SignalTapII

You need to view SignalTap as a convenient, build dependent capture system.

It is has useful trigger system but uses a lot of fpga resource.

With large systems packed into a limited resource, designers tend to have their own capture systems by tapping from various points along processing paths and storing data externally with minimum fpga resource usage.

SignalTap could be big burden on timing/resource critical cases. Its main attraction is either for beginners to see through real time or advanced designers with ample space in their fpga or for an occasional debugging of unexpected issue.