Rockwell Automation 1756-IH16ISOE ControlLogix Sequence of Events Module - Manual (Page 84)

Publication 1756-UM528A-EN-P - April 2004
6-12 Using The Sequence of Events Module in CST Per Point Mode
Acknowledging Latched Timestamp Data
In most cases, Latch CST is enabled when the module operates in
CST Per Point mode. This means that once the module timestamps an
input transition, the module will not timestamp another transition in
the same direction on the same input until you acknowledge the data
from the first timestamped transition; when you acknowledge data,
you clear it from the Sequence of Events module.
To clear data from the Sequence of Events module, you must
acknowledge them via the module’s output tags. You can clear data in
the following ways:
• Clear latched timestamp data for specific inputs – As data is
acknowledged, it is cleared from the module, and the module
will once again timestamp the first new transition for the input
in the cleared direction(s).
To clear timestamp data for specific inputs, you must complete
the following steps:
1. Write to the EventAck tag (i.e., O.EventAck) in the input
point’s output word.
• 0 = clear only the falling edge timestamp (i.e.,
I.Timestamp[x].OnOff)
• 1 = clear only the rising edge timestamp (i.e.,
I.Timestamp[x].OffOn)
• 2 = clear both the falling and rising edge timestamps
2. Change the NewDataAck tag (i.e., O.NewDataAck) to a rising
edge (i.e., set the tag =1).
• If the bit = 0, change the bit to 1.
• If the bit = 1, change the bit to 0, wait for at least one RPI,
and change the bit to 1.
The corresponding I.EventOverflow and I.NewData tags are
also cleared.
• Clear all latched data for the Sequence of Events module –
This transition erases all timestamp data from the module,
clearing data from all inputs simultaneously. Once the data is
cleared, the module timestamps the first transition in each
direction for each input and sends the data to the controller
(assuming those inputs are configured with Enable CST Capture
enabled in each direction).
To clear all data for the module, transition the O.ResetEvents tag
to 1.
– If the bit = 0, change the bit to 1.
– If the bit = 1, change the bit to 0, wait for at least one RPI,
and change the bit to 1.