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

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R<br />

<strong>Ethernet</strong> <strong>MAC</strong> Clocks<br />

Appendix B<br />

This appendix provides an overview of the <strong>Ethernet</strong> <strong>MAC</strong> clocking schemes. The clocking<br />

schemes that are internal to the <strong>Ethernet</strong> <strong>MAC</strong> block are introduced, followed by the clock<br />

connections to and from the <strong>FPGA</strong> logic. Finally, all clock input and output frequencies<br />

and definitions are listed for reference, dependent on the mode of operation.<br />

<strong>Ethernet</strong> <strong>MAC</strong> Internal Clock Logic Overview<br />

<strong>Ethernet</strong> <strong>MAC</strong> Block<br />

The large number of clock signals can give an overwhelming first impression. Figure B-1 is<br />

a simplified diagram to illustrate all <strong>Ethernet</strong> <strong>MAC</strong> input and output clock signals.<br />

E<strong>MAC</strong>#CLIENTTXCLIENTCLKOUT<br />

E<strong>MAC</strong>#CLIENTRXCLIENTCLKOUT<br />

PHYE<strong>MAC</strong>#GTXCLK<br />

CLIENTE<strong>MAC</strong>#TXCLIENTCLKIN<br />

CLIENTE<strong>MAC</strong>#RXCLIENTCLKIN<br />

Clock Generator<br />

Output Clock Products<br />

Input Clock Sources<br />

TX<br />

Client<br />

Datapath<br />

RX<br />

Client<br />

Datapath<br />

TX<br />

PHY<br />

Datapath<br />

RX<br />

PHY<br />

Datapath<br />

E<strong>MAC</strong>#PHYTXGMIIMIICLKOUT<br />

E<strong>MAC</strong>#PHYTXCLK<br />

PHYE<strong>MAC</strong>#MIITXCLK<br />

PHYE<strong>MAC</strong>#TXGMIIMIICLKIN<br />

PHYE<strong>MAC</strong>#RXCLK<br />

Figure B-1: Overview of <strong>Ethernet</strong> <strong>MAC</strong> Clock Circuitry<br />

<strong>UG194</strong>_B_01_072606<br />

TE<strong>MAC</strong> User Guide www.xilinx.com 205<br />

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

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