Xilinx 1000BASE-X - Manual (Page 217)

Ethernet 1000BASE-X PCS/PMA or SGMII v9.1 www.xilinx.com 217
UG155 March 24, 2008
End of Frame Encoding R
Note: The first Idle to follow the frame termination sequence will be a /I1/ if the frame ended with
positive running disparity or a /I2/ if the frame ended with negative running disparity. This is illustrated
as the shaded code group.
Reception of the Odd Case
Figure D-8 illustrates the reception of the in-bound code-group stream, received either
serially using the RocketIO transceiver, or in parallel across the TBI, and translation of this
code-group stream into the receiver GMII. This is performed by the PCS Receive Engine.
Note that, as defined in IEEE 802.3 figure 36-7b, the combined /T/R/R/ sequence results
in the GMII encoding of Frame Extension. This occurs even in full-duplex mode.
Figure D-7: 1000BASE-X Transmit State Machine Operation (Even Case)
gmii_txd[7:0]
gmii_tx_en
gmii_tx_er
FCS
FCS I2 I2 I2 T R I1/I2 R
tx_code_group
PCS Transmit Engine Encoding
Figure D-8: 1000BASE-X Reception State Machine Operation (Odd Case)
gmii_rxd[7:0]
gmii_rx_dv
gmii_rx_er
FCS
rx_code_group FCS I2 I2 I2 T R I1/I2 R
0x0F
PCS Receive Engine Decoding