Article ID: 000081466 Content Type: Troubleshooting Last Reviewed: 09/11/2012

Is the hard transceiver 8B/10B encoder/decoder in Stratix, Arria, and Cyclone family transceiver devices Fibre Channel compliant?

Environment

  • Stratix® GX FPGA
  • Cyclone® IV GX FPGA
  • Arria® II GX FPGA
  • Arria® II GZ FPGA
  • Stratix® IV GT FPGA
  • Stratix® IV GX FPGA
  • Stratix® II GX FPGA
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Description

No, the 8B/10B encoder/decoder does not satisfy all the requirements for the Fibre Channel protocol in Stratix® GX, Stratix II GX, Stratix IV GX/T, Arria® GX, Arria II GX, or Cyclone® IV GX devices.

1) Fibre Channel protocol requirements for 1.062 and 2.125 Gbps states that the transmitter needs to start up with negative running disparity. Further, the standard has disparity rules for Ordered Sets. -The embedded 8B/10B encoder does start up with negative disparity.

However, the encoder does not contain the functionality to force negative current running disparity at any time. This is required to be able to meet the disparity rules for Ordered Sets.

2) Fibre Channel protocol requirements for "Detection of Invalid transmission Word" for 1.062 and 2.125 Gbps state that Ordered Sets received with incorrect beginning running disparity be flagged as an error. -The current 8B/10B implementation determines running disparity on a character-by-character basis and not Ordered Sets.

Due to these non-compliances, customers may or may not be able to use the embedded 8B/10B encoder/decoder in the transceiver megafunction. This decision would have to be based on how the customer is implementing their Fibre Channel or Fibre Channel-like architecture.

Possible workarounds:

  • User would have to implement 8B/10B encoding and decoding blocks in the PLD core to be able to meet the specific requirements in both the transmit and receive directions.
  • User could use 8B10B Encoder/Decoder MegaCore Function from Altera Corporation
  • User could use Multi-Gigabit Fibre Channel Transport Core from MorethanIP

References:

  • Fibre Channel, Physical Signaling Interface (FC-PH) REV 2.13 December 4, 1991
  • Fibre Channel Framing and Signaling (FC-FS) REV 1.90

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