When are the DcsBios:::-functions called?

[marsip]

In my script I have:
void onAltitudeValueChange(unsigned int newValue) { (my code) }
DcsBios::IntegerBuffer altitudeValueBuffer(0x4678, 0xffff, 0, onAltitudeValueChange);

When is this code called by DCS?
During DcsBios::loop() ?

Or is the code (onAltitudeValueCange) called anytime and not necessary only during the call to DcsBios::loop?