ACS800 has what they call an adaptive program. Parameter group 84 is where that is set up. Look for an EVENT function in that group. AD[message] is generated by that event. If you look on page 21 of the Adaptive Program Application Guide [3AFE64527274 (English)], it details the EVENT function. Starting on page 172 in Firmware Manual
ACS800 Standard Control Program 7.x [3AFE64527592 (English)] is the parameter listing for group 84.