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Altera_Forum's avatar
Altera_Forum
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15 years ago

FPGA IO configed as 1.8V not working

Hi,

I read from the device handbook and get that the cyclone2 devices support multi-voltage IO standards, such as 3.3/2.5/1.8/1.5 volt.

I change the IO voltage to 1.5 volt in the device options setting and re-compile, download it to the board and find the output is still 3.3v. Setting them to 2.5 or 1.8v is not working too.

Am I doing something wrong?

https://www.alteraforum.com/forum/attachment.php?attachmentid=3716

4 Replies

  • Altera_Forum's avatar
    Altera_Forum
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    15 years ago

    The I/O voltage setting has the purpose of informing Quartus about the hardware enviroment. The actual voltage is set by connecting the VCCIO pins to a respective supply. Apparently your board (I guess, a development kit) has all or most VCCIO pins wired to 3.3V.

  • Altera_Forum's avatar
    Altera_Forum
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    15 years ago

    --- Quote Start ---

    The I/O voltage setting has the purpose of informing Quartus about the hardware enviroment. The actual voltage is set by connecting the VCCIO pins to a respective supply. Apparently your board (I guess, a development kit) has all or most VCCIO pins wired to 3.3V.

    --- Quote End ---

    Does the IO voltage setting have purpose other than informing quartus?

    eg, if I want to use max-ii device as level shifter, but one side of the shifter's voltage is variable, you know...

    so I hope the IO voltage setting has only information purpose. then i can chose one setting and change VCCIO without re-compile
  • Altera_Forum's avatar
    Altera_Forum
    Icon for Honored Contributor rankHonored Contributor
    15 years ago

    --- Quote Start ---

    so I hope the IO voltage setting has only information purpose.

    --- Quote End ---

    This should be true at least for MAX II. With FPGA, the I/O standard also affects the interpretation of the current strength setting.