[ECOS] Re: CYGACC_CALL_IF_DELAY_US(1000000) fails

Gary Thomas gary@mlbassoc.com
Tue Nov 25 14:56:00 GMT 2003

On Tue, 2003-11-25 at 07:31, Savin Zlobec wrote:
> Uwe Kindler wrote:
> >Hello,
> >
> >if I call  CYGACC_CALL_IF_DELAY_US(1000000) in order to delay one second,
> >then this call returns a lot
> >faster then 1 second. When I debug the code, then I can see, that
> >HAL_DELAY_US provided by the HAL
> >is only used if no kernel package is included. HAL_DELAY_US(1000000) works
> >fine.
> >
> >If the kernel package is included, the the following calculation takes
> >place:
> >
> >// How many ticks total we should wait for.
> >        usec_ticks = usecs*CYGNUM_KERNEL_COUNTERS_RTC_PERIOD;
> >  
> >
> This is already fixed in CVS.
> PS:
> There are better ways to wait for 1 second if you are using the kernel -
> CYGACC_CALL_IF_DELAY_US is a busy wait.

Indeed - first of all, CYGACC_CALL_IF_DELAY_US should really only be 
used for "short" periods.  Often devices may have requirements like
"the reset pulse should be true for 25us" or whatever.  In this case,
the busy wait code (DELAY_US) is the correct way to go.  

If you have the kernel package (i.e. threads), then use
to wait for one second.

Gary Thomas <gary@mlbassoc.com>
MLB Associates

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