My Virtex device will not start the configuration process.
Before any data is loaded into the device, a sync word (0xAA995566) must be loaded. If it is not loaded properly, all data will be ignored. If the configuration is being done via the SelectMAP interface, make sure that D0 is the MSB of the data word. If the data is loaded backwards, it will not be synchronized.
If the mode pins are set incorrectly, the device may not configure. For instance, if the intention
is to configure in Master Serial and the mode pins are accidently set to Slave Serial, the device
will be expecting a clock, but none will come.
If there are no other loads on the mode pins, the internal pull-ups will pull them to a logic level
one. If they require pull-downs, make sure the voltage level is low enough at the pin.
The PROG pin must be released (and the INIT line after it) before the device the configuration
process. If there is an external load pulling either PROG or INIT low, the device cannot be configured
in either serial mode or SelectMAP mode. If INIT is pulled low only, the device may be configured via
JTAG. But if PROG is pulled low, the device cannot be configured in any mode.