Just for reference I almost always make a spreadsheet for each project that captures the various timers and frequency divider equations for the MCU and companion harware in use. I include the main crystal frequency as well. I then produce tables of data that correspond to the settings in the SFRs that will help me determine how to properly setup the project for the task at hand. Later I can use this to see what will happen if the crystal frequency changes or some other rate for something is required. In the end run this XLS file is kept with the project sources to help as documentation for why various settings in the code initializes the SFRs the way it does. The comments in the code can say /* see reference spreadsheet Timers.xls for timing details */ . This is especially useful when you come back five years later and have to recall how it all worked!!

Michael Karas