high speed pulse generation

My experience with the altera PLLs is that they are intended to be tuned once for your design and left at that setting. If I could also perform dynamic adjustments that might be ideal , but I have not seen anything that would suggest it is possible. If you know of any app note or example, please let me know. I believe some of the xilinx parts incorporate DLLs which may be even more applicable provided you can get at those registers after configuration.