What are the IO standards supported by Basys3 FPGA?

[harshgola00]

Hello,

I am new to FPGA and i have made some designs like LED on/off which used LVCMOS33 IO standards, now i am trying to output a differential signal through PMOD, and i have been told to utilize OBUFDS primitive, during the IO mapping, the IO standard available exclude the LVCMOS33 standard which i have always been using and shows DIFF_STL_18 and the like, how do i know which to choose.

Thanks

[zygot]

If you are going to use a complex device like an FPGA you might as well learn something about how it works and its capabilities. AMD/Xilinx tools come with the Documentation Navigator with plenty of user guides, application notes and other information to help with this. Use it.

The 7 Series FPGAs SelectIO Resources User Guide has most of the information that you need to answer your questions. In addition, the schematic for your board is required, because IOSTANDARD availability is limited to the Vccio that powers the IO bank that the pins that you want to use is connected to in the board design. For PMOD IO this is 3.3V. There are no differential IO standards supported for these, except for TMDS_33. The User Guide shows you what termination is required to use that IOSTANDARD.

It would be nice if FPGA board vendors were a bit more informative about the true capabilities of their boards, but most seem to adhere to the "buyer beware" model of advertising. In the case of Digilent's so called "high speed differential PMODs", the advertising is blatantly misleading, even for the boards that have user-selectable Vccio voltage supplies on certain IO banks.

Cheap FPGA boards that allow the user to experiment with all of the IO options of their programmable devices tend to be on the expensive end.

Sadly, you question is a common occurrence on the Digilent forums. The marketing folks at NI don't seem to care.

Edited June 6, 2023 by zygot