More refactoring. This time, normalized the conversion beween: frequency and microseconds, clock ticks and microseconds and freqency and clock ticks. This last one is defined in terms of the first 2 conversions.
The naming is more consistent. 'freqFromTime' is now 'microSecToFreq'. The convention is to use the word 'to', not 'from'.
Tested with Tiva and Cygwin.