Changing I/O Standards


I own a XEM3001v2 board and I am thinking about changing the I/O standards it uses to communicate to external devices. By default it uses LVCMOS25, and I would like to change that to LVCMOS33. I read on the Xilinx user guide (and shown by this forum post:

) that this can be done by modifying the UCF file as follows:

NET “net_name” LOC = “B4” | IOSTANDARD = LVCMOS33;

and since I am using JP2, which is connected to the YBUS, i figure I will have to do something like:

NET “ybus” LOC = “P45” | IOSTANDARD = LVCMOS33

However, what I am not sure about is that if I should do the same for the following UCF definitions:

NET “hi_in” LOC = “P79”;
NET “hi_in” LOC = “P57”;
NET “hi_in” LOC = “P58”;
NET “hi_in” LOC = “P78”;

Or it would be OK for these to keep using LVCMOS25. If anyone has any idea, please share.


Technically, you should be using LVCMOS33 since the VCCOs are actually plugged to 3.3v. Sticking with the default of LVCMOS25 was just a shortcut that didn’t break anything.