On Mon, Jan 19, 2015 at 09:44:53AM -0800, Bill Gray wrote:
> Great!
> 
> BUT... you say that the read-modfiy-write sequence will not be atomic?
> This is the part of the setup that is run by the PRU.  If this is not
> atomic, am I correct in understanding that my PRU program loop will no
> longer run on a predictable frequency?  I suppose I can tolerate timing
> chaos of 20-30ns, but not much more than that... and I would prefer to have
> my PRU loop running very regularly!
> 
Atomic is the operation completes as one indivisible operation. The
read modify write isn't since another operation can happen on the
memory location between the read and write. Atomic doesn't state anything
about how long it takes.

I thought I had seen documentation on what happens with conflicts on
accessing the PRU memory but I can't find it now. I think any additional
delay will be well under your limit.

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