Xilinx 1000BASE-X manual 216

Models: 1000BASE-X

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Appendix D: 1000BASE-X State Machines

Reception of the Even Case

Figure D-6illustrates 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.

rx_code_group

FCS

T R I1/I2 I2

I2

I2

PCS Receive Engine Decoding

gmii_rxd[7:0]

FCS

gmii_rx_dv

 

gmii_rx_er

 

Figure D-6:1000BASE-X Reception State Machine Operation (Even Case)

The Odd Transmission Case

Figure D-7illustrates the translation of GMII encoding into the code-group stream performed by the PCS Transmit Engine; this stream is transmitted out of the core, either serially using the RocketIO transceiver, or in parallel across the TBI.

In response to the deassertion of gmii_tx_en, an End of Packet code group /T/ is immediately inserted. Note that the even and odd alignment described in “Start of Frame Encoding” persists throughout the Ethernet frame. If the /T/ character occurs in the odd position (the frame contained an odd number of bytes starting from the /S/ character), then this is followed with two Carrier Extend code groups /R/. This allows the /K28.5/ character of the following Idle code group to be aligned to the even position.

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Ethernet 1000BASE-X PCS/PMA or SGMII v9.1

 

 

UG155 March 24, 2008

Page 216
Image 216
Xilinx 1000BASE-X manual 216