by support »
Hello,
As you've surely noticed, the Xillybus bundle has no problems meeting timing when implemented by itself.
ISE's critical path report says very little about where the timing problem is, because it doesn't have the information about what clock frequencies are actually going to run on each clock net. In other words, it hasn't looked in the UCF.
The fact that a path in the Xillyvga path showed up is meaningless, as the rough frequency limit estimation is 85 MHz, but the actual clock running there is 65 MHz. So there is no reason to suspect a problem here.
The place to look for timing issues is the post-place-and-route timing report. And that info should be taken with a grain of salt as well, because the failing paths are sometimes a result of some other paths eating up the precious routing resources. So the solution to a timing problem sometimes lies in the paths that appear in the list of worst paths, and sometimes in something completely different, which prevented the paths that failed from getting fast routes.
In short, noone said saving timing problems was easy.
Regards,
Eli
Hello,
As you've surely noticed, the Xillybus bundle has no problems meeting timing when implemented by itself.
ISE's critical path report says very little about where the timing problem is, because it doesn't have the information about what clock frequencies are actually going to run on each clock net. In other words, it hasn't looked in the UCF.
The fact that a path in the Xillyvga path showed up is meaningless, as the rough frequency limit estimation is 85 MHz, but the actual clock running there is 65 MHz. So there is no reason to suspect a problem here.
The place to look for timing issues is the post-place-and-route timing report. And that info should be taken with a grain of salt as well, because the failing paths are sometimes a result of some other paths eating up the precious routing resources. So the solution to a timing problem sometimes lies in the paths that appear in the list of worst paths, and sometimes in something completely different, which prevented the paths that failed from getting fast routes.
In short, noone said saving timing problems was easy. :)
Regards,
Eli