Scan Time - Allen-Bradley Logix5000 Reference Manual

FactoryTalk Alarms and Events Logix-based Instructions (ALMD, ALMA)
Longer message strings, as well as message strings for multiple languages,
consume additional memory from your controller.
Actual memory usage will depend on how the alarm is configured, message
length, and any associated tags passed with the alarm.

Scan Time

These execution times show how ALMD instructions and ALMA instructions
affect total scan time.
Rung State
No Alarm State Change Rung False
Alarm State Change
An alarm state change is any event that changes the condition of the alarm, such
as acknowledging or suppressing the alarm. Minimize the potential for a large
number of alarms changing state simultaneously (alarm bursts) by creating
dependencies on related alarms. Large alarm bursts can have a significant impact
on application code scan time.
Rockwell Automation Publication 1756-RM003N-EN-P - October 2011
Execution Times
Digital Alarm (ALMD)
8 µs
Rung True 8 µs
Rung False 35 µs
Rung True 35 µs
Chapter 1
Analog Alarm (ALMA)
17 µs
60 µs
17 µs
126 µs
85