Xilinx Virtex-4 User Manual

44 www.xilinx.com Embedded Tri-Mode Ethernet MAC User Guide
UG074 (v2.2) February 22, 2010
Chapter 3: Client, Host, and MDIO Interfaces
R
Virtual LAN (VLAN) Tagged Frames
Figure 3-7 shows the transmission of a VLAN tagged frame (if enabled). The handshaking
signals across the interface do not change. However, the VLAN type tag 0x8100 must be
supplied by the client to show the frame as VLAN tagged. The client also supplies the two
bytes of tag control information, V1 and V2, at the appropriate times in the data stream.
More information on the contents of these two bytes can be found in the IEEE Std 802.3-
2002 specification.
Maximum Permitted Frame Length and Jumbo Frames
The maximum length of a frame specified in the IEEE Std 802.3-2002 specification is
1518 bytes for non-VLAN tagged frames. VLAN tagged frames can be extended to
1522 bytes. When jumbo frame handling is disabled and the client attempts to transmit a
frame that exceeds the maximum legal length, the Ethernet MAC inserts an error code to
corrupt the current frame and the frame is truncated to the maximum legal length. When
jumbo frame handling is enabled, frames longer than the legal maximum are transmitted
error free.
For more information on enabling and disabling jumbo frame handling, see
“Configuration Registers,” page 74.
Figure 3-7: Transmission of a VLAN Tagged Frame
ug074_3_09_062105
CLIENTEMAC#TXCLIENTCLKIN
CLIENTEMAC#TXDVLD
EMAC#CLIENTTXACK
CLIENTEMAC#TXFIRSTBYTE
CLIENTEMAC#TXUNDERRUN
EMAC#CLIENTTXCOLLISION
EMAC#CLIENTTXRETRANSMIT
EMAC#PHYTXCHARISK
(SGMII or 1000BASE-X
PCS/PMA only)
EMAC#PHYCHARDISPMODE
(SGMII or 1000BASE-X
PCS/PMA only)
DA SA DATA
L/TVLAN
tag
81 00 V1 V2
CLIENTEMAC#TXD[7:0]
EMAC#PHYTXD[7:0]
(SGMII or 1000BASE-X
PCS/PMA only)
/T/ /R/
PRE
/S/
/I1/ /I2/ /I2/ /I2/ /I2/
FCS
SFD
/I1/
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Xilinx Virtex-4 Specifications

General

Brand	Xilinx
Model	Virtex-4
Category	Motherboard
Language	English