Execute G-code when triggered by an external input (on parallel port input pin)

Hello, i am new to the linuxCNC systems.

I wish to build a simple rotating axis controlled by linuxcnc gcode. And i have a external robot which would perform some machining operations on the rotating part.

Now i want to sync both the machines. such that when i start the robot, the linuxcnc should also start executing the gcode.

Is it possible to execute the gcode when an input is provided through one of the parallel port input pins?
does the M66 code work here?
how to then pause the program if i pause the action of the robot (incase i have to e-stop the robot) and how to make sure then that the gcode is resumed from the paused location once the robot restarts and sends execution trigger to the linux cnc.

thank you for the guide. i am looking into it and so far it seems promising. i might have some questions down the line when i start building my g-code around the suggested solution.