I started to panic a little today with all those different voltages. My last project, everything was using the Xilinx 3.3V LVTTL spec. I was reading the
UG381 IOB spec today and for this project I'll be using the LVCMOS spec which allows 1.2V, 1.5V, 1.8V, 2.5V and 3.3V. It's sort of difficult to read but I believe any pin per IOB can be assigned any of those voltages, as long as the entire IOB is using the LVCMOS spec. Can anyone confirm this?
In preparation for my worst fears, I made most everything a 1.8V standard, the SyncRAMs are capable of this. The UG381 guide also mentioned to use LVCMOS when performing FPGA to FPGA communication so I'm confident there.
I'm going to run a project through ISE and experiment with the constraints file in order to see if it generates any errors.
Also, I may lose a few pins on the Inter FPGA Comm channel. There are some multi-function pins that are best left unused for 100% reliability. Still doing research.
EDIT: Deleted updated Layout.e