

saving on global clocking resources and can be used interchangeably for GMII, based on<br />

user preference.<br />

If the CORE Generator tool is used, the wrapper files for the <strong>Ethernet</strong> <strong>MAC</strong> that are created<br />

will contain the logic described in these sections. By using the CORE Generator tool, the<br />

time required to instantiate the <strong>Ethernet</strong> <strong>MAC</strong> into a usable design is greatly reduced. See<br />

“Accessing the <strong>Ethernet</strong> <strong>MAC</strong> from the CORE Generator Tool,” page 25.<br />

GMII Clock Management for 1 Gb/s Only<br />

Figure 6-6 shows GMII clock management when using a single <strong>Ethernet</strong> <strong>MAC</strong>.<br />

144 www.xilinx.com TE<strong>MAC</strong> User Guide<br />

<strong>UG194</strong> (v1.10) February 14, 2011<br />

R

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