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Thread: Cyclone IV configuration from 1.8V SoC

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    Default Cyclone IV configuration from 1.8V SoC

    I want to configure a Cyclone IV part (EP4CE10F17C7) using passive serial mode from an onboard processor. The processor's I/O pins are all 1.8V logic level. I would think this would be fine if I set VDDIO for bank 1 (nCONFIG, DCLK and DATA0 pins) to 1.8V.

    However, I have seen confusing information in the Cyclone IV handbook/datasheet/configuration handbook about the PS configuration requiring 2.5V IO.

    Does this mean 1.8V is not possible for this?

    Is it possible to configure using 1.8V Passive Serial, or do I have to set bank1 VDDIO to 2.5V and add a level converter?

  2. #2
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    Default Re: Cyclone IV configuration from 1.8V SoC

    Yes - you can configure Cyclone IV devices in PS mode at 1.8V.

    A few gotchas to note. MSEL pins are tied to GND or VCCA, which needs to be powered at 2.5V. Also, CONF_DONE lives in bank 6. So it's pull-up resistor should be connected to the supply for bank 6, not bank 1.

    Cheers,
    Alex

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    Default Re: Cyclone IV configuration from 1.8V SoC

    Alex, thank you very much. That's exactly what I was hoping to confirm. In my case, bank 6 is also 1.8V. And MSEL pins will all be grounded, so I think everything is good.

    Given this, I'm confused by the documentation. Can anyone explain what the meaning of the "Configuration Voltage Standard" listed in the handbook Table 8-5 "Configuration Schemes for Cyclone IV E Devices" (see attached)? Under Passive Serial, MSEL=0000, it lists configuration voltages as 3.3, 3.0, 2.5. No 1.8V, am I missing something?

    table8-5.jpg

    As I had said, I plan to have MSEL=0000 and use 1.8V signals to configure. Despite the docs, I trust it will work.

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    Default Re: Cyclone IV configuration from 1.8V SoC

    I hope I'm not missing something either. Indeed the entry does imply it doesn't support 1.8V I/O in PS mode.

    I don't have anything definitive to offer. I'm hoping the documentation is lacking - although, given how mature the family is, I doubt it.

    Possibly a leftover from programming cable requirements when operating I/O bank 1 below 2.5V. USB-Blasters and other need at least 2.5V to power them...

    Cheers,
    Alex

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