Rockwell Automation Publication 1756-RM003N-EN-P - October 2011 85
FactoryTalk Alarms and Events Logix-based Instructions (ALMD, ALMA) Chapter 1
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.
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.
Rung State Execution Times
Digital Alarm (ALMD) Analog Alarm (ALMA)
No Alarm State Change Rung False 8 µs 17 µs
Rung True 8 µs 60 µs
Alarm State Change Rung False 35 µs 17 µs
Rung True 35 µs 126 µs
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