Rockwell Automation 1756-IH16ISOE ControlLogix Sequence of Events Module - Manual (Page 62)

Publication 1756-UM528A-EN-P - April 2004
5-10 Using the Sequence of Events Module Features
Software Configurable Input Filters
To account for hard contact “bounce”, you can configure ON to
OFF and OFF to ON input filter times in RSLogix 5000 for your
Sequence of Events module. These filters define how long an
input transition must remain in the new state before the
module considers the transition valid.
When an input transition occurs, the Sequence of Events module
timestamps the transition on the initial edge of the transition and
stores data for the transition on-board; the module then scans the
input where the transition occurred every 25
µs for the length of the
filter time setting to verify that the input remains in the new state
(i.e., remained OFF or ON).
• If the input remains in the new state for a time period equal to
the filter time setting, the module sends data for the transition to
the controller.
• If the input changes state again (i.e., returns to the original
state) before the length of time of the filter setting has
elapsed, the module continues to scan that input for up to 4x
the filter setting. During this continued scan period, one of
the following events occurs:
– At some point in the time period that is 4x the length of the
input filter setting, the input returns to the transitioned state
and remains there for a length of time equal to the filter
setting. In this case, the module sends data from the
transition to the controller.
– The input does not remain in the transitioned state for a
time period equal to the filter setting at any point in the
time period that is 4x the length of the input filter setting.
In this case, the module does not consider the original
transition valid and drops the timestamp.
See Figure 5.1 on page 5-11 for an example of how the Sequence of
Events module’s input filters operate.
IMPORTANT
Input filters are applied to all inputs on the
Sequence of Events module. You cannot apply
input filters to individual inputs on the module.