If power is removed from the FPGA without going through the proper power down procedure, it could cause a system crash or hang. This is due to the fact that the host may have outstanding read requests sent to the endpoint and if the endpoint does not respond, it will cause a completion timeout to occur described in
(Xilinx Answer 35034). If power is applied again, most systems will link train again, but will not enumerate and configure the endpoint. A reset would be required.
Similar problems could occur if the FPGA is reconfigured, but the system is not reset. See
(Xilinx Answer 34871).
Revision History
08/13/2010 - Initial Release