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The Configuration Problem Solver
CONCLUSION
The DONE Pin is being held Low externally.
The DONE pin is an Open-Drain driver that must be pulled up to achieve a logic high. While the FPGA does have a programmable internal pullup resistor to the DONE pad, we recommend using an external 4.7Kohm resistor. If necessary, seperate the DONE pin from the board to verify if an external source is holding it low. If the DOUT has gone High then the DONE pin must have been released internally. Double check the STARTUP sequence options selected for Bitstream generation. The SyncToDone is recommended, and required if multiple FPGAs are Daisy-Chained for Express Mode Configuration. The SyncToDone prevents the STARTUP sequence from continuing (ie I/Os become active) until the DONE pin is externally allowed to pull High. If the FPGA is Daisy-Chained then the DONE is probably being held Low by one of the other FPGAs. The recommended STARTUP Options are DONE:C1 OutputsActive:DI GSRinactive:DI. See also the related answers. |
| HISTORY |
| Family: XC4000X |
| Mode: Express |
| DONE: LOW |
| INIT: HIGH |
| DOUT: HIGH |