Make ulp timer clock for sync all time regs like gnns and gps, and gsm messages

[jprpower104]

I need make a continuosly square signal with a width of 0.5 ms in on and 0.5 ms in off, for make a clock system, this clock can operate in normal mode or in deep and ligth sleep, and turn on or turn off a physical led each the logic level of timer changes. this i need do with interruptions because with a polling strategy we can loss a bit of time.

Can you help to me for program a timer signal in ulp with a big grade of exact and presision.