184 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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Features of this configuration include:
Direct internal connections are made between the GMII interfaces between the two
cores.
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 GTP transceiver, the entire GMII is
synchronous to a single clock domain. Therefore userclk2 is used as the 125MHz
reference clock for both cores, an d the transmitte r and receiver lo gic of the 1-Giga bit
Ethernet MAC core now operate in the same clock domain.
Virtex-5 FXT Devices
Figure 13-5 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 13-5: 1-Gigabit Ethernet MAC Extended to Include 1000BASE-X PCS and
PMA Using a Virtex-5 GTX Transceiver
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-5
GTX
RocketIO
no
connection
userclk
userclk2
RocketIO I/F
CLKIN
userclk2 (125MHz)
TXUSRCLK0
TXUSRCLK20
RXUSRCLK0
RXUSRCLK20
REFCLKOUT
component_name_block
(Block Level from example design)
clkin
(125MHz)
IBUFGDS
IPAD
brefclkp
IPAD
brefclkn
DCM
CLKIN CLK0
FB
BUFG
CLKDV
BUFG
userclk (62.5MHz)