RE:re:Re: suggested improvement for EMC

Jon,

Exactly right. For EMC to go backwards, it REALLY just needs to SKIP
the "rest" of the program, and go FORWARDS (from the program
beginning) very quickly (since it is not outputting any motion) to
the desired "backward" block. As you say, it will be re-building the
lookahead on this forward pass through the file to the 'backup'
point...

Hope this helps.

Ballendo

>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