Re: [CAD_CAM_EDM_DRO] re:Re: suggested improvement for EMC

ballendo@... wrote:

> Ian,
>
> It is usually easy to(programming perspective, here) "back up a few
> lines", BUT...
>
> With Gcode, MANY things are modal and will have been set by previous
> lines/blocks in the gcode. Any re-start from Nxxxx (previous line
> number) NEEDS to either "recall" these modal states, or; "re-run"
> through the program, quickly setting such modal flags/variables so
> that when the line requested is run, it will run as expected!

Yes, it sounds simple, but the interpreter was written with forward
lookahead. So, on each move, it is carefully considering this move's
effect on future moves until it has looked far enough ahead that
this move could not affect any moves further ahead in time.
It considers the ability of the machine to accelerate and decelerate,
with respect to blending curves on all axes.

That is why it is not easy to back up with EMC. Now, the interpreter
COULD be reconfigured so that it would rebuild the lookahead
any time there was a program interruption. This would also make
it possible to put loops and subroutines in the programs, which it
does not support now, for that reason. But, nobody who is qualified
has stepped forward and volunteered to do this rewrite.

Jon