Clock and Hardware Timer usage

Cedric Aubert cedric_aubert at
Thu Jul 3 12:13:41 UTC 2003

> My interpretation is he's suggesting that wall-clock
related timer
> functions should operate off a different timer than
the OS time quanta
> tick.

Yes,  should be that, or more interesting use the same
HW Timer for walltime
and OS time quanta tick with some timer queue

> I think this suggests each bsp would make a decision
on how to
> implement it, either continue to use the time quanta
tick or use some
> local RTC function or alternative timer to do it.

Should be for compatibility reason mandatory to have a
choice of how to
use the HW Timer, periodic IT like known, or varying
IT period.

For me the concept of RTC is simple. I think that
RTEMS have it today.
Read HW timer to update TOD, when you need it, is

The difficult is in the usage of the HW timer.

>  To me the problem
> seems to be there are no cross-bsp guarantees that
anything better
> than the OS quanta tick will be used.

I don't really understand what you mean here. Sorry
for my english :-)

> However, I think it might be
> useful to decouple application timer manipulation
from the time quanta
> ticks.
> Gregm


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