Programmable machine control (PMC) .
Sinha, you are mostly correct in you description. You use fanuc ladder to program the PMC.
The CNC is responsible for motion control, program execution through the part program, and interface to the PMC.
Example: part program line: G0X10.0Y0Z0; in the "CNC"
This moves in a rapid move X to position 10, Y to position 0, (Home) Z to position 0 (home).
To start this you have to be in MDI mode. A semi auto mode, signal in the PMC. Press cycle start-a signal in the PMC. X INPUT, but then you connect that after whatever other interlocks you would normally have in that rung section, no alarms, no overtravels, ectect. To a G bit. For instance G7.2 may be cycle start to the CNC. G8.0 may be Estop Ok. G130.0-130.4 may be axis 1-4 servo interlock. You are constantly within the PMC (ladder) interfacing with the CNC and part program through G-and F codes. F signals maybe F3.1 in auto mode.
You program motion moves in the PMC and CNC. You can have CNC or PMC controlled axis same for spindles. All parameters and servos setup is held withing the CNC memory not the drives. Unless you have a older system with stand alone drives and spindles. You tune the servos and such with other software and within parameter sets in the CNC interface.
And many more..
Hope this helps.
Sorry for being kind of vague, I typed this quickly.