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

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

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GTX_CLK<br />

R<br />

IBUFG<br />

TX CLIENT<br />

LOGIC<br />

RX CLIENT<br />

LOGIC<br />

BUFG<br />

x<br />

x<br />

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

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

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

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

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

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

E<strong>MAC</strong>#PHYTXD[7:0]<br />

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

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

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

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

PHYE<strong>MAC</strong>#RXD[7:0]<br />

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

Notes:<br />

1) A regional buffer (BUFR) can replace this BUFG.<br />

In addition, the clock input of IFD can be driven by a BUFIO.<br />

Refer to UG190, <strong>Virtex</strong>-5 <strong>FPGA</strong> User Guide for BUFR usage guidelines.<br />

Figure 6-6: 1 Gb/s GMII Clock Management<br />

Gigabit Media Independent Interface (GMII)<br />

GTX_CLK must be provided to the <strong>Ethernet</strong> <strong>MAC</strong>. This high-quality, 125 MHz clock<br />

satisfies the IEEE Std 802.3-2002 requirements.<br />

The GTX_CLK input is routed onto the global clock network via an IBUFG and BUFG. The<br />

output of the BUFG connects to:<br />

GMII_TXD registers in the <strong>FPGA</strong> logic<br />

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

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

TX client logic<br />

GMII_TX_CLK is forwarded along with the GMII data signals from the <strong>FPGA</strong> to the PHY.<br />

An IOB DDR output register is used; this is a predictable way to produce the clock because<br />

the clock-to-pad delay is the same as that for the GMII_TXD signals. This forwarded clock<br />

TE<strong>MAC</strong> User Guide www.xilinx.com 145<br />

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

x<br />

0<br />

1<br />

BUFG (1)<br />

IFD<br />

Q D<br />

D<br />

OFD<br />

Q<br />

ODDR<br />

D1<br />

D2<br />

IDELAY<br />

IDELAY<br />

OBUF<br />

OBUF<br />

IBUFG<br />

IBUF<br />

GMII_TXD[7:0]<br />

GMII_TX_CLK<br />

GMII_RX_CLK<br />

GMII_RXD[7:0]<br />

<strong>UG194</strong>_6_06_091409

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