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Altera_Forum's avatar
Altera_Forum
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16 years ago

FPGA Configuration Problem

A strange one here. I'm trying to power up a Cyclone III EP3C10 in active serial mode, and even before the device tries to access the PROM it drives all I/O pins low and does not make any attempt at external access.

The 1.2, 2.5, and 3.3 V supplies all rise monotonically within 5 mS of each other, all the right pins are connected to all the right voltages, but the only activity I see is that the nConfig and Init_Done lines rise to about 2V while the device is powering up, and then they go to ground. nStatus, Conf_Done, and all other lines never go high.

I want to blame the chip, but we've installed 2 chips on 2 boards, and we're seeing the same problem. Unfortunately, we don't have any known good designs we can use to test out the chip.

Any ideas? Thanks.

6 Replies

  • Altera_Forum's avatar
    Altera_Forum
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    16 years ago

    If it's an EQFP144 device, did you connect the enhanced pad to GND?

  • Altera_Forum's avatar
    Altera_Forum
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    16 years ago

    --- Quote Start ---

    If it's an EQFP144 device, did you connect the enhanced pad to GND?

    --- Quote End ---

    I just saw that pad. No, it is not grounded, but I can set that up pretty easily. Altera really doesn't draw enough attention to that pad if not connecting it can kill the entire part.

    --- Quote Start ---

    What are your MSEL pins set to?

    Jake

    --- Quote End ---

    --- Quote Start ---

    And how are the MSEL pins wired?

    --- Quote End ---

    MSEL[2:0] is 010, and the lines are tied direct to GND or +2.5
  • Altera_Forum's avatar
    Altera_Forum
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    16 years ago

    --- Quote Start ---

    Altera really doesn't draw enough attention to that pad

    --- Quote End ---

    The fact, that this issue is a series topic in the forum seems to confirm your statement. I found the "exposed pad" thing mentioned in two places in the device manual and also in the Device Pin-Out document. The amount of informations hasn't changed from Device Manual V1.0 to recent V2.1.

    You may want to read a ceterum censeo "Furthermore, don't forget to connect the exposed pad" in each Handbook chapter.
  • Altera_Forum's avatar
    Altera_Forum
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    16 years ago

    Yes, the hidden ground pad just needed to be grounded. The board is now powering up normally.

    That pad should really be listed as a pin in the pinout document, not as a footnote. It seems to be rather important.