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Carlhermann's avatar
Carlhermann
Icon for Occasional Contributor rankOccasional Contributor
12 days ago
Solved

Unable to scan JTAG chain, TCK only 2V

I have trouble with some development board with 10CL006YE144G. While the configuation by JTAG worked a while, the FPGA is no longer recognized by the programmer using Autodetect.  I checked the volt...
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  • FakhrulA_altera's avatar
    FakhrulA_altera
    2 days ago

    Hello Carlhermann,
     

    Thank you for the detailed testing. Your standalone test confirms that the voltage drop is caused by the older USB-Blaster cable rather than the FPGA or development board.


    A 2.5 V target supply and the 1 kΩ TCK pull-down are supported connections. However, older USB-Blaster hardware revisions used a different MAX3378-based output circuit, while later revisions added buffering. The failing cable therefore appears to have insufficient output-drive margin or may be degraded; this does not indicate that the FPGA is damaged.


    Please continue using the known-good cable. No board modification should be required, and we can consider this issue resolved.


    Best regards, 
    Fakhrul

FakhrulA_altera's avatar
FakhrulA_altera
Icon for Regular Contributor rankRegular Contributor
2 days ago

Hello Carlhermann,
 

Thank you for the detailed testing. Your standalone test confirms that the voltage drop is caused by the older USB-Blaster cable rather than the FPGA or development board.


A 2.5 V target supply and the 1 kΩ TCK pull-down are supported connections. However, older USB-Blaster hardware revisions used a different MAX3378-based output circuit, while later revisions added buffering. The failing cable therefore appears to have insufficient output-drive margin or may be degraded; this does not indicate that the FPGA is damaged.


Please continue using the known-good cable. No board modification should be required, and we can consider this issue resolved.


Best regards, 
Fakhrul