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Altera_Forum's avatar
Altera_Forum
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16 years ago

Cyclone III MSEL pin levels

Hi,

Just a quick question regarding the levels required on the MSEL pins for configuration of a Cyclone III device. I was studying the Cyclone III handbook and on page 216 it states the following:

--- Quote Start ---

The MSEL pins are powered by the vccint power supply of the bank in which they reside.

--- Quote End ---

Do they mean Vccio power supply of the bank and not Vccint?

Initially I had the MSEL pins connected to 3.3V in the schematics which will be the configuration voltage, but the IO bank in which the MSEL pins reside is used as LVDS and therefore powered of 2.5V.

So am I right in assuming that I should connect the relevant MSEL pins to 2.5v instead on 3.3V?

Thanks.

4 Replies

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

    There's an exact recommendation in the manual immediately following the said sentence.

    --- Quote Start ---

    hardwire the MSEL pins to VCCA or GND

    --- Quote End ---

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

    Yes, that is the correct way to go, what FvM recommends, which is what the documtation says. The actual trip points will depend on voltage, process, temperature, etc...

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

    Do they mean Vccio power supply of the bank and not Vccint?

    No, it does mean VCCINT, for many devices such as this one, Altera device input buffers are powered by VCCINT. It makes the input buffers independent of VCCIO voltage.