Timing Constraints

Spartan-3 USB 2.0 Modules
1

Hi,

I have been using the Opal Kelly board and its various functionalities such as WireIn and WireOuts for my project. However, one thing I was wondering is if timing constraints should be defined (or is already defined somewhere?) for all the I/O pins. I am worried that if they are left undefined then the I/O latency may be more or less arbitary. If they are not already defined and they should be, I was wondering if there are any suggestions since the timing constraint statements require explicit delay (ie. 25ns delay).

Thanks.

2

Larry–

Are you referring to the timing constraints for the USB/FPGA interface?

The USB/FPGA interface runs at 48MHz which is pretty slow by Spartan-3 standards. We have so far not had any trouble meeting timing without constraints on any implementation we’ve built.