Front or rear, it's the cable and cable alone that controls shifting. The aptly named LIMIT screws do exactly what the name implies, specifically determine the inner and outer limits of the working range.

Imagine an elevator. The motor pulls the cables to raise or lower the car to each floor. The system has limit switches top and bottom to prevent the car from crashing into thd roof or basement.

As Kontact said, your cable is probably too tight, not giving enough slack for low gear (assuming FD). Once you address that, you'll need to reset both limits so the chain won't fall off either end.