AR# 29218 Virtex-5/Spartan-6 GTP/GTX RocketIO - Loss of Sync (LOS) does not behave as expected in certain conditions
Description
Solution
When Channel Bonding is not used, the Loss of Sync state machine inside the GTP/GTX will get stuck in the RESYNC state indefinitely.
To work around this issue in designs that do not use Channel Bonding, you can set:
CHAN_BOND_SEQ_1_1 to 10'b0100000000
CHAN_BOND_SEQ_1_ENABLE to 4'b0001
The graphic below shows the same design with the above attribute changes.
This work-around will not adversely affect single-channel designs since 0x00 is not a valid K character and will not appear in any 8b/10b encoded data stream.
When Channel Bonding is used
When channel bonding is used in the design, you can expect the Loss of Sync state machine to report RESYNC when any K character is detected.
There is no method by which to work around this issue when Channel Bonding is enabled. The Xilinx XAUI Core bypasses this issue by implementing LOS in the FPGA fabric when the Implement IEEE Synchronization State Machine option is selected in the CORE Generator GUI. When this option is not selected, the XAUI Core only uses bit 1 of the RXLOSSOFSYNC port.
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