Rockwell Automation 1756-IH16ISOE ControlLogix Sequence of Events Module - Manual (Page 88)

Publication 1756-UM528A-EN-P - April 2004
7-2 Using The Sequence of Events Module in FIFO Mode
How Does the On-Board
Buffer Work in FIFO Mode? The Sequence of Events module’s on-board buffer stores data for up
to 160 timestamped transitions at one time. For each transition,
specific information is recorded, as shown below and described on
page 7-10. The on-board buffer has 160 slots to store timestamp
information for input transitions. As the transitions occur, the module
timestamps them and fills the 160 slots. The first transition fills the first
slot, the second fills the second slot and so forth.
Figure 7.1
0 1 1 0 0 1 0
0 1 1 0 0 1 0
1 1 0 0 1 1 0 2
1 0
1 5 1
1 5 1
The module is installed, wired to input
devices and ready to begin operation.
At this point, the module’s on-board
buffer is empty because no input
transitions have occurred.
Input 5 transitions from OFF to ON.
The module timestamps the transition
and stores the data in this first slot of
its on-board buffer.
Input 1 transitions from ON to OFF.
The module timestamps the transition
and stores the data in the next slot of its
on-board buffer.
Note that the data from the input 5 OFF
to ON transition is still stored in the first
slot of the module’s on-board buffer.
43805
Timestamp Event # Input # Input State
Timestamp Event # Input # Input State
Timestamp Event # Input # Input State