Use timestamp latching – Rockwell Automation 1732E-OB8M8SR EtherNet/IP Dual Port 8-Point SOE Input and Scheduled Output Modules UM User Manual
Page 76
66
Rockwell Automation Publication 1732E-UM003B-EN-E - March 2014
Chapter 10 Use the Sequence of Events Input and Scheduled Output Modules
2.
The module sends all of its input data, including the new data from the
most recent transition, to the controller immediately after timestamping
the transition and passing the input filter to make sure the transition was
valid.
3.
You copy new data from the controller tags to a separate data structure for
later sorting.
4.
Acknowledge the timestamp, using output tags, so that the module can
capture another timestamp on that input without losing any data.
5.
Once the data is copied to a separate data structure, you may sort the data
in the controller to determine the order of events.
Some of these typical events are described in greater detail in the rest of this
chapter. For typical applications for Sequence of Events modules, refer to High
Performance Sequence of Events Applications in the Logix Architecture on
Use Timestamp Latching
When enabled, timestamp latching prevents the module from overwriting
recorded timestamp data once a transition occurs. This feature is set on a
modulewide basis and is enabled by default. The following table describes how
Timestamp Latching affects the module.
If Timestamp
Latching is:
the following occurs
(1)
(1) This table assumes the transition occurs on inputs that have Timestamp Capture enabled. If Timestamp Capture
is disabled, the module does not timestamp transitions on that input and, therefore, Timestamp Latching does
not affect module behavior.
Enabled
The module timestamps two transitions for each input–one for OFF to ON and one
for ON to OFF. If similar transitions occur on inputs where a transition has already
been timestamped and the data was not yet acknowledged (for more information
on Acknowledge Timestamp Latching Timestamp Data, see
), the module
does not timestamp the new transition.
When a transition is not timestamped, the module sets the I.EventOverflow tag for
that point to inform the controller that an input transitioned but a timestamp was
not produced for the transition.
By default, Timestamp Latching is enabled.
Disabled
The module timestamps each transition for each input as it occurs. In this case,
when multiple transitions occur in the same direction on the same input, the
module records the new timestamp data, overwriting any previously-recorded data
which had yet to be acknowledged (for more information on Acknowledge
Timestamp Latching Timestamp Data, see
When the module overwrites data, it sets the I.EventOverflow tag for that point to
inform the controller that events have been overwritten.
IMPORTANT
We suggest you monitor the I.EventOverflow bits to make
sure you are aware of transitions that were either not
timestamped or when timestamp data was overwritten.