1. Home
  2. Field-Programmable Gate Arrays
  3. Aurora_401 reference allows 8B/10B bypass?

Aurora_401 reference allows 8B/10B bypass?

I am currently using version 1.7 of the VHDL Aurora 401 reference design for Xilinx Vertex II Pro RocketIO interface and trying to find a way to bypass 8B/10B. What I do is to change the configurations of ports and attributes of GT_CUSTOM as suggested in RocketIO transceiver User Guide (page 59 to 61 for Ver2.1). Those ports/attributes are:

TXBYPASS8B10B RX_DECODE_USE TXCHARDISPMODE RXCHARDISPVAL

It turns out that CHANNEL_UP is never asserted. The protocol engine seems sending the Sync sequence, but the link is nerver initialized. Does anybody know if Aurora_401 allows bypassing 8B/10B by some easy reconfiguration? If not, is there any sample codes in VHDL using GT_CUSTOM for RocketIO and bypassing 8B/10B? Thanks!

Best Regards,

Johnson Univeristy of Delaware

Reply to
Johnson
Loading thread data ...

If you are bypassing the 8B/10B encoder on transmit, are you doing something in your logic that guarantees that you are still sending a balanced code? what about max run length of "0" and "1"?

If you have disabled 10B/8B at the receiver, are you still sending it comma characters for it to sync to (K28.5 I think).

I suspect the intention of the 8B/10B bypass is for an occasional character in a transmit stream that is predominantly valid 8B/10B encodes, with the bypass being used to achieve something that is very non-standard. While you could use it to send 100 10B characters of "0000000000", I would not expect a receiver to tolerate this.

What is you reason for wanting to bypass the 8B/10B encoder.

Philip Freidin

Philip Freidin Fliptronics

Reply to
Philip Freidin

Whenever I see stuff discussing a channel being "up", I usually assume it refers to connections that use 8B/10B unless it says otherwise.... so... are you sure that CHANNEL_UP can be asserted even when 8B/10B is not being used?

I have to admit that I don't understand what you are saying here. Unless I'm mistaken, if 10B/8B is disabled, the comma characters wouldn't (and actually, couldn't) be extracted from the datastream. Wouldn't that typically cause problems?

We bypass it to do SONET.

Have fun,

Marc

Reply to
Marc Randolph

ElectronDepot website is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.