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Altera_Forum's avatar
Altera_Forum
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14 years ago

EP3C25 nStatus 1V

I have five EP3C25 borad, 3 of them are working well. But the rest 2 will sometimes boot fail. The working mode is AS or fast AS from EPCS4. There're 10K pull up on nStatus, nConfig, Conf_done, MSELs are 010 or 101, tied to GND or 3V.

Fail boards are in common that the nStatus pin goes from 0V to about 1.1V after power up or after the nConfig is tied to ground then released up, no DCLK or other signals from EP3C25. On the success boot, it can load configuration from EPCS4, while the nStatus is about 1.5V and will slowly move down to 1.2V.

Do you have any idea on this situation? Thx.

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  • Altera_Forum's avatar
    Altera_Forum
    Icon for Honored Contributor rankHonored Contributor
    14 years ago

    I'm not sure... the manual doesn't say anything about being able to change the MSEL pins before a reconfiguration, and even insists on the fact that they should only be directry connected to ground or VCCA and not controlled by an external component. This could indicate that the MSEL pins are only read once, at the beginning of POR (or that they aren't registered at all...)