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Chapter 2
Module Overview and Features
Introduction to the
Sequence of Events Input
Module
14
What is Time Stamping?
Each input has its own individual timestamp recorded for both ON and OFF
transitions. The offset from the timestamp to the local clock is also recorded so
that steps in time can be detected and resolved.
Timestamping uses the 64-bit system time whose time base is determined by
the modules master clock resolved in microseconds. Each timestamp is
updated as soon as an input transition is detected, before input filtering
occurs. When filtering is enabled, the transition is only recorded if the
transition passes the filter.
The module starts timestamping as soon as it powers up, even if it is not
synchronized to a master clock. If it is synchronized to a master clock and then
becomes unsynchronized it continues to time stamp. All time stamps and
offsets have a value of zero at power-up.
For more information on how to use CIP Sync technology, see the Integrated
Architecture and CIP Sync Configuration Application Technique publication
IA-AT003.
The 1732E-IB8M8SOER is an input module that offers sub-millisecond
timestamping on a per point basis in addition to providing the basic ON/OFF
detection. It supports two modes of operation: Per Point Mode and FIFO (First
In First Out) Mode. To learn more about using the modules in these modes of
operation, see
Operational Modes
All input point event times are recorded and returned in a single buffer. The
module returns two 64-bit timestamps for each input, thus allowing:
•
ON and OFF events for each point to be displayed simultaneously in the
input data.
•
Ladder logic not being explicitly required to see events, although needed
to archive events.
•
Events to be kept in the controller memory during remote power loss
thus eliminating data loss.
All inputs on the module can be filtered for both ON to OFF and OFF to ON
transitions. The timestamp for a filtered input will be the time of the initial
transition to the new state and not the time that the filter validates the event as
real.
Selective Event Capturing allows particular events to be disabled per input and
per transition, ON to OFF or OFF to ON.
Event latching ensures that events are not overwritten. A single transition in
each direction is recorded per point. Any new event, which occurs after the
point has captured a timestamp, is dropped until the stored events have been
acknowledged.
If latching is not enabled in point mode, new events will overwrite old events
when they are received. In FIFO mode, up to 256 events per input will be
buffered before events are overwritten. Thus, if inputs are changing rapidly it
may be possible that events will be lost either in the module or the controller
prior to an event being operated on by ladder logic.
When events are lost, either old ones being overwritten or new ones being
ignored due to latching, an EventOverflow bit will be set for each point that
loses an event. The EventOverflow bit will clear when the blocking events for
that point are acknowledged.
Rockwell Automation Publication 1732E-UM003D-EN-E - November 2021
on
page
63.
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