Rockwell Automation 1756-XXXX ControlLogix Digital I/O Modules User Manual
Page 225
Rockwell Automation Publication 1756-UM058G-EN-P - November 2012
225
Use Ladder Logic To Perform Run Time Services and Reconfiguration
Appendix C
The following illustrations show the ladder instructions the program uses. The
rungs perform these tasks:
•
Rungs 0 and 1 capture the rising or falling timestamps for input 0 of a
1756-IB16IF module.
•
Rung 2 executes only once at the transition from Program to Run mode. It
initializes LastInputTimestamp, which is used to detect a change of state
on the input point by checking to see if the timestamp of the input data has
changed. This rung also clears the output module’s TimestampOffset bit
to disable its Time Step Compensation algorithm.
•
Rung 3 is the main rung that checks for a change of state on the input
point by comparing the current input timestamp with the last timestamp
(LastInputTimestamp).