Am Freitag, den 30.03.2007, 16:41 +0200 schrieb Gilles Chanteperdrix: > Richard Cochran wrote: > >>The timer is aperiodic (most of the time) when running Xenomai, so > >>__ipipe_mach_set_dec is called for each timer tick and programs the > >>timer hardware for the next tick. > > > > > > Okay, so does that mean that I should implement a "one-shot" timer, or > > are we talking about resetting the periodic timer once in a while? > > > > (BTW, in one-shot mode, the IXP425 timer does not do what the Developers > > Manual, part 252480-006, says that it does!) > > Yes, the one shot mode is Xenomai default mode. The implementation of a > periodic timer over the one-shot timer is already done by the generic > ARM part of the Adeos patch.
It's better to use a periodic implementation in background, because then you are able to messure the lost ticks between a timer-interrupt and programming next timer-event. Example with 16bit timer: * Periode: 27000 Ticks * Timer counts down to zero (Interrupt) & wrap around to 2^16-1 * Reprogramm Timer with new Periode (lost-ticks = 2^16 - timerval) These lost-ticks should be added to the global time-stamp (returned by get_tsc) and should mentioned at the linux-gettimeoffset-function also. Lost-ticks could sum up to a bothering time-error. - Manfred Schlaegl
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