No program on the controller!

Safety CPU Boot Failure / No Program Loaded

ABB · AC500 Function Block Libraries

What does No program on the controller! mean?

The safety CPU fails to enter RUN mode after power-on, with the DIAG LED on and no boot project loaded. This often occurs if the power-off to power-on pause is less than 1.5 seconds, triggering a power dip detection that prevents the existing boot project from loading.

Source: ABB AC500 Function Block Libraries
View Official PDF