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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 />

TX Client<br />

Logic<br />

RX Client<br />

Logic<br />

R<br />

IBUF<br />

BUFG<br />

BUFG<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 />

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

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

E<strong>MAC</strong>#PHYTXD[3:0]<br />

E<strong>MAC</strong>#PHYTXD[7:4]<br />

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

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

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

PHYE<strong>MAC</strong>#RXD[3:0]<br />

PHYE<strong>MAC</strong>#RXD[7:4]<br />

Notes:<br />

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

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

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

Reduced Gigabit Media Independent Interface (RGMII)<br />

BUFG (1)<br />

Figure 6-15: <strong>Tri</strong>-<strong>Mode</strong> RGMII v2.0 Clock Management<br />

RGMII_TXC is derived from the <strong>Ethernet</strong> <strong>MAC</strong> by routing the<br />

E<strong>MAC</strong>#PHYTXGMIIMIICLKOUT port to an IOB DDR output register, followed by an<br />

ODELAY element and an OBUF (which is then connected to the PHY). The ODELAY<br />

element is used to generate 2 ns of skew required between RGMII_TXC and RGMII_TXD at<br />

the <strong>FPGA</strong> device pads. This delay is specified in the Hewlett Packard RGMII Specification,<br />

v2.0 to provide setup and hold times on the external interface.<br />

The E<strong>MAC</strong>#CLIENTTXCLIENTCLKOUT output port connects to the<br />

CLIENTE<strong>MAC</strong>#TXCLIENTCLKIN input port and transmitter client logic in the <strong>FPGA</strong> logic<br />

through a BUFG. The receiver client clocking is similar.<br />

RGMII_RXC is generated by the PHY and connected to PHYE<strong>MAC</strong>#RXCLK via an IBUFG<br />

and a BUFG. Fixed-mode IDELAYs are instantiated on the RGMII clock and data lines.<br />

These are set to sample a 1 ns setup, 1 ns hold window at the device pads. The<br />

CLIENTE<strong>MAC</strong>#DCMLOCKED port must be tied High.<br />

TE<strong>MAC</strong> User Guide www.xilinx.com 159<br />

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

1<br />

0<br />

ODDR<br />

D1<br />

D2<br />

Q<br />

OBUF<br />

RGMII_TXD[3:0]<br />

(1)<br />

BUFG IBUFG<br />

IDELAY<br />

RGMII_RXC<br />

IDDR<br />

Q1 D IDELAY<br />

RGMII_RXD[3:0]<br />

Q2<br />

ODDR<br />

D1<br />

D2<br />

Q<br />

ODELAY<br />

IBUF<br />

OBUF<br />

RGMII_TXC<br />

<strong>UG194</strong>_6_15_080409

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