Xilinx Virtex-4 User Manual page 41

R
In-Band Parameter Encoding
The Ethernet MAC frame parameters, destination address, source address, length/type,
and the FCS are encoded within the same data stream used to transfer the frame payload
instead of separate ports. This provides the maximum flexibility in switching applications.
Padding
When fewer than 46 bytes of data are supplied by the client to the Ethernet MAC, the
transmitter module adds padding – up to the minimum frame length. However, if the
Ethernet MAC is configured for client-passed FCS, the client must also supply the padding
to maintain the minimum frame length (see
Client-Supplied FCS Passing
In the transmission timing case shown in
have the FCS field passed in by the client (see
client must ensure that the frame meets the Ethernet minimum frame length requirements;
the Ethernet MAC does not pad the payload.
CLIENTEMAC#TXCLIENTCLKIN
CLIENTEMAC#TXDVLD
EMAC#CLIENTTXACK
CLIENTEMAC#TXFIRSTBYTE
CLIENTEMAC#TXUNDERRUN
EMAC#CLIENTTXCOLLISION
EMAC#CLIENTTXRETRANSMIT
CLIENTEMAC#TXD[7:0]
EMAC#PHYTXD[7:0]
(SGMII or 1000BASE-X
PCS/PMA only)
EMAC#PHYTXCHARISK
(SGMII or 1000BASE-X
PCS/PMA only)
EMAC#PHYCHARDISPMODE
(SGMII or 1000BASE-X
PCS/PMA only)
www.BDTIC.com/XILINX
Embedded Tri-Mode Ethernet MAC User Guide
UG074 (v2.2) February 22, 2010
DA
/I1/ /I2/ /I2/ /I2/
Figure 3-4: Frame Transmission with Client-Supplied FCS
www.xilinx.com
"Client-Supplied FCS Passing," page
Figure 3-4, an Ethernet MAC is configured to
"Configuration Registers," page
L/T
SA
/I2/ /S/ PRE
SFD
Client Interface
74). The
DATA FCS
FCS
/T/ /R/
ug074_3_06_072705
41).
/I1/
41