VHDL Data Types

   TYPE TIME IS RANGE 

UNITS
   fs;  -- femtosecond
   ps = 1000 fs;  -- picosecond
   ns = 1000 ps;  -- nanosecond
   us = 1000 ns;  -- microsecond
   ms = 1000 us;  -- millisecond
   sec = 1000 ms;  -- second
   min = 60 sec;  -- minute
   hr = 60 min;  -- hour
   END UNITS;