On Sun, 2010-04-11 at 16:21 -0500, Karl Schmidt wrote:

> I'm also wondering does EMC compile a pulse list and timing before the move 
> so there would be no 
> computation latency, or is it generated on the fly?

Living with the NIST notion of "Sense -> Model -> Act" tends to limit
one from building the buffered motion system you're thinking of.  

EMC started as a servo based system with real position feedback not just
in the drives but at the heart of the computer system doing the control.
Servo position control is still central to all that it does.  Step and
direction signals were an addition with compromises.

I'll grant you that some step and direction systems lack the ability to
sense real hardware position so we get into lots of discussion about how
to detect lost steps.  

But at its core EMC senses all of the machine's state, including
feedrate override and rate of change and factors that state into the
next bit of motion rather than building an entire path ahead and then
apply changing state variables to that predetermined path.




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