You need to separate out preset entry from actual time resolution.
The AB ControlLogix and CompactLogix plcs, for example, have a 32-bit timer preset entry in MILLIseconds. However, you will only get control resolution down to your scan time. In other words you can enter a 1 MILLIsecond preset but the timer will simply delay the action 1 scan and your delay will be whatever the scantime is for the previous scan. So just because you can enter it doesn't mean you can control to it.
Keith