Hi FvM,
Thank you for your answer.
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Did you already try other virtual JTAG instances
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No, I'm ALTERA beginner and I don't know these functions ! If you know quick test that I can do, let me know.
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JTAG variants don't due to signal quality problems of the JTAG chain (ringing TCK)
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I just check the JTAG signals integrity with scope, TCK is clean and is in phase with data.
It seems that ALTERA programmer successfully configure my EP2C50 but got error when trying to program the flash memory device (EPCS16).