Radio LCD displays the word "CAL"

What does it mean when the radio LCD displays "CAL". I installed a new ECU into the car and it kept flashing the word "CAL". For one, I know it's the wrong ECU model for the car, so I took it out. The car is a 2000 Impala. I'm assuming it means "Calibrate"...

i would start with the correct control unit for the car. but yes i would assume it means calibrate. gm may ship their computers blank and its up to the tech to transfer the software from one module to the other. if it sees a module with the incorrect program it may just assume that it is a blank new one.

I heard that if you buy one from a wreckers, calibration is just an option. To be honest, I don't even want the ECU calibrated to my car because my car has enough issues as it is. I would prefer that it acts like a regular impala for once :P.