Rockwell Automation 1756-IH16ISOE ControlLogix Sequence of Events Module - Manual (Page 63)

Publication 1756-UM528A-EN-P - April 2004
Using the Sequence of Events Module Features 5-11
In the example, a Sequence of Events module:
• is Enable CST Capture-enabled for all of its points
• uses a 2ms input filter setting for OFF to ON transitions
Three possible scenarios can result after an input transitioning from
OFF to ON in the given circumstances.
• Scenario #1 (no bounce) – The input turns ON and remains
for the full 2ms. In this case, the module considers the
transition valid and sends the data recorded at the transition
to the controller.
Figure 5.1
• Scenario #2 – The input turns ON but turns OFF before 2ms
(length of the input filter setting) elapses. In this case, the
Sequence of Events module continues to scan the input every
25
µs for 4x the length of the input filter setting (i.e., for 8ms).
At some point in those 8ms, the input turns ON again and
remains for at least 2ms (i.e., the input filter setting). In this
case, the module considers the transition valid and sends the
data timestamped at the original transition to the controller.
Figure 5.2
0 1 2 3 4 5 6 7 8
Input turns ON;
timestamp recorded
Time in milliseconds
Input remains ON for at least 2ms; transition is considered
valid and the timestamp is sent to the controller
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0 1 2 3 4 5 6 7 8
Time in milliseconds
Input turns ON and remains ON for at
least 2ms in the time period that is 4x the
input filter setting (i.e., 8ms).
The module sends the timestamp
recorded at the original transition point to
the controller.
Input turns OFF before
2ms have elapsed.
43672
Input turns ON;
timestamp recorded