Forum Discussion
Altera_Forum
Honored Contributor
17 years agoThe clamping diode is controlled by "PCI I/O" in the Assignment Editor. The Description field for the assignment says this:
--- Quote Start --- Turns on Peripheral Component Interconnect (PCI) compatibility for a pin. For example, when the VCCIO of an EP20K400 device operates at 3.3 V and PCI I/O is turned on for a pin, the Compiler clamps the pin's signal to the VCCIO value, thus making the pin 3.3-V PCI-compliant. This option is ignored if it is applied to anything other than a pin or a top-level design entity. --- Quote End ---