Transceiver PCS Question

[Altera_Forum]

When implementing GIGE on CycloneV transceiver using Custom Phy is needed to perform "running disparity rules" on FPGA logic outside transceiver phy? 

 I think the answer is yes, but I would to check with experts ;-)  Thank you!

[Altera_Forum]

Are you referring to running disparity checking? If I remember it correct the Custom PHY has this function available where it will flag error when running disparity is incorrect. The output status port is rx_disperr.

[Altera_Forum]

thank you! I will check them.

[Altera_Forum]

Yes. If you transmit even length packet, the FCS must be followed by /T/R/ (tx_paralleldata = 16'hFDF7, tx_datak = 2'b11). If you transmit odd length frames, the FCS must be followed by /T/R/R/ (tx_paralleldata = 24'hFDF7F7, tx_datak = 3'b111). 

 BTW, the GIGE mode is tricky. You should go through AN537 if you plan to use 1000BASE-X/SGMII Auto-Negotiation. https://www.altera.com/content/dam/altera-www/global/en_us/pdfs/literature/an/an537.pdf

[Altera_Forum]

Ok, so I need to transmit control codes on the line and check if extra /R/ is need based on even/odd packet but PCS will check running disparity to perform 8b/10b job. 

 e.g., I'm on sync phase and want to transmit data 8'hAA. I will send a /S/ 8'hAA /T/R/R ((tx_paralleldata = 40'hFBAAFDD7D7 ) , tx_datak = 5'b10111)) and then check if rx_disperr still no error. It is correct?  Cheers! ps. I'm not planning auto negotiation for now :)

[Altera_Forum]

Hi kkaibara, 

 Thanks for sharing the AN.

[Altera_Forum]

Yes, correct. If I test the phy, I monitor rx_runningdisp and rx_errdetect status signals too. Because the running disparity of K28.5 in IDLE code (/I/) must be minus disparity (rx_runningdisp = 1). 

 The simple test pattern will be /I/I/I/I/I/I/I/I/S/8'hAA/T/R/R/I/I/I/I/I/I/I/I. rx_disperr and rx_errdetect should be low, and rx_runningdisp should be high when rx_paralleldata = 8'hBC, tx_datak = 1'b1.

[Altera_Forum]

Thank you kkaibara this helps me a lot. 

 I will run this test pattern when I write sync state machine. ;-)  cheers!