Difference in actual VCCIO used on board and I/O standard selected in Quartus project

Hi Alex and all,

Here is what I was replied by Altera team:

the switching threshold is determined by both the vccio and the i/o standard chosen. if they are mismatched, the functionality is undetermined and we will need to check with the i/o team to see if they can characterize the behavior. some standards (like lvttl) can scale in some (not all) parts, but other standards require specific voltages to function correctly. it really depends on the part and standard chosen...

Thanks to Altera team.

Anyway, as Alex suggested, it's always better ( and safe! ) to choose I/O standard that matches actual VCCIO on board. So while designing Quartus project, we should also consider this. Only assigning pin locations might not be enough.

Have a Great day!:)

Regards,

Bhaumik