Timer driver vs. timer manager, etc.

Kenneth Peters Kenneth.J.Peters at jpl.nasa.gov
Thu Jun 5 18:08:18 UTC 2003

I want to make sure I understand the timer and clock elements of RTEMS 
correctly, since some of the same terms are used in different places, with 
no real connection between them (I think). Please comment on the following:

The "Timer Driver" referred to in the "BSP and Device Driver Development 
Guide" is only used by the provided OS test suite, and has nothing to do 
with the "Timer Manager" from the "RTEMS C User's Guide".

The "Timer Manager" does need the "Clock Driver" from the "BSP and Device 
Driver Development Guide", as does the "Clock Manager".

The "Rate Monotonic Manager" needs the "Timer Manager" and thus the "Clock 
Driver" (or does the RMM use the "Clock Driver" directly?). The "Task 
Manager" needs the "Timer Manager" (or does the Task Manager use the "Clock 
Driver" directly?) only if timeslicing or delay functions are needed?

The "Real-Time Clock Driver" from the "BSP and Device Driver Development 
Guide" is not actually required for anything. If it is provided, the user 
can call its functions to synchronize the "Clock Manager" and the RTC 
device, or as substitutes for some of the "Clock Manager" functions.


Ken Peters

More information about the users mailing list