Yes no question, different voltage level in a bank.

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Is it possible to drive a bank that works at 2.5 Volt with 3v3V ttl/cmos voltage levels without any modification.

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Which device?

For example, this works fine with Stratix II devices; I have a board with 2.5V devices communicating with 3.3V devices.

If you look in the device handbook, they typically have a table of I/O voltage compatibility.

Cheers,

Dave