04-02-2019 08:10 PM - edited 04-02-2019 08:26 PM
Is it ok to power the two Vref pins on bank 14 and bank 34 respectively at 2.5V which is my VCCO voltage?
If it's not ok, can I configure Vref as a regular IO in which supplying 2.5V would be ok? How do I configure Vref as a regular IO?
04-02-2019 08:17 PM
No. If you cannot provide a half-Vcco power rail for the Vref pins, you can just just the INTERNAL Vref attribute and leave the pins as GPIO.
04-02-2019 08:34 PM
Unfortunately on the PCB, the Vref pins are now connected to 2.5V. It looks like I can salvage this by using the internal Vref attribute. Correct?
How do i turn on INTERNAL Vref attribute?
04-02-2019 09:36 PM
INTERNAL_VREF_BANK14 = 0.75;
like this. Check for more info in UG471.
04-02-2019 09:48 PM
Thanks. I've set this in Vivado .xdc constraint file as:
set_property INTERNAL_VREF 0.9 [get_iobanks 14]
set_property INTERNAL_VREF 0.9 [get_iobanks 34]
Hope it works.
04-02-2019 11:12 PM
At boot up when nothing is programmed into the Spartan 7, is the internal reference turned on by default? Will the 2.5V on the Vref pins damage the part on boot up?