On May 12, 2011, at 11:38 AM, Ernest L. Williams Jr. wrote:
> Mark Rivers wrote:
>>> 1ms period should be fine but I haven't
>>> checked the least time period that epicseventwait can use. Maybe Mark has better idea?
>>>
>>
>> That depends on the OS and how it is configured. With vxWorks it is
>> determined by the value of sysClkRateGet/Set. The default clock period
>> on vxWorks is normally 50/60Hz, but it can easily be increased with
>> sysClkRateSet(). If you are using RTEMS I don't know what the rate of
>> the system clock is. Also, typically if you specify a time of X for
>> epicsEventWait the actual time will be X +- epicsThreadSleepQuantum(),
>> which is the system clock period. In other words if I ask for 16.6 ms
>> on a standard 60Hz vxWorks system I will get 0 to 16.6 ms, because the
>> next system tick can happen immediately (=0) or we may have just missed
>> one and it will happen in 16.6ms.
>>
>
> Hi Mark,
>
> Awesome, thanks for the info.
>
> Till and Eric can you weigh in on this question for RTEMS?
>From <base>/src/RTEMS/base/rtems_config.c
#define CONFIGURE_MICROSECONDS_PER_TICK 20000
If you want a different value you can copy rtems_config.c to your application source directory, add it to the Makefile and make any changes you wish. Note that this won't work for those of you dynamically loading your EPICS applications.
--
Eric Norum
[email protected]
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