Rockwell Automation 1756-IH16ISOE ControlLogix Sequence of Events Module - Manual (Page 104)

Publication 1756-UM528A-EN-P - April 2004
7-18 Using The Sequence of Events Module in FIFO Mode
Retrieval by Point
Retrieval by Point is similar to Standard Retrieval by time except that
with this method, the controller only retrieves timestamp data for
input transitions that occurred on a specific point.
The Sequence of Events module still timestamps input transitions
for any events that occur on Enable CST Capture-enabled inputs. The
module also stores the data in its on-board buffers as described on
page 7-2 for up to 160 input transitions.
IMPORTANT
Although the Sequence of Events module can still
store the data for up to 160 timestamped transitions
in its on-board buffer when you use the Retrieval
by Point method, the module only stores up to
10 timestamps per input.
You must manage the module buffer effectively to
make sure that the module timestamps all transitions
on a specific input.
Consider the following example:
You are using Retrieve by Point to retrieve
timestamp data from input 4, and 10 of the first
34 input transitions that the Sequence of Events
module timestamps occur on input 4.
If Latch CST is enabled for the module and you
fail to clear any of the timestamp data for input 4
before the input transitions again, the Sequence
of Events module will not timestamp the next
transition for input 4, even though there are 126
slots still available in the module’s on-board
buffer.