Rockwell Automation 1756-IH16ISOE ControlLogix Sequence of Events Module - Manual (Page 93)

Publication 1756-UM528A-EN-P - April 2004
Using The Sequence of Events Module in FIFO Mode 7-7
Disabled The Sequence of Events module timestamps input transitions as they occur, and stores the data for those
transitions in its on-board buffer. However, the module can only store the data for up to 160 transitions in its
on-board storage buffers. If you fail to empty the buffer (as described on page 7-10) faster than it is filled, after
160 timestamped input transitions, the module overwrites the timestamp from the first transition in its on-board
buffer with data from the most recent transition.
If the Sequence of Events module overwrites data, it sets the I.EventOverflow bit to one for the point where a
timestamp was previously recorded but has been deleted to inform the controller that events have been
overwritten.
(1) This table assumes the transition occurs on inputs that have Enable CST Capture enabled. If Enable CST Capture is disabled, the module does not timestamp transitions on
that input and, therefore, Latch CST does not affect module behavior.
Table 7.2
If Latch CST is
the following occurs
(1)
:
0 1 1 0 0 1 0
1 1 0 0 1 1 0
0 1 0 0 0 1 0
1 1 0 0 1 1 0
1 0 1 0 0 1 0
1 1 0 0 1 1 0
1 0 1 0 0 1 1
0 0 0 0 1 1 0
1 1 0 0 1 0 1
1 0 0 1 1 1 0
1 1 1 0 0 1 1
1
2
3
4
5
6
7
8
9
159
160
4
2
8
11
9
1
2
7
10
12
5
0
1
1
0
0
0
1
1
0
0
1
0 1 1 0 0 1 0
1 1 0 0 1 1 0
0 1 0 0 0 1 0
1 1 0 0 1 1 0
1 0 1 0 0 1 0
1 1 0 0 1 1 0
1 0 1 0 0 1 1
0 0 0 0 1 1 0
1 1 0 0 1 0 1
1 0 0 1 1 1 0
1 1 1 0 0 1 1
161
2
3
4
5
6
7
8
9
159
160
3
2
8
11
9
1
2
7
10
12
5
1
1
1
0
0
0
1
1
0
0
1
The Sequence of Events
module has timestamped and
recorded enough input
transitions since the controller
last retrieved data, that the
on-board buffer is full.
Input 3 transitions for OFF to ON.
Because Latch CST is disabled,
the module timestamps the
transition and records the data in
slot #1 of its on-board buffer.
In this case, the oldest data (i.e.,
data in slot #1) is automatically
deleted from the module. The
module sets the I.EventOverflow
tag for that point.
Note that the
timestamp data for
event #1 has been
deleted from the buffer.
The timestamp from the
most recent transition
overwrites the data in
slot #1 and becomes the
current event sent to the
controller.
Timestamp data #1
Timestamp data #160
43807
Timestamp Event # Input # Input State
Timestamp Event # Input # Input State