I don't know what I was thinking last night, Bob! There isn't a need to do anything with the charge pump--that only lets the machine know that Mach is in control. What is needed, is when the spindle contactor drops out, to send a code 1001 (feed hold) back to Mach. Since the parallel port I/O lines are already fully used, this would require a second parallel port. But it is easily doable. Another project to add to the list...
BTW, on the Tormach hitting a limit switch does seem to interrupt the charge pump signal, because the "ref'd" LED's go red, and the "Machine OK" LED goes blinking red. That's a little more drastic than I would want to happen for a head door come ajar. The Tormach is set for pretty good accel/decel so I think a controlled stop might work (though I know that in some cases, depending on the vector being processed it doesn't alway decel immediately and that could be a problem).
The more I think about it, the more the pragmatist in me votes for a baby catch (or similar to an automobile hood safety catch) next to the camlock, and a long-stroke interlock switch. That way if the camlock comes un-cammed during a run, the run will continue without a hitch and the door will just rattle a little until the next toolchange...
Randy