Xilinx Virtex-4 User Manual

Embedded Tri-Mode Ethernet MAC User Guide www.xilinx.com 149
UG074 (v2.2) February 22, 2010
Ethernet MAC Configuration
R
PCS/PMA mode, EMAC#CLIENTTXGMIIMIICLKOUT is derived from the
PHYEMAC#GTXCLK. See Chapter 4, “Physical Interface” for clock usage.
Receive Clocking Scheme
Figure 5-2 shows the clocks used in the receive module of the Ethernet MAC. In this figure,
RX_CORE_CLK and RX_GMII_MII_CLK are internal clock signals.
The clock generation module takes the PHYEMAC#RXCLK from the physical interface
and generates the EMAC#CLIENTRXCLIENTCLKOUT to run the circuitry in the FPGA
fabric connecting to the client side. CLIENTEMAC#RXCLIENTCLKIN runs the client logic
and receive engine inside the Ethernet MAC. This clock signal must be from the FPGA
clock drivers (BUFG) of EMAC#CLIENTRXCLIENTCLKOUT.
When configured in MII/GMII/RGMII mode, the internal RX_GMII_MII_CLK is derived
from the PHYEMAC#RXCLK and used to run the MII/GMII/RGMII sublayer. When the
Ethernet MAC is configured in either SGMII or 1000BASE-X PCS/PMA mode, the clock to
run the PCS/PMA sublayer is generated from the PHYEMAC#GTXCLK. See Chapter 4,
“Physical Interface” for clock usage.
Ethernet MAC Configuration
The Ethernet MAC can be configured using hardware or by accessing the registers through
the host interface in software. The three methods for configuration are described in the
following sections:
1. Tie-off pins in hardware (see “Tie-Off Pins” in Chapter 2)
2. Generic host bus using the host interface (see “Generic Host Bus” in Chapter 3)
3. DCR using the host interface (see “Using the DCR Bus as the Host Bus” in Chapter 3)
Table 5-6 shows the register addresses for each of the two Ethernet MACs.
Figure 5-2: Receive Clocks
CLKGEN
RX
Core
RX
Client
Datapath
Synchronous
Buffer
GMII/MII
PCS/PMA
RX_CORE_CLK
RX_GMII_MII_CLK
RXCLK
from PHY
EMAC#CLIENTRXCLIENTCLKOUT
PHYEMAC#RXCLKPHYEMAC#GTXCLK
CLIENTEMAC#RXCLIENTCLKIN
ug074_3_02_102004
GMII/MII
Logic
Client
Logic
BUFG
BUFG
Ethernet MAC Block
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Xilinx Virtex-4 Specifications

General

Brand	Xilinx
Model	Virtex-4
Category	Motherboard
Language	English