I am using AD9959 to create a pulse lasting for couple microseconds to 100 microseconds. The scheme is shown as below
I found that above code doesn't work, I don't see any output to the scope. I can make it work only with waiting time at least couple millisecond. I don't understand why. The system frequency is said to be 500MHz so the time resolution is 2ns, SYNC_CLK is 1/4 of fsys so it will have 125MHz, IO_UPDATE is greater than at least 1 SYNC_CLK so 8ns. So does it mean I should see the pulse output 8ns after IO_UPDATE triggered? But I don't see anything if the waiting is not long enough (at least 5ms), why?