Re: accessing internal h/w timers
- From: Michael Schnell <mschnell_at_lumino_dot_de@xxxxxxxxxxx>
- Date: Tue, 08 Aug 2006 13:22:40 +0200
techietone wrote:
Hello All!
Can we have access to internal h/w timers on an embedded board having
linux. The purpose behind this is to keep track of time - any of the
time related system calls are not usful; as the jiffies value itself is
beyond the required resolution.
See the thread "Linux system clock tick?" in this forum.
When in Kernel space, AFAIK, jiffies (frequency defined by the "HZ" constant in 1/sec) _is_ the resolution of the hardware timer used by the Kernel. The frequency used depends on the architecture (and can be changed by modifying a .h file and recompiling the Kernel). With not too fast CPUs it's 100 Hz, faster values not recommended.
In user space jiffies/HZ is always 100 Hz and changing it is not recommended. I don't think you can access the Kernel jiffies from user space.
Anyway, pure Linux is not meant to be a hard realtime system, so relying on fast timer stuff - especially in user space - usually fails.
-Michael
.
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