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182 www.xilinx.com Ethernet 1000BASE-X PCS/PMA or SGMII v9.1
UG155 March 24, 2008
Chapter 13: Interfacing to Other Cores
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• If both cores have been generated with the optional management interface, the MDIO
port can be connected up to that of the 1-Gigabit Ethernet MAC core, allowing the
MAC to access the embedded configuration and status registers of the Ethernet
1000BASE-X PCS/PMA or SGMII core.
• Due to the embedded Receiver Elastic Buffer in the MGT, the entire GMII is
synchronous to a single-clock domain. Therefore, userclk2 is used as the 125 MHz
reference clock for both cores, and the transmitter and receiver logic of the 1-Gigabit
Ethernet MAC core now operate in the same clock domain.
Virtex-4 Devices
Figure 13-2 illustrates the connections and clock management logic required to interface
the Ethernet 1000BASE-X PCS/PMA or SGMII core (when used in 1000BASE-X mode) to
the 1-Gigabit Ethernet MAC core.
Figure 13-3: 1-Gigabit Ethernet MAC Extended to Include 1000BASE-X PCS and
PMA Using a Virtex-4 MGT
1-Gigabit Ethernet
MAC
LogiCORE
gmii_rx_clk
gmii_rxd[7:0]
gmii_rx_dv
gmii_rx_er
gmii_txd[7:0]
gmii_tx_en
gmii_tx_er
gtx_clk
mdc
mdio_in
mdio_out
mdio_tri
Ethernet 1000BASE-X
PCS/PMA or SGMII
LogiCORE
gmii_rxd[7:0]
gmii_rx_dv
gmii_rx_er
gmii_txd[7:0]
gmii_tx_en
gmii_tx_er
mdc
mdio_in
mdio_out
mdio_tri
Virtex-4
GT11
RocketIO
no
connection
userclk
userclk2
RocketIO I/F
IPAD
IPAD
brefclkn
(250 MHz)
Virtex-4
GT11CLK_MGT
MGTCLKP
MGTCLKN
SYNCLK1OUT
brefclkp
(250 MHz)
REFCLK1
userclk2
(125 MHz)
TXUSRCLK
TXUSRCLK2
RXUSRCLK
RXUSRCLK2
synclk1
(250MH
z
‘0’
‘0’
BUFG
TXOUTCLK1
component_name_block
(Block Level from example design)