[ECOS] to consume cpu time

[Doug Fraser]

One method of forcing nanosecond delays that I have
used is to read from FLASH. It is usually not cached
(to avoid programming problems) and also responds
in fixed time to a read cycle for most hardware.
For example, on our MPC850 based hardware, a FLASH
read (Intel Strata) responds in exactly 150nS.
You can get very consistent delay loops this way.

Doug Fraser

> -----Original Message-----
> From: Nick Garnett [mailto:nickg@ecoscentric.com]
> Sent: Wednesday, October 22, 2003 6:17 AM
> To: Luca Formaggio
> Cc: ecos-discuss@sources.redhat.com
> Subject: Re: [ECOS] to consume cpu time
> 
> 
> Luca Formaggio <luca_formaggio@yahoo.it> writes:
> 
> > Hi. I need to consume a cpu time in a program. This
> > time is in nanoseconds. Is there a ecos function that
> > consume time in nanoseconds? If it exists, how I call
> > this function from my program?
> 
> There's nothing in eCos that can handle that. The best we have is
> HAL_DELAY_US() which approximates a given microsecond delay.
> 
> If you want to insert delays for sub-microsecond periods then the best
> approach is probably to use timed code loops. Even then, your timing
> is going to be thrown out by any interupts. Even cache misses or DRAM
> refresh cycles may affect you.
> 
> -- 
> Nick Garnett                    eCos Kernel Architect
> http://www.ecoscentric.com      The eCos and RedBoot experts
> 
> 
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