Hi. Does anyone know how to acknowledge a pidcon alarm from pc-program in the AC450. I am writing to property :115.169 ALARM_UNACK and the alarm disappears but in the faceplate is an unacknowledge alarm remains. How can acknowledge this in faceplate from pc-programs? Regards
The ALARM_UNACK bit in the database is a current status indication and not an order, or command bit. It is under system software control, and should never be written to. Set up a GRPALARM and add the PIDCON to the group together with a DIC as an alarm acknowledge master. Pulse the CALC_VAL on the DIC from PC program to acknowledge alarm on PIDCON.
ALARM_UNACK is written to FALSE from the alarm control (triangle in top of faceplate) so, yes, from a HMI perspective it can be used to acknowledge.
However, Alarm Global Properties:IsAlarmUnack is also, in parallel set to FALSE from the alarm control. This acknowledges the alarm in the Alarm Manager of 800xA, catering the alarm lists.
To clear the alarm in the Alarm Manager, the RTA/PU410 must receive an Enabled, Inactive, Acknowledged event from the controller over MB300.
I suspect the design in Advant Controller 400 may not cover this use case when addressing ALARM_UNACK from PC program. Unfortunately our lab is currently in molecules and I cannot verify what I just wrote. Maybe Peter can fill in here?