Procurve 5308xl LINK Auto negotiation generates repeated "5E" byte

[Mike Vigil]

While debugging a LINK issue with a Procurve 5308xl, I noticed that the switch generates a stream of repeating data between LINK negotiation bytes. The data through a XILINX Vertex5 FPGA SERDES indicates the following pattern; BC -> B5 -> 20-> 00 -> BC -> 42 -> 5E (repeated 330 times) -> BC -> B5 -> 00 -> 00, but the 5E data genertates a disparity error.

This only occurs with the "Auto" configuration. The "1000mbs" configuration does not generate "5E" bytes, nor does any other Procurve switch (5406zl), regardless of the configuration.

Does anyone know what the "5E" byte represents?

MIKE