Rockwell Automation 1756-IH16ISOE ControlLogix Sequence of Events Module - Manual (Page 96)

Publication 1756-UM528A-EN-P - April 2004
7-10 Using The Sequence of Events Module in FIFO Mode
Managing the Data in
FIFO Mode In FIFO Mode, the Sequence of Events module sends input data for
the current event to the controller immediately after the first input
transition has been timestamped and at each RPI. You must
manage the data coming from the Sequence of Events module.
The following occurs in the process of the managing data coming
from the Sequence of Events module in CST Per Point mode:
1. The controller retrieves current event data from the Sequence
of Events module in one of two retrieval methods.
2. The controller copies the relevant portions of the current
event data to a separate array.
3. At the user’s discretion, controller clears current data from the
Sequence of Events module by copying the current event
number (I.EventNumber) to the O.EventAck tag, preparing
the module send data from the next current event.
This process is described in the rest of this section.
Retrieving Data in FIFO Mode
In FIFO Mode, the Sequence of Events module automatically sends
the controller the data from the first timestamped transition in its
buffer. The controller must retrieve the data for the remaining
timestamped transitions in the Sequence of Events module’s
buffers.
The controller can retrieve data in one of the following ways:
• Standard Retrieval – By default, the module uses this retrieval
method which returns events in order of occurrence.
• Retrieval by Point
Regardless of retrieval method, the controller retrieves data in the
format described in Table 7.3 on page 7-11: