The Configuration Problem Solver

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CONCLUSION

LengthCount Match has not been met.

In order for the FPGA to enter the Startup Sequence and complete the configuration process two conditions must be satisfied:

(1) All Data Frames must be correctly loaded into memory resulting in the memory being Full.

(2) LengthCount Match must occur.

LengthCount Match occurs when the total number of CCLK cycles used so far in the configuration process equal in value to the 24 bit LengthCount Number in the Header of the bitstream. LengthCount Match must occur after all Data Frames have been loaded and the configuration memory is full. If LengthCount Match happens too early, before memory is full, then the 24 bit LengthCount counter will need to "roll over" before these conditions can both be satisfied. This can be tested by allowing the FPGA to apply 2^24 (~18,000,000) extra CCLK cycles.

If the FPGA completes configuration and Startup after the extra CCLKs then this condition was most likely caused by extra ones '1' or null bits present before the beginning of the configuration data. This can be verified by checking again how many fill bits are observed on DOUT prior to the Preamble. The number should not be more than 8 plus 1.5 CCLK delay time.

Another possible cause may be that the configuration process was not allowed to complete or was terminated to early. Check that the CCLK is still running. See also related answers.

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