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Altera_Forum's avatar
Altera_Forum
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17 years ago

CYCLONE III can't CONFIGURE !...

Hi Everybody,

We use Cyclone III (EP3C25E144C8N) fpga in our project. We use EPCS16 for serial programmer.

Problem is, fpga cannot finish the configuration. I watched the signals with a logic analyser on the EPCS16 and saw that fpga cyclically asks the STATUS byte from the EPCS16, and it replies as 0x00, but fpga doesn't do anything different, asks the status byte again and again, forever. thus, config done pin never goes up and never enters initialization.

Please look at my schematic and Logic analyzer data stream and help me ...

Best Regards...

6 Replies

  • Altera_Forum's avatar
    Altera_Forum
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    17 years ago

    i have added another logic analyzer picture, this time including nSTATUS pin.

    Still no comment?

    No idea?
  • Altera_Forum's avatar
    Altera_Forum
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    17 years ago

    Is this waveform your first cycle?

    Usually EPCS being asked report status after erase or write as I understand.
  • Altera_Forum's avatar
    Altera_Forum
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    17 years ago

    i have loaded successfully a simple program into the EPCS16. I know this because i made verification and no errors occured.

    secondly, this is the first command sent by the fpga and it is Reading Status command. it is something normal to read it as 0x00. this is the normal condition.

    but when fpga reads it, nSTATUS bit is held down and a reset is initiated. after that it again tries to read status info in a locked loop. no way out.
  • Altera_Forum's avatar
    Altera_Forum
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    17 years ago

    The only thing I saw your schematic different to datasheet is nCE (FPGA pin8, EPCS pin 1) didn't add a 10Kohm to Gnd...

  • Altera_Forum's avatar
    Altera_Forum
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    17 years ago

    You connected 1A power schottky diodes with about 100 pF junction capacitance, that can't work. Signal diodes as BAS40 would be O.K. as protection.

  • Altera_Forum's avatar
    Altera_Forum
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    17 years ago

    Thanks everybody!..

    I have solved the problem, it was the wrong value of R506 resistor. My technician had mounted 24K ohm instead of 24 ohm.

    funny but real..

    this study shows the importance of the value of this resistor.

    Regards..