If you don't specify IO standards, drive etc. in the UCF for a Spartan3, what default settings are used ?
What are IO standard defaults in S3 ?
Aug 09, 2005
2 Replies
First reply
Mike, Dunno, but it's easy to find out. Build a noddy design that's a wire from an input to an output. No UCF. Run P&R. Use FPGA editor to look at the IOBs' properties. This method has the advantage of showing you what the software ACTUALLY does, rather than what it SHOULD do!…
Read the full reply
Unless you specify otherwise, ISE sets the I/O standard to ...
- LVCMOS25
- 12 mA output drive
- SLOW slew rate.
The output will follow whatever voltage level you have connected to the respective VCCO input. In other words, even if ISE sets the I/O to LVCMOS25 and you have VCCO = 3.3V, the output will drive 3.3V levels.
However, it's best to always set the I/O level appropriately so the software can make sure that all your I/O assignments end up in the proper I/O banks.
Join the Discussion
Have something to add? Share your thoughts — no account required.
Didn't find your answer?
Ask the community — no account required