Forum Discussion
New ContributorVREFB pin in Cyclone V
Hello,
Since it is mentioned in the Pin Connection Guideline that the pin needs to connect either GND or VCCIO if not used, then I am afraid you can't leave it floating.
Although I can't confirm with you that this is the cause of those faulty JTAG pins, I guess what will happen to the pin if left floating is the output of the buffer logic will be undefined since those pins are voltage-reference pins. It means that the pin should be connected to a valid logic for the hardware to work as expected.
Super ContributorHi,
VREF pins are only used for voltage referenced I/O-standards HSTL and SSTL. IMHO you can leave it open if you enable weak pull-up for unused pins.
VREF[#]N0 means all VREF pins. Pin connection guidelines are suggesting "If the VREF pins are not used, you should connect them to either the VCCIO in the bank in which the pin resides or GND".
New ContributorThank you for your prompt response.
To add a weak pull-up to the VREF pins, I should set "As input tri-stated with weak pull-up" in Device and Pin Options -> Unused Pins, correct? I didn't realize that VREF pins could be set as unused pins.
Although there is no mention of a pull-up for "VREFB3AN0" in the *.pin file, considering that other unused user I/O pins are set to "RESERVED_INPUT_WITH_WEAK_PULLUP," can I assume that the VREFB3AN0 pin is also pulled up?
