Got it! I needed to switch to GPIO 005 (TX5) and invert it.
Pin 5 (TX5) is low when Lcnc is not running, Inverting it makes it low when lcnc is running but not enabled, and finally high when enabled.
The graphic shows the relationship between the Pin names, Pin parameters and 7i85s terminal block association.
Peter, thank you for pointing me in the right direction, and not just doing it for me. This has been a very worth while and desperately needed hal / hostmot2 education for me.
